Effect of induced plant resistance on soybean looper (Chrysodeixis includens) in soybean

Soybean looper, Chrysodeixis includens (Walker), is one of the most destructive pests of soybean.  Soybean looper defoliation exceeding 20% from R1 (1^st flower) to R6 (full pod fill) can result in significant yield loss.  In addition, soybean looper is highly resistant to many insecticides.  An alternative control tactic is induced host plant resistance.  In this study, three different known SARs; acibenzolar-S-methyl, extract of Reynoutria sachalinensis, and methyl jasmonate (MeJA), were applied to soybean at R2 (full flowering) and R5 (pod filling) to determine if these chemicals could induce plant resistance and lower soybean looper fitness.  In addition, water and flubendiamide were added as checks.  Forty-eight hours after application, leaf tissue was used in a laboratory bioassay.  Leaf cores were cut and fed to neonate soybean looper larvae.  Each experiment was replicated three times with 50 neonates per replicate.  None of the SARs significantly reduced mortality.  However, MeJA reduced pupal weights by 6.8% and increased leaf consumption by 4.8%.  Twenty adults from each treatment were allowed to mate and oviposit and % egg hatch was calculated.  None of the SARs impacted egg hatch.  Amongst soybean growth stages, soybean looper had higher pupal weights and consumed more on R2 tissue than R5.