Photo:© Bruce Marlin
Gardeners new to growing fruit and nut trees typically panic around the early part of June. This is when “June drop” occurs – the natural shedding of excess fruit from a tree. University of California master gardener Jim Borland calls it “a self-regulated thinning process that keeps the tree from bearing too large of a crop.” While June drop is a natural phenomenon, there are a number of additional reasons a pecan tree may drop fruit at during other parts of the growing season.
If the tree experiences an additional drop, either before June drop or in July, suspect poor pollination as the reason. When it happens in early June the nuts are so small you may not even notice they’ve fallen from the tree. During July, however, they are larger and it’s more obvious that the tree is shedding fruit. Planting different varieties to assure cross-pollination solves the problem.
If the pecan tree is shedding fruit during late May, suspect an insect infestation. Pick up a few of the fallen pecans and inspect them for small holes. These are caused by the pecan nut casebearer (Acrobasis nuxvorella). The grey moths, active only at night, lay their eggs on the nuts and the hatched larvae tunnel into the nuts. Insecticides control the larvae but the product must be applied before the larvae enter the nut. Scout the tree frequently during pollination and just after, looking for the small white eggs on the pecans. Use an insecticide that contains spinosad, carbaryl or Bacillus thuringiensis that is labeled for use on pecan trees.
Lack of Water
Pecan trees need 100 to 200 gallons of water a day, April through October, in the hotter areas of the country, according to extension horticulturists with Texas A&M University. Two inches of water, supplied slowly at the tree’s dripline every week, will provide the pecan tree its water requirement. Water-stressed trees typically drop their fruit in late July and early August.
Potassium deficiencies are a common problem in pecan trees grown in the southern United States. The lack of potassium leads to poorly filled nuts and nut drop. The cure for potassium deficiency in the pecan tree isn’t a quick fix and it may take a season or two to get the level adjusted. Adjust the ratio of nitrogen to potassium in your fertilizer to 1:1.5. Make the application when buds break.