Does prior feeding behavior by previous generations of the maize weevil (Coleoptera: Curculionidae) determine future decedents feeding preference and oviposition suitability?

Authors: Stuhl, Charles

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2018
Publication Date: 6/14/2019
Citation: Stuhl, C.J. 2019. Does prior feeding behavior by previous generations of the maize weevil (Coleoptera: Curculionidae) determine future decedents feeding preference and oviposition suitability? Florida Entomologist. 102(2):366-372. https://doi.org/10.1653/024.102.0212.
DOI: https://doi.org/10.1653/024.102.0212

Interpretive Summary: The maize weevil, Sitophilus zeamais is an important pest of stored grains world-wide. Adults and larvae can survive on a wide variety of food substances, but are predominantly a pest of corn, wheat, rice, and sorghum. Chemical cues from the weevil’s hosts and the substrates in which the hosts develop are known to be fundamental components of orientation for foraging, adult food, oviposition opportunities and mating sites. Unfortunately, there is no effective trapping system for maize weevils. Pheromone traps are helpful in monitoring insects and provide information about mating activity and population density, but do not offer the necessary control for large scale grain storage. This study investigates the weevil’s attraction to dry grains with and without the presence of the pheromone lure. Additionally, an assay was performed to evaluate the ovipositional preference to host grains. Weevils were fed four different grains. Assays were conducted to determine if there is a bias in orientation dependent upon previous feeding history. Results indicated that the strongest attraction for males and females was corn. A high percentage of females were attracted to brown rice. When the pheromone lure was placed in the grain, there was no effect on the weevil’s choice, they preferred corn. Results show that there is no bias for a host grain dependent upon previous feeding history. The ovipositional study results showed that brown rice produced the most males, while brown rice and barley produced the most females. The results from this experiment will help in determining which grain was most attractive. Future research will focus on isolating the odor from the grain to be used to develop a trapping system. The development of a novel, inexpensive method for monitoring and control weevils would help reduce loss due to this pest.

Technical Abstract: The maize weevil, Sitophilus zeamais is an important pest of stored grains, predominantly corn, wheat, rice, and sorghum. Infestation begins in the field where it becomes a destructive pest when the grain is stored. The female weevil chews a hole in the grain and lays an egg inside the kernel; the hole is then sealed to protect the egg. The egg hatches and the lava consume the valuable commodity. At the end of the life cycle, an adult weevil emerges from the kernel. Currently, the only control method is the application of an insecticide applied to the grain. Unfortunately, there is no effective trapping system for maize weevils. The current commercial pheromone traps do not offer large scale population reduction. They are best used for monitoring population density, but do not offer the necessary control. Previous studies have indicated that the odors associated with the grains upon which the weevil’s feed, mate and oviposit are known to be attractive. In an effort to better understand this behavior, we developed a study to investigate the weevil’s attraction to dry grains with and without the presence of the commercial pheromone lure. Additionally, we investigated the weevil’s preference to oviposit into specific host grains. The weevils were reared on four types of grain to determine if presented a choice, would they prefer the grain on which they previously fed. Results indicated that the strongest attraction for males and females was corn. Brown rice was also significantly attractive to female weevils. The placement of the pheromone lure in the different grains did not affect choice; weevils preferentially selected corn. Results show that there is no bias for a host grain dependent upon previous feeding history. The ovipositional study results indicate that there was a significantly greater emergence of males from the brown rice, whereas brown rice and barley had a significantly greater emergence of females. The results from this experiment will help in determining which odors initiated the greatest attraction. Thus, future research will focus on isolating these odors to be used to develop a trapping system. The synergistic effect of a pheromone in conjunction with a specific host volatile (food or oviposition) will greatly enhance attraction. The development of a novel, inexpensive method for monitoring and control would help reduce loss due to this pest.