Pest Control Strategies for Northern Pecans William Reid Extension Specialist, Nut Crops Pecan Experiment Field Kansas State University There are many insects and diseases that can injury pecan trees and the nuts they produce but only a few cause significant damage. Pecan producers need to learn how to identify common pest problems and determine if and when those pests need to be controlled. These recommendations are intended for pecan producers in Kansas, Missouri, and Illinois. Primary Pests Two insects and one disease make up the primary pest complex that growers must deal with on an annual basis. Pesticides Pecan weevil adults (pictured above) emerge recommended for use in controlling pecan from the soil starting in early August and insect pests are given in Table 1. continue emerging until early September. Female weevils bore through the shuck and shell of a nut to lay 5-7 eggs. These eggs hatch into legless larvae which completely devour the kernel of the nut. Left untreated, pecan weevil can completely destroy a pecan crop. Growers should install trunk-mounted weevil traps (pictured below) to determine peak adult emergence periods and apply an insecticide to kill adults before they can lay eggs. Pecan nut casebearer larvae attack small nutlets shortly after pollination (pictured above) and can quickly destroy and entire cluster of nuts. Growers should develop a regular scouting program for pecan nut casebearer starting the 4th week in May. An insecticide should be applied when 2% of clusters are damaged. female flowers. Leaf phylloxerans create smaller galls on the leaf blades and can cause early defoliation. Once growers discover phylloxera galls in their orchards it is too large to control the insect during the current season. Growers need to mark phylloxera infested trees then treat those marked trees the following spring during bud break. Timing for control of these two species is slightly different. To control stem phylloxera, spray at inner scale split or when the first bit of new green tissue starts to emerge. To control leaf phylloxera, spray when the first leaf has burst from the expanding bud. Pecan scab (pictured above) is the most Hickory shuckworm populations are often serious disease of pecan and can infect both kept in check by insecticide treatments aimed at leaves and nuts. Scab infected leaves will drop controlling pecan weevil. However, if pecan off the tree prematurely, while a scab infection weevil is not a problem in your orchard, hickory on the shuck of pecan nuts will reduce nut size, shuck at build up to large populations and cause inhibit kernel filling, and prevent proper shuck nut drop in July (2nd summer generation) and opening. If scab has been a problem in your reduce kernel fill in August (3rd summer orchard, a preventive schedule of fungicide generation). Growers should monitor their applications will prevent economic losses. orchards for signs of hickory shuckworm Recommended fungicides are listed in Table 2 damage then plan on making insecticide while a weather based schedule for scab control treatments the following summer if damage in given in Table 3. begins to increase dramatically. Fall Webworm and Walnut Caterpillar are Secondary Pests two species of caterpillars that feed in large colonies and can defoliate pecans. The fall Several pecan insects fall into a category of webworm spins a dirty white web over the secondary pests. These insects should be colony while the walnut caterpillar feeds controlled on “as-needed” basis. The key to without a protective web. Growers should scout keeping secondary pests from become primary for these insects and apply an insecticide only if problems is to follow a strict orchard they find more than 5 colonies per acre. Each monitoring program. insect has two generations per year. New colonies appear in mid-July and again in late- Two species of phylloxera can create galls August. on pecan trees. Stem phylloxerans form large galls on new stems and leaf mid-ribs distorting twig growth and inhibiting the initiation of Table 1. Recommendations for insect control Insect Pest Timing Pesticide Rate/acre Stem Phylloxera Inner scale split Asana XL ® 4.8 -14.5 oz. Lorsban 4E ® or 2.0 - 4.0 pts. Nufos 4E ® Provado 1.6F 3.5 - 7.0 oz. Warrior ® 2.56 - 5.12 oz. Leaf Phylloxera Leaf burst Asana XL ® 4.8 -14.5 oz. Lorsban 4E ® or 2.0 - 4.0 pts. Nufos 4E ® Provado 1.6F 3.5 - 7.0 oz. Warrior ® 2.56 - 5.12 oz. Pecan Nut Casebearer 2% cluster damage Ammo 2.5 EC ® 3.0 - 5.0 oz. Asana XL ® 4.8 -14.5 oz. Confirm 2F 8 - 16 oz. Imidan 70WSB 1.0 - 3.125 lbs. Intrepid 2F 8.0 oz. Lorsban 4E ® or 1.5.0 - 4.0 pts. Nufos 4E ® Spintor 25C 4 -10 oz. Warrior ® 2.56 - 5.12 oz. Hickory Shuckworm July 5 - July 14 Ammo 2.5 EC ® 3.0 - 5.0 oz. Asana XL ® 4.8 -14.5 oz. Confirm 2F 8 - 16 oz. Imidan 70WSB 1.0 - 3.125 lbs. Intrepid 2F 8.0 oz. Lorsban 4E ® or 1.5.0 - 4.0 pts. Nufos 4E ® Spintor 25C 4 -10 oz. Warrior ® 2.56 - 5.12 oz. Fall Webworm & When colonies appear Ammo 2.5 EC ® 3.0 - 5.0 oz. Walnut Caterpillar Asana XL ® 4.8 -14.5 oz. Confirm 2F 8 - 16 oz. Imidan 70WSB 1.0 - 3.125 lbs. Intrepid 2F 4.0 - 8.0 oz. Lorsban 4E ® or 1.5.0 - 4.0 pts. Nufos 4E ® Pecan Weevil In August, based on Imidan 70WSB 1.0 - 3.125 lbs. trap catch data. Sevin 80S 2.5 - 6.25 lbs. Warrior ® 2.56 - 5.12 oz. ® = restricted use pesticide Table 2. Recommendations for disease control Disease Timing Pesticide Rate/acre Pecan Scab Post pollination Abound 9.2 - 12.3 oz. Orbit 4 - 6 oz. Enable 8 oz. Flint 2 - 4 oz. Headline 6 - 7 oz. Pristine 10.5 - 14.5 oz. Sovran 3.2 - 4.8 oz Stratego 10 oz Super-Tin 80WP ® 5.0 - 7.5 oz. Additional Abound 9.2 - 12.3 oz. applications at 2 Orbit 4 - 6 oz. week intervals Flint 2 - 4 oz. based on weather Headline 6 - 7 oz. conditions Pristine 10.5 - 14.5 oz. Sovran 3.2 - 4.8 oz Stratego 10 oz Super-Tin 80WP ® 5.0 - 7.5 oz. ® = restricted use pesticide Table 3. A weather based method for timing pecan scab control measures Fungicide application Timing First cover immediately after pollination Second cover 14 days after first cover spray, if: (1) No rain has occurred, but the 5 day forecast for rain is > 50%, OR (2) One rain event has occurred, and the 5 day forecast for rain is >40%, OR (3) Two rain events have occurred, and the 5 day forecast for rain id >20%, OR (4) Immediately after three rain fall events Third cover Begin weather based rule 14 days after second cover.
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