Evaluation of insect, disease, and bird damage in grain, silage and forage sorghum hybrids in 2022

Authors: Ni, Xinzhi; Harris-Shultz, Karen; Knoll, Joseph - Joe; 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: 2/13/2023
Publication Date: 2/28/2023
Citation: Ni, X., Harris-Shultz, K.R., Knoll, J.E., Toews, M.D., Dunn, D., Buntin, G. 2023. Evaluation of insect, disease, and bird damage in grain, silage and forage sorghum hybrids in 2022. In D.J. Mailhot, D. Dunn, and G. Ware (eds). Georgia 2022 Corn, Sorghum, and Summer Annual Forages Performance Tests. Georgia Agricultural Experiment Station Annual Publication. pp. 41-45.

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 four rows by 20 ft with a randomized complete block design and three replications, while the grain sorghum trial was planted with a similar design with two-row plots and four replications. The field season of 2022 had very low sugarcane aphid infestations in all trials, possibly due to frequent rainfalls. While silage and forage sorghum trials were planted on May 3, 2022, the grain trial was planted on June 8, 2022. The forage trial was evaluated twice on July 6, and August 31, 2022, respectively, prior to the two harvests. The silage trial was evaluated on July 27, 2022 before the harvest. The grain sorghum trial was evaluated before harvest on September 26, 2022. A total of seven groups of insect pests were observed throughout the field season of 2022: foliar-feeding fall armyworm, sugarcane aphid (also known as sorghum aphid at present), 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, stink bugs, chinch bug, and leaf-footed bug) occurred, they were not included in this report because the infestations caused minimal damage. It is worth noting that sugarcane aphid infestation and aphid damage were relatively low in all three trials, when compared to the data from the previous years as showing in the three tables. The sugarcane aphid (Melanaphis sacchari) has been re-designated as the sorghum aphid (Melanaphis sorghi). However, we are using the sugarcane aphid in the current report for easy comparison of the severity of this invasive pest damage across recent years (2015-2022). Rating scales used for hybrid evaluations: In all trials, growth stage was assessed based on 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). 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. The number of sugarcane 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. The root and/or stalk lodging was assessed by percentage of plants with root or stalk lodging per plot. In addition, headworm and midge, and bird damage were assessed by the percentage of damaged kernels per panicle for the grain sorghum trial. Hybrid ranking criteria: The overall hybrid rankings in 2022 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 22 grain sorghum hybrids were evaluated. Sugarcane aphid, headworm and sorghum midge damage, as well as anthracnose infection severity, were evaluated. S