Slowing the Spread of Pecan Nut Casebearer - West Coast Nut

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Slowing the Spread of Pecan Nut Casebearer

By Cecilia Parsons | Associate Editor
Published: March 26, 2021 • 493 views

Pecan nut casebearer larvae inside a nutlet. Timing of insecticide application prior to larvae burrowing into the nutlet is critical (photo courtesy Gordon Watts Entomology Labs.)

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Pecan nut casebearer is among the most devastating widespread pests of pecan and is established in about two thirds of New Mexico’s pecan growing regions. The encouraging news about pecan nut casebearer is that New Mexico Department of Agriculture surveys have not found any evidence of this pest in the counties where pecan case bearer is not known to be established. The department monitors cooperator orchards in Luna, Hidalgo and Valencia counties.

Although data in counties with established populations of PNC is not collected, NMDA program specialist Tiffany Johnson said the department believes that as new pecan acres are planted in PNC infested areas, those trees do become infested as trees begin to produce.

Pecan nut casebearer, Acrobasis nuxvorella Neunzig, is one of the most devastating nut-feeding insects in pecans. This pest infests orchards from Florida to southern New Mexico and can produce three or four generations per year in New Mexico. Adult PNC moths lay eggs on the terminal end or side of nutlets or at the base of the calyx lobes. Eggs hatch in four to five days and the larvae burrow into nuts and may damage an entire cluster.

Pecan nut casebearer has been present in the eastern pecan-growing region of the New Mexico for the past 30 years. Currently, PNC has established itself in over 70% of the pecan-producing areas in the western region of New Mexico. Within the next four years, it is estimated that PNC will establish in the majority of the remaining pecan acres.

In the majority of pecan orchards, adult PNC emergence is monitored using species-specific pheromone traps. Once adults being to emerge, the need for pesticide applications and timing are based on a number of factors, including the number of moths caught in pheromone traps, percentage of pecan nut casebearer egg-infested nuts, crop load, days of post-peak adult emergence and percent of egg-hatch. Pesticide applications remain the primary control method. They must be applied before young larvae tunnel into the nutlets.

Optimal timing for insecticide treatment is determined by scouting the orchard for casebearer eggs and early nut entry by larvae.

In the past, pecan growers were uncertain as to when to invest time in scouting. This changed with the identification of the sex attractant pheromone of the pecan nut casebearer and development of pheromone traps, which growers currently use to monitor orchards to determine when casebearer moths become active each spring. A degree-day model was also developed to better use trap data in predicting egg-laying activity, and that model, called PNCforecast, has been made available online so growers can have easy access to it. Growers can find the model at pecan.ipmpipe.org/Maps/pncForecastMap.