Pecan trees are a popular addition to home orchards for many Louisianians. Native to Louisiana and the southern United States, pecan trees are well adapted to our climate and growing conditions. For centuries, Native Americans relied on native stands of pecan trees as an important food source. As European settlement spread throughout Louisiana, settlers learned of the nutritious and flavorful pecan nut and incorporated it into their diets.
Despite being a native species, producing a consistent, high-quality pecan crop is not without challenges in Louisiana. Last week's article addressed the importance of pecan scab disease and how homeowners can reduce disease problems by planting resistant cultivars. However, disease is only one of several factors that can affect yield and nut quality.
If you have mature pecan trees on your property, you may have noticed large numbers of immature green nuts falling from trees in late summer, typically between August and September. These nuts often drop before the shucks begin to dry and split. The kernels inside may be blackened, shriveled, poorly filled, or even absent. Much of the late-summer pecan drop observed this year is likely related to the exceptionally dry conditions experienced during July and August.
Common causes of premature nut drop include insect damage from pecan weevils and stink bugs, pecan scab disease, excessive crop load, drought stress, and nutrient deficiencies. If late-summer nut drop is a persistent problem with your pecan trees, there are several corrective measures that may help improve production.
First, consider conducting a soil test to identify and correct nutrient deficiencies. Leaves that appear pale yellow or exhibit tip burn may indicate nutritional problems. Poorly filled nuts and blackened kernels can also be symptoms of nutrient stress. Correcting deficiencies can improve nut quality, yield, tree vigor, and disease resistance. Pecan trees often benefit from routine fertilizer applications based on soil test recommendations. Year-by-year fertilization guidelines can be found in The Louisiana Home Orchard: Pecans publication available on the LSU AgCenter website.
Second, during periods of drought, provide supplemental irrigation when necessary. Watering should begin before trees show visible signs of drought stress. During extended dry periods, apply water slowly over the root zone to allow moisture to penetrate deeply into the soil. Applying mulch beneath the tree canopy can also help conserve soil moisture while reducing competition from grasses and weeds.
Third, monitor trees for signs of insect and disease activity. Damage from stink bugs and pecan weevils is a common cause of premature nut drop. Insects may leave puncture marks on the green shuck and can cause kernel deterioration. Also watch for symptoms of pecan scab on developing nuts and foliage. While scab is generally more severe during wet years, maintaining healthy trees and selecting resistant varieties can help minimize disease pressure. Management of insects and diseases can be challenging for homeowners because of the limited number of pesticides labeled for residential use and the size of mature trees.
Finally, remember that pecan trees naturally exhibit alternate bearing, producing a large crop one year followed by one or more lighter crop years. In commercial orchards, crop load is sometimes reduced early in the season to improve nut size and quality. Poor pollination may also contribute to poor kernel fill. Pollination can be improved by planting both Type I and Type II pecan varieties within pollination range of one another.
Caring for pecan trees throughout the year improves tree health, longevity, disease resistance, yield, and nut quality. Pecan trees are a long-term investment, with many living well beyond 150 years. Proper site selection, cultivar choice, planting practices, and routine maintenance can help ensure that your pecan trees remain productive for generations to come.
