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Penetration of Sitophilus zeamais (Coleoptera: Curculionidae) through diatomaceous earth-treated bulk maize grain

  • B.M. Mvumi (a1), T.E. Stathers (a2), P. Golob (a2) and D.P. Giga (a3)
Abstract
Abstract

The penetration of adult Sitophilus zeamais Motschulsky through maize grain bulks (0.75 m deep), treated with Protect-It®, a diatomaceous earth (DE) at 0, 0.05, 0.1 and 0.2% (w/w), was determined 12 weeks after weevils were released at the upper surface of the grain. Maize was stored in columns in polyvinyl chloride (PVC) pipes, under controlled conditions of 26±2°C and 70±10% RH. Grain samples were collected from various pre-determined depths and the numbers of S. zeamais adults counted. Differences in insect numbers between treatments and at different depths from which samples were collected were highly significant (P<0.001). The bottom 2–3 layers (0.65–0.75 m deep) had significantly more insects than the upper layers for all the DE concentrations. No significant differences in total insect numbers (live+dead) were found between the DE concentrations. Dead S. zeamais weevils were found at the bottom of grain treated with Protect-It®, indicating that insects can penetrate through DE-treated grain 0.75 m deep but then subsequently die. There was no strong evidence that DEs admixed with bulk grain restrict S. zeamais movement within the grain.

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*E-mail: mvumibm@agric.uz.ac.zw
References
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Z. Korunic , S. Cenkowski and P. G. Fields (1998) Grain bulk density as affected by diatomaceous earth and application method. Postharvest Biology and Technology 13, 8189.

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T. E. Stathers , B. M. Mvumi and P. Golob (2002) Field assessment of the efficacy and persistence of diatomaceous earths in protecting stored grain on small-scale farms in Zimbabwe. Crop Protection 21, 10331048.

G. Surtees (1964) Laboratory studies on dispersion behaviour of adult beetles in grain. VI. Three-dimensional analysis of dispersion of five species in a uniform bulk. Bulletin of Entomological Research 55, 723725.

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International Journal of Tropical Insect Science
  • ISSN: 1742-7584
  • EISSN: 1742-7592
  • URL: /core/journals/international-journal-of-tropical-insect-science
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