Put Leaffooted Bug Monitoring on Your To-Do List

Written By Kris Tollerup, UC IPM Advisor for the San Joaquin ValleyUnlike 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 physiological or diseases often appear amber.  To help confirm that the damage occurred from LFB feeding, cut the nut beneath the gummosis and a distinct puncture wound should be visible.  No economic thresholds exist therefore growers and PCAs must assess the economic threat based on the number of bugs observed, damaged nuts, as well as the orchard’s history.Over the past few years, I have learned a great deal about the life history for leaffooted bug.  My data indicates that the species moves into pomegranate in September, lays eggs and produces the lion share of an overwintering generation by mid-November.  As individuals develop into adults they move to more sheltered overwintering sites.  This aspect of their life history provides an opportunity to 1) effectively assess populations that can affect neighboring almond, as well as pistachio orchards.  And 2) provides the chance to kill the leaffooted bug as nymphs before developing into adults.The bottom line is that when leaffooted bug are found in an orchard and deemed an economic threat, chemical intervention remains the only option.  Several compounds have California registration on almond, however only pyrethroids provide any residual activity.  I have evaluated pyrethroid alternatives, such as pyrethrum, and clothianidin but these compounds have no residual activity.If you have questions regarding monitoring and or management of leaffooted bug please contact me directly at : ketollerup@ucar.edu.Insecticide use should occur only if monitoring indicates the presence of leaffooted bug and/or its feeding damage.  Apply insecticides only after considering the potential risks of the compound 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 > Agricultural pests > Almond