Pecan Nut Casebearer: A Brief Introduction & Updates for 2025 Crop

Pecan nut casebearer is no stranger to the pecan growers of southwest Georgia. Just like pecans are native trees of the south, the nut casebearer is also a native insect of the region. We see and talk about this insect every year in late spring. Most of you might already have seen this pest in your groves this season. In this blog, I am going to discuss the key points to remember about the identification of this insect, monitoring and management strategies for the pecan producers.

Identification

Adults: The adults are small, dark grayish moth with a distinct ridge of dark scales across the forewings. It is hard to see them from distance during the day as they rest on pecan twigs and branches and remain well camouflaged.

Eggs: The eggs are bluish-white when deposited, but they become pink or red within a few hours. They are oval and small (0.65 mm long and 0.36 mm wide). Adults lay eggs on tip or the grooves of the recently pollinated nuts. They are deposited singly (no egg masses) although more than one egg may be found on a nut.

Larva & Pupa: A typical mature pecan nut casebearer larva is 10 – 17 mm long, olive-gray with a yellowish-brown to brown head and finely wrinkled skin. The larva spins a flimsy 8 – 10 mm cocoon which is initially jade green but becomes brown within a few hours.

Life Cycle

1. The overwintering larva becomes active when buds begin to swell in the spring and feeds on the new succulent growth.
2. The adults from the overwintering larvae deposit first-generation eggs on pecan nuts soon after pollination.
3. The first-generation larvae from these eggs feed on the buds and nutlets in the spring. This is the most vulnerable stage of the insect for any insecticide spray. Once the larvae enter into the nutlet, they are less exposed to insecticide applications and spray programs may not have the desired efficacy.
4. After feeding for nearby buds for 2 – 3 days, the larvae tunnels into the nutlet and feeds inside the tunnel.
5. The larva pushes black frass outside the tunnel that accumulates in the silk web outside the nut. This is diagnostic of pecan nut casebearer infestation. The damaged nutlets are hollow, shriveled and brown.
6. The later generations of larvae also cause similar damage by feeding on nuts and shucks.
7. The third-generation larvae emerge as adults in August and October. The fourth generation larvae overwinters for next season.

Management Strategies

1. Light infestations causing occasional damage do not require control in most crop years. Some early-season nut loss due to pecan nut casebearer is desirable in years when trees set an excess number of nuts that must be thinned later by shaking the trees.  In making a treatment decision, growers must assess crop load and growing conditions in addition to pecan nut casebearer infestations.
2. The most serious damage usually occurs in mid-May. Begin sampling for nut casebearer in the first week of May. Examine the nut clusters for eggs, larva, presence of black frass mixed with webbing at the nut penetration site. Pay particular attention to orchards not under a spray program the preceding year and orchards with a recent history of nut casebearer problems. Try to time sprays to stop injury before more than one nut per cluster is infested.
3. Adult emergence should be monitored with pheromone traps. UGA Extension tracks the activity of pecan nut casebearer in Georgia every year using the pheromone traps in commercial pecan orchards in several locations. Growers should utilize this program to make spray decisions for this pest.
4. It is recommended that broad-spectrum contact insecticides, such as the pyrethroids, not be used in early-or mid-season to conserve beneficial insect populations. Beneficial insects such as lady beetles and lacewings provide natural assistance in suppressing aphid and mite populations. Beneficials are of particular value in early season. Elimination of unneeded early-season insecticide sprays conserves existing populations of beneficial insects and reduces the potential for severe aphid problems later in the season.
5. There are several insecticidal chemistries labelled for pecan nut casebearer. Growers commonly use methoxyfenozide products such as Intrepid, Intrepid Edge, Zylo and Troubadour. Methoxyfenozide has a residual activity up to 7-10 days, and is highly effective against caterpillar pests such as the pecan nut casebearer. Another caterpillar-specific product is Rynaxypyr®, which is an active ingredient found in several commercial products (such as Vantacor or Coragen) and can also be used for PNC management. Growers should refer to the individual label and specific instructions before applying any of these products. If you have any questions, please reach out to the local county extension agent. For Dougherty County Extension, please call (229) 436-7216 or email uge4095@uga.edu.

Updates for 2025 cropping season

The pecan nut casebearer traps were placed in several commercial pecan groves in South Georgia by the local county extension agents. The data from these traps indicated that we reached biofix (the first day of the two consecutive days of moth capture) some time during the last week of April. Considering the biofix in later April, the forecast model indicates that the 50% of egg laying is expected in the first couples of days in the second week of May. Accounting for the 4-5 days for hatching of these eggs, we should expect to see the damage from larvae by mid May. Considering all the available information, the optimum time for an insecticide application for this year would be around the second week of May. I recommend producers to scout their pecan trees daily and look for the first-generation larva feeding on the nutlets to make best management decisions for your pecan production.

If you have any questions, please contact UGA Dougherty County Extension at (229) 436-7216 or email uge4095@uga.edu.

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