Effects of maize variety and planting date on susceptibility to fall armyworm spodoptera frugiperda (JE Smith); lepidoptera noctuidae attack

Abstract

Fall armyworm (FAW) Spodoptera frugiperda, (J E Smith) has been devastating to Zimbabwe’s agriculture with losses sometimes getting to 100 % and yet there are no confirmed means of managing the pest. The objectives of the experiment were to determine the effect of maize variety and planting date on FAW attack. In an effort to find a solution to the problem a 3x4 factorial experiment was set up in completely randomized block design to determine the effect of maize variety and planting dates on fall armyworm attack in Mashonaland East province of Zimbabwe. Four commercial maize hybrids (commonly planted in Zimbabwe) were planted over three planting dates. The planting dates were early planting (15 Nov), mid season, (15 Dec), and late planting, (28 December). Leaf damage score and number of plants affected were recorded on a fortnightly basis for maize stages V5,V8, VT and R5 while average exit holes(AEH),kernel average score (KAS), yield(t/ha) and discard % were measured at R5 stage. The experiment was under natural FAW infestation and was established at a site where pest abundance was high. Leaf damage and kernel score were evaluated using the Davies scale. The effect of maize variety was not significant (p>0.05) on all the measured data. Time of planting was significant for all observed data (p>0.05) except for exit holes. The interaction of planting dates and maize variety was not significant on all observed data. Early planting had the least damage on all observed data and had the highest yield compared to mid season and late planted crops. Leaf damage score for early planting at maturity stage (R5 stage) was 1.57 compared to 4.63 for Late planting. Kernel damage for early planting was 1.27 compared to 4.37 for late planting. Observed data on yield indicated 10% percent discard (as a result of FAW damage and subsequent fungal infections) compared to 20.93% and 30.64% for mid season and late planting respectively. Early planting had the highest yield of 3.93t/ha compared to 1.77 t/ha for late planting. The results obtained indicated that early planting can be used as the best site specific cultural control measure for FAW in areas where the pest has a migratory habit during cold winters.

Key words: 1.Endemic pest 2.Early planting 3. Mid season planting 4. Late planting