Location: Crop Genetics and Breeding ResearchTitle: Resistance to insect and bird damage in sorghum hybrids - 2016
|Knoll, Joseph - Joe|
|TOEWS, MICHAEL - University Of Georgia|
|BUNTIN, G. DAVID - University Of Georgia|
Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 12/5/2016
Publication Date: 12/1/2016
Citation: Ni, X., Harris-Shultz, K.R., Knoll, J.E., Toews, M.D., Buntin, G. 2016. Resistance to insect and bird damage in sorghum hybrids - 2016. In: J.D. Gassett, D. Dunn, A.E. Coy, H. Jordan, Jr., and J.L. Day (eds.). Soybean, Sorghum Grain and Silage, and Summer Annual Forages Performance Trials, Georgia Agricultural Experiment Station, Annual Publication 103-8, pp. 63-69.
Interpretive Summary: not required.
Technical Abstract: A total of 80 (7 for pearl millet and 73 for grain and forage sorghum) hybrids and a pair of sugarcane aphid resistant and susceptible controls were evaluated for resistance to insect and bird damage in Tifton, Georgia. Sugarcane aphid resistance also was evaluated in a separate trial near Griffin, Georgia. In Tifton, a total of 10 insect pests were observed. The insect pests in order of importance are: sugarcane aphid, fall armyworm, corn earworm, sorghum webworm, sorghum midge, leaf-footed bug, corn leaf aphid, stink bugs (southern green and brown stink bugs), and chinch bug. In comparison with sugarcane aphid and fall armyworm damage, damage from other insect pests and birds was relatively low in 2016. Foliar diseases were of minimal importance in this trial, and were not included in this report. Heavy sugarcane aphid infestation occurred at the late seedling stage (or close to flowering) was observed in the experimental plots that were planted on June 9, 2016. Sugarcane aphid infestation occurred later than the previous year (2015), and all grain sorghum entries produced panicles in 2016. Missing values in the “Days to Anthesis” column of Table 1 indicate these hybrids did not flower by September 25, 2016. Hybrids that did not flower were forage lines and were photoperiod sensitive. In addition to the heavy aphid infestation, fall armyworm damage at the whorl stage in 2016 was high. Thus, the overall insect resistance rankings (i.e., Very Good, Good, Fair. and Poor) for 2016 was based mainly on the combined sugarcane aphid and fall armyworm damage ratings (LSD=0.42), and adjusted with panicle damage as shown in Table 1. Fall armyworm damage was rated using the 1-9 scale with 1= no damage and 9 = all plants in a plot is completely defoliated. Sorghum webworm, midge, and bird damage were ranked before harvest on September 15-16, 2016. Headworm damage (i.e., sorghum webworm and corn earworm), and midge damage were assessed in combination with grain loss according to the following rating scale: 1 = 0-25% empty glumes on any of the sorghum panicles in an experimental plot; 2 = a few empty glumes (26-50%) observed on a panicle; 3 = 51-75% empty glumes on a sorghum panicle; and 4 = majority of sorghum panicles with more than three quarters (> 75%) empty glumes. Finally, bird feeding damage on developing kernels was determined by presence of partial kernels on panicles, and evidence of splattering of broken developing kernels falling on top leaves of a plant. Bird damage was rated with the following scale: 1 = less than 10% grain loss; 2 = 11-25% loss; 3 = 26-50% loss; and 4 = > 50% loss of grains per panicle. Sorghum hybrids were rated for susceptibility to sugarcane aphid infestation and damage in trials at Tifton and near Griffin, GA. At Tifton. sugarcane aphid damage was rated multiple times throughout the season, but the ratings recorded on August 28, and September 15-16, 2016 was used for this report, because these two ratings best characterized the aphid damage (leaf discoloration) before regrowth of green tillers appeared. SCA damage in Tifton was ranked using the following 1-5 scale: 1 = no visible aphid damage, and only a few winged aphids colonizing the leaves; 2 = a lot of aphids without visible leaf damage symptoms, but with honeydew visible on the surface of lower leaves; 3 = high aphid population with lower leaves covered with honeydew, sooty mold and aphid exuviae (or whitish-caste skins); 4= heavy aphid infestation with visible leaf discoloration; and 5 = sorghum plants were killed by heavy aphid infestation. In Griffin, entries were planted in plots of 2 rows by 20 ft and replicated three times. SCA infestations were counted on 6 leaves per plot on Aug. 15 and plant injury was rated August 19 and September 1, 2016. Plant injury was rated on a 0 – 9 scale of Burd et al. (1993) where 0 = no injury a