Control of the Apple Clearwing Moth, Synanthedon myopaeformis, with Tree-Trunk Applications of Reduced-risk Insecticides, Nematodes and Barriers

Apple clearwing moth (ACM), Synanthedonmyopaeformis Borkhausen (Lepidoptera: Sesiidae), wasdiscovered in an apple orchard in Cawston, British Columbia in 2005.  This xylophagous, invasive Europeanspecies has become a serious problem in high-density apple orchards wheresize-controlling rootstocks are attacked by the wood-boring larvae.  Seven screening trials with reduced-riskinsecticides for conventional (seven treatments) and organic apple production (threetreatments) were established in two commercial high-density mixed-variety appleplantings in Cawston.  Our objectiveswere (1) to screen several new synthetic insecticides having novel chemistriesthat purportedly have reduced risks, (2) to evaluate use of several organically-approvedspray materials, including nematodes, and (3) to compare the efficacy ofvarious products when applied at different times during the growing season.  Single, hand-gun sprays delivering treatmentsin 2000 L of water ha-1 at 200 psi were applied as curative sprays targeting mature larvae inrootstock-scion graft unions in May and October 2008, and June 2009.  Among seven treatments tested, only theinsect growth regulator, Rimon® 10 EC (10% novaluron), at 2.4 L a.i.ha-1, caused significant reductions in adult emergence compared withuntreated controls in all experiments.  Whenapplied twice as preventativetreatments during flight of male ACM in 2008, Altacor®, Belt®,Delegate™ and Rimon all caused significant reductions in adult emergence thefollowing year; Rimon caused the greatest reduction (-96.4%).  In a similar 2009 trial only Rimon reducedpopulations the following year.  One curative or two preventative applications of the organic materials, Entrust®,Crocker’s Fish Oil®, or Purespray Green Oil™, at anyspray timing, did not control ACM.  The nematode,Steinernema feltiae (Filipjev) (1×105infective juvenile nematodes / 100 ml of water / tree) provided significant controlof ACM in one spring 2008 trial.  In two 2009nematode-only experiments, a sawdust paste tree-trunk barrier applied over nematodeapplications made either in May or August, caused significant reductions in emergenceof ACM adults.  Curative tree-trunk spraysof Rimon 10 EC at the tested rate are recommended for control of ACM inconventional apple orchards.  There is noeffective organic control for ACM at this time, but tree-trunk barriers andnematodes may warrant further study.