Next Article in Journal
Chronic Exposure to Field-Level Thiamethoxam Impairs Gut Tissue and Reduces Honeybee (Apis cerana) Survival
Next Article in Special Issue
Leaffooted Bugs, Leptoglossus phyllopus (Hemiptera: Coreidae), Are Attracted to Volatile Emissions from Herbivore-Damaged Cotton Bolls
Previous Article in Journal
Species Delimitation and Cryptic Diversity in Rheotanytarsus Thienemann & Bause, 1913 (Diptera: Chironomidae) Based on DNA Barcoding
Previous Article in Special Issue
Untargeted Volatile Profiling Identifies Key Compounds Driving the Attraction of Western Flower Thrips to Alstroemeria Cultivars
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Insects
Volume 16
Issue 4
10.3390/insects16040371
insects-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Population Dynamics of Galerucella birmanica and Its Aggregation Behavior in Brasenia schreberi Aquaculture System

by
Yini Wang
,
Yahong Wang
and
Changfang Zhou
*
School of Life Sciences, Nanjing University, Nanjing 210023, China
*
Author to whom correspondence should be addressed.
Insects 2025, 16(4), 371; https://doi.org/10.3390/insects16040371
Submission received: 27 January 2025 / Revised: 27 March 2025 / Accepted: 28 March 2025 / Published: 1 April 2025
(This article belongs to the Special Issue Advances in Chemical Ecology of Plant–Insect Interactions)
Browse Figures
Versions Notes

Simple Summary

The aquatic macrophyte watershield, Brasenia schreberi Gmel., with its young buds coated in a thick mucilage served as a famous vegetable, has been cultivated in China for a long time. However, its production has been threatened by a pest, Galerucella birmanica Jacoby. This study investigated the population dynamics of G. birmanica throughout the entire growth season of B. schreberi from May to November and identified the aggregation behavior of the pest, with a preference for severely chewed leaf areas. Further analysis revealed that it was 2-phenylethyl isothiocyanate released from the damaged leaves that attracted G. birmanica. Our findings provide valuable insights for pest management in B. schreberi cultivation fields, and the attractant effect of 2-phenylethyl isothiocyanate on G. birmanica offers a new perspective for the development of attractants for this insect.

Abstract

The aquatic vegetable Brasenia schreberi Gmel. (Nymphaeales: Cabombaceae), widely cultivated in China, faces severe challenges from pest disturbances. With a field investigation, G. birmanica occurred for several generations in the Brasenia mono-cultivation system. The first visual peak on leaf surfaces appeared in July, with eggs, larvae, pupae and adults all being recorded. The highest number of flying adults were trapped in August in reverse to the absence of beetles on leaves, followed by an extraordinary high number of eggs in September. G. birmanica exhibited a conspicuous aggregation in distribution, with severely chewed areas having a G. birmanica abundance 21.6 times that of the non-chewed areas. Laboratory studies with GC–MS and two-choice tests revealed four volatiles significantly discrepant in contents released from chewed/intact leaves: cis-3-hexenyl acetate (917.33 ± 29.56 vs. 604.034 ± 23.24 ng, chewed vs. intact), 2-phenylethyl isothiocyanate (595.37 ± 28.42 vs. 356.00 ± 13.44 ng), undecane (771.44 ± 34.72 vs. 1003.28 ± 47.88 ng) and methyl salicylate (1079.84 ± 49.39 vs. 532.11 ± 18.23 ng); among them, 2-phenylethyl isothiocyanate could significantly attract G. birmanica adults. Our study suggests that G. birmanica can be a severe threat to mono-cultivated B. schreberi, whereas the damaged leaves may sacrifice themselves by attracting the beetles with an herbivore-induced volatile, thus protecting the whole plant population from pest disturbance.

1. Introduction

The watershield, Brasenia schreberi Gmel., is a monotypic genus in the Cabombaceae family [1,2] (also listed in the Nymphaeaceae family in some references [3,4]). The perennial, floating-leaved aquatic macrophyte is widely but sporadically distributed in lakes and ponds across East Asia, Australia, West Indies, Africa and North and Central America, with the exception of Europe, where the species has been extinct [3,5]. The submerged shoots and leaves, especially young buds of the plants, are coated with thick mucilage containing multiple polysaccharides, like D-galactose, D-glucose, L-rhamnose, L-fucose, etc., and are considered for both nutritional and medical values [6,7,8]. Hence, young buds of B. schreberi have been served as a popular aquatic vegetable for a long time in China, Japan and some other eastern Asian countries, though only in China, B. schreberi are regularly farmed and harvested in shallow areas of ponds, lakes and irrigated fields with a water depth maintained at 30–80 cm [4,9].
Aquatic plants generally host a high diversity of insects on their leaf surfaces. Among which, the leaf beetle Galerucella birmanica Jacoby (Coleoptera: Chrysomelidae) is a holometabolous insect that has four stages, egg, larva, pupa and adult, with larvae and adults exhibiting a high consumption of leaves [10,11,12]. G. birmanica overwinters as an adult in weed residues and soil crevices on banks, starting activity in early April and moving to the overwintering sites in late October, with multiple and overlapping generations occurring annually in central and southern China [10,13]. G. birmanica prefers the water chestnut Trapa natans L. (Lythraceae) as its host [12,14], which grows in similar habitats as B. schreberi in natural aquatic areas. From late April to early May, when T. natans leaves emerge from the water, G. birmanica migrates to the leaves, feeds on the leaf tissue and enters a mating peak and lays eggs after 3–4 days [10]. Damaged T. natans leaves caused by G. birmanica exhibit numerous holes, and in severe cases, only the veins remain [13].
In North America, G. birmanica has been considered as a potential biocontrol agent against T. natans, which is a major invasive species in the continent [11,12,15]. Earlier research demonstrated that G. birmanica oviposited and was able to complete development on both Trapa spp. and B. schreberi in no-choice experiments [11], and in field choice tests, a strong preference for T. natans and only occasional “spill-over” onto B. schreberi were found. The recent report from Simmons and Blossey also suggested that the potential risk of G. birmanica towards B. schreberi was low [12]. However, with our field observation, we found that, in the mono-cultivation system of B. schreberi where the plants were harvested as a vegetable, the leaves suffered severe infestation by G. birmanica. Such infestation was unevenly distributed, with notable aggregation phenomena occurring in parts of the areas. Further research on the interaction between G. birmanica and B. schreberi is required, especially in mono-cultivation systems where T. natans is not available for the beetles.
The relationships between insects and their hosts are complicated. Plants have evolved multiple strategies to resist herbivory insects, including constitutive defense, induced response, etc. [16,17,18]. Reversely, insects may locate their hosts through visual, olfactory and gustatory cues, etc. [19,20,21,22]. For the olfactory cues, herbivorous insects may be attracted by specific components of plant volatiles. For example, nonanal emitted from tobacco during vegetative growth greatly attracted female Helicoverpa assulta (Lepidoptera: Noctuidae) [23]; (Z)-3-hexenyl-acetate emitted from maize attracted females of Spodoptera frugiperda (Lepidoptera: Noctuidae) and stimulated their oviposition [21]; cotton volatiles induced by the attack of Anthonomus grandis (Coleoptera: Curculionidae) were attractive to conspecifics [24]. Multiple volatile compounds from B. schreberi have been identified [25]; however, whether such volatiles function in the Brasenia–herbivore interaction remains unknown. In this study, we focused on the mono-cultivation system where B. schreberi was the only crop cultivated and no T. natans coexisted. We tried to verify if G. birmanica would accept B. schreberi as a substitute and to what extent this could occur. The monthly occurrence of the beetles with different developmental stages in the system through the whole growth period of B. schreberi was recorded. Additionally, by analyzing the volatile compounds emitted from B. schreberi leaves and their potential role as olfactory cues for the beetles, possible dynamics for the aggregation of G. birmanica in B. schreberi field were explored.

2. Materials and Methods

2.1. Study Location

The research field is located in Changshu Ecological Agricultural District of the Taihu Lake basin in East China (120°33′–121°03′ E, 31°33′–31°50′ N), which has the longest history of B. schreberi cultivation and remains one of the four major B. schreberi production areas of the country. A typical subtropical monsoon humid climate dominates in the area, with the annual average temperature being 15.4 °C, from an extreme minimum temperature of −11.3 °C to an extreme maximum temperature of 40.2 °C, and the annual average precipitation being 1135.6 mm. A human-maintained B. schreberi cultivation pond in the center of the district was selected for the survey of G. birmanica, where toxic pesticides have been forbidden for years before the study and only limited organic fertilizers are used. The pond is irrigated by the Wangyu River, which connects the third-largest freshwater lake, Taihu, and the longest river, Yangzte River, in China. The water depth in the pond is maintained at about 30 cm in early spring to help crop rejuvenation and about 60 cm in the other seasons for growth and overwintering. The total area of the pond is approximately 2400 m2.

2.2. Monitoring of Galerucella birmanica

The presence and density of G. birmanica in the B. schreberi field were investigated by performing direct visual inspection of leaf surfaces and yellow board sticky trapping (25 cm × 20 cm, double-sided adhesive) once a month, covering the growth season of the crop from April to November 2023 (as no beetles were recorded in April, all data presented in this paper started in May). Three parallel transects with a distance no less than 10 m between one and another were set in the B. schreberi pond; along each transect, 12 sampling sites that were 4 m apart were marked, resulting in a total of 36 sites. At each site, the number of insects with different developmental stages within a 0.5 m × 0.5 m quadrat was first recorded by visual inspection on leaf surfaces. Since the eggs of the beetles were clustered together and the individual was too small to count, the number of eggs was recorded by every clutch (see the eggs in Figure 1; we treated them as 2 clutches). The number of larvae, pupae and adults was recorded by every individual, and the total number of beetles was counted as clutches of eggs plus individuals of the rests.
As a supplement for the flying adults of G. birmanica, yellow sticky traps were temporarily placed at each sampling site immediately after visual inspection for an additional log of the number of G. birmanica (Figure 2). The trap was positioned as close to the water surface as possible, and after 24 h, the adults on the trap were counted.
Besides the beetles, the number of intact leaves and chewed leaves of B. schreberi was also counted, respectively, in each 0.5 m × 0.5 m quadrat; thus, the leaf chewed rate was calculated as
l e a f   c h e w e d   r a t e = n u m b e r   o f   c h e w e d   l e a v e s n u m b e r   o f   i n t a c t   l e a v e s + n u m b e r   o f   c h e w e d   l e a v e s × 100 %
Then, seven leaves that exhibited the most severe chewed damage were selected to calculate the leaf damaged level:
l e a f   d a m a g e d   l e v e l = a r e a   o f   t h e   d a m a g e d   p a r t   o f   t h e   l e a f t o t a l   a r e a   o f   t h e   l e a f × 100 %
The mean value of these calculations was used to represent the maximum extent of herbivore-induced damage at each sampling site.

2.3. Comparison of Galerucella birmanica Occurrence in Relatively Intact and Severely Chewed Areas

As visible aggregation of G. birmanica in the B. schreberi pond was noticed, two additional groups of quadrats, one in areas with relatively intact B. schreberi leaves and the other in areas where the leaves were severely chewed, were randomly marked in the pond in November of the same year. In each group, 42 quadrats were marked with an interval of at least 4 m, and then, the number of G. birmanica on the leaf surfaces was counted. As the total amount of beetles was reduced in November, each quadrat area here was enlarged to 2 m × 2 m.

2.4. Two-Choice Tests

To investigate the possible behavioral significance of adult G. birmanica in response to intact and chewed B. schreberi leaves, the volatiles from the two types of leaves were collected, followed by two-choice tests to evaluate beetle preferences.
For the collection of leaf volatiles, a headspace adsorption method was used [20,26]. Intact (non-chewed) and severely chewed leaves of B. schreberi were harvested from the field and taken back to the lab. They were kept moist and wrapped in a sampling bag made of heat-resistant nylon resin. The inlet of the sampling bag was connected to an air pump with a glass scrubber filled with 20/50 mesh activated-carbon adsorbent. The outlet of the sampling bag was connected to an adsorption column with 80/100 mesh Porapak Q (Supelco, Bellefonte, PA, USA). Teflon tubes were used for the accessory passages. The volatile collection for each sample was maintained for 24 h, with the gas flow rate at 400 mL min−1. Immediately after collection, the volatile sample on the column was eluted with chromatographic grade n-hexane (Aladdin Biochemical Technology Co., Ltd., Shanghai, China), and the eluent was then concentrated to 200–300 µL with nitrogen. A total of 200 ng of n-octane (Macklin Biochemical Co., Ltd., Shanghai, China) was added to each eluent as an internal standard. The collection for each type of leaf was repeated five times, with each sampling consisting of 15 leaves.
The two-choice tests were based on the commonly used Y-tube olfactory test [27] but conducted in a self-designed, three-chamber olfactometer (Figure 3). First, one beetle was placed in the middle chamber (b) to adapt to the environment for 10 min. Then, 10 µL of the eluent from intact/chewed leaves of B. schreberi was applied to a 2 cm2 filter paper, which was placed in sequence into the left (a)/right (c) chamber of the olfactometer. Clean air at a flow rate of 500 mL min−1 was pumped into the chamber on each side of the olfactometer to make sure the beetle in the middle could perceive the odors from both sides. The air was pumped out from the top of the middle chamber (b) to ensure a controlled olfactory environment for the behavioral assays. The temperature in the olfactometer was maintained at about 25 °C during the tests. If the beetle remained in the selected chamber for more than 30 s, it was recorded as having made a choice for the volatile in that chamber. If the beetle remained in the initial middle chamber for 15 min without making a choice, it was considered to have no response and excluded.
The two-choice tests were repeated until 26 adult beetles were recorded to have made choices. To eliminate possible position effect, every 5 beetles that had made a choice were treated as one group; after each group, the positions of the filter papers with volatiles from intact/chewed leaves were swapped between the two sides of the olfactometer [27]. The system was ventilated for 30 min each time when swapping to remove possible residue. An additional blank assay was also carried out before the test to determine whether there was any difference in the beetle’s preference when both sides of the olfactometer contained only clean air.

2.5. GC–MS Analysis for Volatiles from Intact and Chewed B. schreberi Leaves

Gas chromatography–mass spectrometry (GC–MS, Agilent 6890 GC and 5975C MS, USA, equipped with an HP-5MS capillary column (30 m × 0.25 mm ID × 0.25 μm film thickness, Agilent, Santa Clara, CA, USA) was used to analyze the volatile components from intact and chewed B. schreberi leaves. Referring to the conditions described by Zhang et al. [20,26], the temperature was initially set at 40 °C for 5 min, increased to 185 °C at a rate of 5 °C min−1, further increased to 280 °C at a rate of 30 °C min−1 and then held for 1 min. Helium was used as the carrier gas at a flow rate of 1 mL min−1. The inlet temperature of GC–MS was set at 250 °C. The mass spectrometer was equipped with an electron ionization (EI) source, operating in full-scan mode across 30–500 m z−1. Temperature-controlled modules maintained the ion source at 230 °C and quadrupole at 150 °C, with acquisition parameters set to 3.2 scans s−1 and a 3 min solvent delay. We injected the samples using a 10 μL manual syringe, delivering 1 µL of concentrated B. schreberi volatile eluent through the front inlet. Volatile components were identified by comparison with the NIST 10.0 library. For quantification, we used the internal standard of octane, calculating the relative abundances from the total ion current (TIC) peak area ratios. All analyses were conducted using Agilent MassHunter Qualitative Analysis software 10.0.

2.6. Verification of Volatile Substance Attracting Galerucella birmanica

Four standard chemical solutions, cis-3-hexenyl acetate (Yuanye Bio-Technology Co., Ltd., Shanghai, China), 2-phenylethyl isothiocyanate (Bailingwei Chemical Technology Co., Ltd., Shanghai, China), undecane (Aladdin Biochemical Technology Co., Ltd., Shanghai, China) and methyl salicylate (Yuanye Bio-Technology Co., Ltd., Shanghai, China) in hexane of 1 µg µL−1, representing each of the volatiles that had exhibited remarkable discrepancy in contents between intact and chewed leaves, were prepared to further verify the choice preference of G. birmanica. Similarly, 10 µL of standard solution or hexane (as the control) on filter paper was placed in either side of the three-chamber olfactometer for selection by the beetle in the middle. Each standard solution was repeated until 26 beetles had made choices.

2.7. Statistical Analysis

Mann–Whitney U tests were used to compare the abundance of G. birmanica (both on leaves and on yellow sticky traps) between different months and between intact and severely chewed areas in November and were used for leaf damage conditions between different months. Spearman correlation analyses were performed on the degree of leaf damage and the abundance of G. birmanica. Paired sample t-tests were used to compare the differences in volatile contents between intact and chewed leaves. Chi-square tests were used to compare the two-choice test results of G. birmanica between volatiles of intact/chewed B. schreberi leaves and between reagents representing separated volatiles and the control.

3. Results

3.1. Monthly Occurrence of Galerucella birmanica in Brasenia schreberi Pond

With our field visual inspection, four typical developmental stages of G. birmanica, the egg, larva, pupa and adult, were found on the leaf surface of B. schreberi in the investigated pond (Figure 1). Their monthly occurrence on the leaf surfaces is shown in Figure 4a. B. schreberi in the research site started to rejuvenate in April, while no G. birmanica was found at the first month, when only sporadic leaves of the plants floated on the water surface. In May, when the leaves of the crop reached a coverage of more than 80%, the beetles on the leaves were first recorded, with relatively more larvae, followed by pupae and adults but no eggs. The total number of beetles on the leaves kept increasing until August, when the beetles almost disappeared during the hottest weather conditions. In September, the total beetle number on the leaves rebounded remarkably to 3.4 times that in July, with 96.0% of them being eggs. The beetles reduced quickly the following October and kept a limited occurrence in November, when the plants started to senesce. As for the different stages of the beetles, besides the remarkable peak of eggs in September, a small peak of eggs also appeared in June. Relatively abundant larvae, pupae and adults appeared in July.
As an additional record for the emergence of G. birmanica in the B. schreberi cultivation system, yellow sticky boards were deployed right after the visual inspection. The number of flying G. birmanica trapped on the boards showed a different trend compared to the direct record on the leaf surfaces. A significantly high number of adult beetles were recorded in August (Figure 4b). Small amounts of beetles were also trapped in June and November, but almost no beetles were trapped in May and July.

3.2. Leaf Damage Condition of Brasenia schreberi and Its Correlation with Galerucella birmanica Occurrence

Leaf damage condition was recorded at the same time of the beetles’ inspection. Since no pesticide was applied in the cultivation system, intact elliptic leaves of B. schreberi could only been found in April, when they first expanded on the water surface, and most of the leaves were more or less chewed in the subsequent seasons. Careful calculations revealed that 70.2% of the leaves were marked as being chewed in May (Figure 5a). The leaf chewed rate generally increased, peaking at 91.9% in September. October was an exception, as only 25.9% of the leaves were chewed. The chewed rate rebounded to over 70% in November.
Although most of the leaves showed signs of chewing damage, the average damaged level of each leaf was not so severe. As shown in Figure 5b, the leaf damaged level was lower than 2% in May, which increased to 3.7% in July and then decreased to the lowest point of 0.6% in August. The highest leaf damaged level occurred in September, as 6.3% of the leaf area was damaged. The leaf damaged level decreased to less than 2% in October and November.
The typical correlation between leaf damaged level of B. schreberi and G. birmanica occurrence on the leaf surfaces is shown in Figure 6. The trends of beetle numbers on the leaf surfaces through the growth season, both per m2 and per 100 leaves, closely mirrored the trend of leaf damaged levels. A visible but less remarkable correlation between leaf chewed rate and beetle numbers was also found.
With Spearman two-tailed tests, a detailed correlation between the occurrence of G. birmanica and the damage on B. schreberi leaves was further verified (Table 1). Positive correlations were found between the leaf chewed rate, leaf damaged level and number of beetles on the leaves, including eggs, larvae, pupae and total amount (p < 0.05); however, no significant correlation was found between the number of adult beetles on the leaves and leaf chewed rate (p > 0.05). The number of adult beetles trapped on the board was found to be positively correlated with the leaf chewed rate but negatively correlated with the leaf damaged level (p < 0.05). As for an additional calculation, the number of beetles per one hundred leaves on the leaf surfaces was significantly correlated with chewed damage (p < 0.05).

3.3. Aggregation of Galerucella birmanica in Brasenia schreberi Pond

The field investigation also found that the occurrence of G. birmanica in the B. schreberi pond was not uniform but inclined to aggregate in certain areas. Hence, an additional visual inspection was carried out in relatively intact/severely chewed areas in November. The number of G. birmanica at each insect stage was significantly higher in areas where B. schreberi leaves were severely chewed compared to that in areas where the leaves were relatively intact (p < 0.05), which not only further proved the correlation between the number of beetles and leaf damage but also indicated a certain mechanism for the aggregation of G. birmanica (Figure 7).

3.4. Volatiles Differed Between Intact and Chewed Brasenia schreberi Leaves

A GC–MS analysis was conducted to identify the components of the volatile samples collected from intact and severely chewed leaves of B. schreberi. Altogether, 51 volatile compounds as well as the internal standard octane were identified, among which, four components, cis-3-hexenyl acetate, 2-phenylethyl isothiocyanate, methyl salicylate and undecane, exhibited significant discrepancies in contents between intact and severely chewed leaves (Figure 8, Table 2). The emission of cis-3-hexenyl acetate, 2-phenylethyl isothiocyanate and methyl salicylate from severely chewed leaves was promoted by 51.9%, 67.2% and 102.9%, respectively, whereas the emission of undecane was reduced by 23.1% compared to those from intact leaves (p < 0.05).

3.5. Two-Choice Tests of Volatiles from Brasenia schreberi by Adult Galerucella birmanica

With the self-designed, three-chamber olfactometer, the volatiles from severely chewed and intact leaves of B. schreberi were extended to G. birmanica for choices. Strong preferences of the beetles were exhibited (Figure 9). Out of 26 adults, 21 of them selected the chamber with volatiles from severely chewed leaves, showing a statistically significant difference between the two types of leaves by the chi-square test (p < 0.01).
For the four components showing remarkable discrepancies in contents between volatiles from intact and severely chewed leaves, adult G. birmanica showed different performances (Figure 9). Using the solvent hexane as the control, a significantly higher number of the beetles tested showed a preference for 2-phenylethyl isothiocyanate (p < 0.01), whereas no preferences were found for cis-3-hexenyl acetate, methyl salicylate, undecane and the control (p > 0.05).

4. Discussions

Environmental factors strongly influence the seasonal variations in the population dynamics of insects. Temperature, in particular, plays a crucial role in the development and behavior of insects [28,29]. The detailed effect of temperature on the demography of G. birmanica has been studied in the laboratory [30]. In our field investigation, the population density of G. birmanica in the B. schreberi agricultural system exhibited significant seasonal variations. The population of G. birmanica generally increased from spring to summer, with temperature increasing, and reached its peak in September. The visual inspection data on leaf surfaces decreased dramatically in August, whereas the number of flying adults trapped by the sticky board was significantly high. Since the average temperature in our research site reached 29.2 °C in August and the daily highest temperature generally surpassed 30 °C, we suggest such high temperatures might stimulate the mating and oviposition of G. birmanica but inhibit egg development or impair egg viability, leading to the disappearance of G. birmanica of younger developmental stages on leaf surfaces in August but quantitative eggs in September. Similar patterns have been observed in other insects; for instance, when the temperature reaches 33 °C, the larval survival, pupation and adult emergence rates of Diorhabda rybakowi (Coleoptera: Chrysomelidae) all decrease significantly [31].
As for the discrepancy of G. birmanica peaks on leaf surfaces and sticky boards, we suppose such phenomenon was caused by the mating activity of the beetles. High temperature may stimulate the female or male G. birmanica to release sex pheromones. The beetles, in search of the pheromone source, would fly upwind along the pheromone gradient [32]. This also explains the significant number of eggs found in the next month.
The decrease in G. birmanica in October and November in the B. schreberi field might be caused by the lower temperature. Low temperature can inhibit the development of many insects [33]. For instance, the fecundity of Mythimna separata (Lepidotera: Noctuidae) and Harmonia axyridis (Coleoptera: Coccinellidae) was reduced, and their preoviposition period was extended under low temperatures [34,35]. Similarly, the feeding amount and fecundity of Liriomyza huidobrensis (Diptera: Agromyzidae) decreased significantly under low temperatures [36]. Afterwards, G. birmanica began its overwintering process.
Besides the temperature, rainfall might also affect the G. birmanica dynamics in the B. schreberi system. Our research site is characterized by a subtropical monsoon climate, and the B. schreberi field had just experienced a rainy season prior to our survey of the beetles in August. Heavy rain likely washed away many individuals previously present on the leaves. The lethal effect of rainfall on G. birmanica has been also reported by Lu et al. [10].
Based on the field observations of the G. birmanica population and leaf damaged condition of B. schreberi, we inferred that the first generation of adults likely originated from overwintering beetles near the pond, with the first batch of eggs laid in late April. Over the whole growth season of B. schreberi, there could be nine generations of G. birmanica that occurred in the system as follows: 1: late April–early June; 2: early June–early July; 3: early July–late July; 4: late July–early August; 5: early August–late August; 6: late August–early September; 7: early September–late September; 8: late September–mid-October; 9: mid-October–mid-November.
The trend of leaf damage of B. schreberi, both chewed rate and damaged level, corresponded to the fluctuations in the population of G. birmanica. Our findings confirmed that, in the absence of T. natans, G. birmanica treated B. schreberi as a substitute. Especially in areas like our research site, where B. schreberi is mono-cultivated as an important aquatic vegetable, G. birmanica poses a severe threat to the yield of B. schreberi. Therefore, careful consideration should be given before introducing G. birmanica as a biological agent to control the invasive T. natans in areas where B. schreberi is native.
For the uneven distribution of G. birmanica in the B. schreberi field, a similar aggregation scenario of G. birmanica has also been reported by Zheng et al. [37] with a T. natans system, and the authors suggested it may due to the biological characteristics of the beetles and the growth status of the plants. In our study, we revealed that damaged leaves of B. schreberi emitted increased amounts of cis-3-hexenyl acetate, 2-phenylethyl isothiocyanate and methyl salicylate but a decreased amount of undecane, among which, 2-phenylethyl isothiocyanate exhibited a strong attractant effect on G. birmanica. We suppose that the aggregation of G. birmanica is influenced by the plant volatile 2-phenylethyl isothiocyanate promoted by chewing. Isothiocyanates (ITCs) are typical herbivore-induced plant volatiles (HIPVs) that are produced when plant tissues are damaged by insect herbivory or mechanical injury [38].
In nature, the diverse array of HIPVs contributes to the complexity of plant defense and signaling processes [39]. ITCs generally play a crucial role in protecting plants from various pests and microorganisms [40], acting as deterrents and toxins [41], impairing the herbivore’s survival and growth and increasing their development time [42]. Whereas, in certain exceptional cases, ITCs emitted from plants can attract herbivores. Earlier reports suggested that the herbivore Ceutorhynchus assimilis (Coleoptera: Curculionidae) was attracted to ITCs in oilseed rape (Brassica napus L.) volatiles [43], and 3-butenyl, 4-pentenyl and 2-phenylethyl isothiocyanates might function as attractants to the pollen beetle Meligethes aeneus (Coleoptera: Chrysomelidae) [44]. In our research, 2-phenylethyl isothiocyanate, promoted in severely chewed B. schreberi leaves, acted as an attractant for the G. birmanica, indicating that G. birmanica has evolved to overcome the defense of B. schreberi through the utilization of ITCs. G. birmanica may track the 2-phenylethyl isothiocyanate as the signal of a food resource, mating partner or suitable habitat and thus aggregate in severely chewed areas in the B. schreberi pond. Similar attractant mechanisms of other HIPVs have also been found, as the leafminer Tuta absoluta (Lepidoptera: Gelechiidae) preferred infested tomato plants with up-regulated β-caryophyllene and tetradecane, supposed that infested plants might be more suitable for future larvae or might result in a decreased likelihood of predation or parasitism [45].
Cis-3-hexenyl acetate and methyl salicylate are also HIPVs that are frequently detected in plant–insect interactions [46,47]. Previous studies have demonstrated that both compounds were emitted by rice infested with Nilaparvata lugens (Hemiptera: Delphacidae), significantly enhancing parasitism rates of the parasitoid wasp Anagrus nilaparvatae (Hymenoptera: Mymaridae) on eggs of the planthopper [48]. The volatiles have been reported to trigger defense mechanisms both in the emitting plants and in neighboring plants [49,50]. Relatively higher levels of cis-3-hexenyl acetate and methyl salicylate were also detected in severely chewed B. schreberi leaves, whereas no preference was found for G. birmanica in two-choice tests. Such results may be caused by a specific gustatory perception of G. birmanica. Healthy leaves may also generate certain secondary metabolites that function as feeding deterrents to the beetles [46,51,52], meaning these compounds may cause the beetles to perceive a bitter taste or pungency, thereby discouraging them from feeding [47].
Undecane is a type of alkane plant volatile. A study with the common tobacco Nicotiana tabacum L. (Solanaceae) and its relative Nicotiana benthamiana Domin showed that a greater attraction of the latter to whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) was due to a higher amount of the volatile undecane [53]. In another study, up-regulated undecane from B. tabaci-infested potato attracted more Tuta absoluta (Lepidoptera: Gelechiidae) [54]. With our study, the emission of undecane from severely chewed B. schreberi leaves was reduced. The mechanism for such down regulation was unknown, but still, undecane showed no preference for G. birmanica.
Altogether, 51 different volatiles from B. schreberi leaves were identified in our study, which were similar in amounts but differed substantially in composition compared to those reported by Zhang and Chen [25]. Such a discrepancy may be caused by different methods for sample collections. Leaf sources may also contribute to the discrepancy, as our sample was collected from East China, and their samples were from Central China. Differences could arise from plant genotypes, cultivation protocols (here, pesticides may be enrolled), environmental pollution, etc. Nevertheless, all four volatiles that showed significant differences in contents between chewed and intact leaves in our study have been nominated in other plant–insect interactions.
At the population or community level, herbivore damage to some leaves may promote defensive advantages to the entire plant and even their neighbors, with the latter being both conspecific and interspecific [55]. Our study indicates that, through the emission of 2-phenylethyl isothiocyanate, severely chewed B. schreberi leaves may sacrifice themselves to mitigate the harm of G. birmanica to other intact leaves. The neighboring defensive advantages are usually promoted by repelling signals that either resist the herbivore directly [56] or attract natural enemies [57], whereas in our study, 2-phenylethyl isothiocyanate acts as an attractant to the herbivore, further complicating the herbivore–plant interaction. Since B. schreberi is a clonal species and its rhizome in silt can extend for several meters, we still lack the evidence to verify if such defensive advantages only happen within leaves of the same individual or also extend to neighboring plants. As G. birmanica has been reported to prefer T. natans to B. schreberi when they coexist [11], it will also be interesting to explore if 2-phenylethyl isothiocyanate exhibits a further role in the interspecific neighboring effect between B. schreberi and T. natans.
From the point of view of B. schreberi aquaculture, artificially synthesized reagent 2-phenylethyl isothiocyanate may be considered as a potential attractant to control the burst of G. birmanica. HIPVs have been nominated in push–pull strategies to repel herbivores from crop plants while simultaneously attracting them to nearby trap plants [58]. Here, we suppose that the artificially synthesized reagent may play a similar role as natural HIPVs in aquaculture management. Compared with traditional pesticides that have been frequently used in B. schreberi aquaculture, like cypermethrin and permethrin, with notable toxicity that pollutes the food as well as the cultivation environment, 2-phenylethyl isothiocyanate, with its low dose and high attracting efficiency, can be a relatively safer substitute. Our research, with the population peaks of G. birmanica that burst along the growth period of B. schreberi, has indicated a proper time schedule for pest control measures. Further experiments are still expected for the detailed dose of 2-phenylethyl isothiocyanate that is needed in an open cultivation system.

5. Conclusions

In the mono-cultivation system of the aquatic vegetable B. schreberi, the leaf beetle G. birmanica caused severe damage to the floating leaves of the plants, with multiple generations occurring throughout the growth season of the crop and significant aggregation phenomena. Among the herbivore-induced plant volatiles released from damaged leaves of B. schreberi, 2-phenylethyl isothiocyanate could significantly attract adult G. birmanica, suggesting that the attacked plant leaves may sacrifice themselves to protect healthy neighboring leaves. The enhancement of the emission of 2-phenylethyl isothiocyanate is supposed to be a group defense strategy adopted by the crop to preserve population stability and to reduce the cost of individual plant defenses against G. birmanica.

Author Contributions

Conceptualization, Y.W. (Yini Wang) and C.Z.; methodology, Y.W. (Yini Wang) and C.Z.; software, Y.W. (Yini Wang); validation, Y.W. (Yini Wang) and Y.W. (Yahong Wang); formal analysis, Y.W. (Yini Wang); investigation, Y.W. (Yini Wang) and Y.W. (Yahong Wang); resources, C.Z.; data curation, Y.W. (Yini Wang); writing—original draft preparation, Y.W. (Yini Wang); writing—review and editing, Y.W. (Yini Wang), Y.W. (Yahong Wang) and C.Z.; visualization, Y.W. (Yini Wang); supervision, C.Z.; project administration, C.Z.; funding acquisition, C.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Jiangsu Agriculture Science and Technology Innovation Fund (JASTIF) (CX(20)2018), Fundamental Research Plan (Modern Agriculture) of Jiangsu Province (BE2015357) and Emerging Agricultural Education Research and Innovation program of Chinese Ministry of Education (2020265).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

We thank Qingwei Li for his help during revision process.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Taylor, M.L.; Osborn, J.M. Pollen ontogeny in Brasenia (Cabombaceae, Nymphaeales). Am. J. Bot. 2006, 93, 344–356. [Google Scholar] [CrossRef] [PubMed]
  2. Drzymulska, D. On the history of Brasenia Schreb. in the European Pleistocene. Veg. Hist. Archaeobot. 2017, 27, 527–534. [Google Scholar] [CrossRef]
  3. Feng, S.; Luan, D.; Ning, K.; Shao, P.; Sun, P. Ultrafiltration isolation, hypoglycemic activity analysis and structural characterization of polysaccharides from Brasenia schreberi. Int. J. Biol. Macromol. 2019, 135, 141–151. [Google Scholar] [CrossRef]
  4. Zhou, C.; Zhong, Z. Watershield (Brasenia schreberi J. F. Gmel.), from popular vegetable to endangered species. World J. Agric. Soil Sci. 2021, 6, 2020. [Google Scholar] [CrossRef]
  5. Schneider, E.L.; Carlquist, S. Vessels in Brasenia (Cabombaceae): New perspectives on vessel origin in primary xylem of angiosperms. Am. J. Bot. 1996, 83, 1236–1240. [Google Scholar] [CrossRef]
  6. Liu, G.; Feng, S.; Yan, J.; Luan, D.; Sun, P.; Shao, P. Antidiabetic potential of polysaccharides from Brasenia schreberi regulating insulin signaling pathway and gut microbiota in type 2 diabetic mice. Curr. Res. Food Sci. 2022, 5, 1465–1474. [Google Scholar] [CrossRef] [PubMed]
  7. Wan, J.; Yu, X.; Liu, J.; Li, J.; Ai, T.; Yin, C.; Liu, H.; Qin, R. A special polysaccharide hydrogel coated on Brasenia schreberi: Preventive effects against ulcerative colitis via modulation of gut microbiota. Food Funct. 2023, 14, 3564–3575. [Google Scholar] [CrossRef]
  8. Wang, Y.; Zou, Y.; Fang, Q.; Feng, R.; Zhang, J.; Zhou, W.; Wei, Q. Polysaccharides from Brasenia schreberi with great antioxidant ability and the potential application in yogurt. Molecules 2023, 29, 150. [Google Scholar] [CrossRef]
  9. Xie, C.; Li, J.; Pan, F.; Fu, J.; Zhou, W.; Lu, S.; Li, P.; Zhou, C. Environmental factors influencing mucilage accumulation of the endangered Brasenia schreberi in China. Sci. Rep. 2018, 8, 17955. [Google Scholar] [CrossRef]
  10. Lu, Z.; Zhu, J.; Zhu, S.; Chen, Z. Preliminary studies on the beetle (Galerucella birmanica Jacoby)—An insect pest of waterchestnut and watershield. Sci. Agric. Sin. 1984, 5, 73–76. [Google Scholar]
  11. Ding, J.; Blossey, B.; Du, Y.; Zheng, F. Galerucella birmanica (Coleoptera: Chrysomelidae), a promising potential biological control agent of water chestnut, Trapa natans. Biol. Control 2006, 36, 80–90. [Google Scholar] [CrossRef]
  12. Simmons, W.; Blossey, B. Host plant phylogeny does not fully explain host choice and feeding preferences of Galerucella birmanica, a promising biological control herbivore of Trapa natans. Biol. Control 2023, 180, 105201. [Google Scholar] [CrossRef]
  13. Han, Q.; Huang, M.; Li, S.; Zeng, X.; Hu, G.; Tang, C. Occurrence and integrated control measures of Galerucella birmanica Jacoby. J. Anhui Agric. Sci. 2015, 43, 80–82. [Google Scholar] [CrossRef]
  14. Ding, J.; Wang, Y.; Jin, X. Monitoring populations of Galerucella birmanica (Coleoptera: Chrysomelidae) on Brasenia schreberi and Trapa natans (Lythraceae): Implications for biological control. Biol. Control 2007, 43, 71–77. [Google Scholar] [CrossRef]
  15. Pemberton, R.W. Natural enemies of Trapa spp. in Northeast Asia and Europe. Biol. Control 1999, 14, 168–180. [Google Scholar]
  16. Schuman, M.C.; Baldwin, I.T. The layers of plant responses to insect herbivores. Annu. Rev. Entomol. 2016, 61, 373–394. [Google Scholar] [CrossRef] [PubMed]
  17. Aljbory, Z.; Chen, M.S. Indirect plant defense against insect herbivores: A review. Insect Sci. 2018, 25, 2–23. [Google Scholar] [CrossRef] [PubMed]
  18. de Bobadilla, M.F.; Vitiello, A.; Erb, M.; Poelman, E.H. Plant defense strategies against attack by multiple herbivores. Trends Plant Sci. 2022, 27, 528–535. [Google Scholar] [CrossRef]
  19. Pinero, J.C.; Souder, S.K.; Vargas, R.I. Vision-mediated exploitation of a novel host plant by a tephritid fruit fly. PLoS ONE 2017, 12, e0174636. [Google Scholar] [CrossRef]
  20. Zhang, J.; Bisch-Knaden, S.; Fandino, R.A.; Yan, S.; Obiero, G.F.; Grosse-Wilde, E.; Hansson, B.S.; Knaden, M. The olfactory coreceptor IR8a governs larval feces-mediated competition avoidance in a hawkmoth. Proc. Natl. Acad. Sci. USA 2019, 116, 21828–21833. [Google Scholar] [CrossRef]
  21. Wang, J.; Wei, J.; Yi, T.; Li, Y.Y.; Xu, T.; Chen, L.; Xu, H. A green leaf volatile, (Z)-3-hexenyl-acetate, mediates differential oviposition by Spodoptera frugiperda on maize and rice. BMC Biol. 2023, 21, 140. [Google Scholar] [CrossRef]
  22. Zhang, Z.J.; Zhang, S.S.; Niu, B.L.; Ji, D.F.; Liu, X.J.; Li, M.W.; Bai, H.; Palli, S.R.; Wang, C.Z.; Tan, A.J. A determining factor for insect feeding preference in the silkworm, Bombyx mori. PLoS Biol. 2019, 17, e3000162. [Google Scholar] [CrossRef]
  23. Wang, C.; Li, G.; Miao, C.; Zhao, M.; Wang, B.; Guo, X. Nonanal modulates oviposition preference in female Helicoverpa assulta (Lepidoptera: Noctuidae) via the activation of peripheral neurons. Pest Manag. Sci. 2020, 76, 3159–3167. [Google Scholar] [CrossRef]
  24. Magalhães, D.M.; Borges, M.; Laumann, R.A.; Blassioli Moraes, M.C. Influence of multiple- and single-species infestations on herbivore-induced cotton volatiles and Anthonomus grandis behaviour. J. Pest Sci. 2018, 91, 1019–1032. [Google Scholar] [CrossRef]
  25. Zhang, C.; Chen, S. GC-MS analysis of volatile oil content for Brasenia schreberi. In Proceedings of the 2011 International Conference on Electronics and Optoelectronics, Dalian, China, 29–31 July 2011. [Google Scholar] [CrossRef]
  26. Zhang, J.; Komail Raza, S.A.; Wei, Z.; Keesey, I.W.; Parker, A.L.; Feistel, F.; Chen, J.; Cassau, S.; Fandino, R.A.; Grosse-Wilde, E.; et al. Competing beetles attract egg laying in a hawkmoth. Curr. Biol. 2022, 32, 861–869.e8. [Google Scholar] [CrossRef] [PubMed]
  27. Zhan, Y.D.; Liu, Y.J.; Liu, J.H.; Liu, Y. Pheromones emitted by both female and male moths regulate coordination between the sexes for Agriphila aeneociliella (Lepidoptera: Crambidae). Insect Sci. 2023, 30, 1481–1492. [Google Scholar] [CrossRef] [PubMed]
  28. Ekholm, A.; Faticov, M.; Tack, A.J.M.; Berger, J.; Stone, G.N.; Vesterinen, E.; Roslin, T. Community phenology of insects on oak: Local differentiation along a climatic gradient. Ecosphere 2021, 12, e03785. [Google Scholar] [CrossRef]
  29. Owens, C.H.; Lee, M.J.; Grim, M.; Schroeder, J.; Young, H.S. Interactions between temperature and predation impact insect emergence in alpine lakes. Ecosphere 2023, 14, e4619. [Google Scholar] [CrossRef]
  30. Zheng, F.S.; Du, Y.Z.; Wang, Z.J.; Xu, J.J. Effect of temperature on the demography of Galerucella birmanica (Coleoptera: Chrysomelidae). Insect Sci. 2008, 15, 375–380. [Google Scholar] [CrossRef]
  31. Liu, N.; Gou, W.; Ma, W.; Tang, L.; Hu, G.; Sun, Y. Effects of temperature on the growth, development and reproduction of Diorhabda rybakowi (Coleoptera: Chrysomelidae). Plant Prot. 2023, 49, 220–226. [Google Scholar] [CrossRef]
  32. Rao, S.; Cossé, A.A.; Zilkowski, B.W.; Bartlelt, R.J. Aggregation pheromone of the cereal leaf beetle: Field evaluation and emission from males in the laboratory. J. Chem. Ecol. 2003, 29, 2165–2175. [Google Scholar] [CrossRef]
  33. Lacoume, S.; Bressac, C.; Chevrier, C. Sperm production and mating potential of males after a cold shock on pupae of the parasitoid wasp Dinarmus basalis (Hymenoptera: Pteromalidae). J. Insect Physiol. 2007, 53, 1008–1015. [Google Scholar] [CrossRef] [PubMed]
  34. Zhao, J.; Chen, Z.; Qu, J.; Zhang, F.; Yin, X.; Xu, Y. Responses of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) adults to cold acclimation and the related changes of activities of several enzymes in their bodies. Acta Entomol. Sin. 2010, 53, 147–153. [Google Scholar] [CrossRef]
  35. Qin, J.; Zhang, L.; Cheng, Y.; Luo, L.; Lei, C.; Jiang, X. Age-stage two-sex life table for laboratory populations of oriental armyworm Mythimna separata (Walker) under different temperatures. Acta Phytophylac. Sin. 2017, 44, 729–736. [Google Scholar] [CrossRef]
  36. Huang, L.H.; Chen, B.; Kang, L. Impact of mild temperature hardening on thermotolerance, fecundity, and Hsp gene expression in Liriomyza huidobrensis. J. Insect Physiol. 2007, 53, 1199–1205. [Google Scholar] [CrossRef]
  37. Zheng, F.; Zheng, Y.; Lu, Y.; Qiang, C.; Ding, J. Spatial distribution pattern of water chestnut beetle (Galerucella birmanica Jacoby). Chin. J. Eco-Agric. 2006, 14, 171–175. [Google Scholar]
  38. Chen, Y.; Yan, X. The role of glucosinolates in plant-biotic environment interactions. Acta Ecol. Sin. 2007, 27, 2584–2593. [Google Scholar] [CrossRef]
  39. Turlings, T.C.J.; Erb, M. Tritrophic interactions mediated by herbivore-induced plant volatiles: Mechanisms, ecological relevance, and application potential. Annu. Rev. Entomol. 2018, 63, 433–452. [Google Scholar] [CrossRef]
  40. Ahuja, I.; Rohloff, J.; Bones, A.M. Defence mechanisms of Brassicaceae: Implications for plant-insect interactions and potential for integrated pest management. A review. Agron. Sustain. Dev. 2010, 30, 311–348. [Google Scholar] [CrossRef]
  41. Renwick, J.A.A. The chemical world of crucivores: Lures, treats and traps. Entomol. Exp. Appl. 2003, 104, 35–42. [Google Scholar] [CrossRef]
  42. Agrawal, A.A.; Kurashige, N.S. A role for isothiocyanates in plant resistance against the specialist herbivore Pieris rapae. J. Chem. Ecol. 2003, 29, 1403–1415. [Google Scholar] [CrossRef] [PubMed]
  43. Bartlet, E.; Blight, M.M.; Hick, A.J.; Williams, I.H. The responses of the cabbage seed weevil (Ceutorhynchus assimilis) to the odor of oilseed rape (Brassica napus) and to some volatile isothiocyanates. Entomol. Exp. Appl. 1993, 68, 295–302. [Google Scholar] [CrossRef]
  44. Smart, L.E.; Blight, M.M. Response of the pollen beetle, Meligethes aeneus, to traps baited with volatiles from oilseed rape, Brassica napus. J. Chem. Ecol. 2000, 26, 1051–1064. [Google Scholar] [CrossRef]
  45. Rodrigo, F.; Burgueno, A.P.; Gonzalez, A.; Rossini, C. Better together: Volatile-mediated intraguild effects on the preference of Tuta absoluta and Trialeurodes vaporariorum for tomato plants. J. Chem. Ecol. 2023, 49, 725–741. [Google Scholar] [CrossRef]
  46. Engelberth, J.; Alborn, H.T.; Schmelz, E.A.; Tumlinson, J.H. Airborne signals prime plants against insect herbivore attack. Proc. Natl. Acad. Sci. USA 2004, 101, 1781–1785. [Google Scholar] [CrossRef]
  47. Wari, D.; Aboshi, T.; Shinya, T.; Galis, I. Integrated view of plant metabolic defense with particular focus on chewing herbivores. J. Integr. Plant Biol. 2022, 64, 449–475. [Google Scholar] [CrossRef]
  48. Wang, P.; Lou, Y.-G. Screening and field evaluation of synthetic plant volatiles as attractants for Anagrus nilaparvatae Pang et Wang, an egg parasitoid of rice planthoppers. Chin. J. Appl. Entomol. 2013, 50, 431–440. [Google Scholar] [CrossRef]
  49. Gong, Q.; Wang, Y.; He, L.; Huang, F.; Zhang, D.; Wang, Y.; Wei, X.; Han, M.; Deng, H.; Luo, L.; et al. Molecular basis of methyl-salicylate-mediated plant airborne defence. Nature 2023, 622, 139–148. [Google Scholar] [CrossRef]
  50. Yao, C.; Du, L.; Liu, Q.; Hu, X.; Ye, W.; Turlings, T.C.J.; Li, Y. Stemborer-induced rice plant volatiles boost direct and indirect resistance in neighboring plants. New Phytol. 2023, 237, 2375–2387. [Google Scholar] [CrossRef]
  51. Yang, K.; Gong, X.L.; Li, G.C.; Huang, L.Q.; Ning, C.; Wang, C.Z. A gustatory receptor tuned to the steroid plant hormone brassinolide in Plutella xylostella (Lepidoptera: Plutellidae). eLife 2020, 9, e64114. [Google Scholar] [CrossRef]
  52. Hao, X.; Wang, S.; Fu, Y.; Liu, Y.; Shen, H.; Jiang, L.; McLamore, E.S.; Shen, Y. The WRKY46-MYC2 module plays a critical role in E-2-hexenal-induced anti-herbivore responses by promoting flavonoid accumulation. Plant Commun. 2024, 5, 100734. [Google Scholar] [CrossRef] [PubMed]
  53. Zhang, X.Y.; Han, W.H.; Zhang, F.B.; Wang, J.X.; Liu, S.S.; Wang, X.W. Attraction of Nicotiana benthamiana to Bemisia tabaci is related to a chemical signal in plant volatile, undecane. Pest Manag. Sci. 2024; in press. [Google Scholar] [CrossRef]
  54. Shivaramu, S.; Damodaram, K.J.P.; Bhatnagar, A.; Naga, K.C.; Byregowda, V.Y.; Bairwa, A.; Sharma, S.; Singh, R.K.; Singh, B.; Kempraj, V. Influence of Bemisia tabaci-induced plant volatiles on the host-choice behavior of Tuta absoluta. J. Chem. Ecol. 2025, 51, 3. [Google Scholar] [CrossRef] [PubMed]
  55. Holmes, K.D.; Agrawal, A.A. Induced resistance mitigates the effect of plant neighbors on susceptibility to herbivores. Ecosphere 2021, 12, e03334. [Google Scholar] [CrossRef]
  56. Foba, C.N.; Shi, J.H.; An, Q.Q.; Liu, L.; Hu, X.J.; Hegab, M.; Liu, H.; Zhao, P.M.; Wang, M.Q. Volatile-mediated tritrophic defense and priming in neighboring maize against Ostrinia furnacalis and Mythimna separata. Pest Manag. Sci. 2023, 79, 105–113. [Google Scholar] [CrossRef]
  57. Choh, Y.; Ozawa, R.; Takabayashi, J. Do plants use airborne cues to recognize herbivores on their neighbours? Exp. Appl. Acarol. 2013, 59, 263–273. [Google Scholar] [CrossRef]
  58. Gurr, G.M.; Wratten, S.D.; Landis, D.A.; You, M. Habitat management to suppress pest populations: Progress and prospects. Annu. Rev. Entomol. 2017, 62, 91–109. [Google Scholar] [CrossRef]
Insects 16 00371 g001
Figure 1. Galerucella birmanica at different developmental stages.
Figure 1. Galerucella birmanica at different developmental stages.
Insects 16 00371 g001
Insects 16 00371 g002
Figure 2. Sticky boards deployed in Brasenia schreberi field for trapping Galerucella birmanica. (a) yellow sticky boards deployed in the B. schreberi field; (b) one sample of the yellow sticky boards after deployed in the field for 24 h; (c) one sample of the adult G. birmanica captured on the sticky board.
Figure 2. Sticky boards deployed in Brasenia schreberi field for trapping Galerucella birmanica. (a) yellow sticky boards deployed in the B. schreberi field; (b) one sample of the yellow sticky boards after deployed in the field for 24 h; (c) one sample of the adult G. birmanica captured on the sticky board.
Insects 16 00371 g002
Insects 16 00371 g003
Figure 3. Three-chamber olfactometer. (a) left chamber with one of the volatiles; (b) middle chamber with the beetle; (c) right chamber with another volatile for compare.
Figure 3. Three-chamber olfactometer. (a) left chamber with one of the volatiles; (b) middle chamber with the beetle; (c) right chamber with another volatile for compare.
Insects 16 00371 g003
Insects 16 00371 g004
Figure 4. Abundance of Galerucella birmanica in different months. Bars represent standard error of immature and mature stages of beetles (a) or adult beetles (b), n = 36. Different letters represent a statistically significant difference (Mann–Whitney U test, p < 0.05).
Figure 4. Abundance of Galerucella birmanica in different months. Bars represent standard error of immature and mature stages of beetles (a) or adult beetles (b), n = 36. Different letters represent a statistically significant difference (Mann–Whitney U test, p < 0.05).
Insects 16 00371 g004
Insects 16 00371 g005
Figure 5. Leaf damaged condition of Brasenia schreberi. (a) Leaf chewed rate of Brasenia schreberi; (b) Leaf damaged level of Brasenia schreberi. Bars represent standard error, n = 36. Different letters represent a statistically significant difference (Mann–Whitney U test, p < 0.05).
Figure 5. Leaf damaged condition of Brasenia schreberi. (a) Leaf chewed rate of Brasenia schreberi; (b) Leaf damaged level of Brasenia schreberi. Bars represent standard error, n = 36. Different letters represent a statistically significant difference (Mann–Whitney U test, p < 0.05).
Insects 16 00371 g005
Insects 16 00371 g006
Figure 6. Correlation between leaf damage and beetle density. Bars represent standard error, n = 36.
Figure 6. Correlation between leaf damage and beetle density. Bars represent standard error, n = 36.
Insects 16 00371 g006
Insects 16 00371 g007
Figure 7. Beetles in the relatively intact and severely chewed areas. Bars represent standard error, n = 42. Different letters represent a statistically significant difference between intact and chewed areas (Mann–Whitney U test, p < 0.05).
Figure 7. Beetles in the relatively intact and severely chewed areas. Bars represent standard error, n = 42. Different letters represent a statistically significant difference between intact and chewed areas (Mann–Whitney U test, p < 0.05).
Insects 16 00371 g007
Insects 16 00371 g008
Figure 8. Four volatiles showing significant differences in contents between intact and severely chewed leaves analyzed by GC–MS. (a) 1, cis-3-Hexenyl acetate; (b) 2, 2-Phenylethyl isothiocyanate; (c) 3, Undecane; (d) 4, Methyl salicylate.
Figure 8. Four volatiles showing significant differences in contents between intact and severely chewed leaves analyzed by GC–MS. (a) 1, cis-3-Hexenyl acetate; (b) 2, 2-Phenylethyl isothiocyanate; (c) 3, Undecane; (d) 4, Methyl salicylate.
Insects 16 00371 g008
Insects 16 00371 g009
Figure 9. Two-choice tests of volatiles from Brasenia schreberi by Galerucella birmanica adults. ** represents p < 0.01 by chi-square tests, n = 26.
Figure 9. Two-choice tests of volatiles from Brasenia schreberi by Galerucella birmanica adults. ** represents p < 0.01 by chi-square tests, n = 26.
Insects 16 00371 g009
Table 1. Correlation between Galerucella birmanica abundance and leaf damage of Brasenia schreberi.
Table 1. Correlation between Galerucella birmanica abundance and leaf damage of Brasenia schreberi.
Beetles on Leaves (per m2)Beetles on Leaves (per One Hundred Leaves)Beetles on Board
EggLarvaPupaAdultTotal
Leaf chewed rate0.3846
(0.0000)		0.2416
(0.0001)		0.2264
(0.0003)		0.1011
(0.1095)		0.4533
(0.0000)		0.4641
(0.000)		0.1586
(0.0117)
Leaf damaged level0.6431
(0.0000)		0.3919
(0.0000)		0.3509
(0.0000)		0.2691
(0.0000)		0.7809
(0.0000)		0.7783
(0.0000)		−0.3034
(0.0000)
Note: Data shown here are R (p) values (boldface represents p < 0.05) analyzed by Spearman correlation analysis. Beetles on board only included adults, whereas those on leaves included all developmental stages.
Table 2. Volatiles emitted from Brasenia schreberi leaves (n = 5 pairs of severely chewed/intact leaves).
Table 2. Volatiles emitted from Brasenia schreberi leaves (n = 5 pairs of severely chewed/intact leaves).
No.Retention Time/MinCompoundsCAS NumberContents *b (ng)t-test *c
(p Value)
Chewed LeavesIntact Leaves
13.959Toluene108-88-358.39 ± 4.1458.97 ± 4.06
24.499Octane *a111-65-9200.00 ± 0.00200.00 ± 0.00
34.7373-ethyl-Hexane 619-99-8366.01 ± 24.49365.64 ± 21.61
45.988Ethylbenzene100-41-4187.36 ± 26.85179.84 ± 24.95
56.185p-Xylene106-42-3546.35 ± 55.36543.52 ± 54.18
66.714Styrene100-42-5289.524 ± 23.44289.64 ± 17.76
77.046Heptanal111-71-7230.112 ± 15.65230.132 ± 12.64
87.564-Ethylbenzoic acid619-64-786.316 ± 12.50101.932 ± 6.81
98.559Benzaldehyde100-52-7665.544 ± 24.83670.554 ± 13.43
108.7221,2,3-trimethyl-Benzene526-73-859.346 ± 3.9458.646 ± 3.41
118.893(1S)-(1)-beta-Pinene18172-67-3161.38 ± 15.37159.63 ± 16.62
129.2726-methyl-5-Hepten-2-one110-93-0276.52 ± 16.61282.864 ± 10.41
139.308cis-3-Hexenyl Acetate3681-71-8917.33 ± 29.56604.034 ± 23.240.001
149.552Octanal124-13-0232.19 ± 22.16223.388 ± 19.23
159.822Phenol108-95-2224.094 ± 17.12226.398 ± 15.62
1610.289D-Limonene138-86-3304.58 ± 21.10300.4 ± 18.07
1710.3572-ethyl-1-Hexanol104-76-7177.65 ± 9.31176.19 ± 10.34
1810.8262-Phenethyl isothiocyanate2257-09-2595.37 ± 28.42356.00 ± 13.440.000
1911.3163-Carene13466-78-9189.00 ± 34.52185.05 ± 30.89
2012.1262,6,10-trimethyl-Dodecane3891-98-3222.22 ± 8.25217.92 ± 8.77
2112.192γ-Chlorobutyrophenone939-52-6287.82 ± 43.66323.826 ± 22.37
2213.306(E)-2-Hexenyl benzoate76841-70-8157.74 ± 11.90142.974 ± 14.15
2313.337Undecane1120-21-4771.44 ± 34.721003.28 ± 47.880.000
2414.1122-butyl-1-Octanol3913-02-8160.01 ± 14.42158.91 ± 10.25
2514.261Nonanal124-19-6175.60 ± 7.44159.80 ± 8.25
2615.278Camphor76-22-2154.43 ± 13.11156.30 ± 11.13
2716.212Naphthalene91-20-3184.13 ± 6.60191.71 ± 7.12
2816.502Methyl salicylate119-36-81079.84 ± 49.39532.11 ± 18.230.000
2916.9022,6,10-trimethyl-Tetradecane14905-56-7109.19 ± 22.45113.38 ± 16.37
3017.234Benzothiazole95-16-9171.96 ± 3.68171.95 ± 2.95
3118.075Stearic acid57-11-4142.30 ± 4.94149.25 ± 4.72
3218.4482-methyl-Undecane97659-99-9318.48 ± 26.72314.55 ± 21.37
3318.421Tridecane629-50-5377.56 ± 21.05387.42 ± 11.08
3418.5613-methyl-Tridecane6418-41-3107.24 ± 19.29109.31 ± 17.34
3518.933Oleic acid112-80-1372.65 ± 39.87380.96 ± 31.36
3619.151Tetradecane629-59-4200.07 ± 22.43195.71 ± 11.36
3720.1322-methyl-1-Hexadecanol2490-48-4579.88 ± 105.67557.93 ± 35.53
3820.363Dimethyl phthalate131-11-3211.96 ± 27.77202.21 ± 17.90
3921.424α-Farnesene502-61-4948.01 ± 8.00947.66 ± 4.68
4021.569Butylated Hydroxytoluene128-37-01608.61 ± 164.071612.82 ± 131.27
4122.316(Z)-9-Octadecenoic acid8051-88-51766.76 ± 129.921743.13 ± 77.81
4222.903Diethyltoluamide134-62-3101.82 ± 7.3898.55 ± 5.20
4323.3852-Dodecen-1-ylsuccinic anhydride26544-38-7256.41 ± 35.97287.61 ± 29.21
4424.215Behenic alcohol661-19-8512.80 ± 18.80522.41 ± 11.97
4524.771tert-Hexadecanethiol25360-09-2131.28 ± 12.63137.69 ± 8.46
4625.134Methyl cis-9,10-epoxyoctadecanoate2566-91-8336.41 ± 26.73307.52 ± 13.27
4726.3122,6-Ditert-butyl-4-ethylphenol4130-42-1157.00 ± 10.54158.95 ± 12.13
4827.438Albocycline25129-91-3112.61 ± 14.01123.36 ± 6.15
4927.5361-Heptatriacotanol105794-58-9150.99 ± 9.91160.01 ± 11.11
5028.548Obtusilactone56799-51-0186.20 ± 31.83189.92 ± 10.50
5129.694Dibutyl phthalate84-74-2725.29 ± 39.45698.03 ± 20.26
5232.045Heptacosane593-49-7472.62 ± 25.03454.58 ± 21.81
*a Here, octane is the internal standard set at 200 ng in content; *b relative contents of volatiles were calculated by comparing to that of octane; *c for t-test results, only statistically significant differences were listed (p < 0.05) in the table, and blank means p > 0.05.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Wang, Y.; Wang, Y.; Zhou, C. Population Dynamics of Galerucella birmanica and Its Aggregation Behavior in Brasenia schreberi Aquaculture System. Insects 2025, 16, 371. https://doi.org/10.3390/insects16040371

AMA Style

Wang Y, Wang Y, Zhou C. Population Dynamics of Galerucella birmanica and Its Aggregation Behavior in Brasenia schreberi Aquaculture System. Insects. 2025; 16(4):371. https://doi.org/10.3390/insects16040371

Chicago/Turabian Style

Wang, Yini, Yahong Wang, and Changfang Zhou. 2025. "Population Dynamics of Galerucella birmanica and Its Aggregation Behavior in Brasenia schreberi Aquaculture System" Insects 16, no. 4: 371. https://doi.org/10.3390/insects16040371

APA Style

Wang, Y., Wang, Y., & Zhou, C. (2025). Population Dynamics of Galerucella birmanica and Its Aggregation Behavior in Brasenia schreberi Aquaculture System. Insects, 16(4), 371. https://doi.org/10.3390/insects16040371

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop