Damage rates to pearl millet by adults of five grasshopper species and Psalydolytta blister beetles in Mali

Abstract

Five grasshopper species were caged over milk stage millet panicles to determine relative damage rates. Psalydolytta spp. blister beetles were caged over flowering stage millet panicles. The grasshopper Hieroglyphus daganensis was caged on flowering, milk and dough stage panicles. The standard treatment used was two insects caged per panicle for 4 days. Highest damage rates per insect were obtained from Psalydolytta spp., at 10.3 cm² millet surface area per day, Kraussaria angulifera at 4.3 cm² per day, and Cataloipus cymbiferus at 3.3 cm² per day. The average insect weight was correlated with damage rate (r = 0.93), and the number of insects requiring replacement was negatively correlated with damage rate (r = —0.69). Damage per insect dry weight (g) was highest for Psalydolytta spp. and the smaller grasshoppers Kraussella amabile and Oedaleus senegalensis at 25.8, 7.9, and 6.4 cm²/g per day, respectively. Highest damage levels from H. daganensis occurred during the early and middle milk stage. Damage rates were relatively low during the early flowering and mid‐late dough stages. The percentage weight of grain kernels remaining after grasshopper feeding was 35–70% when exposed to grasshoppers during late milk and dough stages and 10–35% when exposed during the early milk stage. A formula and example calculations for estimating economic injury levels are provided.

Keywords:

• Pearl millet
• Pennisetum americanum
• Psalydolytta
• Kraussaria
• grasshopper
• economic injury level
• crop loss