Influence of tree size on suceptibility to pecan nut casebearer in New Mexico

Pecan nut casebearer (Acrobasis nuxvorella) is an important pest of pecan in New Mexico. While older trees are frequently treated for pecan nut casebearer infestations small trees are not monitored or treated because the nuts are not harvested. Field experience suggested that smaller trees might harbor higher infestations that could act as a reservoir for the bearing trees. The influence of tree size was examined by comparing microclimate, predation and bollworm sentinel egg hatch in 3 sets of adjoining orchards with trees 7-12 and 30 plus years old. Eggs were examined after 48 hours for predation and maintained to evaluate hatch rates. Initial results indicated that eggs in the smaller trees had higher hatch rates, 68% vs 47% in large trees. Also, eggs hatched faster as a result of higher temperatures in smaller trees, with 22% hatch by 72 hours in trees vs. 0.2% hatch in larger trees. Eggs in the smaller trees also had lower predation rates than eggs in larger trees 92% vs 67% respectively. These initial results suggest that growers could monitor small trees as well as their large harvestable trees to ensure that the small trees don’t act as a reservoir for pecan nut casebearer.