# Evaluation of Bacterial Communities of Listronotus maculicollis Kirby Reared on Primary and Secondary Host Plants

## TL;DR

This study examines how the bacterial communities in annual bluegrass weevils differ based on their host plants and developmental stages.

## Contribution

The study identifies specific bacterial taxa associated with weevil development and host plant interactions, offering insights into pest management.

## Key findings

- Adult weevils on a new creeping bentgrass cultivar (A4) had more diverse bacteria than larvae.
- Pseudomonas sp. was common in larvae and may influence their development.
- Wolbachia was more prevalent in adults and not linked to host plant type.

## Abstract

The annual bluegrass weevil (Listronotus maculicollis) is a serious pest affecting golf courses, mainly damaging annual bluegrass (Poa annua) and, to a lesser extent, creeping bentgrass (Agrostis stolonifera). Weevils developing with creeping bentgrass develop slower and experience greater mortality rates than weevils within annual bluegrass. This study looked at the different bacterial communities within weevil adults and larvae raised on these two types of grass and cultivars to determine if plant nutrition affects these outcomes. Adult weevils feeding on a newer creeping bentgrass cultivar (A4), had more diverse bacteria than their larvae. Significant differences in the bacteria taxa between adult weevils and larvae were observed regardless of which grass they consumed. Pseudomonas sp. was common in larvae and may be linked to their growth and development. Wolbachia, a bacterium known to affect insect reproduction, was more common in adults and probably not influenced by their host plant type. The most common bacterium found was Candidatus Nardonella, which assists in the rigidity of the weevil’s exoskeleton. A further study of these relationships between the annual bluegrass weevil, host plants, and bacteria associated with exoskeleton hardening may better inform management programs and reduce the impact of insecticide resistance populations.

The annual bluegrass weevil (Listronotus maculicollis Kirby) is a devastating insect pest of annual bluegrass (Poa annua L.) and, to a lesser extent, creeping bentgrass (Agrostis stolonifera L.) on golf courses. Listronotus maculicollis-reared A. stolonifera, a comparatively tolerant host, incurs fitness costs, including longer developmental periods and reduced larval survivorship. This study sought to characterize microbiota diversity in L. maculicollis adults and larvae reared on P. annua and A. stolonifera cultivars (Penncross & A4) to explore whether intrinsic factors, such as microbial community composition, vary across host plants and developmental stages, potentially influencing host suitability. Alpha diversity analyses showed adults feeding on A4 exhibited higher bacterial species richness than their offspring reared on the same cultivar. Beta diversity analysis revealed significant dissimilarities between L. maculicollis adults and offspring regardless of host. Pseudomonas sp. was consistently abundant in larvae across all turfgrasses, indicating a potential association with larval development. Elevated levels of Wolbachia sp., known for insect reproductive manipulation, were observed in adults, but appear to be unrelated to host plant effects. The most prevalent bacterium detected was Candidatus Nardonella, a conserved endosymbiont essential for cuticular hardening in weevils. Given the role of cuticular integrity in insecticide resistance, further investigations into insect–microbe–plant interactions could guide the development of targeted pest management strategies, reducing resistance and improving control measures for L. maculicollis.