Evaluation of insect, disease, and bird damage in grain, silage, and forage sorghum hybrids in 2024

Authors: Ni, Xinzhi; MAILHOT, DANIEL - University Of Georgia; Harris-Shultz, Karen; Knoll, Joseph; UYI, OSARIYEKEMWEN - University Of Georgia; TOEWS, MICHAEL - University Of Georgia; DUNN, DUSTIN - University Of Georgia; BUNTIN, G. DAVID - University Of Georgia

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 10/25/2024
Publication Date: 12/16/2024
Citation: Ni, X., Mailhot, D.J., Harris-Shultz, K.R., Knoll, J.E., Uyi, O., Toews, M.D., Dunn, D., Buntin, G. 2024. Evaluation of insect, disease, and bird damage in grain, silage, and forage sorghum hybrids in 2024. pp. 41-46 In: Mailhot, D.J., et al. (eds.). Georgia 2024 Corn, Sorghum, and Summer Annual Forages Performance Tests. Georgia Agricultural Experiment Station, Annual Publication. 101-16.

Interpretive Summary: not required.

Technical Abstract: Basic field plot information: The commercial hybrids of grain, silage and forage sorghum were evaluated at Tifton, GA to identify the best performing hybrids. For the silage and forage trials, the plots were planted as 20-foot, four-row plots in a randomized complete block design with three replications, while the grain sorghum trial was planted with a similar design of two-row plots and four replications. In contrast to previous growing season, the 2024 season had very low sorghum aphid infestations in all trials, possibly due to frequent rainfalls. While silage and forage sorghum trials were planted on April 9, 2024, the grain trial was planted on June 3, 2024. The forage trial was evaluated prior to the two harvests on July 1, and August 13, 2024, respectively. The silage trial was evaluated on July 29, 2024, before the harvest. The grain sorghum trial was evaluated for anthracnose and corn leaf aphid on July 16, 2024, before flowering. Sorghum aphid damage was rated on August 12, and panicle feeding insect and bird damage were evaluated before harvest on September 20, 2024. A total of ten insect pests were observed throughout the 2024 field season. Foliar-feeding insects included fall armyworm, sorghum aphid (Melanaphis sorghi, also known as sugarcane aphid), corn leaf aphid, and chinch bug at the seedling stage. Panicle/kernel-feeding insects included sorghum headworm complex (corn earworm and sorghum webworm), stink bugs (southern green and brown stink bugs), sorghum midge, and leaf-footed bug after flowering. Although the infestations of some insect pests (such as foliar-feeding fall armyworm and chinch bug, and kernel-feeding sorghum midge, stink bugs, and leaf-footed bug) occurred in 2024, they were not included in this report because their very low infestations caused minimal damage. For sorghum diseases, only prevalent anthracnose infection was evaluated. Bird damage on grain sorghum was also evaluated. The main bird species has been identified previously as brown-headed cowbird. Rating scales used for hybrid evaluations: In all trials, sorghum growth stage was assessed using a scale of 0-9 based on the publication S3 by the Kansas-State Research and Extension Service (https://bookstore.ksre.ksu.edu/pubs/MF3234.pdf). Lodging percentage was estimated on the silage and forage sorghum trials. The number of sorghum aphids was estimated by averaging the number of aphids on 6 mid-canopy leaves (or top and bottom green leaves of three randomly sampled plants) per plot. The number of aphids per leaf was estimated using the following scale: 0=no aphid, and then estimated as 1 =1-25 aphids, 2 =26-50, 3 =51-100, 4 =101-500, 5 =501-1000, and 6 =over 1000 aphids. Aphid damage on plants was rated using a 1-9 scale. The scale of 1-9 is described as follows; 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. However, in grain sorghum, sorghum aphid infestation was limited, but corn leaf aphid infestation and damage on whorl tissue was prevalent. Corn leaf aphid damage on sorghum plants was assessed at pre-flowering, using a binary rating scale, 0 = no infestation; and 1 = whorl tissue of sorghum plants was colonized with corn leaf aphids, and purple leaf discoloration was observed. In addition, headworm, and bird damage were assessed by the percentage of damaged kernels per panicle for the grain sorghum trial. Severity of anthracnose infection was rated using a 1-5 scale, where 1 = no symptoms, 2 = colored spots on leaves but no sporulation, 3 = some sporulation on lower leaves, 4 = moderate sporulation, 5 = heavy sporulation up to the flag leaf. In addition, bird feeding damage on grain sorghum was visually assessed by per centage of kernel loss per panicle in an experimen