The potential for using entomopathogenic nematodes and fungi in the management of the maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae)

Authors: MBATA, GEORGE - Fort Valley State University; IVEY, CLEVELAND - Fort Valley State University; Shapiro Ilan, David

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2018
Publication Date: 6/21/2018
Citation: Mbata, G., Ivey, C., Shapiro Ilan, D.I. 2018. The potential for using entomopathogenic nematodes and fungi in the management of the maize weevil, Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae). Biological Control. 125:39-43. https://doi.org/10.1016/j.biocontrol.2018.06.008.
DOI: https://doi.org/10.1016/j.biocontrol.2018.06.008

Interpretive Summary: Maize is an important cereal that is widely cultivated globally. In storage, maize is infested by the maize weevil; the importance of this insect pest is more severe in certain sub-tropical regions such as sub – Saharan Africa, where maize constitutes a staple. The control of this pest has in the past depended almost entirely on chemical pesticides, but factors such as insect resistance to pesticides and contamination of food and environment are challenges that may be overcome with natural enemies including the use of environmentally friendly biopesticides. Natural biopesticides consisting of various beneficial nematode species (small round worms) and insect killing fungi were evaluated for the control of the maize weevil. The nematodes investigated were all able to kill the weevils but a species called Steinernema carpocapsae was most virulent. High doses of the fungi investigated were caused significant weevil mortality compared to the control. In sub-Saharan Africa, maize is often stored in cloth bags called “jute bags”. Therefore, trials to determine an acceptable mode of biopesticide application was implemented by exposing the weevils to jute bags treated with the fungus called Beauveria bassiana. Weevils that walked for 30 min over jute bags treated with B. bassiana experienced 100% mortality 14 D post-inoculation. Thus, the potential for using a wettable powder of B. bassiana to protect storage containers and commodities was demonstrated.

Technical Abstract: Maize (Zea mays L.) is an important cereal that is widely cultivated globally. In storage, maize is infested by the maize weevil (Sitophilus zeamais Motchulsky); the importance of, the pest is more severe in certain sub-tropical regions such as sub – Saharan Africa, where maize constitutes a staple. The control of this pest has in the past depended almost entirely on chemical pesticides, but factors such as insect resistance to pesticides and contamination of food and environment are challenges that may be overcome with natural enemies including the use of entomopathogens. Entomopathogenic nematodes and fungi, were evaluated for the control of the maize weevil. Six strains of nematodes, namely Heterorhabditis bacteriophora Poinar (Lewiston, and Oswego strains); H. indica Poinar, Karunakar, and David (Homl strain), H. georgiana (K22), Steinernema feltiae (SN), and S. carpocapsae (All), and two species of fungi, Beauveria bassiana (GHA) and Metarhizium brunneum (F52) were evaluated for pathogenicity to adult weevils. The nematodes investigated were all pathogenic to the weevils but S. carpocapsae was most virulent. High doses of the fungi investigated were caused significant weevil mortality compared to the control. In sub-Saharan Africa, maize is often stored in cloth bags called “jute bags”. Therefore, trials to determine an acceptable mode of entomopathogen application was implemented by exposing the weevils to jute bags treated with B. bassiana. Weevils that walked for 30 min over jute bags treated with B. bassiana experienced 100% mortality 14 D post-inoculation. Thus, the potential for using a wettable powder of B. bassiana to protect storage containers and commodities was demonstrated.