What drives host plant choice? Linking Australian plague locust (Chortoicetes terminifera) host plant preference to water content, leaf thickness, and plant nutrient content

Host plant choice by herbivorous insects can be driven by a variety of factors including plant nutrient composition and mechanical properties. In this study, I investigated the role of plant protein and carbohydrate composition, water content, and leaf thickness on plant preference for the Australian Plague Locust (Chortoicetes terminifera). For this, I used four economically important cereal crop species: barley Hordeum vulgare, wheat Triticum aestivum L., rye Secale cereale, and corn Zea mays. Using a full factorial design, I gave the choice to the locusts between two plant species then I measured 1) visual preference by pairing, 2) surface area consumed, and 3) dry mass consumed. For each leaf, I measured protein content, carbohydrate content, foliar wet mass, and Specific Leaf Area (SLA, a measure of plant thickness). I found plant nutrient content was not a good predictor of host plant choice in the short term, however, leaf thickness had a significant relationship with dry amount of leaf consumed and defoliation. Overall locusts preferred plants that were thinner. I discuss these results in light of our current knowledge of the nutritional ecology of this important cereal crop pest.