Horticulture: May 2004

Now is the time of the year when many pecan producers have fertilized and are looking forward to a crop on the tree. Most of you are still stinging from the freeze damage of the last years. We need to do everything possible to keep the crop we have; this can be done by monitoring insect and diseases. This brings up the next management hurdle, which is just around the corner ? the pecan nut casebearer (PNC).

Photo 1: Pecan Nut Casebearer Moth Photo 2: Pecan Nut Casebearer Egg

The PNC is a grayish moth approximately 1/3 inch in size (see photo 1). They have multiple generations, which are some 42 days apart, depending on weather conditions. Entry damage from PNCs can be seen later in the season as immature nutlets are easily knocked out of the cluster. Examine the immature nutlet for a small entry hole near the attachment end of the nutlet that has webbing and fass (sawdust like material) around or near the entrance. The entire cluster may be destroyed by the female laying her eggs. At this point, we are concerned with the first and second generation of PNC. The insect community is sensitive to temperature fluctuations ? PNC is no different. PNC growth and development in various temperatures have been determined by entomologists, and we can use this information to monitor the PNC activity.

PNC pheromone is the tool of choice for monitoring. It is placed in the orchards and groves early in the season. (Note: You should already have them in orchards and groves.). It will attract potential mates to the pheromone in cardboard traps. Check the traps three times per week to observe the number of PNC and record this information.

Remember: This is only a tool to give us an idea when to monitor the insect activity in our orchards and groves. After you start recording the PNC moth counts, research has shown that egg laying begins roughly seven to 10 days after a moth flight. Start looking for the eggs on the immature nutlet. It will be a whitish flattened oval which can be seen with the unaided eye (see photo 2). The PNC pheromone can be purchased from dealerships that cater to the pecan industry or can be purchased from mail-order vendors. Order three to five traps per 50 acres or less. For larger acreage, use five traps per 50 acres. Remember to order extra when purchasing because the traps are small, lightweight and can easily be destroyed by wind storms. Trap destruction would disrupt the number of insects to be counted, but with replacement traps and pheromone on hand, one can continue monitoring the PNC count.

An additional tool to monitor the PNC is through the OSU Web site for PNC Modeling (http://www.hortla.okstate.edu/pecan/weather_models.htm). This site gives the number of local temperature days for emergence of PNC moth activity. This site also gives the names and rates of products to control PNC.

Also, visit Dr. Bill Ree and Dr. Alan Knutson?s PNC article at http://insects.tamu.edu/extension/bulletins/l-5134.pdf.