On healthy pecan trees, the thick corky shuck surrounding the pecan nut will split open, releasing the pecan to drop to the ground. Pecans that drop to the ground still enclosed in the shuck are almost always no good.
No matter how you pronounce it, the pecan is a southern treat. Its sweet, buttery flavor is delicious when baked in pies or cakes, added to salads, or simply eaten straight out of the shell. Though not native to the East Coast, pecan trees are common sights in our area. So are pecan problems. It’s easy to find bags full of perfect, plump pecans in the grocery store this time of year, but if you have ever collected pecans from local trees, there is a good chance you have come across a less-than-perfect crop.
Poorly Filled Pecans
The most common problem encountered in locally grown pecans is small, shriveled nuts that fail to fully fill out. This can be caused by poor growing conditions, low nutrients, or insect and disease problems. Producing a crop of high-quality nuts takes a lot of energy. Trees will only be able to produce this energy if they have a steady supply of moisture, nutrients, and plenty of healthy leaves to capture sunlight.
Drought, particularly in August and September, when pecan nuts are filling out, is a common cause of poorly filled pecans. Pecan trees growing in deep sandy soils are more likely to produce small, shriveled nuts because water drains too quickly from these soils, allowing trees to dry out between rainfalls. Low nutrient levels can also contribute to poorly filled nuts. This is more common in sandy soils because they are naturally low in nutrients and cannot hold onto them, even when fertilizer is added. Watering trees during late summer drought can help trees produce a better crop. Soil testing to find out which nutrients and how much of each needs to be added may also increase productivity.
Pests and diseases that cause pecan trees to lose a lot of leaves contribute to the problem of poorly filled nuts. Fall webworms, a type of caterpillar that make large webbed tents on the ends of branches, often feed on pecan leaves in late summer. Heavy feeding can defoliate trees and reduce their ability to ripen nuts. Scab disease can also produce this effect, which causes black spots on the leaves, reducing their ability to capture sunlight. Both of these problems can technically be treated with pesticides. Since these products have to be sprayed throughout the tree canopy, treatment is usually not realistic because pecan trees are large.
Some varieties of pecan trees fail to produce high-quality pecans because they are not adapted to our growing season. Trees bred for production in areas with a longer grower season such as the Gulf Coast or Texas may not be able to ripen nuts in our area. Recommended varieties for southeastern North Carolina include Pawnee, Sumner, Stuart, and Cape Fear.
Empty Shells and Bitter Spots
Pecan weevil damage
If you have ever found pecans with a small perfect hole drilled in their shell and the nut inside was missing, then you have encountered the work of the pecan weevil, the most destructive insect pest of pecans. Sometimes you may actually find a plump cream-colored weevil grub still inside the shell, feeding on the pecan meat. At this point in the season, nothing can be done to manage this pest. Controlling pecan weevils requires several applications of the pesticide carbaryl, often sold as Sevin, in August and September. No effective organic treatments for this pest are available.
Stink bug injury
Dark, bitter spots on the pecan kernel are the result of stink bug feeding. Several types of stink bugs feed on pecan nuts in late summer. These pests are difficult to control with insecticides, but they can be reduced when weeds around pecan trees are controlled.
Several factors can contribute to trees producing little to no crop in a given year, including drought stress, low nutrients, and pest problems. Seedling pecan trees usually only produce very small nuts, no matter how much they are watered or fertilized. Newly planted grafted trees often take 12 to 15 years to start bearing.
Trees that consistently produce few to no nuts are most likely not being pollinated. Pecan trees are wind pollinated and require more than one variety for pollination to occur. Where pollination problems are suspected, more trees should be planted within a few hundred feet of existing trees. Check with your local extension office for recommendations of varieties for this area and their pollination requirements.
To find out more about growing pecans, see the NC Extension publication, Growing Pecans in NC, available online at http://www.ces.ncsu.edu/depts/hort/hil/ag81.html, or contact your local extension office. In Pender County, call (910) 259-1235 or visit our office at 801 S. Walker Street in Burgaw, Mon – Fri, 8 a.m. – 5 p.m.
You can also post your questions online using our ‘Ask an Expert’ widget available at http://pender.ces.ncsu.edu/index.php?page=askanexpert. Visit the Pender Gardener blog, http://pendergardener.blogspot.com/, to stay up-to-date with all the latest gardening news.
Charlotte Glen is a Horticulture Agent at the Pender County Cooperative Extension. This article appeared as a guest column in the November 2012 Gardening Newsletter.