Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2004
Publication Date: 9/1/2004
Citation: Perez Mendoza, J., Flinn, P.W., Campbell, J.F., Hagstrum, D.W., Throne, J.E. 2004. Detection of stored-grain insect infestation in wheat transported in railroad hopper-cars. Journal of Economic Entomology. 97(4):1474-1483. Interpretive Summary: Acceptance of a specific grain lot by millers depends mainly on the numbers of live insects and insect-damaged kernels (IDK) detected before the grain is unloaded from a railcar. Grain buyers need to make rapid decisions about the quality of individual lots of grain to accept or reject the product. However, there are indications from the buyers that the method used to detect infestations may not be accurate. Therefore, insect infestation, spatial distribution, and the relationship between IDK and the number of insects present in wheat transported in railroad cars were studied. Six of eight sampled cars were infested mostly with lesser grain borers and rusty grain beetles. More than 90% of those insects were immatures at sampling time. IDK and insect density were not correlated for any of the different stage-specific insect populations, present in the grain samples. The mean numbers of IDK and insects differed among railcars and compartments within railcars, but not among grain depths. The results indicate that each compartment of a railcar should be sampled to determine insect infestation, and that there is a need to develop rapid technologies for detection of immature insects inside wheat kernels.
Technical Abstract: Levels of insect infestation, insect spatial distribution, and the relationship between the numbers of insect-damaged kernels (IDK) and the number of insects present in grain samples in three-hopper railcars transporting wheat from country elevators to a mill were studied. Six of eight samples railcars were infested with more than two species of insects. The most abundant species collected were the lesser grain borer, Rhyzopertha dominica (F.), and rusty grain beetle, Cryptolestes ferrugineus (Stephens), with the larval stage of the two species being the more prevalent (>90%). The spatial distributions of these two species within the grain mass were typically clumped in car compartments containing more than 0.4 insects/sample, and these foci of high infestation levels varied in compartments within the railcars and among the sampled railcars. There were no significant correlations between IDK and insect density for any of the different stage-specific insect populations that were collected in the grain samples. Mean numbers of immatures and IDK differed among railcars and compartments within railcars, but not among grain depths. Number of insects in the first discharge sample was not correlated with mean numbers of insects in the entire compartment. This indicates that each compartment of a railcar should be sampled to determine level of insect infestation, but that sampling at different depths within a compartment is less important.