Ecosystem Services Within the Vegetable Integrated Push-Pull (VIPPT) Protect Brassicas against Diamondback Moth with Improved Yield and Quality

Diamondback moth (DBM), Plutella xylostella is a key pest of cruciferous vegetables in the tropics including sub-Saharan Africa. Recognizing the need for sustainable intensification of cropping ystems to boost food production and nutritional diversity, we recently integrated kales, Brassica oleracea, a high value vegetable preferred by the farmers into the cereal push-pull technology to form the VIPPT. The VIPPT involves intercropping maize and vegetables with Desmodium companion plants, with Brachiaria grasses as border crop around the plot. The semiochemicals produced by the Desmodium and Brachiaria companion plants are known to be important for controlling key lepidopteran pest of maize including the fall armyworm Spodoptera frugiperda through stimulo-deterrent diversion strategy. To test a similar stimulo-deterrent mechanism of VIPPT on DBM, we conducted on-station full-factorial trials with different spatial/agronomic arrangements of the VIPPT and assessed the population of DBM on kales. We also assessed the percentage of kales damaged, total yield and quantity of spoiled yield that was not fit for consumption for each plot. We also assessed the impact of VIPPT on DBM with 50 farmers randomly selected from a pool practicing VIPPT in western Kenya in the short rain and long rain seasons from 2021 to 2022. Our results showed DBM infestations reduced by over 60% in kales within the VIPPT both on-station and in the farmer’s fields. This was followed by yield increase of 35% and limited losses due to crop damage. Further standard oviposition choice tests under greenhouse conditions showed non-preference by DBM for kales paired with Desmodium compared to the sole ones. Interestingly, our olfactometry assays also revealed higher attraction for the DBM larval parasitoid, Cotesia vestalis to Desmodium. We therefore conclude that kales benefit from the pest control ecosystem services provided by the companion plants leading to improved productivity.