Grain, silage, and forage sorghum hybrid resistance to insect, disease, and bird damage 2019

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

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: 1/27/2020
Publication Date: 3/4/2020
Citation: Ni, X., Buntin, G., Harris-Shultz, K.R., Knoll, J.E., Toews, M.D., Dunn, D. 2020. Grain, silage, and forage sorghum hybrid resistance to insect, disease, and bird damage 2019. In: D.J. Mailhot, D. Dunn, and H. Jordan Jr. (eds), Georgia 2019 Corn, Sorghum Grain and Silage, and Summer Annual Forages Performance Tests. Georgia Agricultural Experiment Stations, Annual Publication. 101-11, pp. 51-59.

Interpretive Summary: not required

Technical Abstract: A total of 52 grain sorghum hybrids (Table 1) were evaluated for resistance to insect and bird damage in Griffin and Tifton, Georgia. At both locations, plots were two rows by 20 ft and entries were planted in a randomized complete block design with 3 replications at Griffin and 4 replications at Tifton. The Griffin and Tifton trials were planted on June 17th and July 11th of 2019, respectively. The Griffin location was evaluated only for sugarcane aphid infestation and damage. At Tifton a total of 10 insect pests were observed with low infestation: fall armyworm, corn earworm, corn leaf aphid, stink bugs (southern green and brown stink bugs), sorghum webworm, sorghum midge, leaf-footed bug, sugarcane aphid, and chinch bug. Sugarcane aphid infestation was very low with no damage on the grain sorghum plots at Tifton in 2019, perhaps because of the late planting on the 11th of July. Bird damage and anthracnose infection were also evaluated at Tifton. Due to very low insect infestation levels in general and no statistical difference among entries in the trial at Tifton, insect damage-related data are not included; however, only lodging, anthracnose, and bird damage are included in the report. In 2019 at Griffin, the number of sugarcane aphids was counted on July 9th and 25th, respectively, by averaging the number of aphids on 6 mid-canopy leaves per plot. Aphid damage on plants was rated using a 1-9 scale on July 9th and Aug. 16th and 25th, respectively. 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 percentage of plants with grain panicles (heads) with viable grain was rated near crop maturity on September 14th. An overall rating of sugarcane aphid resistance/tolerance was determined from results collected at Griffin. The number of sugarcane aphids and aphid damage at pre-harvest of the grain sorghum was rated on September 6th. A percentage of panicle development was also assessed. Aphid resistance was rated as Resistant (R), Moderately Resistant/Moderately Susceptible (MR/MS), and Susceptible (S) at Griffin. Because no aphid damage was observed on the grain sorghum plots at Tifton, only lodging, bird damage and anthracnose infection were rated. While lodging and bird damage were rated as percentage data, anthracnose leaf disease severity was rated using an 1-5 scale: 1 = no disease symptoms, 2 = colored spots or necrotic flecks, but no fungal sporulation, 3 = some sporulation on lower leaves (<25%), 4 = moderate sporulation on lower and middle leaves (<75%), and 5 = heavy sporulation including the flag leaf. Principal component analysis was used to rank all hybrid entries with data of lodging, bird damage, and anthracnose damage, and to determine an overall hybrid rating as Very Good (VG), Good (G), Fair (F), and Poor (P). Results of the grain sorghum trials are shown in Table 1. At Griffin, a total of 14 sorghum grain hybrids were rated as Resistant (R) to sugarcane aphid, and six grain hybrids were rated as Moderately Resistant or Moderately Susceptible (MR/MS) to sugarcane aphid. The remaining 32 hybrids were rated as Susceptible (S). At Tifton, plant lodging, bird damage and anthracnose infection data were to complement the Annual Publication 101-11 | Georgia 2019 Corn, Sorghum Grain and Silage, and Summer Annual Forages 51 aphid damage data from Griffin. Although the late planted grain sorghum trial at Tifton performed well in 2019, the principal component analysis ranked 16 hybrids Very Good (VG) and 11 hybrids Poor (P) (Table 1). For the silage sorghum trial (Table 2), a total of 40 commercial hybrids were planted on April 17, 2019 at Tifton, and 37 hybrids were planted on June 17, 2019 at Griffin. Plots, 4-row by 20-ft, were arrang