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ARS Home » Plains Area » Fargo, North Dakota » Edward T. Schafer Agricultural Research Center » Sunflower and Plant Biology Research » Research » Publications at this Location » Publication #324862

Title: Efficacy of insecticides to limit caterpillar damage to prairie cordgrass seed

item Prasifka, Jarrad
item PRASIFKA, PATRICIA - Dow Agrosciences
item LEE, D. - University Of Illinois

Submitted to: Arthropod Management Tests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/18/2016
Publication Date: 4/29/2016
Citation: Prasifka, J.R., Prasifka, P.L., Lee, D.K. 2016. Efficacy of insecticides to limit caterpillar damage to prairie cordgrass seed. Arthropod Management Tests. 41(1):tsw030. doi:10.1093/amt/tsw030.

Interpretive Summary: Larvae of the small moth, Aethes spartinana, feed on developing seeds and within stems of prairie cordgrass. When infestations are severe, these caterpillars destroy almost all seed produced by cordgrass plants. This interferes with the use of prairie cordgrass in conservation plantings of native species (seed often provided by NRCS), but also with breeding, as this species is being developed as a biomass crop. Larvae spend the winter in the base of plants and tunnel into new growth the following spring, so they may also limit the number of stems and biomass produced by infested plants. Because there are no effective options for managing this pest, insecticide trials were conducted in small plots in Illinois during 2010-2011. The insecticide Cobalt, was very effective at limiting seed damage in both years (reduced by 86-94% compared to untreated), while Radiant SC and Intrepid 2F provided slightly less protection in both years. These results show that Cobalt is effective at limiting damage to prairie cordgrass seed, but that Radiant and Intrepid are suitable options for using in a rotations to preserve efficacy of all insecticide classes.

Technical Abstract: The moth Aethes spartinana (Tortricidae) is a severe pest of prairie cordgrass, a native perennial grown for biomass and habitat restoration. Small larvae may damage 75% or more of developing seed as they feed, crawling through spikes. After feeding in the spikes, larvae enter stems and crawl downward, leaving clear evidence of infestation at the point of tiller entry. Overwintered larvae also tunnel into new growth the following spring, potentially limiting density of tillers and biomass production. To assess management options for serious infestations, two successive years of tests were used to evaluate the utility of conventional and reduced-risk insecticides in limiting caterpillar damage to prairie cordgrass. In 2010, biweekly applications in of a conventional insecticide (chlorpyrifos + gamma-cyhalothrin [Cobalt]), and a rotation of reduced-risk insecticides (spinetoram [Radiant SC] or methoxyfenozide [Intrepid 2F]) both succeeded in limiting A. spartinana damage, though Cobalt was more effective than the insecticide rotation. In 2011, Cobalt was again very effective. Radiant or Intrepid (evaluated separately), provided intermediate protection when damage was scored on the percentage of tillers with visible damage; when damage was assessed based on damage to spikelets, all three insecticides were statistically similar. When the percent of damaged spikelets was regressed onto the percent of damaged tillers for all plots, tiller damage was generally effective in predicting damage to spikelets. Data suggest that the conventional insecticide is effective at limiting A. spartinana damage, but use of reduced-risk options in a rotation may be beneficial. Also, within the range of spikelet damage observed (˜0–30%), examination of tillers may provide a more time-efficient estimate of losses than dissection of cordgrass spikes.