Evaluation of Tarsonemus bilobatus and Podosphaera xanthii as suitable resources for Proprioseiopsis mexicanus in cucurbit systems in the Southeast USA

Authors: FARFAN, MONICA - Colorado State University; Coffey, John; Schmidt, Rebecca

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2021
Publication Date: 8/27/2021
Citation: Farfan, M.A., Coffey, J., Schmidt-Jeffris, R.A. 2021. Evaluation of Tarsonemus bilobatus and Podosphaera xanthii as suitable resources for Proprioseiopsis mexicanus in cucurbit systems in the Southeast USA. Experimental and Applied Acarology. 85:31-40. https://doi.org/10.1007/s10493-021-00658-8.
DOI: https://doi.org/10.1007/s10493-021-00658-8

Interpretive Summary: Tritrophic relationships, situations where three organisms are associated with each other either by being consumed by one of more of the other organisms or being the predator of one or more of the other organisms, are extremely common in agricultural systems. Often, researchers do not know if these relationships have consequences for the crops they were collected from. In South Carolina, three organisms are frequently found together on watermelon and pumpkin plants: a pathogen of these plants (Podosphaera xanthii), a mite that eats fungus (Tarsonemus sp.), and a predatory mite (Proprioseiopsis mexicanus). Researchers at the USDA-ARS in Wapato, WA, in collaboration with Clemson University, conducted a series of laboratory studies to see if P. mexicanus is able to survive and reproduce on either P. xanthii, Tarsonemus sp., or both. We found that P. mexicanus was not able to survive on P. xanthii, so we did not complete any more experiments with P. xanthii. However, we were able to rear Tarsonemus mites on P. xanthii, and P. mexicanus was able to survive and reproduce on these mites. P. mexicanus females were able to develop from egg to adults in 3 days when fed the Tarsonemus. When we placed a male and female who both were consuming Tarsonemus sp. together, it took 2.2 days for the female to lay an egg. On average, P. mexicanus females laid 1.7 eggs per day when consuming Tarsonemus. Female P. mexicanus consumed 6.5 Tarsonemus mites in one hour. This is important information because Tarsonemus sp. are closely related to other mites that are important plant pests, and the ability for P. mexicanus to consume Tarsonemus could help us understand how effective P. mexicanus would be in controlling the pest mites. Additionally, Tarsonemus sp. may help keep predators like P. mexicanus, who consume many other pests as well, on crop plants to prevent a future infestation.

Technical Abstract: Tritrophic relationships involving tarsonemids and predatory phytoseiids are common in a variety of agroecosystems, but due to the wide range of diets in both families, it is necessary to understand what food resources they are consuming to determine potential impact on crops. We investigated a frequent association of cucurbit powdery mildew (Podosphaera xanthii), Tarsonemus sp., and Proprioseiopsis mexicanus in watermelon and pumpkin fields to determine if P. mexicanus is consuming either or both of the other organisms. We also examined developmental and reproductive capability of P. mexicanus on these diets. If P. mexicanus is an effective predator of Tarsonemus, it may also be useful in controlling pest tarsonemids, such as broad mites. Proprioseiopsis mexicanus either starved or escaped from arenas rather than consume P. xanthii. Tarsonemus sp. were successfully cultured on P. xanthii. When consuming Tarsonemus sp., P. mexicanus females developed from egg to adult ~3 d. On this diet, the preoviposition period was ~2 d and P. mexicanus laid 1.7 eggs/day. Starved female P. mexicanus consumed 6.5 Tarsonemus sp. of mixed stages in 1 h. This study provides support for further research into the importance of non-pest tarsonemids as a resource to maintain the presence of generalist predatory mites as an early-intervention natural enemy. Further work should examine the efficacy of P. mexicanus as a natural enemy of economically important pest tarsonemids.