Grain, silage and forage sorghum hybrid resistance to insect and bird damage, 2017

Authors: BUNTIN, G - University Of Georgia; Ni, Xinzhi; Harris-Shultz, Karen; Knoll, Joseph - Joe; TOEWS, M - University Of Georgia; DUNN, D - University Of Georgia

Submitted to: Experiment Station Bulletins
Publication Type: Experiment Station
Publication Acceptance Date: 12/15/2017
Publication Date: 12/29/2017
Citation: Buntin, G.D., Ni, X., Harris-Shultz, K.R., Knoll, J.E., Toews, M.D., Dunn, D. 2017. Grain, silage and forage sorghum hybrid resistance to insect and bird damage, 2017. In D.J. Mailthot, D. Dunn, H. Jordan, Jr., and J.L. Day (eds), Georgia 2017 Soybean, Sorghum Grain and Silage, and Summer Annual Forages, Georgia Agricultural Experiment Stations, Annual Publications. 103-9, pp. 74-80. http://www.swvt.uga.edu/2017/SYSR17/AP103-9-sr-resist.pdf.

Interpretive Summary: not required.

Technical Abstract: A total of 32 grain and 30 forage type sorghum hybrids were evaluated for resistance to insect, disease, and bird damage in Tifton, Georgia. These hybrids plus 33 silage type and 5 pearl millet hybrids also were evaluated for sugarcane aphid resistance near Griffin, Georgia. A total of 10 insect pests were observed in Tifton. The insect pests in order of importance are: sugarcane aphid, sorghum webworm, sorghum midge, leaf- footed bug, fall armyworm, corn earworm, corn leaf aphid, stink bug (southern green and brown stink bug), and chinch bug. In comparison with the sugarcane aphid population and its damage, sorghum webworm, midge, and bird damage were relatively low in 2017. Due to low populations, fall armyworm, corn earworm, leaf-footed bug, stink bug, and chinch bug damage data were not included in this report. In addition, diseases were of minimal importance in grain sorghum trials. Sugarcane aphid numbers and damage were rated several times at each location and the average aphid numbers and damage ratings are presented. At Tifton, aphid numbers were estimated using a 0-6 scale: 0 = no aphid, 1 = 1-25, 2 = 26-50, 3 = 51- 100, 4 = 101-500, 5 = 501-1000, and 6 = over 1000 aphids, but at Griffin the number of aphids per leaf were counted. At both locations, aphid damage was rated using a 1-9 scale: 1 = no damage, 2 = 1-20%, 3 = 21-30%, 4 = 31-40%, 5 = 41-50%, 6 = 51-60%, 7 = 61-70%, 8 = 71-80%, and 9 = greater than 81% of the leaves are dying, which also included aphid-killed plants. At Tifton, sorghum webworm and midge damage were assessed in combination with grain loss according to the following rating scale: Very Good (VG) = 0-15% empty glumes on any of the sorghum panicles in an experimental plot; Good (G) = a few empty glumes (16-30%) observed on a panicle; Fair (F) = 31-75% empty glumes on a sorghum panicle; and Poor (P) = majority of sorghum panicles with more than three quarters (> 75%) empty glumes. Finally, bird-feeding damage on developing kernels was determined by the presence of partial kernels on panicles, and evidence of splattering of broken developing kernels falling on the top leaves of a plant. Bird damage was rated with the following scale: Very Good (VG) = less than 10% grain loss; Good (G) = 11- 25% loss; Fair (F) = 26-50% loss; and Poor (P) = > 50% loss of grains per panicle. Large sugarcane aphid infestations were observed on seedling and vegetative stage plants planted on June 9 at Tifton and June 11 at Griffin. Sugarcane aphid infestation, which generally occurred between mid-July and early August, was so severe that it halted normal plant development before flowering; as a result 19 grain sorghum hybrids did not produce panicles (Table 1A). Although 13 entries produced panicles, only 8 of them consistently produced panicles in all four replications. Any panicles from delayed tillers after aphid population crash were not included in the table. Most of these hybrids aborted their panicle development at the flag leaf (or boot) stage. Results from 2017 showed that sugarcane aphid infestation at the seedling stage is much more severe than the post-flowering infestation observed in previous years. Only eight of the 13 grain sorghum hybrids consistently produced normal panicles from all four replications of the trial in both Griffin and Tifton locations. Four of the eight hybrids are from Dyna-Gro, ‘GX15371’, ‘GX16833’, ‘GX17818’, and ‘M74GB17.’ The other four best performing hybrids are ‘CHROL2042’ from Chromatin, ‘SP7715’ and ‘SP78M30’ from Sorghum Partners, and ‘DKS48-07’ from DeKalb. It is important for us to point out that some of these best performing hybrid seeds were treated with insecticides. ‘CHROL0029’ from Chromatin showed better aphid resistance at the Griffin location than in Tifton (Table 1A). While Dyna-Gro treated with DS Imidacloprid and DeKalb seeds were treated with Pon