Insecticide resistance and efficacy of novaluron and flonicamid for control of Lygus bugs in alfalfa seed
Parma Research and Extension Center, Department of Plant Soil and Entomological Sciences, University of Idaho, Parma, ID, USA
Correspondence: jbarbour@uidaho.edu
Lygus bugs, mostly Lygus hesperus Knight and L. elisus Van Duzee (Heteroptera: Miridae) are the most important insect pest of alfalfa seed in Idaho, commonly exceeding established economic thresholds and commonly require three or more pesticide applications each growing season for their control. Because alfalfa seed yields are highly dependent on the number and activity of bees used for pollination, management strategies that limit negative impacts on pollinators are key elements in integrated management programs for Lygus bugs in alfalfa seed. Lygus bugs in alfalfa seed are primarily managed by application of broad spectrum organophosphate, carbamate and pyrethroid insecticides. Although a number of compounds are currently available, the usefulness of these compounds is limited by a number of factors including their toxicity to pollinators, insecticide resistance management, and the presence of other pests and presence of predators and parasitoids of Lygus bugs and other pests. Experiments were conducted in 2006 to determine if two new, low risk compounds, novaluron and flonicamind, could provide effective control of Lygus when applied pre-bloom (prior to bee release). Numbers of Lygus were very high during the study with peak numbers exceeding 70 per sweep on untreated plots. Although most treatments reduced numbers of Lygus nymphs below levels found in untreated plots, none reduced numbers to threshold levels. Numbers of nymphs were lower on plots treated with flonicamid or lambda cyhalothrin, but remained above threshold on all plots. Treatments combining novaluron with lambda cyhalothrin appeared to give better control than novaluron alone. Alfalfa seed yields which were also higher in plots treated with flonicamid, lambda cyhalothrin and lambda cyhalothrin plus novaluron than in untreated plots.
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