cis-Jasmone treatments affect pests and beneficial insects of wheat (Triticum aestivum L.): the influence of doses and plant growth stages

cis-Jasmone (CJ) is a natural plant volatile derived from linolenic acid via the octadecanoid pathway, and acts as a semiochemical and plant defense elicitor. In the present study, the effects of three different CJ doses (25 g.ha(-1); 50 g.ha(-1); 100 g.ha(-1)), applied at two different wheat growth stages (flag leaf just visible and emergence of inflorescence completed), on wheat insect pests and beneficial insects were investigated using three different sampling methods (direct visual counting, sweep-netting, colored sticky traps) under semi-arid conditions during 2011-2013. Depending on the insect species, CJ dose-effects varied with study years, plant growth stages and/or sampling methods. Among the pest species, cereal aphids (apterous and alate) were the most prominently affected by CJ treatment, irrespective of the dose; fewer aphids were detected on the CJ-treated plants than on untreated control plants by direct visual counting, sweep net and yellow sticky trap samplings. CJ treatment also had deterrent effects on phytophagous thrips species and wheat stem sawflies (Hymenoptera: Cephidae), whereas CJ was an attractant for aphid parasitoids, coccinellid species and the wheat stem sawfly parasitoid Collyria coxator (Hymenoptera: Ichneumonidae). CJ treatment had no effect on syrphid species (Diptera: Syrphidae). There was no significant effect of CJ treatment on wheat yield; however, CJ-treated plants were taller than untreated control plants. Although the behavioral responses of the studied species to CJ treatment varied with the plant growth stage and treatment dose, and were not consistent across all sampling methods, our findings indicate CJ treatment may be used to reduce some insect pest populations and manipulate some natural enemy species under field conditions.