Development of binomial sequential sampling plans for sugarcane aphid melanaphis sacchari zehntner (Hemiptera: Aphididae) in commercial grain sorghum

Authors: LINDENMAYER, JESSICA - Texas A&M University; GILES, KRIS - Oklahoma State University; Elliott, Norman - Norm; KNUTSON, ALLEN - Non ARS Employee; BOWLING, ROBERT - Non ARS Employee; GORDY, JOHN - Texas A&M University; MCCORNACK, BRIAN - Kansas State University; BROWN, SEBE - Louisiana State University; BREWER, MICHAEL - Texas A&M University; CATCHOT, ANGUS - Mississippi State University; ROYER, TOM - Oklahoma State University; SEITER, NICK - University Of Illinois

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2019
Publication Date: 3/12/2020
Citation: Lindenmayer, J.C., Giles, K.L., Elliott, N.C., Knutson, A.E., Bowling, R., Gordy, J.W., McCornack, B., Brown, S.A., Brewer, M., Catchot, A.L., Royer, T.A., Seiter, N.J. 2020. Development of binomial sequential sampling plans for sugarcane aphid melanaphis sacchari zehntner (Hemiptera: Aphididae) in commercial grain sorghum. Journal of Economic Entomology. 1-9. https://doi.org/10.1093/jee/toaa064.
DOI: https://doi.org/10.1093/jee/toaa064

Interpretive Summary: The sugarcane aphid is a severe pest in grain sorghum in the Southern US. Current economic thresholds for insecticide treatment are based on mean number of aphids per leaf. Counting aphids per leaf is tedious and time consuming because there can be over 100 aphids per leaf and sometimes over 1,000 aphids per leaf. As a result, binomial sequential sampling plans that characterize a two-leaf sample unit as infested if over 50 sugarcane aphids are present on the two leaves (defined as a tally threshold of 50) were developed that allow users to quickly classify the economic status of field populations of sugarcane aphid to determine if an economic threshold has been exceeded. The tally thresholds of 50 aphids per two leaf sample was selected based on the basis of goodness of fit and practicality. Stop lines for both tally thresholds were developed for selected economic thresholds using Wald’s sequential probability ratio test. Model validation using data for 48 fields that were not used for model development demonstrated that reliable ‘treat’ versus ‘don’t treat’ decisions could be made with an average of 11 samples regardless of geographic location in southern states. This sampling system will allow users to easily and rapidly determine when sugarcane aphid infestation in grain sorghum need to be treated.

Technical Abstract: Sugarcane aphid, Melanaphis sacchari Zehntner (Hemiptera: Aphididae) is a significant economic pest in grain sorghum in the Southern US. Current economic thresholds are based on mean number of aphids per leaf. Because enumerating aphids per leaf is tedious and potentially time consuming, binomial sequential sampling plans for M. sacchari were developed that allow users to quickly classify the economic status of field populations and determine when an economic threshold has been exceeded. During 2016 and 2017, counts of M. sacchari were recorded from 281 sampling events in 140 sorghum fields located in six states (OK, KS, TX, AR, LA, MS). Regression analysis was used to describe the relationships between the mean M. sacchari density per plant and proportion of plants infested with one or more aphids. Tally thresholds of T50 and T100 aphids per two leaf sample were selected based on fitness and practicality. Stop lines for both tally thresholds were developed for selected economic thresholds using Wald’s sequential probability ratio test (SPRT). Model validations using an additional 48 fields demonstrated that reliable classification decisions could be made with an average of 11 samples regardless of location. This sampling system, when adopted, can allow users to easily and rapidly determine when M. sacchari infestations need to be treated.