Impact of agricultural practices and landscape context on abundance of Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract

Helicoverpa armigera Hübner, 1808 is a major polyphagous pest of vegetable crops, capable of causing significant economic losses, especially on tomatoes and cabbages. This study was conducted in ten plots in Malika, distributed between the areas of Malika Mountain and Malika Beach. The objective of this work is to evaluate the effect of agricultural practices and landscape context on the abundance of H. armigera caterpillars. Data were collected through field observations and surveys to producers. Results show that none of the practices had a statistically significant effect on caterpillar abundance: (tillage, p-value=0.2812), (crop association p-value=0.4006), (previous crops p-value=0.192). However, trends were observed: Plots without association have a relatively low mean abundance (17.5±20.79 caterpillars) compared to plots with crop association (52.67±91.44). Tomato plot with potato as previous crop have a much higher caterpillar abundance (237±0.00) than those with green onion (31.0±8.49) or mint (17.00±0.00), this difference is not significant (p-value=0.192). Plots where farmers use, in addition to organic fertilizers, mineral fertilizers have fewer caterpillars (22±20.66). A higher abundance of caterpillars in complex landscapes was observed however this difference is not significant (p-value=0.8555). These results suggest that simple changes in agricultural practices may not be sufficient to reduce infestations. The integration of landscape factors and the strengthening of the role of natural enemies appear as promising avenues for an agroecological management of H. armigera.