Antixenosis, Antibiosis, and Potential Yield Compensatory Response in Barley Cultivars Exposed to Wheat Stem Sawfly (Hymenoptera: Cephidae) Under Field Conditions

Abstract

Wheat stem sawfly, Cephus cinctus Norton, is an economically serious pest of cereals grown in North America. Barley cultivars were previously planted as resistant crops in rotations to manage C. cinctus, but due to increasing levels of injury to this crop, this is no longer a valid management tactic in Montana. Therefore, we aimed to understand antixenosis (behavioral preference), antibiosis (mortality), and potential yield compensation (increased productivity in response to stem injuries) in barley exposed to C. cinctus. We examined these traits in eight barley cultivars. Antixenosis was assessed by counting number of eggs per stem and antibiosis was assessed by counting infested stems, dead larvae, and stems cut by mature larvae. Potential yield compensation was evaluated by comparing grain yield from three categories of stem infestation: 1) uninfested, 2) infested with dead larva, and 3) infested cut by mature larva at crop maturity. We found the greatest number of eggs per infested stem (1.80 ± 0.04), the highest proportion of infested stems (0.63 ± 0.01), and the highest proportion of cut stems (0.33 ± 0.01) in ‘Hockett’. Seven out of eight cultivars had greater grain weight for infested stems than for uninfested stems. These cultivars may have compensatory responses to larval feeding injury. Overall, these barley cultivars contain varying levels of antixenosis, antibiosis, and differing levels of yield compensation. Our results provide foundational knowledge on barley traits that will provide a framework to further develop C. cinctus resistant or tolerant barley cultivars.

Plant Volatiles and Oviposition Behavior in the Selection of Barley Cultivars by Wheat Stem Sawfly (Hymenoptera: Cephidae)

“…We found a greater number of eggs per stem in 'Hockett' than in 'Craft' at both developmental stages (Table 3). Several previous studies have reported that 'Hockett' is preferred over 'Craft' by the number of eggs per stem (Varella et al 2018, Achhami et al 2020. Our results align with previously reported results that female prefers volatiles from susceptible cultivars and thus lays more eggs in wheat (Weaver et al 2009, Varella et al 2016) and now, in barley cultivars (Achhami et al 2020 a, b, c).…”

“…Second, barley production in Montana is the third highest in the United States (US Department of Agriculture 2020) and barley is becoming a more common host to C. cinctus. Third, in the past, barley was described as a resistant crop to C. cinctus (Farstad and Platt 1946), but recent studies have reported that both infestation rate and larval survival rate in barley are in increasing (Varella et al 2018, Achhami et al 2020c. Therefore, the question arises does the ovipositing female display a similar host selection and oviposition behaviors as is known for wheat cultivars?…”