*3.4. Fruit Fly Traps and Ground Tarps*

Fruit fly traps were statistically significant (*p* < 0.05) in reducing PHL incurred at the point of sale (Figure 6), although the effect size of the reduction was weak (Epsilonsquared = 0.017). Additionally, PHL reduction was detected during transportation due to SHF using fruit fly traps over traditional production practices. However, this reduction was not statistically significant (*p* < 0.05). Moreover, no PHL reduction was detected during harvest from SHF using fruit fly traps over traditional production practices (Figure 6). Meanwhile, moderate PHL increases during harvest (*p* < 0.05, Epsilon-squared = 0.04) and during transportation (*p* < 0.05, Epsilon-squared = 0.06), and a weak PHL increase (*p* < 0.05, Epsilon-squared = 0.017) at the point of sale were detected from SHF using ground tarps over any other harvest practice (Figure 6).

**Figure 6.** Comparing fruit fly traps to alternative production practices. Values with different letters are significantly different at *p* < 0.05 from the Kruskal–Wallis analysis, Dunn test, and Benjamini–Hochberg adjustment. Eˆ2 = Epsilon-squared value for effect size. YWI refers to the technology that the Yieldwise Initiative promoted. (*n*) refers to the number of farmers who reported using a given practice or technology. 'Other' refers to practices that combined both YWI promoted technologies and traditional practices.

#### **4. Discussion**

While mango SHF have reported seeing a PHL reduction due to using harvesting tools [28,29], traditional harvesting practices such as handpicking can also reduce damage caused during harvest [30–32]. Hence, increasing the adoption of correct mango handpicking practices could be effective, if not more effective, than harvesting tools (Figure 3).

Cold stores utilized by SHF (photovoltaic-powered coolers, charcoal evaporative coolers, and brick evaporative coolers) effectively preserve mangos [33,34]. However, they are costly for individual farmers to own. Hence, most mango cold stores are owned by farmers' cooperatives [33], requiring farmers to inspect mangos during harvest and only store fruits that can be well preserved in the cold stores. Therefore, PHL increase during harvest from SHF using cold stores (Figure 4) can be attributed to large quantities of poor fruit quality set aside during the inspection process before storage.

Packaging mangos in plastic crates instead of sacks allows adequate packaging and storage of mangos [35] needed to preserve quality and provide greater wholesale value for the fruit [36,37]. Packaging mangos in crates can also reduce damage caused to the fruit during transportation (Figure 5), and by extension, reduces PHL at the point of sale (Figure 5). Furthermore, plastic crates had the highest adoption (*n* = 320, Figure 5) of all the YWI promoted technologies as SHF and value chain actors saw value in using them.

Fruit fly traps were statistically significant in reducing PHL at the point of sale as their adoption was relatively higher (*n* = 125, Figure 6) than the other YWI promoted technologies, except for plastic crates. Two major factors were reported related to slowing the adoption of fruit fly traps. First, farmers' beliefs that fruit fly traps attract fruit flies from other farms caused the farmers to remove traps, leaving mangos susceptible to infestation and diminishing fruit fly traps' efficacy over traditional production practices [35]. Second, although farmers reported having fruit fly trap containers, without adequate financing, they could not refill the fruit fly trap containers with bait refills frequently enough for the traps to be effective [35]. Thus, overcoming these challenges could result in higher adoption of fruit fly traps.

Although essential, increased adoption and access to the technologies can be difficult to achieve. Cold stores, for example, are too expensive for SHF to own or utilize, especially without access to affordable credit [28,29]. Hence their adoption within the YWI was relatively low (*n* = 18, Figure 4). On the other hand, technologies easily accessible to farmers, such as plastic crates and fruit fly traps [38], had a relatively higher adoption rate. Hence, providing SHF easier access to affordable credit through innovative financing [35] or lower discount rates [39] could be an essential and initial step toward enabling increased adoption of preferred technologies. Alternatively, facilitating access to postharvest technologies through innovative subsidy programs could also increase the adoption of preferred technologies [40,41].

Lastly, discussions with Kenyan SHF revealed that buyers mainly do the harvesting and thus due to the informal and often hierarchal relationships between the two groups, farmers cannot intervene with the harvesting. Therefore, they do not have a say about whether or not ground tarps are used, increasing the chances of experiencing PHL during harvesting and, by extension, several other PHL types along the value chain (Figure 6). Moreover, training and promotion of ground tarps delivered through the YWI may lose their impact over time, and refresher training will be necessary [36].

#### **5. Conclusions**

This study quantitatively compared postharvest technologies and their effects on mango PHL in Kenya via the Rockefeller Foundation's YWI. Five YWI promoted technologies were compared to Kenyan SHF's traditional practices at three value chain stages. Subsequently, the following conclusions were inferred from analyzing the YWI mango dataset:

Efforts to reduce PHL in the mango value chain should prioritize adopting plastic crates and fruit fly traps. These technologies were statistically significant in reducing PHL incurred at the point of sale. In addition to preserving quality, plastic crates and fruit fly traps can be easily accessed and adopted by SHF compared to harvesting tools, cold stores, and ground tarps.

Harvesting tools as a YWI promoted technology and handpicking as a traditional practice to harvest mangos are similar in that both require careful handling of the fruit when picking. Therefore, PHL reduction from SHF using harvesting tools was not statistically significant because handpicking can effectively reduce mango PHL when done correctly. Further research is needed to determine factors other than increased adoption that increase the effectiveness of harvesting tools in reducing PHL.

PHL reduction from SHF using cold stores was not statistically significant. While several factors can contribute to this lack of statistical significance, this study posits that the low adoption of cold stores among SHF is due to their high cost of ownership or utilization.

The benefits of ground tarps should be further investigated because SHF are not always involved in the harvest and do not have a say about whether or not ground tarps are used, resulting in increased PHL. Additionally, training and promotion of technologies delivered through the YWI may lose their impact over time, and refresher training is recommended.

While this study asserts that increased technology adoption is necessary to obtaining better PHL reduction efficacy, further research is needed to identify additional factors of importance that favor technologies' efficacy in reducing PHL in similar food value chains.

**Author Contributions:** Conceptualization, H.C., D.M. and S.S.; data curation, H.C.; formal analysis, H.C.; investigation, H.C., D.M. and S.S.; methodology, H.C., D.M. and S.S.; software, H.C.; visualization, H.C. and D.M.; roles/writing—original draft, H.C.; writing—review and editing, H.C. and D.M.; funding acquisition, D.M. and S.S.; project administration, D.M. and S.S.; resources, D.M. and S.S.; supervision, D.M. and S.S.; validation, D.M. and S.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by The Rockefeller Foundation (Grant 2018 FOD 004), the Foundation for Food and Agriculture Research (Grant DFs-18-0000000008), and the Iowa Agriculture and Home Economics Experiment Station.

**Data Availability Statement:** An online interactive mango PHL dashboard was created at (https:// phldashboard.shinyapps.io/phldashboard/ (accessed on 2 June 2021)) to support this study's results and to further explore average mango PHL as a function of several factors and combinations thereof.

**Acknowledgments:** Funding for this study was provided by The Rockefeller Foundation (2018 FOD 004), the Foundation for Food and Agriculture Research (DFs-18-0000000008), and the Iowa Agriculture and Home Economics Experiment Station. The authors would also like to thank the following individuals and their respective organizations for assistance in better understanding the YWI and data collection procedures: Amos Kioko at The Rockefeller Foundation (formally), Paul Ngugi, Isaiah Kirema, and Onesmus Kinene (formally) at Technoserve.

**Conflicts of Interest:** The funders had no role in the design of this study, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.
