*3.5. Habitat Manipulation*

Elaterid species are capable of exploiting both cultivated and uncultivated areas in the agricultural landscape [53]. Their movement from suitable habitats where populations thrive, i.e., source habitats such as grasslands, to vulnerable crops determines the colonization process and eventually crop damage. Thus, habitat connectivity in space and time [194,195] is a key driver of pest dispersal success in dynamic agricultural landscapes. Indeed, numerous studies have demonstrated that the spatial and temporal arrangemen<sup>t</sup> of land uses can provide a lever for action to control species abundances with regard to landscape compositional constraints (see for example [196–198]). Nevertheless, implementing such pest control strategies demands an extensive knowledge of pest biology and ecology, notably species-specific life traits such as life-cycle duration and dispersal ability.

The presence of uncultivated area in the field history or in the field vicinity [22–24,56,199] is clearly identified as a risk source in terms of wireworm infestation and/or crop damage; hence, it is often considered by farmers (e.g., managing the crop rotation within a field). More generally, while landscape context has been identified as a risk factor (Section 2.1), habitat manipulation remains underused. In their theoretical study, Poggi et al. [34] addressed the role of grassland in the field history, field neighborhood, and both. They have shown that species with a short life cycle are highly responsive to changes in land use, and that the neighborhood effect strongly relies on assumed dispersal mechanisms (random vs, directed movements). They also illustrated how the arrangemen<sup>t</sup> of grassy landscape elements in space and time can mitigate crop infestation by soil-dwelling pests, thereby emphasizing the relevance of managing grassland regimes. Thus, habitat manipulation may provide another component within an IPM approach.

#### **4. Crop Damage Management**

Wireworms are among the most destructive soil insect pests on potatoes and other crops, including corn and cereals (see Figure 5). Practices targeting limitation of damage despite substantial larval densities rely on identifying optimal planting and harvest conditions, protecting the sensitive crop with attractive companion plants, increasing seeding rates, and planting more tolerant cultivars.

**Figure 5.** Illustration of crop damage and symptoms. (**A**) Damage in maize caused by mixed populations of *A. obscurus* and *A. lineatus*. (**B**) Damage in winter wheat caused by *A. sputator*. (**C**) Symptoms of wilting on maize small plants. (**D**) Damage on potato caused by *A. obscurus*. Photographs A, B, and D: JKI. Photogaph C: Arvalis.

## *4.1. Cultural Control*

#### 4.1.1. Optimal Sowing and Harvest Timing

If substantial larval density is observed before maize planting, it is common to recommend delaying the sowing date as higher temperatures lead to shorter sensitive crop period, which should allow seedlings to resist damage. As regards planting time strategy, we have to consider that a population's capacity to damage sensitive plants varies with the season, e.g., in late spring, very high *A. ustulatus* populations do not damage maize stands because most of their larvae are in a non-feeding phase [9]. Therefore, adjusting planting times, when possible, to coincide with low pest populations or with non-damaging life stages can be effective. This recommendation cannot be generalized, since it is strictly depending on the species' life-cycle. Furlan et al. [23] showed that late sowing significantly increased damage risk on maize, mainly by *A. brevis* and *A. sordidus*, when compared with the ordinary sowing date. They explained this result by biological factors, as late sowing implies that most of the population is in the feeding phase due to higher temperatures accelerating larval molting, while small plants are still susceptible. Saussure et al. [52] also identified sowing date as a minor variable for explaining damage, contrary to the conclusions reached thus far. Poggi et al. [25], however, highlighted that soil temperature at maize sowing date influences damage. In potato production, recent studies in Germany and in Italy have shown that early harvest may reduce tuber damage [85,200]. Generally speaking, the less time potatoes stay in the field, the lower the wireworm damage risk; thus, short-cycle varieties may represent another synergic agronomic strategy.

#### 4.1.2. Resistant Varieties

As for the variety/hybrid resistance to wireworm attacks, little is known and practically exploited. For example, recent achievements [201] sugges<sup>t</sup> that there is potential for maize variety/hybrid tolerance/resistance to wireworms, but seed bags with this declared feature are unavailable. Likewise, less-susceptible-to-wireworm-feeding potato varieties have been identified, but based on the increasing potato damage claim from farmers reported by researchers [172], it seems that this agronomic strategy has not been exploited significantly. In potato production, several studies [202–205] highlighted reduced incidence

and severity of wireworm damage according to varieties. For example, Kwon et al. [205] tested 50 potato cultivars for resistance to several wireworm species. Injury rates varied between 80% and 96% in susceptible cultivars, and several varieties were found to be highly resistant.

#### *4.2. Pest Behavior Manipulation: Feeding Pest as an IPM Strategy*

Soil-dwelling wireworms are usually generalist herbivores, feeding on a wide range of species and usually feeding on most abundant species in their habitat [206]. They may also feed on animal prey [112] and be cannibalistic when larval density is too high for food resources [9,94]. The orientation of wireworms towards host plants is described as a three-step process [75,179]. First, wireworms orient towards carbon dioxide by klinotaxis. The next foraging step involves plant–root volatiles that allow host-specific recognition [207,208]; one example is aldehyde compounds influencing the ability of *A. sordidus* to locate barley roots [180]. The last step consists in the biting and the retention in the root systems containing asparagine, to which wireworms are sensitive, with the wireworms then remaining in the vicinity of the roots [209]. As their feeding phase only lasts 20% to 30% of their entire development [9,10,19], a promising and inexpensive pest managemen<sup>t</sup> strategy could lie in feeding wireworms, thereby luring them away from the crop during the host susceptibility period [210]. Previous highly effective managemen<sup>t</sup> strategies have tested pest behavior manipulation using trap cropping or companion plants.
