Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: December 15, 2010
Publication Date: January 10, 2011
Citation: Ni, X., Buntin, G., Wilson, J.P. 2010. Insect and bird resistance in 11 grain sorghum hybrids - 2010. In: Day, J. L., Coy, A. E., and Rose, P. A., editors. Georgia 2010 Soybean, Sorghum Grain and Silage, and Summer Annual Forages Performance Tests, Georgia Agricultural Experiment Stations, Annual Publication 103-2, Athens, GA. Interpretive Summary: not required
Technical Abstract: Grain sorghum is a good rotation crop in the southern Coastal Plain region, where it can be affected by a variety of insects and pathogens from the seedling stage through maturity. Diseases were of minimal importance in 2010. Although their damage was relatively low, nine insect pests were recorded on sorghum in southern Georgia in 2010. They could be listed in order of importance as follows: fall armyworm, corn leaf aphid, sorghum midge, stink bugs (southern green and brown stink bugs), leaf-footed bug, chinch bug, sorghum head worm complex (mainly sorghum webworm, and corn earworm). It was the first time in 7 years we observed corn leaf aphid damage on sorghum plants at the 6- to 8-leaf stages. The damage symptom could be identified by its typical reddish discoloration at the whorl or on the young developing leaves. Eleven hybrids were evaluated for resistance to sorghum midge in 2010. The hybrids were planted with 4 replications on June 23, 2010. The flowering date (or days to anthesis) was recorded during August. The fall armyworm and aphid damage was assessed on July 23, and August 2, 2010, respectively. Because the foliar damage ratings were not statistically significant among the 11 hybrids, the data were not included in the report. Sorghum midge damage was rated on Oct. 2, 2010. Midge damage was rated according to the visual estimates of grain loss. Grain loss caused by midge infestation can be separated from other factors using the whitish-cast skins hanging at the tip of glumes during pre-harvest examination. Sorghum midge damage was assessed according to the following rating scale; Very Good = 0 - 15% of empty glumes on any of the sorghum panicles in an experimental plot; Good = a few empty glumes (16-30%) observed on a panicle; Fair = 31-75% of empty glumes on a sorghum panicle; and Poor = majority of sorghum panicles with more than three quarters (> 75%) of empty glumes. Because bird damage on sorghum panicles is usually observed every year, we began to assess the hybrid resistance to bird feeding on developing kernels this year. Bird-feeding resistance was rated by following rating scale; Very Good (VG) = less than 10% grain loss; Good (G) = 25% loss; Fair (F) = 50% loss; and Poor (P) = over 75% loss. The sorghum midge is a cyclic insect pest in grain sorghum production in the southern Coastal Plain region. The overall damage caused by sorghum midge is usually high on late flowering hybrids. Midge damage was low in general for 2010, which could be the result of dry weather conditions, although we planted late this year. For midge resistance, most of the hybrids (7 of the 11 entries) were rated as Very Good (VG) with at least 2-year rating data. At the same time, seven of the 11 hybrids were also identified for bird-feeding resistance (differed from the midge resistance) in 2010. It is highly recommended that growers use available insect and disease-resistant hybrids, which is one of the most economical pest management strategies for sorghum production in our region. The information on bird resistance might vary based on planting dates. For further integrated insect management information, please consult with your local county agent and/or extension entomologists. This test was maintained and flowering-date data were collected by Penny Tapp from the Crop Genetics and Breeding Research Unit, USDA-ARS, Coastal Plain Experiment Station, UGA-Tifton, Georgia.