Effect of the Lepidoptera Stem Borers, Busseola fusca (Fuller) and Chilo partellus (Swinhoe) on Green Mealies Production

The maize stem borers, Busseola fusca and Chilo partellus cause qualitative and quantitative losses on green mealies as they attack maize from seedling up to harvesting. A study was conducted to evaluate stem borer damage and management in green mealies on maize varieties SC 608, PHB 30B50 and SC 513. Two field trials similar in set-up and treatments were conducted. The first trial was planted on the 4th/August/2014 and the second was planted on the 4th/ October/ 2014. The essence of staggering planting was to determine whether B. fusca and C. partellus were problematic in the first part or second part of the dry season before the onset of the rain. For each variety, four treatments were applied, namely; whorl applications of ammonium nitrate (AN), Bulldock® 0.05GR (beta- cyfluthrin), Dipterex® 2.5 GR (trichloforn) and untreated control. The treatments were applied at 6 and 4 weeks after crop emergence (WAE) in the first and second trials, respectively and subsequently at 14 day intervals up to tasseling. The parameters assessed were; plant heights, number of plants with windowed leaves, number of plants with dead- hearts, plant biomass (t/ha), fresh cob weights (t/ha), number of damaged cobs and stem borer parasitism and predation. Results showed that the October planting was less infested with B. fusca and C. partellus than the August planting. Dipterex® 2.5 GR and Bulldock® 0.05 GR were effective to manage B. fusca and C. partellus infestations in green mealies. The effectiveness of the two granular insecticides was not significantly different (P˃0.05) on the assessed parameters. A stem borer larval parasitoid recorded in the August planting was Schembria eldana Barraclough (Diptera: Tachinidae) with 5.9% parasitism on both stem borer species. For the October planting, the parasitoids that were recovered from both stem borer species were S. eldana Barraclough and Cotesia sesamiae Cameron (Hymenoptera: Braconidae) with parasitism levels of 13.5 and 21.6% respectively. Recovered species preying on stem borer larvae and pupae included earwigs (Dermaptera: Forficulidae), wasps (Hymenoptera: Vespidae) and ants (Hymenoptera: Formicidae) Overall, applying AN in the funnel was not effective in managing B. fusca and C. partellus. Farmers are therefore encouraged to use Dipterex® 2.5 GR and Bulldock® 0.05 GR with other IPM methods such as planting period manipulation, to manage B. fusca and C. partellus infestation in green mealies.