Grain, silage, and forage sorghum hybrid resistance to insect, disease, and bird damage, 2018

Authors: BUNTIN, G. DAVID - University Of Georgia; Ni, Xinzhi; 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: 12/17/2018
Publication Date: 12/21/2018
Citation: Buntin, G., Ni, X., Harris-Shultz, K.R., Knoll, J.E., Toews, M.D., Dunn, D. 2018. Grain, silage, and forage sorghum hybrid resistance to insect, disease, and bird damage, 2018. In: D.J. Mailhot, D. Dunn, and H. Jordan Jr., (eds.), Georgia Agricultural Experiment Station Publication 103-10, pp. 65-72.

Interpretive Summary: not required.

Technical Abstract: A total of 37 grain sorghum hybrids (Table 1) were evaluated for resistance to insect and bird damage in Tifton and Griffin, Georgia. In both locations, plots were two rows by 20 feet and entries were planted in a randomized complete block design with three replications at Griffin and four replications at Tifton. The Griffin trial was planted on June 21, 2018 and at Tifton on June 12, 2018. The Griffin location was evaluated only for sugarcane aphid infestation and damage. At Tifton, a total of 10 insect pests were observed (in order of importance): sugarcane aphid, sorghum webworm, sorghum midge, leaf-footed bug, fall armyworm, corn earworm, corn leaf aphid, stink bugs (southern green and brown stink bugs), and chinch bug. In comparison with the sugarcane aphid population and its damage, sorghum webworm, midge and bird damage, and anthracnose infection were variable, but commonly observed among the entries in 2018. Due to low populations, fall armyworm, leaffooted bug, stink bug, and chinch bug damage data were not included in this report. In 2018 at Tifton, the number of sugarcane aphids was not sampled and only sugarcane aphid damage at pre-harvest of the grain sorghum was rated on September 6, 2018. A simple binomial rating for panicle development was used: 0 = no panicle or aborted panicle development, and 1 = fully developed panicles. Aphid damage on sorghum leaves was rated using a 1-9 scale: 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. Sorghum webworm, corn earworm, and sorghum midge damage were assessed in combination with grain loss according to the following rating scale: very good (VG) = 0-15% empty glumes on any of the sorghum panicles in an experimental plot; good (G) = a few empty glumes (16-30%) observed on a panicle; fair (F) = 31-75% empty glumes on a sorghum panicle; and poor (P) = majority of sorghum panicles with more than three quarters (> 75%) empty glumes. Bird feeding damage on developing kernels was determined by the presence of partial kernels on panicles and evidence of splattering of broken developing kernels falling on the top leaves of a plant. Bird damage was rated with the following scale: very good (VG) = less than 10% grain loss; good (G) = 11-25% loss; fair (F) = 26-50% loss; and poor (P) = >50% loss of grains per panicle. Lastly, anthracnose leaf disease was rated on a 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. A principal component analysis was used for the Tifton results of all assessed parameters (i.e., lodging, aphid number, aphid damage rating, and anthracnose infection rating) to determine an overall hybrid rating. Sugarcane aphid damage is only one component of the overall variety ratings at Tifton. At Griffin, the number of sugarcane aphids was counted at peak infestation on August 8, 2018, by averaging the number of aphids on six mid-canopy leaves per plot. Aphid plant damage was rated using the 1-9 scale on August 16 and 24 and September 14, 2018. The percentage of plants with grain panicles (heads) with viable grain was rated near crop maturity on September 14, 2018. An overall rating of sugarcane aphid resistance/tolerance was determined from results at both locations. Results of the grain sorghum trials are shown in Table 1. Heavy sugarcane aphid infestation at the seedling stage in the grain trial at Tifton was observed in plots that were planted on June 12, 2018. In fact, the severe sugarcane aphid infestation halted normal plant development before flowering, resulting in seven hybrids that did not produce panicles in all