Insecticides are usually applied when the number of tarnished plant bugs on strawberry exceeds a preset threshold. The entomopathogenic fungus Beauveria bassiana is a potential nonchemical alternative that was tested, along with physical barriers, for tarnished plant bug control in a University research plot in Iowa. A commercial formulation of B. bassiana (Mycotrol) was compared with a standard insecticide (Danitol) and a 3 foot high plastic construction fence surrounding the plants beginning July 1.
Weekly applications of the fungus did not provide significant control of tarnished plant bug. Although there was a trend toward reduction in bug injury (buttoning), yield was not significantly different than for untreated plants. The plastic barrier reduced yield and berry number, possibly because insect pollination and/or light intensity was reduced.
On average, more than 40% of the tarnished plant bug nymphs collected from the fungus-treated plots had B. bassiana in or on their bodies, compared to about 7% in the untreated plots. Live spores were reaching their targets fairly often where the fungus was applied, but why didn't this result in reduced injury or increased yield? Perhaps adult bugs were not infected as often as the nymphs that were sampled, and those adults were responsible for most of the damage. Or maybe the spores that were on the collected nymphs didn't infect the bugs efficiently enough to have an effect on their feeding behavior or mortality. Further research is needed to determine whether timely overhead irrigation could increase the impact of B. bassiana on tarnished plant bug activity and mortality.
Gleason, M.L., N. Zriba, R. Elenz, G.R. Nonnecke, J. J. Obrycki, and D. R. Lewis. 1999. Field evaluation of Mycotrol (Beauveria bassiana) and physical barriers for control of tarnished plant bug (Lygus lineolaris) in day-neutral strawberries. Strawberry IPM Update 4(1): 1-3.
Biological Control Products Evaluated for Disease Control on Strawberry
Several biological control products are under trial for suppressing various plant pathogens. T22 (Bioworks Inc., Geneva, NY) is a strain of Trichoderma harzianum registered for use against Pythium, Rhizoctonia solani, Fusarium and Sclerotinia homeocarpa on a variety of vegetable crops and greenhouse ornamentals. T22 and Messenger (Eden Bioscience, Poulsbo, WA) were tested in Iowa against strawberry anthracnose and gray mold. Disease control products were applied to runoff.
None of the treatments significantly reduced disease incidence or improved yield in these trials. The biological control treatments even had lower yield than the unsprayed controls in the gray mold trials.
Gleason, M.L., N. Zriba, G.R. Nonnecke, and C. A. Dilley. 1999. Evaluation of biological control products for control of anthracnose on day-neutral strawberries. Strawberry IPM Update 4(1): 3.
Gleason, M.L., N. Zriba, G.R. Nonnecke, and C. A. Dilley. 1999. Evaluation of biological control products for control of gray mold on June-bearing strawberries-1998. Strawberry IPM Update 4(1): 4.
Weed Control by Corn Gluten Meal
Twenty-two plant species were screened for susceptibility to the natural herbicide corn gluten meal. Corn gluten meal reduced plant survival, shoot length and root development of all species tested. Black nightshade, common lambsquarters, creeping bentgrass, curly dock, purslane and redroot pigweed were the most susceptible species. Plant survival and root development for these weeds were reduced by >75% and shoot length was decreased by >50%. Catchweed bedstraw, dandelion, giant foxtail and smooth crabgrass had suvival and shoot length reduction of >50% and rooting reduction of >80%. Barnyardgrass, quackgrass and velvetleaf were the least susceptible species, with survival reduced by <30%.
Christians, N. 1999. Spectrum of weed control by the natural herbicide corn gluten meal (CGM). Strawberry IPM Update 4(1): 4-5.
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