Predation of lepidopteran eggs in New Mexico pecan orchards

Pecan nut casebearer (Acrobasis nuxvorella) is an important pest in pecan fields in New Mexico. Large infestations can destroy or damage 5% or more of the nuts expected to be harvested. Most orchards make an application for first generation pecan nut casebearer every year. However, small trees are not treated because the nuts are not harvested. Small trees might act as a reservoir infesting the harvestable trees. Initial field trials indicated that eggs in those smaller trees tend to hatch faster as a result of higher temperatures due to more direct sunlight. Cotton bollworm (Helicoverpa zea) eggs were placed in 10-15 and 30-40 foot trees to determine predation rates. Eggs were then examined and classed by predator group based on the feeding damage to the egg. Results from 2010 indicated little difference in predation between 10-15 ft and 30-40 ft trees. Predation was only significantly higher in September with 66% predation in 30-40 ft trees vs in 47% in 10-15 ft trees. However, at this point pests are not likely an issue. Predation rates varied widely among orchards early season with 51-98% predation in early June. However, by late season there was little variation in predation among orchards. Predators with sucking mouthparts often provided higher levels of control in 30-40 ft trees compared to 10-15 ft trees.