EFFECT OF WEED INFESTATION AND TIME-OF-DAY INSECTICIDE APPLICATION ON FALL ARMYWORM AND MAIZE YIELD
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Date
2024-02-12
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University of Ilorin
Abstract
Maize production is affected by several factors such as weeds, insects and most recently fall armyworm (FAW) causing low yields in Nigeria. This study therefore, examined the effect of weed infestation on fall armyworm and maize yield. The objectives of the study were to: (i) ascertain the presence of FAW in the study area; (ii) identify dominant weed species that were natural hosts of FAW; (iii) evaluate the efficiency of weed control methods on FAW infestation and maize yield; and (iv) examine the effect of time-of-day application of insecticide on FAW.
Field trials were conducted at the University of Ilorin Teaching and Research Farm during 2019, 2020 and 2021 seasons. The experiment was a factorial design with a split-split plot arrangement and replicated three times. Maize varieties (Oba-super 6 and Oba-super 4) comprised the main plots, time-of-day application of insecticide (9 am and 4 pm) constituted sub-plots while weed control (pre-atrazine, pre-atrazine+post-Nicosulfuron, pre-metolachlor, pre-metolachlor+post-Nicosulfuron and pre-primextra, 4 weeks of weedy, 3 weeks of weedy, and weed check) were the sub-sub plots. The field was ploughed, harrowed, and ridged; maize seeds were sown at a spacing of 1 m x 0.25 m to give 40,000 plants/ha. Data collected were weed host, weed density and biomass at 3, 6, and 9 weeks after sowing. Number of infested/harvested plants, yield and yield components of maize at harvest were subjected to analysis of variance. Significant means were separated using new Duncan`s multiple range test at p<0.05. Insect larvae collected from the maize plots were taken to the laboratory for preservation and identification using “four-dot’’ square on the 8th abdominal segment, body length and head capsule widths.
The major findings of the study were:
i. fall armyworm larvae with six distinct instars and 21-day developmental period were observed;
ii. dominantnatural hosts of FAW in the study area were Digitariasanguinalias, Dactylocteniumaegyptium, Echinochioacrusgalli, Narcissus papyraceus, Commelinabenghalensis and Gossypiumhirsutum;
iii. atrazine controlled 94% of broadleaved weeds and 6% of grasses, while metolachlor controlled 89.6 and 20.4% of grasses and broadleaves, respectively;
iv. between40-47% low FAW infestation in delayed hoe-weeded and weed-checked plots compared to herbicide-treated plots and 16.5% increase in atrazine-treated plots;
v. delayed weed removal for 3 weeks yielded 3.63 t/ha of grain yield, 36.9% and 9.4% increase over plots treated with herbicides once (2.29 t/ha) and twice (3.29 t/ha), respectively; and
vi. time-of-day application of insecticide had no significant(p>0.05) effect on FAW and maize yield although plots treated at 4 pm had 3.08% increase in grain yield.
The study concluded that prolonging the time of weed removal allowed the natural hosts of FAW to dominate, thereby reducing the level of infestation on the maize. The study therefore recommended that farmers should delay weed removal for 3 weeks to reduce FAW infestation and improve maize yield