Identifying and Investigating Sublethal Effects of a Novel Biocontrol Agent of Stable Flies

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Commodities

• Animals: bovine, equine

Practices

• Animal Production: animal protection and health
• Education and Training: extension, on-farm/ranch research
• Pest Management: biological control
• Sustainable Communities: sustainability measures

The purpose of this project is to determine how a potential new biological control agent, phoretic mites (Mesostigmata: Macrochelidae), impacts flight and host-seeking behavior of stable flies (Diptera: Muscidae) on livestock farms, as well as to survey endemic macrochelid mites in the region. Stable flies are a global pest that create economic and animal welfare issues and cost U.S. cattle farmers billions of dollars each year due to reduced milk yields and feed conversion rates. Yet farmers lack effective biological control agents and instead rely on pesticides for fly management. Livestock farmers need environmentally friendly stable fly management options and macrochelid mites have shown potential as a biological control agent of pest flies. Macrochelid mites feed on the eggs and larvae of stable and house flies, and then use phoresy for dispersal, attaching themselves to adult flies for transportation to new feedings areas. During this two-year project, I will measure the potential sublethal effect of phoretic mites on 1) flight activity of host-seeking stable flies in the field at different temperature ranges and 2) flight endurance of stable flies carrying mites in the lab. I also will 3) conduct a survey of endemic macrochelid mites in Maine to identify candidate biocontrols for inundative release. Our results will be shared at agricultural outreach events, through printed insect pest factsheets, at scientific conferences and in scientific publications. Ultimately, research into new biological control agents will benefit livestock and equine farmers and help prevent pesticide resistance, reduce environmental contamination, and improve animal welfare.

1) Can phoretic mites limit the host-seeking activity of stable flies?

I will conduct an observational field study of host-seeking stable flies on livestock farms across different temperature ranges to test the hypothesis that mites can reduce host-seeking flies during sub-optimal flight temperatures. I will capture host-seeking stable flies during varying temperatures throughout the day and will count the proportion that are carrying mites at sub-optimal and optimal temperatures. I hypothesize that stable flies carrying mites will be unable to host-seek during suboptimal temperatures (below 20°C) and therefore we will see a smaller proportion of stable flies with mites during cooler temperatures compared to the optimal warmer temperatures above 20°C. Thus, mites could have the sublethal effect of shortening the duration each day that livestock is under fly pressure, improving animal welfare and livestock productivity.

2) Do phoretic mites limit the flight endurance of stable flies?

I will conduct a laboratory experiment to measure the flight potential of stable flies with and without phoretic mites attached using flight mills (a device that measures flight time and distance). I hypothesize that flies without mites will have longer flight periods compared to flies with mites, and that flight endurance will decrease with increasing numbers of attached mites. I expect that this relationship between mite burden and flight endurance will be a linear relationship and will identify the mite load threshold at which flight endurance is significantly impacted. If mites can limit flight endurance, stable flies may not be able to fly as far or as long to seek out a blood meal which may help relieve the total amount of pest pressure on livestock.  

3) What are the common endemic macrochelid mite species in Maine?

I will survey and identify macrochelid mites associated with stable flies on livestock farms in New England to create a pool of new potential macrochelid biological control agents. I will collect stable flies and soil samples where stable flies breed from six mixed livestock farms during stable fly activity to collect and identify phoretic mites in the region. Surveys of endemic stable fly predatory mites have only taken place in Brazil, Columbia, and the United Kingdom (McGarry & Baker 1997, Azeveda et al. 2017, Zapata-Usuga et al. 2022) and this will be the first survey of macrochelid mites in the United States.