Grasshopper Injury to Potato: Consumption, Effect on Photosynthesis, and Economic Injury Level

Abstract

Generalist grasshopper species feed at agricultural field edges, often triggering management practices because of defoliation injury. Few controlled studies in agroecosystems, however, have quantified grasshopper consumption or plant photosynthetic response to feeding. Consequently, we examined if injury caused by the red‐legged grasshopper Melanoplus femurrubrum (DeGeer), would influence the gas exchange parameters on the remaining tissue. We conducted this examination on three potato (Solanum tuberosum L.) cultivars (Norkotah, Atlantic, and Frito‐Lay proprietary) and at three times during potato growth (all post flowering). With injury rates of about 10 to 25%, we observed no significant change in photosynthetic rates on the remaining leaf tissue in any cultivar or in any of the three experiments. Additionally, we measured potato canopy area and, in the laboratory, placed individual M. femurrubrum on premeasured potato leaflets. Individual grasshoppers consumed a mean of 4.4 cm2 d−1 of leaf area. Early in the season when potato plant leaf area indices (LAIs) are less than about 4.5, grasshoppers have the potential to significantly reduce yield. When potato canopies reach LAIs of 5.0, however, which in Nebraska typically occurs in July when grasshopper numbers also increase, grasshopper densities are rarely high enough to justify treatment.