Evaluation of insect, disease, and bird damage in grain, silage and forage sorghum hybrids in 2021

Authors: Ni, Xinzhi; UYI, OSARIYEKEMWEN - University Of Georgia; 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: 1/11/2022
Publication Date: N/A
Citation: N/A

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. The experimental plots were four rows by 20 ft and entries were planted in a randomized complete block design, with three replications for the silage and forage trials, and four replications for the grain sorghum trial. The field season of 2021 had very low sugarcane aphid infestations in all trials, because of unusual frequent rainfalls. While silage and forage sorghum trials were planted on April 21, 2021, the grain trial was planted on June 28, 2021. The number of sugarcane aphids and aphid damage on sorghum plants were evaluated before harvests on June 23, and July 29, 2021 for the forage and silage trials, respectively. The grain sorghum trial was evaluated before harvest on October 14, 2021. A total of seven groups of insect pests were observed throughout the field season of 2020: sorghum headworm complex (corn earworm and sorghum webworm), stink bugs (southern green and brown stink bugs), sorghum midge, and leaf-footed bug, fall armyworm, chinch bug, aphids (corn leaf aphid and sugarcane aphid). Bird damage was also evaluated. Although the infestations of some insect pests (such as, chinch bug, and stink bugs) occurred, they were not included in this report because the infestations caused minimal damage. The number of sugarcane aphids and their damage were not assessed in the late planted grain sorghum trial (Table 1), because there was extremely low level of aphid infestation and no aphid damage were observed throughout the crop cycle. Similarly, when compared to the data from the previous years, sugarcane aphid population and damage were also low in the silage and forage trials that were planted in April of 2021, as shown in Tables 2 and 3, respectively. Rating scales used for hybrid evaluations: Headworm, sorghum midge, and bird damage were assessed by the percentage of damaged kernels per panicle in the grain sorghum trial, while growth stage, lodging, and anthracnose damage were evaluated in the silage and forage trials. The growth stage was assessed based on a scale of 0-9 based on the publication S3 by the Kansas-State Research and Extension Service. The lodging was assessed by percentage of plants with root or stalk lodging per plot. 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. Hybrid ranking criteria: Hybrid performance was ranked based on the principal component analysis results (biplot separation). All hybrids were designated as Very Good (VG), Good (G), Fair (F), and Poor (P), respectively. The overall hybrid rankings in 2021 for grain and silage sorghum were based on principal component analysis, while the forage trial was rated VG for all entries, because no differences were detected among the entries based on the results of analysis of variance. Results from grain, silage and forage trials: A total of 18 grain sorghum hybrids (Table 1) were evaluated. Although sugarcane aphid damage was not observed