The Impact of Push-pull Technology on Incidence and Severity of Maize ear rots and Mycotoxins in Western Kenya

Abstract

Studies show there is less ear damage by insect pests and increased soil fertility from maize/legume intercropping system. These are two main benefits with pre-harvest potential on ear rots incidence and severity which result into mycotoxins reduction. Therefore, in a two season study, impact of push-pull technology (PP), maize desmodium intercrop edged by Brachiaria or Napier grass, was assessed on incidence and severity of four common ear rots:Fusarium, Gibberella, Diplodia and Aspergillus in the Push-Pull (PP) and Maize Monocrop (MM) fields in Vihiga, Butere, Siaya and Kisumu sub-counties of western Kenya. A total of 78 symptomatic (rotten) and asymptomatic (clean) ears samples were analyzed for Zearalenone (ZEA), Deoxynivalenol (DON), total Aflatoxins (AF) and Fumonisins (FB) using indirect Enzyme-Linked Immunosorbent Assay (ELISA) method. The distribution of Aspergillus and Fusarium ear rot fungal species was determined after cultural identification of Aspergillus and Fusarium ear rot causal fungi in 120 soil samples from PP and MM fields. Further identification of species in Fusarium section Liseola were done by molecular methods using species-specific primers (Translation Elongation Factor-1 alpha). The result showed low incidence of ear rot in PP (7.3%) than MM (20.8%). Similar pattern was observed on severity. The respective ear rots severities under PP and MM were: diplodia (1.15 and 1.85), gibberella (0.62 and 0.84), aspergillus (0.09 and 0.25), fusarium (0.19 and 0.68) and penicilium (0.03 and 0.05). Result showed high proportion of ZEA (100%), AF (93.3%), DON (80.0%) and FB (65.9%) in symptomatic samples compared to proportion of ZEA (90.3%), DON (51.6%), FB (38.7%) and AF (3.2%) in asymptomatic samples. The density (CFUg1) of Aspergillus and Fusarium species in soil from PP (2,282.8) and MM (2,516.6) was insignificant (P=0.86) showing no difference in fungal distribution. However, Aspergillus (80%) had high distribution in soil compared to Fusarium (4.4%). These findings suggest potential of PP in managing ear rots and ultimately limiting mycotoxins. However, potential exposure to aflatoxins from the field was seen by high distribution of Aspergillus in soil from both PP and MM. These studies also suggest likelihood of aerial infection from external sources as observed in low Fusarium distribution in soil samples compared to high incidence of fusarium and gibberella ear rot from fields where samples were taken. Additionally, there were increased other mycotoxins such as ZEA and DON. These findings are vital for formulation of management of different ear rots and their mycotoxins