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Northwest Iowa Dairy Outlooks

A local discussion of current science and issues concerning dairying in northwest iowa

I’ve had several questions on the pecan nut casebearer this past week. The pecan nut casebearer is one of the most important nut infesting insect pests of pecans. Casebearer larvae tunnel into nutlets shortly after pollination, often destroying all of the nutlets in a cluster. The most effective and reliable method of control is a well-timed insecticide application(s) made in the spring to kill hatching larvae before they tunnel into the nutlets. However, insecticides should only be applied if infestations and nut load justify treatment.

Typically, we will start looking for PNC around May 10 and spraying will progress late in the month, but it is all based on scouting for the first egg hatch.

The PNC Forecast System at http://pncforecast.tamu.edu  provides information about pecan nut casebearer activity to assist pecan producers with management decisions. The System allows the user to predict activity of first generation pecan nut casebearer in his/her orchard using data from pheromone traps operated in that orchard and local temperatures. The System generates predicted dates when first generation eggs are expected to be found in the orchard and the date when PNC larvae first begin to feed on pecan nutlets.

The PNCforecast System also provides information on pecan nut casebearer egg-laying activity and nut entry from selected sites across Texas and Oklahoma. These forecasts are based upon data collected by county Extension agents and entomologists with Texas AgriLife Extension and the Oklahoma Cooperative Extension Service, Master Gardeners and by volunteer pecan growers working with Extension.

Often a single carefully timed insecticide application provides adequate control for first-generation casebearer.  Time insecticide applications accurately to control newly hatched casebearer larvae before they enter the nuts. Once inside nuts, larvae are protected from insecticides.

To determine whether treatment is needed and when to apply insecticide, examine nuts carefully in spring for casebearer eggs. Apply insecticides within 2 to 3 days after the first eggs hatch. At this time, the first larvae begin entering nuts. Infested clusters can be flagged to monitor egg hatch.

Delaying treatment until the first nut entry occurs maximizes the insecticide’s residual activity. However, consider the time required to treat the orchard and possible weather delays so that insecticide is applied before significant nut entry occurs. A second insecticide application may be required if unhatched eggs are found after the residual period of the insecticide has passed.

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