Pecan tree ‘warts’ causing woes in county

Published 3:00 am Tuesday, June 21, 2016

The Pike County Extension Office is receiving calls and visits from county residents concerning “warts, bumps and knots” on their pecan trees.

“This is causing quite a bit of concern because people don’t know what these ‘warts’ are, what’s causing them and what effect they will have on their fall crops and their trees down the road,” said Heath Wesley, Pike County Extension coordinator. “These warts or galls are actually the result of an insect called pecan phylloxera.”

Wesley said there are two phylloxera species that attack pecan trees in the Southeast.

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“These tiny aphid-like insects are extremely hard to see without a hand lens,” he said. “They overwinter as eggs within the cracks and crevices of pecan trees. The eggs being to hatch in early April and continue throughout the month.”

Wesley said although the leaf phylloxera is unsightly they normally cause minimal damage to the tree because they affect only the leaflets.

“The stem phylloxera, however, is where the ‘stem mother’ is feeding and causing the tree to form the wart,” Wesley said. “Inside the wart, the stem mother lays eggs; the wart enlarges and eventually cracks open and releases phylloxera to lay eggs in the crevices of the tree which is the beginning of next year’s cycle.”

Wesley said the stem phylloxera can cause major loss of the nut crop and also weaken small branches, which causes considerable breakage under windy conditions.

“Both of these phylloxera are sporadic pests,” Wesley said. “That means they don’t appear every year.”

Control for commercial pecan producers is relatively simple, Wesley said. Preventative insecticides can be sprayed through the orchard to kill stem mothers. Sprays for control are applied at bud break and repeated every 10 to 14 days until new growth is about one-inch long.

“But control for home owners can be more difficult,” Wesley said. “Having access to effectively labeled insecticides and having a sprayer with enough pressure and volume to reach new growth areas throughout the tree, especially mature trees, are the problems.”

Products such as dormant oil prior to bud break and Malathion, when new growth is between one-fourth and one-half inches long, can be effective.

Homeowners who are experiencing “warts” on their pecan trees and need treatment information about phylloxera or other home grounds questions are encouraged to visit the Pike County Extension Office at 306 South 3 Notch Street in Troy or call the office at 334-566-0985.