Abstract
Sorghum (Sorghum bicolor (L.) Moench) is an important summer grain crop in the U.S. Southern Great Plains because it is one of the few crops that consistently produces acceptable yields in the harsh summer weather that characterizes the region. Damaging infestations of the sugarcane aphid, Melanaphis sacchari (Zehntner), occur commonly in sorghum throughout Texas and Oklahoma, two of the leading sorghum producing states. Grain sorghum fields were sampled at two locations in Texas and three locations in Oklahoma. Fields were sampled approximately weekly by examining two leaves on each of 54 plants and counting all sugarcane aphids and aphid natural enemies on each leaf. Sampling began at an early growth stage and continued until the crop either matured or was treated with insecticide to suppress the sugarcane aphid infestation. For a total of 123 fields in 2017 and 2018, aphids, Aphelinus nigritus Howard mummies, adult coccinellids, larval coccinellids, larval lacewings, and larval dipterans were counted, and relative density estimates were determined. When natural enemy and sugarcane aphid count data were aggregated at the scale of geographic locations and multiple years, there was no evidence for a numerical response by natural enemies to sugarcane aphid density. When fields were compared within locations, a numerical response was consistently observed. A natural enemy importance index was developed that incorporated cumulative degree days of first occurrence of a natural enemy taxa in a field, the average density of the natural enemy in a field, and natural enemy voracity. Factorial analyses of variance indicated that cumulative degree days at first occurrence and average relative density differed significantly among natural enemy taxa and locations, as did natural enemy importance. Averaged across locations larval coccinellids had the largest importance index, I = 1.47, and A. nigritus had the smallest, I = 0.61. Among locations, the Texas Coastal Plains had the largest importance index, I = 1.27 whereas the Oklahoma Panhandle had the smallest, I = 1.02. Results suggest that differences occur in the biological control contributions of various natural enemies and in biological control efficacy among locations.
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Claims 11
Claim · model-written summary
Aggregated across locations and years, natural enemies showed no evidence of a numerical response to sugarcane aphid density.
- Interactor
- sugarcane aphide0pest
- Outcome
- numerical response by natural enemiese0
- Direction
- no evidencee0
- Qualifier
- geographic locations and multiple yearse0
SorghumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When natural enemy and sugarcane aphid count data were aggregated at the scale of geographic locations and multiple years, there was no evidence for a numerical response by natural enemies to sugarcane aphid density”
t0“Sorghum Fields”
Claim · model-written summary
Within locations, natural enemy counts consistently showed a numerical response to sugarcane aphids.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When fields were compared within locations, a numerical response was consistently observed”
e1“sugarcane aphid count data”
t0“Sorghum Fields”
Claim · model-written summary
A natural enemy importance index was developed from timing of first occurrence, density, and voracity.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A natural enemy importance index was developed that incorporated cumulative degree days of first occurrence of a natural enemy taxa in a field, the average density of the natural enemy in a field, and natural enemy voracity”
t0“Sorghum Fields”
e1“sugarcane aphid infestation”
Claim · model-written summary
First occurrence degree days differed significantly among natural enemy taxa and locations.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cumulative degree days at first occurrence and average relative density differed significantly among natural enemy taxa and locations”
t0“Sorghum Fields”
Claim · model-written summary
Average relative natural enemy density differed significantly among taxa and locations.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cumulative degree days at first occurrence and average relative density differed significantly among natural enemy taxa and locations”
t0“Sorghum Fields”
Claim · model-written summary
Natural enemy importance differed significantly among taxa and locations.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“as did natural enemy importance”
e1“differed significantly among natural enemy taxa and locations”
t0“Sorghum Fields”
Claim · model-written summary
Larval coccinellids had the largest mean importance index, 1.47, across locations.
- Interactor
- larval coccinellidse0biocontrol_agent
- Outcome
- importance indexe0
- Direction
- largeste0
- Value
- I = 1.47e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Averaged across locations larval coccinellids had the largest importance index, I = 1.47”
t0“Sorghum Fields”
Claim · model-written summary
A. nigritus had the smallest mean importance index, 0.61, across locations.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A. nigritus had the smallest, I = 0.61”
e1“larval coccinellids had the largest importance index”
t0“Sorghum Fields”
Claim · model-written summary
Texas Coastal Plains had the largest location importance index, 1.27.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Texas Coastal Plains had the largest importance index, I = 1.27”
t0“Sorghum Fields”
Claim · model-written summary
Oklahoma Panhandle had the smallest location importance index, 1.02.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Oklahoma Panhandle had the smallest, I = 1.02”
e1“the Texas Coastal Plains had the largest importance index”
t0“Sorghum Fields”
Claim · model-written summary
The results suggest biological control contributions vary among natural enemies and efficacy varies among locations.
- Outcome
- biological control contributions of various natural enemies and in biological control efficacye0
- Direction
- differencese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“differences occur in the biological control contributions of various natural enemies and in biological control efficacy among locations”
t0“Sorghum Fields”