Now in peak soil emergence, the pecan weevil is the most damaging late-season pest for both commercial and hobby pecan growers. A late start to the growing season may have pushed the emergence back, giving producers an opportunity to scout and monitor for the pest, ensuring a course of action is in place, should infestation reach economic threshold.
The life cycle of the pecan weevil begins when a female weevil lays an egg. The weevil’s development through the subsequent larva and pupa stages typically takes two to three years to complete.
Adult pecan weevil emergence typically peaks between the last week of August and the first two weeks of September, with weather conditions greatly influencing emergence.
Adult weevils will feed on nuts through the gel stage, laying eggs inside the pecan, with a single female infesting as many as 30 nuts. The infested pecan will remain on the tree with the full-grown larvae emerging from the shell early to mid-winter, about 42 days after infestation. Adult larvae will burrow into the soil to finish maturing, adult weevils emerge during late-August and early-September of the following year. Only around 10% of pecan weevils fail to pupate during the first year, those remaining larvae will emerge from the soil as adults during the third year.
The best control of the pecan weevil will be achieved by monitoring populations through the emergence cycle and can be achieved by shaking weevils from the pecan tree onto a white sheet on the ground where they can be easily seen and counted. This method also allows a producer the opportunity to survey fallen nuts for weevil damage in estimating threshold.
Weevils can also be monitored through the use of traps and is the most accurate estimation of threshold in relation to treatment. Traps may be bought or made and should be monitored as pecans enter the gel stage with 10 to 15 traps recommended per orchard.