Integration of systemic fungicides and permethrin for control of nursery-attacking ambrosia beetles

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are important pests of nursery crops. This study evaluated systemic fungicides alone or with an insecticide (permethrin) for preventing ambrosia beetle attacks on flood-stressed containerized Eastern redbud (Cercis canadensis L.) trees in the presence or absence of Phytophthora cinnamomi Rands. For Objective, effective fungicides such as (Orkestra Intrinsic [hereafter Orkestra], Segovis, or Subdue MAXX [hereafter Subdue] applied 3 wk before flooding) were tested in repeated trials with or without permethrin trunk sprays (applied 2 d before flooding). In all experiments, treatments were divided into groups with or without P. cinnamomi inoculations.  Tests were conducted near forest borders at the Tennessee State University Otis L. Floyd Nursery Research Center, McMinnville, TN.  Results for this Objective, Orkestra with permethrin consistently reduced ambrosia beetle attacks and inhibited gallery formation in inoculated or non-inoculated trees. In addition, permethrin with Segovis or Subdue reduced ambrosia beetle attacks and gallery formation, but inconsistently in different trials. Overall, fungicides applied 3 wk before flooding was more effective in preventing beetle attacks than 1 wk before flooding, indicating more time before flooding events may improve fungicide translocation and protection. Moreover, trees inoculated with Phytophthora received more ambrosia beetle attacks than non-inoculated trees, indicating disease stress was detrimental to trees and fungicide protection from beetles. In conclusion, some fungicides can prevent ambrosia beetle damage in tree crops and combining fungicides with an insecticide like permethrin provided a greater enhancement of tree protection from ambrosia beetles.