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FIND MORE ARTICLES AT NOBLE.ORG A MONTHLY PUBLICATION FROM APRIL 2019 | VOLUME 37 | ISSUE 4 NOBLE RESEARCH INSTITUTE NOBLENEWS&VIEWS PECANS How to Identify and Control Pecan Nut Casebearer by Charlie Graham, Ph.D., senior pecan specialist | [email protected] here are more than 200 Native geographic distribution of pecans and the pecan nut casebearer. insects that feed on the roots, wood, foliage and nuts of a pecan tree. TOf these insects, 17 are nut feeders, with one of the most important nut-infesting insect pests being the pecan nut case- bearer (Acrobasis nuxvorella Neunzig). WHERE ARE CASEBEARERS FOUND? The pecan nut casebearer (PNC) has a wide Pecan Native Range geographical range, extending from Florida to PNC Range southeastern New Mexico, and north to southern Illinois. This covers most of the pecan producing Source: D.E. Stevenson, et. al.. regions in the U.S., excluding Arizona, California Pecan Nut Casebearer Pheromone and parts of New Mexico. Monitoring and Degree-Day Model Validation Across the Pecan Belt, Southwestern Ento- mologist, Suppl No. 27, Dec 2003, pp 57-73 Story continues on next page 2 | NOBLE NEWS&VIEWS HOW DO YOU CONTROL WHEN SHOULD I SPRAY FOR CASEBEARERS? CASEBEARERS? WHAT THE PECAN NUT Casebearer larvae tunnel into nut- There is a fairly small window CASEBEARER LOOKS LIKE lets shortly after pollination, often of opportunity for insecticide destroying all nutlets in a cluster. The applications to control newly hatched casebearer larvae. Figure 1. Silk most reliable method of control is a properly timed insecticide appli- Once the larvae has bored into and black frass the nutlet, they are protected (excrement) are cation to the tree to kill the recently hatched juveniles before they can from insecticide treatments. visible outside As mentioned earlier, the infested nuts. enter the young nutlets. However, treatment is a judgement call based necessity of control measures on moth catch, egg scouting and is determined on the severity pecan crop load. So part of this of the infestation and the size equation depends on properly iden- of the nut crop. The alternate tifying the adult male moths cap- bearing cycle of pecan trees tured in orchard traps. often has an impact on your management decisions. In LARVAE WHEN DO CASEBEARERS the “on” years, when the crop load is heavy, many growers Newly hatched larvae are white with a brown head. They CAUSE THE MOST have three pairs of legs located just behind the yellowish will opt not to treat and allow DESTRUCTION? brown head. The tiny larva feeds for a day or two on a PNC to naturally thin exces- First-generation larvae are usually secondary bud at the base of a compound leaf before it sive nuts from the tree. How- considered to cause the most eco- enters the pecan nut. Larvae generally tunnel in at the ever, in the “off” years, when nomic loss. This early in the season, base of the nutlet and feed for about four to five weeks, the crop load is light or if the a single larvae can destroy an entire depending on the temperature. Silk and black excrement infestation levels are severe, nut cluster due to the small nutlet are often visible outside of the infested nuts (Figure 1). treatment will be necessary to size. Later generations will typically As the larvae mature, they become olive to jade green in maintain a commercial crop only have to feed on a single nut color and are about a half inch in length. Full grown lar- load on the trees. to complete development. For this vae enter the pupal stage inside the nut with the mature reason, control is directed primarily moth emerging nine to 14 days later. at the spring generation. Story continues on next page Figure 2. PNC egg on the stigma of a pecan nutlet. WHERE TO FIND PNC TRAPS AND PHEROMONES Credit: Bill Ree, Texas A&M ALPHA SCENTS OLIVER PECAN CO. INC. Agrilife Exten- 1089 Willamette Falls Drive, 1402 W. Wallace, San Saba, TX sion. West Linn, OR 97068 76877 Phone: 503-342-8611 or 971-998- Phone: 1-800-657-9291 8248 Email: [email protected] Fax: 314-271-7297 EGGS www.alphascents.com PAPE’S PECAN HOUSE Moths are active at night when seeking a mate. Each female P.O. Box 1281 lays 50 to 150 eggs during her five- to eight-day lifespan. GEMPLER’S 101 S. Hwy 123 Bypass The eggs are flat, very small and white when newly laid but P.O. Box 44993 Seguin, TX 78155 are large enough to be seen with the unaided eye (Figure 2). Madison, WI 53744-4993 Phone: 830-379-7442 They develop red dots/lines after two or three days (appear- Order by Phone: 1-800-382-8473 ing pinkish in color) and turn entirely red before hatching. SOUTHERN NUT ‘N TREE GREAT LAKES IPM INC. EQUIPMENT INC AND PPI 10220 Church Road 324 SH 16 South Vestaburg, MI 48891-9746 Figure 3. Arrows Goldthwaite, TX 76844 Phone: 989-268-5693 or pointing to the Phone: 1-800-527-1825 989-268-5911 ridge of scales Fax: 325-938-5490 Toll Free: 1-800-235-0285 on the forewing Email: [email protected] Fax: 989-268-5693 of a male pecan www.sntequipment.com Email: [email protected] nut casebearer www.greatlakesipm.com moth. TRECE (for bulk orders only) ISCA TECHNOLOGIES / P.O. Box 129 MORITOR TECHNOLOGIES Adair, OK 74330 P.O. Box 5266 Phone: 918-785-3061 Riverside, CA 92517 Order Center: 866-785-1313 ADULT MOTHS Phone: 951-686-5008 Fax: 918-785-3063 Adult PNC moths are generally about 0.3 to 0.4 inches long Fax: 815-346-1722 Email: [email protected] and range in color from a brownish gray to a grayish black. PNC Email: [email protected] moths have a unique raised ridge of dark scales extending across www.trece.com the middle of each front wing. When the wings are folded back, www.iscatech.com this ridge looks like a dark line running across the width of the insect just behind the head (see arrows in Figure. 3). A MONTHLY PUBLICATION FROM THE NOBLE RESEARCH INSTITUTE | 3 HOW DO I KNOW HOW BAD AN percent or more of the nut clusters sampled INFESTATION I HAVE? are infested during the “on” years. During the Determination of the infestation severity “off” year (light crop), reduce the threshold is based on egg counts on nut clusters. to only 3 to 5 percent infestation. Usually, To pinpoint when you should be scout- one insecticide application is needed to con- ing for egg lay, many growers rely on trol the first generation of pecan nut case- monitoring PNC pheromone traps bearer. However, if infestations are extremely (Figure 4). heavy or emergence of adults is prolonged, a second application may be necessary. WHAT IS A PHEROMONE TRAP? The pheromone trap uses a lure contain- HOW MANY TRAPS SHOULD ing PNC female pheromone that attracts I SET, AND WHERE? males looking to find a mating partner. Three to five traps are usually adequate for You will need to monitor the traps often — Figure 4. Pecan nut casebearer pheromone orchards smaller than 50 acres. Larger orchards at least three times per week — and record trap with lure attached. will utilize more than five traps to provide the first capture of male PNC moths. The adequate coverage. You may want to use addi- optimum time to apply an insecticide to WHEN SHOULD I START SCOUTING tional traps if your orchard has considerable control PNC larvae is about 14 days fol- FOR EGGS? changes in topography, such as a river bottom lowing the first capture. However, this is Research suggests that trap catches cannot site transitioning to an upland site. Traps are also the time that misidentification can be used to predict the threat of casebearer usually attached to a nut-bearing limb at an have the greatest impact on your spray larvae damage or the need to apply an insec- easily accessible height to allow easy monitor- program. ticide. Instead, you should begin scouting for ing. While it is true that traps placed higher in eggs on the nutlets approximately seven to the canopy will capture more moths, you must WHAT IMPOSTERS SHOULD I WATCH FOR? 10 days after the first PNC moth is captured remember that you are monitoring moth activ- A common imposter moth that can be in the pheromone trap. Nut entry will occur ity, not the actual number of moths captured. caught in the pheromone trap before 14 to 20 days after the first capture. PNC flight is the pecan bud moth. It WHAT ELSE SHOULD I KNOW WHEN is slightly larger than the PNC moth WHAT AM I LOOKING FOR WHEN I SPRAYING FOR PECAN NUT CASEBEARER? and lacks the raised wing scales on the SCOUT FOR EGGS? Before purchasing and applying any insecticide, forewings. Its numbers increase in the When scouting for egg lay, remember that always read the label to determine if the prod- orchard earlier than PNC, but it does not most casebearer eggs are found on the uct is labeled for use on the target plant or site. feed on the young pecan nutlets. Mis- stigma (distal tip of nutlet) or hidden just Many insecticides are labeled for controlling identifying moths in the trap can result under the sepals of the nutlet. Many find pecan nut casebearer on pecans. Base your in wasted hours scouting for PNC eggs that a good hand magnifying lens makes the insecticide choice on applicator safety, grazing when there aren’t any in the orchard job easier to find the eggs and also deter- restrictions if livestock are present, and potential yet.