Effect of legume companion cropping on fall Armyworm (Spodoptera frugiperda) incidence and damage on maize in Uganda

Abstract

Maize production in Africa has always been constrained by biotic and abiotic stresses. However, the recent outbreak of fall armyworm (FAW) (Spodoptera frugiperda) has escalated the problem of low maize crop performance. FAW is an economically important pest that has recently invaded Africa and is threatening crop production, especially of maize. In order to manage this pest effectively, farmers have quickly resorted to application of chemical pesticides. However, their use is associated with many challenges including negative impacts on environment, and ineffectiveness of some pesticides. This therefore, has left farmers in a dilemma with no other options to use against the pest. Therefore, this has raised a need to try other management options that might address challenges encountered through use of chemical pesticides. This research was therefore, conducted to establish the effect of farmers’ practices on FAW control, and to evaluate the potential of systematic legume companion cropping in combating effects of FAW in small holder maize production systems. The first study, assessed the infestation of FAW in farmer’s fields in relation to their management practices and conducted using a survey. A total of 87 farms were sampled in classified cropping systems as: maize monocrop (20 farms), maize and bean intercrop (18), maize and soybean intercrop (19), maize and cassava intercrop (20), and maize mixed with two or more companion crops (10); from the districts of Iganga (n=29), Mayuge (n=30) and Namutumba (n=29). The management practices considered were pesticide application, intercropping pattern, and maize variety grown. Results indicated that pesticide frequency and intercropping system significantly reduced FAW infestations, whereas type of maize variety grown, and intercropping pattern had less influence on FAW infestations. What stood out was that integrating intercrop system with pesticide usage had a reducing effect on FAW damage where using pesticide on monocropped maize was not effective in reducing FAW damage. In the second study, type of legume companion crop and time of introducing the companion crops in maize were investigated to determine their efficacy on reducing damage and infestation of FAW on maize. Trials were established at Wakiso, Mayuge and Namutumba for two seasons (2018A and 2018B). The legume companion crops tested were common beans, soybean, and groundnuts versus the maize monocrop stands. A split plot factorial arrangement in randomized complete block design was used with time of introducing the companion crop in maize (for same time versus after 21 days after planting) as the main plot factor and type of companion crop the subplot factor. Main plots measured 26m X 5m while subplots 5m X 5m. Data on FAW incidence, egg batches and larvae counts, and damage severity were collected weekly from emergence to physiological maturity. At harvest data was taken on fall armyworm incidence and severity on cob, and grain yield. From this study, intercropping beans with maize significantly (p<0.05) reduced FAW eggs, larvae and damage more than intercropping maize with soybean and groundnuts. Moreso, legume intercropping reduced FAW damage in most districts than when was planted as a monocrop. Planting the companion crop at same time with maize significantly (p<0.05) reduced pest damage compared to when the companion crop was planted when maize had established. In terms of maize grain yield, planting companion crop after maize has established yielded more than planting maize and companion crop at the same time. Overall, this study provides a documentation of FAW infestation levels amongst varying management practices in farming communities in Eastern Uganda. The study indicates that beans are most FAW suppressive as companion crops, and simultaneous planting of maize and the companion crop created the best environment for lower FAW damage. Therefore, farmers who normally practice intercropping are encouraged to use beans as the companion crop and should plant the two crops at the same time.