Assessment of fall armyworm behavioral response on three repellent plants for potential integration in push pull technology

Abstract

Maize (Zea mays) remain one of the important crop cultivated worldwide. In Mozambique, it is a staple food crop for the majority of the population. However, pests such as Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) threatens maize production with complete crop loss being reported. The use of insecticides remains common choice of FAW management coupled with human and environmental hazards leading to increasing concerns over their long- term sustainability. This highlights the need for shift of interest to Integrated Pest Management (IPM) practices among which are behavioral manipulation methods. A promising nature based FAW management technique within the scope of IPM is Push Pull technology which involve repelling (Push) FAW away from the economical crop using volatile stimuli and driving them towards attractive crop (pull). However, use of desmodium has limited adoption necessitating need of diversifying push plants. Basil (Ocimum basilicum), coriander (Coriandrum sativum L.) and mint (Mentha × piperita) are repellent intercrops, with food and direct economic value, may represent better options in place of desmodium and remain largely underexplored. This study assesses the behavior of FAW when exposed to basil, coriander and mint. Laboratory oviposition studies were conducted in no choice and two choice, extended also in semi field conditions. Additionally, FAW survival, development duration and reproductive parameters were estimated when reared on the test plants. In laboratory conditions a Y tube olfactometer was used to study behavioral responses to various stimuli. The no choice tests revealed high mean number of eggs (191.9 ± 35.4) and egg masses (1.6 ± 0.3) oviposited on basil, followed by coriander (103.7 ± 37.6; 1.1 ± 0.4), while mint had the least (46.1 ± 26.9; 0.5 ± 0.3). Two choice oviposition revealed high oviposition in basil (328 ± 33.9 eggs; 3.2 ± 0.3 egg masses) and coriander (222.8 ± 43.6; 2 ± 0.4), while mint showed oviposition mainly on cage walls (473 ± 64.8; 3.6 ± 0.3) and least on mint (136.6 ± 38.5; 1.5 ± 0.4). Semi field two choice experiment revealed high eggs (1237 ± 135) and egg masses (7.5 ± 0.5) on basil, while mint had the least (826 ± 25.0; 4.25 ± 0.25). Basil-fed larvae showed highest survival, shortest development, highest pupal weight, pupation rate, and highest fecundity in F 1 and F 2 , followed by coriander, while mint caused total mortality. Y tube olfactometer response showed high attractiveness to basil (75%) and coriander (57.1%), while mint showed low relative olfactory selection rate (14.3%). The trial between test plants against maize showed selection rates of 30% for basil, 28.6% for coriander and 10% for mint. When combined with maize, basil showed highest preference (40%), followed by coriander (25%), while mint had the least (20%). Generally, mint exhibited potential repellent properties