Submitted to: Journal of Stored Products Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/10/2009
Publication Date: 2/1/2010
Publication URL: http://hdl.handle.net/10113/40284
Citation: Flinn, P.W., Hagstrum, D.W., Reed, C., Phillips, T.W. 2010. Insect Population Dynamics in Commercial Grain Elevators. Journal of Stored Products Research. 46(1): 43-47. doi: http://dx.doi.org/10.1016/j.jspr.2009.09.001. Interpretive Summary: It is estimated that economic losses caused by insects to stored wheat in the USA range from 5 to 10% per year, or about 1.25 to 2.5 billion dollars. Many of the insecticides used by the cereal foods industry are being lost due to insecticide resistance or regulatory changes. Thus, alternative, economically viable methods for controlling these insects and reducing losses to raw commodities are required. In a study in which over 20,000 grain samples were taken in commercial grain elevators in Kansas, the primary insect pests in stored wheat were the lesser grain borer (44%), rusty grain beetle (36%), and red flour beetle (19%). The rusty grain beetle was the most prevalent species in June. In September through November, the rusty grain beetle and lesser grain borer were found at equal numbers in the grain. From February to March, the lesser grain borer became the most common species. Insect numbers were highest in the top layers of the grain and decreased with grain depth. In June, insect numbers were low but increased rapidly in September and remained relatively high through February. In March through May, insect numbers were relatively low. The data showed that the optimal time to fumigate the grain in Kansas would probably be in October or November. The findings from this study will be used to improve insect pest management programs for stored grain.
Technical Abstract: Data were collected in 1998-2002 from wheat stored in commercial grain elevators in south-central Kansas. Storage bins at these elevators had concrete walls and were typically 6-9 m in diameter and 30-35 m tall. A vacuum-probe sampler was used to collect ten 3-kg grain samples in the top 12 m of the wheat in each bin. In addition, several bins were sampled to a depth of 30 m in 1998-2000. The primary insect species found in the wheat samples were: Cryptolestes ferrugineus (Stephens), Rhyzopertha dominica (Fabricius), and Tribolium castaneum (Herbst). In the top 0 to 3.7 m of grain, R. dominica, C. ferrugineus, T. castaneum and S. oryzae made up 44, 36, 19 and 1% of the insect species found in the samples, respectively. From 3.8 to 12.2 m, R. dominica, C. ferrugineus, T. castaneum and S. oryzae were present at 84, 8, 8, and 1%, respectively. The most prevalent species also changed over time. In June, the start of wheat harvesting and storage in Kansas, insect density was low in the bins with wheat. At this time, C. ferrugineus was the most common insect, and it was found mostly in the top grain sample (0-1.2 m). In September through November, C. ferrugineus and R. dominica were at approximately equal densities; however, from February to March, R. dominica was the most common species. In general, insect density was greatest in the top layers and decreased with grain depth. Very few insects were found in samples collected greater than 12 m in depth (most of the bins contained grain in depths of 24 to 36 m). Insect density for all species increased rapidly from June through October. During this period less than 20% of the bins had economically significant insect densities (>2 insects/kg). From October until February, the average insect density remained fairly constant. Average insect density was greatly reduced in April, May, and June. Bins that had high insect densities (>2 insects/kg) tended to be located adjacent to other highly infested bins.