Attraction of Sitophilus zeamais (Coleoptera: Curculionidae) to four host plants

Authors: Stuhl, Charles; Romero, Maritza

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2021
Publication Date: 9/23/2021
Citation: Stuhl, C.J., Romero, M.I. 2021. Attraction of Sitophilus zeamais (Coleoptera: Curculionidae) to four host plants. Florida Entomologist. 104(3):158-161. https://doi.org/10.1653/024.104.0302.
DOI: https://doi.org/10.1653/024.104.0302

Interpretive Summary: The maize weevil, Sitophilus zeamais can be found in numerous tropical regions around the world and is an important pest of stored grains. Adults and larvae can survive on a wide variety of grains, but are typically a pest of corn, wheat, rice, and sorghum. Odors comprised of chemical compounds are essential for this insect pest to find the grains it uses for foraging, adult food, egg laying (oviposition) opportunities and mating sites. Currently, there is no effective field or storage trapping system for maize weevils. The current use of pheromone traps can be helpful in monitoring insects for mating activity and population density, but do not offer the essential control for large scale grain production. In this study scientists from the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL, investigated the weevil’s attraction to the plants that produce the host grains. Weevils were reared on four grains and behavioral assays were conducted to determine if there is a predisposition in orientation dependent upon the grain that was previously fed upon. The assay was designed to account for all weevils being used in the study. Therefore, weevils located on the plant, soil and roots were considered. The results indicated that the strongest attraction for male and female weevils were the rice plants. Female weevils showed a slightly higher preference for rice than males. Results show there was no bias for a host plant dependent upon previous feeding. There were considerably more barley-reared males and females located on the soil surrounding all plants. The male and female barley, maize, milo and rice-reared weevils showed no significant difference amongst their location on the plant roots. Future research will focus on isolating specific plant odors to be used in the development of an attractant for use in a trapping system. The use of the weevil’s sex pheromone in conjunction with a host volatile (food or oviposition) will greatly enhance attraction. This will allow for the development of a novel, inexpensive method for monitoring and control and would help reduce crop loss from this pest.

Technical Abstract: Studies have indicated that the odors associated with the grains upon which the maize weevil Sitophilus zeamais (Motschulsky) (Coleoptera: Curculionidae) the feed, mate, and oviposit are known to be attractive. Weevil infestations occur in the field and the weevils are carried to the storage facility after harvest. This weevil is an important pest of stored grains, predominantly maize (Zea mays), wheat (Triticum spp.), rice (Oryza spp.), and sorghum (Sorghum bicolor) (all Poaceae). There is no effective field or storage trapping system for maize weevil control. Therefore, pesticide application and the development of resistant grain are the current control methods. Investigations into host plant produced volatiles and their associations with the maize weevil have not been fully investigated. To better understand the weevil’s attraction to crop plants, a study was developed to investigate the weevil’s preference for immature host plants. The weevils were reared on 4 types of grain to determine, if presented a choice, would they prefer the host plant that produce grain upon which their parents and they themselves fed as larvae. This research demonstrated that previous feeding did not influence the weevil’s attraction to a certain host plant, with the immature rice plants having the greatest attraction. The isolation of key rice plant semiochemicals will be the focus in the development of an attractant for S. zeamais and may also prove effective for the control of Sitophilus oryzae.