Written by Kris Tollerup and David Haviland
University of California Cooperative Extension and UC Statewide IPM Program
Pest control advisors need to be on the lookout for leaffooted bug. All indications are that 2015 has the potential to be a significant year for leaffooted bug damage to almonds. This prediction is based on observations of very high populations of LFB during the fall of 2014 and a high overwintering survival rate due to mild winter weather. During the past few days (~March 15th) multiple reports from across Kern County have been sent to UC Cooperative Extension offices that PCAs are starting to see movement into crops. Although no known reports of leaffooted bugs have occurred in the mid and more northern growing areas, it would be prudent to begin monitoring now.
Monitor for LFB at least once a week from mid-March through May, and then every one to two weeks through June. The most effective monitoring method is to do a visual survey for the presence of bugs. This can be done by using a long pole to knock branches in the upper tree canopy, causing the bugs to fly such that they can be seen or heard.
Visual inspections should be coupled with inspections of the fruit by looking for gummosis on the almond hull. However, by the time gummosis is seen, damage has already occurred. Gummosis can also occur due to physiological damage. Therefore, if the method is used, cross-section the area with gummosis to determine the presences of a pin-sized discolored wound caused by the penetration of the insect’s mouthparts. Also inspect fruit on the ground for the presence of gummosis and a stinging wound to determine if LFB is the culprit. Be sure not to confuse gummosis caused by LFB (clear to light amber color) with gummosis caused by bacterial spot (dark amber to orange color).
The primary control method for leaffooted bug is insecticides. Studies funded by the almond board in 2014 determined that the pyrethroids bifenthrin (Brigade) and lambda-cyhalothrin (Warrior II) have excellent contact activity and residual activity against adult bugs for two to four weeks. The organophosphate chlorpyrifos (Lorsban Advanced) also had excellent contact activity and provided one week of residual control. Three reduced-risk insecticides containing abamectin (Agri-Mek), sulfoxaflor (Sequoia- label pending) and clothianidin (Belay) provided moderate to excellent activity when sprayed directly on the bugs. However, once residues dried none of these three products provided any residual control.
Growers that use insecticides should do so only if monitoring indicate that leaffooted bug is present and is causing damage. Applications of insecticides should also only be made after considering any potential risks of product use to beneficial organisms, including bees and biological control agents, and to air or water quality. For more information on these topics please consult the UC IPM Pest Management Guidelines for Almonds at http://ucipm.ucanr.edu/PMG/crops-agriculture.html.