Effect of Telenomus remus Nixon (Hymenoptera: scelionidae) density on control of Spodoptera frugiperda (Smith) (Lepidoptera: noctuidae) egg masses upon release in a maize field.

The impact of releasing different densities (0, 6, 9 and 12 adult females m-2) of the egg parasitoid Telenomus remus Nixon on maize plants artificially infested with Spodoptera frugiperda (Smith) egg masses (one m-2) was evaluated. Egg masses were pinned in the mid-rib of the plant 36 days after planting. One egg mass contained approximately 65 eggs. The experimental design was in a randomized complete block design with five replications (16 m2 plots). There was a significant effect on percentage of parasitism egg masses. The highest parasitism values were verified in plots where 9 or 12 females of T. remus m-2 were released, respectively, 74 and 88.3 %. The relationship between percentage of parasitized egg masses and parasitoid densities was quadratic (Y = 16.8 + 9.98 X - 0.35 X2, r2 = 0.99). The natural occurrence of Trichogramma spp. was relatively constant over the egg masses fixed on maize plants (52.5%). However, the average T. remus parasitism on the eggs of a mass was much higher, representing 80.4% while the parasitism was only 21.3% in the case of Trichogramma. The presence of both parasitoids was responsible for up to 97.5% of parasitism, obtained from plots with a released density of 12 T. remus female m-2

Effect of a nuclear polyhedrosis virus on Spodoptera frugiperda (Smith) (Lepidoptera:noctuidae) larvae, its damage and yield of maize crop.

The efficiency of Baculovirus in a wettable powder formulation to control the fall armyworm Spodoptera frugiperda (Smith) was evaluated using variations of the recommended 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, of 25+25, 25 + 50, 50+25 and 50+50 g ha-1, compared to untreated plots. The treatments were arranged 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 at 40 PSI (2.8 kg cm-2) and a regular flat fan nozzle. Larval mortality rate obtained from plots with the application of 50 g of Baculovirus wettable formulation ha-1, at once (96.2%), was significantly higher than that obtained with the application of 25+25 g ha-1 (85.3%) or 25 + 50 g 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 1 to 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) than plants unprotected (6,140 kg ha-1), that is, 23.4% higher