Evaluation of insect, disease, and bird damage in grain, silage and forage sorghum hybrids in 2023

Authors: Ni, Xinzhi; MAILHOT, DANIEL - University Of Georgia; Harris-Shultz, Karen; Knoll, Joseph - Joe; 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: 11/13/2023
Publication Date: 11/15/2023
Citation: Ni, X., Mailhot, D.J., Harris-Shultz, K.R., Knoll, J.E., Uyi, O., Toews, M.D., Dunn, D., Buntin, G. 2023. Evaluation of insect, disease, and bird damage in grain, silage and forage sorghum hybrids in 2023. In: D.J. Mailhot, D. Dunn, and G. Ware. D. Buntin, X. Ni, and M. Toews (eds). Georgia 2023 Corn, Sorghum, and Summer Annual Forages Performance Tests. Georgia Agricultural Experiment Station Annual Publication. pp. 45-49.

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 2023 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 21, 2023, the grain trial was planted on May 31, 2023. The forage trial was evaluated on July 3, 2023, prior to the harvest. The silage trial was evaluated on July 20, 2023, before the harvest. The grain sorghum trial was evaluated before harvest on September 21, 2023. A total of ten insect pests were observed throughout the 2023 field season foliar-feeding fall armyworm, sorghum aphid (Melanaphis sorghi, also known as sugarcane aphid), corn leaf aphid, and chinch bug at the seedling stage, and 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. Bird damage on grain sorghum was also evaluated. 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 2023, they were not included in this report because their very low infestations caused minimal damage. 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). 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. Hybrid ranking criteria: The overall hybrid rankings in 2023 were based on principal component analysis results. Hybrids in a trial were designated as Very Good (VG), Good (G), Fair (F), and Poor (P), respectively. Results from grain, silage and forage sorghum trials: A total of 20 grain sorghum hybrids (Table 1) were evaluated. While low sorghum aphid infestation and minimal sorghum aphid damage was observed, corn leaf aphid infestation was prevalent on whorl tissue at pre-flowering stage in 2023 as shown in Table 1. Thus, the parameters used for grain sorghum evaluation in