Texas Pecan Pest Alert: Emerging Pecan IPM Information
Pecan nut casebearer (PNC) is the major spring insect pest of pecan trees throughout Texas. The pest is a moth that emerges from hibernation in April to mate and lay eggs on small, developing pecan fruit. The IPM approach to control PNC is to correctly identify the egg-laying period of adult PNC moths through pheromone trapping and visual scouting of nut clusters for the presence of eggs or hatching larvae. Where scouting detects a damaging population—usually 2 eggs or nut entries in less than 310 clusters, insecticide treatments should be made to protect 5% or higher crop loss. PNC crop damage may go unnoticed or economically insignificant on trees showing heavy female flowers (cluster appearance), but where the crop set is light to moderate, the damage can be catastrophic—70 percent or greater!
PNC adult moth flights and egg laying are staggered in Texas, with occurrence in South Texas before Central Texas and then North Texas last. Activity for PNC is exceptionally early this year due to warm temperatures in March and April. As of April 25, orchards in the College Station and Bastrop areas have been catching adult moths in traps since around April 13, with eggs discovered as early as April 22. The Texas A&M pecan orchard observed 2 percent eggs and 1 percent nut entry on April 25. These scouting observations trigger immediate insecticide spraying of trees in those orchards with light to moderate crop with similar scouting outcomes. Moderate cropping is 34-50% terminal branches bearing nut clusters. Light cropping is 10 to 33 percent terminals with clusters. Weather conditions—wind and rain—are an impediment to effectively spraying pecan trees. While heavy rains at night may stymie or slow moth mating and egg-laying activity, the wind does not disrupt or slow moth activity. Growers using recommended larvicides like methoxyfenozide, spintorem/Spinosad, or Bacillus thuringiensis (Bt) must get excellent coverage of the small developing nuts to obtain control, which may require spraying at nighttime when wind conditions are less.
PNC damage will begin to show up around the state according to local day-night temperatures over the next four weeks. Without a reduction in current temperatures, growers should be scouting in earnest earlier than usual. For those growers with pheromone traps, oviposition and nut entry can be expected to occur anywhere from 10 to 14 days after capturing moths in two consecutive nights. There is some potential for the first-generation PNC flight to be high this year due to an unusually high occurrence of third- or fourth-generation PNC that caused late-season crop damage in August and September 2023. Second-generation PNC, usually occurring 35 to 45 days after the first generation, could likewise cause greater crop injury this year. Moth activity is no predictor of damage. Beneficial insects play an important and unpredictable role in PNC population control, so growers should scout their orchards carefully and regularly to make informed decisions.
To learn where to get more information about pecan nut casebearer and other annual pecan management challenges, contact your local county AgriLife Extension office.
Monte L. Nesbitt, Ph.D.
Extension Specialist & Assistant Professor, Department of Horticultural Sciences
Texas A&M AgriLife Extension Service
College Station, Texas