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

  • B. M. MvumiEmail author
  • T. E. Stathers
  • P. Golob
  • D. P. Giga
Article

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.

Key words

Sitophilus zeamais diatomaceous earth grain protectant vertical insect movement bulk maize 

Résumé

La pénétration des adultes de Sitophilus zeamais Motschulsky dans des stocks de 0,75 m de profondeur de grains de maïs, traités avec du Protect-Itw, un sol à diatomées (DE) aux doses de 0, 0,05, 0,1 et 0,2% (w /w) a été déterminée 12 semaines apre`s que les charancçons aient été lâchés à la surface des grains. Le maïs était stocké dans des colonnes constituées par des tuyaux de chloride de polyvinyle (PVC), en conditions contrôlées à 26,28C et 70 10% HR. Les échantillons de grains ont été prélevés à différentes profondeurs préalablement déterminées et les charancçons dénombrés. Le nombre d’insectes étaient tre`s significativement différent entre traitement et selon la profondeur (P < 0,001). La partie inférieure (entre 0,65 et 0,75 m) héberge significativement plus d’insectes que les parties supérieures quelque soit le traitement. Les cadavres de charancçons ont été trouvés à la partie inférieure des stocks traités au Protect-Itw, indiquant que les insectes ont pu pénétrer les stocks traités avant de mourir. Il n’a pas été possible de montrer que les stocks traités limitaient les déplacements des charancçons.

Mots Clés

Sitophilus zeamais sol à diatomées agent protecteur mouvement vertical des insectes stock de maïs 

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Copyright information

© ICIPE 2006

Authors and Affiliations

  • B. M. Mvumi
    • 1
    Email author
  • T. E. Stathers
    • 2
  • P. Golob
    • 2
  • D. P. Giga
    • 3
  1. 1.Department of Soil Science and Agricultural EngineeringUniversity of ZimbabweHarareZimbabwe
  2. 2.Natural Resources InstituteUniversity of GreenwichKentUK
  3. 3.BulawayoZimbabwe

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