Put Leaffooted Bug Monitoring on Your To-Do List

Written By Kris Tollerup, UC IPM Advisor for the San Joaquin Valley Unlike many of the moth pests, we do not have an effective lure that acts to attract leaffooted bug (LFB) to a monitoring trap of some sort.  An LFB lure could be used in almond beginning at mid-March for detecting the pest when they first begin moving into the crop.  Unfortunately, development of a lure remains elusive; researchers out of the University of California, Riverside have worked on the issue for several years now.  They have recently identified compounds used by LFB for sexual and aggregation communication, but synthesis of the compounds has proven quite difficult. This means that good-old visual scouting provides the only viable option.  About this time (mid-March – early April) leaffooted bug begin moving into almond from their overwintering sites.  A caveat to this is that the recent cool weather may have slow their movement and caused some individuals to re-aggregate.  For instance, during early March, we observed signs that LFB had begun to disperse from overwintering sites; however, stopped short and reformed aggregations on nearby citrus trees.  This likely occurred due to cool, wet weather. With warmer weather certainly coming soon, begin monitoring in locations that historically have sustained damage and notably locations near pomegranate and riparian areas.  The bug typically prefers the sunny side of the tree and will rest on nuts on the outside area of the canopy.  Take about 15 seconds to visually inspect about 100 nuts per tree; monitoring 15 to 20 trees in a 5 to 10-acre area. Moreover, the University of California, Pest Management Guidelines recommends monitoring by examining nuts on the ground and in the tree for gummosis.  Keep in mind that gummosis from LFB or other stink bug feed appears clear while gummosis from other

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Leaffooted Bug Aggregations Have Begun to Disperse

  Winter temperatures this 2016 / 2017 season were not cold enough to have any negative impact on overwintering populations of leaffooted bug.  Since mid-October we have monitored large populations on a ½ mile-long pomegranate hedgerow in the Parlier area.  Aggregations averaged about 206 individuals on 19 October with just over 50% of the individuals at the 4th and 5th instar stage.  Temperatures remained mild through November and by the month’s end aggregation size averaged ~30 individuals with 16 and 66% of the bugs at the 5th and adult stage respectively.  The decrease in aggregation size likely occurred due to new adults leaving and not adult or nymph mortality.  The temperature did reach a low of 27° F during the early morning hours of 20 December yet no adult or nymph mortality occurred. Our data suggest that female leaffooted bug began laying eggs on the pomegranate during early September and an entire generation was produced by the end of November.  As the temperatures cooled and the pomegranates began losing leaves and the fruit rotted and dropped, essentially all the adults left for more sheltered overwintering sites. In this case, several thousand of those individuals moved to a nearby palm tree and large Cyprus trees. We have closely monitored the aggregations on the Cyprus trees since mid-February and until early-March the aggregations have remained compact consisting of roughly 5 to 40 adults.  Temperatures have now warmed and we are seeing smaller aggregations, greater flight activity, and individuals on nearby citrus trees.  I interpret this increase in leaffooted bug activity as an indicator that the bugs have begun to disperse and will soon move into almond in search of food. Weekly monitoring should begin within the next seven to 10 days through May, and then every one to two weeks through June. 

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