Extension Master Gardeners – Take Care of Pesky Pecan Weevils Now!
Care of Pecan Trees
When the height of a pecan tree gets to be over about 25 feet, it is difficult if not impossible for the home orchardist to apply insecticides or fungicides to the tree. The life span of the pecan tree can be 75 years or more and reach heights well in excess of 50 feet. Sine pecan trees also tend to be a somewhat brittle, it is not unusual for big limbs of larger trees to break off suddenly for no other apparent reason.
The primary pest of the pecan tree is the pecan weevil, which emerges from the ground from mid-August through early September. The weevils then climb up the tree trunk to bore holes into the shucks and destroy the kernels of the pecans. The good news is that the damage from the pecan weevils can be easily minimized by applying a proper insecticide to the ground under the tree once the weevils are detected. One recommended insecticide that is readily available has carbyl (Sevin) as the active ingredient. The orchardist should monitor the tree trunk daily during August to detect when the weevils start their climb.
There are 3 main reasons why pecans drop from trees prematurely starting in late August. They are lack of sufficient pollination, insects and diseases, and stress conditions.
– Having adequate pollination requires having 2 varieties of trees (typically the Cape Fear and the Stuart) and good weather during the pollination period in the spring.
– The insects that mainly cause premature drop during the summer are the pecan weevil, nut casebearer, and shuckworm, which bore holes into the base of the nuts. Other insects causing damage to the nuts include the stink bug, aphids, and the twig girdler that girdles the twig ends of the branches. Once identified to be present, weevils and other insects can be controlled by using appropriate insecticides. Of the diseases, scab is the most prevalent and damaging in causing defoliation that also can lead to some premature nut drop.
– Stress conditions can be caused by many conditions, including successive humid sunless days that limit essential photosynthesis. Severe stress, however, occurs mainly from lack of proper watering, particularly during dry periods. Late July through the middle of August is the critical period for beginning kernel formation when uniform and thorough watering is essential. Too much water (storms) and too little water (droughts) will severely stress the trees and cause considerable premature nut drop, as much as 50%. Since incorrect fertilization can also be a cause of some premature nut drop, getting periodic soil tests that are free (Apr – Nov) through the N.C. Cooperative Extension is recommended. With pecan trees growing to be very large, they need to be planted in well drained, deep fertile soil (sandy loam preferred) typically spaced 60 feet apart.
Call the Beaufort County Extension Master Gardener Volunteer hotline on Mondays and Wednesdays between 10:00am and 12:00pm at (252)946-0111 to inquire further about this or other subjects pertaining to consumer horticulture. You can also send questions to Gene Fox, the Beaufort, Hyde, Tyrrell, and Washington County Consumer Horticulture Extension Agent at (252)946-0111. Visit the Blacklands Area Horticulture facebook page or the Beaufort County Extension website www.beaaufort.ces.ncsu.edu for information on upcoming events or issues. Follow Gene Fox on Twitter @Foxplantguy.
– Written by Dan Bergbauer, Beaufort County Extension Master Gardener Volunteer