Delaware Cooperative Extension
Investigators: J. Whalen, Extension IPM Specialist; Martin Spellman, Extension IPM Associate, Gordon Johnson, Extension Agricultural Agent; Kimby Tarburton – University of Delaware Summer Assistant
Cooperators: Thomas Farms, Mills Farms, Heatwole Farms, and Greg Knutsen
Background: Fly management on dairy farms was identified by producers in Delaware as a key pest management issue on their farms. If not controlled, fly problems can contribute to 5-25% loss in milk production. In addition, lower profit margins, loss of pesticides, resistance management, and increased residential development are all factors that point to the need for the development of an IPM program for flies on dairy farms.
(1) To continue to identify key fly breeding areas on individual dairy farms
(2) To monitor fly population cycles throughout the season to identify key times when populations may warrant selective chemical controls and evaluate the effectiveness of alternative control strategies.
(3) To evaluate the effectiveness of an integrated approach to fly management which includes the use multiple strategies: manure removal(cultural control), fly tapes (physical control), targeted parasite releases in calf barns (biological controls), monitoring to make selective pesticide applications (use of pre-season sprays and baits in-season) and alternative bedding (cultural control).
(1) Adult fly populations were monitored using spot cards placed on key fly resting surfaces in multiple locations on cooperating farms. In general, cards were monitored on a weekly basis from May through early September
(2) Practices used to manage flies:
- Use of fly tapes and bait applications for adult fly populations: season-long on all 4 participating farms
- Residual space sprays for adult flies (dimethoate and Tempo) : one application on 4 farms when fly populations exploded
- Parasite releases season long in calf barns in 2 locations (Thomas and Mills) - 1000 parasites per pen per week from May 15 - Aug 30.
- Hister beetles relases in one calf barn (Mills) for egg and maggot control : released in 2 pens at a rate of 500 per pen ; release dates: May and July
- Alternative bedding evaluated on all 4 farms: peanut hulls mixed in straw bedding in calf areas
- Use of Citric Acid along edges of pens to reduce maggot numbers - all four locations
- Use of Potash in Outside Cow Pack Areas to reduce moisture levels - Thomas farms only
(1) Adult Fly Monitoring Using Spot Cards: Overall, numbers of spots were found on cards were similar to 2001 and higher than the 2000 season. This was a result of the warm weather conditions and late season rains.
(2) Maggot and Pupal Surveys: Observations of maggot populations in various areas around the farm indicated that the highest levels continue to be found in areas with moist (around an 18% moisture level), undisturbed organic material. Maggots are not found in very dry or wet areas. Manure, bedding and spilled feed provides material for fly breeding. The highest concentration of maggots were found in calf hutches, spilled feed areas within barns, and in areas along posts and walls were manure was not removed routinely Since maggot control is a key component in total fly management, these areas need to be continually targeted for cultural practices including improved sanitation and alternative bedding.
(3) Alternative Controls:
(a) White Fly Tapes: These tapes continue to be an integral part of adult fly management. Adults prefer these thin tapes over the old yellow "fly strips".
(b) Fly Baits: Fly baits are also an important part of an adult fly management program. They continue to provide effective adult knockdown but work best when used in combination with the tapes. The baits are safe to use with parasite releases.
(c) Parasites: Maggot and pupal densities were observed at clean outs in calf pens receiving parasites. In general, populations were lower in pens receiving parasites. However, this did not always translate into lower spot card counts. It appears that there were other sources of adult flies on each farm that also needed to be controlled. In both cases, the effectiveness of the parasites was eventually overwhelmed by other sources of flies. These results demonstrate the fact that sanitation and manure management is needed to get the benefit of parasite releases.
(d) Hister Beetle Predators: Hister beetles continue to show promise as a biological control tool since they are effective egg and maggot predators. In general, pupal counts were lower in pens receiving hister beetles. However, only 2-3 beetles were recovered from each pen using a Berlesse funnel to sample the bedding for adult beetles. Additional work is need on release rates and sampling methods to determine if populations are established.
(e) Fly Cracker - Citric Acid - Although this material was evaluated in the calf barns in all 4 locations, it was difficult to determine if it can be effectively incorporated into a total management program. At least in one location (Heatwole's), it did appear to help reduce maggot numbers in calf pens. In order for it to be effective, it must used as one of tools in a total fly management program. New methods of evaluation need to be evaluated to determine if it can be used in a cost-effective manner.
(f) Use of Alternative Bedding: This strategy showed the most promise as a fly management tool for inside barns. The use of peanut hulls mixed with the straw resulted in lower maggot and pupal counts at the time of calf removal. In addition, seepage was lower from these pens. However, it appears that the advantage is only seen during the first month that calves are in the pens. When calves were larger, the benefits were minimal. The trial conducted at Thomas farms suggests that other bedding materials may provide more promise including coconut hulls and pine bark. In order to be cost effective, a combination of these materials with straw will need to be considered.
(g) Use of Potash in Pack Areas: Early in the season, the use of potash did appear to help reduce maggot populations on edges and around posts. However, it was difficult to get a thick enough layer throughout the pack to effectively reduce populations season long.
(1) Maintain Adult Fly Management Program on participating farms including pre-season sprays, sticky tapes, baits and in-season sprays timed when fly populations increase above the threshold of 50 flies per trap.
(2) Focus on 3 main management strategies to manage maggot populations:
· Evaluate Hister Beetle - egg and maggot predators on in calf barns in all locations
· Expand alternative bedding demonstration to include all farms using coir and pine bark
· Evaluate a better method to incorporate Fly Cracker into a management system
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