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United States Department of Agriculture

Agricultural Research Service

Research Project: ENVIRONMENTALLY SOUND MANURE MANAGEMENT FOR REDUCTION OF GAS EMISSIONS, NUTRIENTS, AND PATHOGENS

Location: Agroecosystem Management Research

Title: Temporal characterization of bacteria in hayrings serving as stable fly larval development sites

Authors
item Durso, Lisa
item Taylor, David
item Wienhold, Brian
item Friesen, Kristina

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: June 7, 2013
Publication Date: N/A

Interpretive Summary: Stable flies are common pests of grazing cattle. They are blood feeders with painful bites. When stable flies are active, they can significantly stress cattle, resulting in distress to the animal, and reduced weight gains. The focus of stable fly control has historically been on preventing adult stable flies from biting cattle. While the adult files biting the cattle are the immediate problem, it is only one part of a complex ecological system that involves the entire life-cycle of the fly in pastured settings. The larval stage has been proposed as a strategic target for control measures, since they have limited motility and are likely spatially concentrated. Previous work has identified hayring feeding sites as larval development sites that serve as important sources of early summer stable flies. These large round stationary feeders are used to supplement grazing on pastured systems. The loose hay mixes with cattle feces and urine, creating a matrix that supports larval development. One component hypothesized to play a role in larval development is an interaction between stable flies and environmental bacterial communities. Bacteria are thought to serve as a source of nutrition for the larvae, and bacterial are thought to give off odors that attractant females to lay their eggs. We used standard microbiological culture methods to characterize the bacterial population numbers in hay ring substrates from stable fly larval development sites. The results of this study provide baseline information on population levels of multiple types of bacteria in hayrings over time, and highlight the complexity of the bacterial communities in hayring substrates. The data reveal variability even among similar hayrings. No correlations were noted between the large functional groups of bacteria surveyed and stable fly larval or adult populations.

Technical Abstract: Stable flies, Stomoxys calcitrans (L.) (Diptera: Muscidae) are important pests of pastured cattle, reducing weight gains, and causing discomfort to the animals. The focus of stable fly control has historically been on preventing adult stable flies from biting cattle. While the adult files biting the cattle are the immediate problem, it is only one part of a complex ecological system that involves the entire life-cycle of the fly in pastured settings. The larval stage has been proposed as a strategic target for control measures, since they have limited motility and are likely spatially concentrated. Previous work has identified hayring feeding sites as larval development sites that serve as important sources of early summer stable flies. These large round stationary feeders are used to supplement grazing on pastured systems. The loose hay mixes with cattle feces and urine, creating a matrix that supports larval development. One component hypothesized to play a role in larval development is an interaction between stable flies and environmental bacterial communities. Bacteria are thought to serve as a source of nutrition for the larvae, and bacterial metabolites are thought to serve as attractants for oviposition by gravid females. We used standard microbiological culture methods to characterize the bacterial population numbers in hay ring substrates from stable fly larval development sites. Samples were collected from three hayrings from mid-March through late August, and from a fourth hayring starting in mid-June. Samples were plated on Maconkey media, Tryptic Soy Agar, and mEntero media, and all samples were enumerated for fecal indicators including E. coli, total coliforms, and enterococcus. Additionally, early samples were plated on CIN media to detect and enumerate Citrobacter. The primary defining characteristic of all bacterial parameters measured was variability. It was not uncommon to find log-level differences among the four hayrings sampled on the same day. Standard aerobic plate counts ranged between 1.00E+02 and 1.00E+08, with a mean of 2.00E+07 and a median of 3.00E+06. The two lowest counts both occurred in June, on consecutive sample days in two different hayrings. MacConkey agar plates contain bile and other selective agents that inhibit soil and waterborne bacteria, and select for lactose fermenting intestinal bacteria. Hayring averages on MacConkey agar ranged from 1.00E+01 through 1.00E+05 cfu/g substrate. The highest average numbers were found in March and April. The lowest average numbers were found in early June. Total coliform count averages were highest in May and June. Together, these data provide baseline information on population levels of multiple types of bacteria over time, and highlight the complexity of the bacterial communities in hayring substrates. The data reveal variability even among similar hayrings. No correlations were noted between the large functional groups of bacteria surveyed and stable fly larval or adult populations.

Last Modified: 10/1/2014
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