|TOEWS, MICHAEL - University Of Georgia|
|BUNTIN, G. DAVID - University Of Georgia|
Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 12/1/2013
Publication Date: 12/1/2013
Citation: Ni, X., Toews, M.D., Buntin, G. 2013. Assessment of 25 grain sorghum hybrids for resistance to insect and bird damage at three planting dates in 2013. In: J. L. Day, A. E. Coy, and J. D. Gassett (eds.). Georgia 2013 Soybean, Sorghum Grain and Silage, and Summer Annual Forages Performance Tests. Georgia Agricultural Experiment Station Publication. 103-5.
Interpretive Summary: not required
Technical Abstract: Twenty-five grain sorghum hybrids were evaluated for resistance to insect and bird damage with three planting dates in 2013, at the Belflower Research Farm near Tifton, GA. Although the damage was relatively low in 2013, five insect pests were observed on the grain sorghum hybrids. In order of importance they include: headworm complex (i.e., corn earworm, and sorghum webworm), leaf-footed bug, stink bugs (southern green stink bug and brown stink bug), sorghum midge, and fall armyworm. Generally speaking, insect infestation and disease infection rates were low in the experimental plots of these hybrids in 2013. Hybrids were planted with 4 replications each on May 21, May 29, and June 6, 2013, respectively, and maintained with irrigation. The flowering date (or days to anthesis) was recorded throughout July and August. Flowering time (50% plants with flowering panicles) of the 25 hybrids ranged from 51 to 67 days after planting (Table 1). The whorl damage by natural fall armyworm population was minimal and therefore not assessed. Sorghum midge and bird damage were rated 14 weeks after planting (on August 27, September 3, and September 10, 2013, respectively). The sorghum midge damage was rated according to the visual estimates of grain loss. Grain loss caused by the midge infestation can be separated from other factors using the whitish-cast skins hanging at the tip of glumes during pre-harvest examination. The sorghum midge damage was assessed according to the following rating scale: Very Good (VG) = 0-15%; Good (G) = 16-30%; Fair (F) = 31-75%; and Poor (P) = = 76% empty glumes per sorghum panicle. In addition, the assessment of bird damage on developing kernels was based on the following scale: Very Good (VG) = less than 10% loss; Good (G) = 11-25% loss; Fair (F) = 26-50% loss; and Poor (P) = = 51% loss of grains per panicle. The sorghum midge is a cyclic insect pest in grain sorghum production in the southern Coastal Plain region. Overall damage caused by sorghum midge is generally greater on late flowering hybrids, or late planted hybrids. The midge damage was very low in these 25 hybrids in 2013 across planting dates. Of the three planting dates in 2013, no midge damage was observed in the May 21 planting; the majority of observed damage occurred only in a few hybrids planted on June 6. Average midge damage was rated as Very Good (< 15% grain loss), in 11 of the 25 hybrids evaluated. In addition, all entries showed relatively high levels of bird damage when compared with the previous year. The midge and bird damage was evaluated 98 days after planting and approximately one month after flowering. The bird damage ratings in 2013 were relatively high (= 26% or ¼) in comparison with the previous years. Only two hybrids ‘NK8828’ and ‘NK8831’ exhibited low bird damage ratings (= 25%). Of the three planting dates in 2013, experimental plots from the first planting showed more bird damage than either of the two late plantings. Managers should be aware that bird damage could be reduced by timely harvest as well. 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 the southern Coastal Plain. The information on both insect and bird damage might vary based on planting dates, with later plantings tending to have increased insect pest pressure. 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, Jonathan Roberts, and Austin Overton from the Crop Genetics and Breeding Research Unit, USDA-ARS, University of Georgia, Tifton, Georgia, with assistance from Xing Wei at the Department of Entomology, University of Georgia at Tifton, Georgia.