Revista Brasileira de Milho e Sorgo (Aug 2002)
EFFECT OF A NUCLEAR POLYHEDROSIS VIRUS ON Spodoptera frugiperda (SMITH) (LEPIDOPTERA: NOCTUIDAE) LARVAE, ITS DAMAGE AND YIELD OF MAIZE CROP
Abstract
The efficiency of Baculovirus in a wettable powder formulation to control thefall armyworm Spodoptera frugiperda (Smith) was evaluated using variations of therecommended dose of 50 grams per hectare (2.5 x 1011 polyhedron inclusion bodies - PIB ha-1):50 or 100 g ha-1 applied once, and variations of two applications at seven-day intervals, of25+25, 25 + 50, 50+25 and 50+50 g ha-1, compared to untreated plots. The treatments werearranged in a randomized complete block design with six replications. Each plant at 6-8 or 8-10-leaf growth stages, was artificially infested with 10 newly hatched larvae. The virus suspension(300 L ha-1) was applied 24 hours after larvae infestation using a back-pack-manual sprayer at40 PSI (2.8 kg cm-2) and a regular flat fan nozzle. Larval mortality rate obtained from plots withthe application of 50 g of Baculovirus wettable formulation ha-1, at once (96.2%), wassignificantly higher than that obtained with the application of 25+25 g ha-1 (85.3%) or 25 + 50g ha-1 (87.8%). However, it was lower than that obtained from the other virus treatments,which had no significant difference among them (mean of 99.2%). The damage caused by S.frugiperda on the leaves of plants of untreated plots (average of 4.5 in an visual scale from 1to 5) was significantly different from that observed in plots sprayed with virus (1.75 to 2.33).Plants protected with the virus produced significantly higher yield (mean of 7,577 kg ha-1) thanplants unprotected (6,140 kg ha-1), that is, 23.4% higher.
