Contents
Summary
Introduction
Life Cycle
Drench Toxicity to Dung Beetles
How to help dung beetles around drenching
Tips for drenching around dung beetles
Summary
- Drenching doesn’t affect adult dung beetles, just the eggs they lay in dung in the first few days after drenching.
- As only half a generation of eggs become unviable after drenching, responsible drench programs don’t have long term negative effects on dung beetle populations.
- Hold animals in a designated area/paddock after drenching for a week or two if you want to mitigate that effect, regardless.
Introduction
One of the unintended and unwelcome consequences of the introduction of domestic cattle in Australia was the proliferation of bush flies, and the introduction of the Buffalo Fly. Both of which are dung breeding insects.
In the 1950’s it was found by the CSIRO that dung beetles could provide a solution by burying dung which reduces fly breeding sites and overall fly numbers. Through their burying activity, dung beetles have also been found to reduce the number of worm larvae on the pasture. This activity also replaces nutrients and aerates the soil. It is important when treating cattle with important animal health products, to try to minimise unintended effects on beneficial insects such as the dung beetle.
As a result, in 1998, the Australian Pesticides and Veterinary Medicines Authority (APVMA) which was previously the National Registration Authority (NRA), conducted a major investigation into the effects of macrocyclic lactone (‘mectin) drenches on dung beetles, and concluded that there were no long term detriment to dung beetle populations (National Registration Authority, 1998). Along with contemporary research, this investigation allowed many products to stay on the market and for many more to be approved.
Life Cycle of Dung Beetles
Most species spend 95% of their time underground and within dung pats, leaving these spaces only in search of a new dung pat in which to lay their eggs. Dung beetles generally live for 1-2 years and their life cycle, from laying of eggs to emergence of adults, can be 3 weeks to 3 months. In northern states, dung beetles are most active from October to March (wet season) and in southern states, they are most active in spring (Wormboss, 2022).
Life cycle processes explained:
- Adult beetles are attracted to fresh dung and will fly to find it.
- Male and female pairs mate and create a nest environment that will provide their eggs the best chance of development and survival.
- Eggs are laid, either in the dung pat itself or in a dung ball (brood ball). Some species lay their eggs, so they remain attached to their backs. Once they partition a ball of dung from the pat, they place a single egg in that ball of dung and close it up. Other species lay their eggs and then individually wrap eggs in dung until it forms a ball shape. Females typically lay 10-80 eggs in their lifetime.
- Eggs hatch in 1-2 days, transitioning to the larval stage.
- Majority of development occurs in the larval stage. The larvae feed on dung while they develop and grow, normally consuming 40-55% of their dung ball.
- After 1-4 weeks, the larvae pupate and move into stage 4.
- The transition from larvae to adult begins during pupation. The pupal stage may last from 2 weeks to several months and is the most variable stage between different species. The pupal stage determines the population spikes seen among dung beetles. The pupae remain in dung balls until they fully mature, at which point the beetles emerge as adults.
- In the final stage, adults are ready to relocate to a fresh dung pat to start the life cycle process again. They must find a mate with which to pair bond and start preparing a new nesting environment. Even though dung beetles are modest sized insects, they can fly up to 48km in search of fresh dung.
Drench Toxicity to Dung Beetles
For dung beetles, the effects of ivermectin and other macrocyclic lactones have been extensively researched. No adult mortality was recorded when studying the effects of ivermectin on dung beetles, however, 100% mortality of larvae was observed when laid in dung collected a day after treatment (Jacobs & Scholtz, 2015). Most articles come to the general conclusion that ivermectin residues in dung are of greater risk to the dung beetles’ larvae as opposed to adult dung beetles. This is due to the feeding mechanism difference between the life stages. Larvae have biting mouthparts that feed on entire dung. Whereas adults have specialized mouthparts that screen out the larger fragments of digesta (Holter, 2003) – to which ivermectin attaches strongly (Halley, Nessel, & Lu, 1989). Therefore, with this filter feeding technique, adults are likely to consume less ivermectin than the larvae with their bulk feeding habits (Floate, Wardhaugh, Boxall, & Sherratt, 2005). Concentrations of ‘mectin residues found in dung after treatment peak after a day or two and then taper off back to normal over one to two weeks. As such, no larval mortality was observable six days after treatment (Jacobs & Scholtz, 2015).
It is interesting to note that due to its chemical and lipophilic properties, studies have found that moxidectin doesn’t cause any fatalities to adult or larvae dung beetles (Jacobs & Scholtz, 2015). This is great news for long acting moxidectin injections including Vetmec Moxiguard Long Acting for Sheep and Vetmec LA for Cattle. White and clear drenches including albendazole and levamisole (in Vetmec Dual and Vetmec LEV Pour-On) are also very safe drenches for dung beetles (Dung Beetle Ecosystem Engineers, 2023). All these drenches can still be used as a strategic tool in a drenching regime without needing to worry about harming dung beetle populations.
How to help dung beetles around drenching
All sheep, and most cattle at some stage during their lifetimes, will need drenching with a ‘mectin product, for example, Vetmec LV + Selenium, Vetmec Injection, Vetmec F Injection or Vetmec Pour-On. This is done for obvious animal welfare and production performance reasons. All the research concludes that drench residues in dung will only have a very short effect on dung beetle larvae survival, only affecting eggs when they’re laid into treated dung pats (i.e., dung with ‘mectin residues). Adult dung beetles will continue laying eggs in safe dung pats meaning, overall, only half of a generation is likely to be inviable following drenching of cattle. Research suggests that with responsible drenching practices (i.e., not over-drenching), then a couple of drenches per year will be safe for the dung beetles on your property.
If you have a thriving dung beetle population that you’ve invested time and/or money into, you don’t want necessary worming treatments to send you backwards, so here’s some tips to be able to drench your cattle AND have a constantly happy dung beetle family.
Tips for drenching around dung beetles
- When using ivermectin, abamectin, doramectin, or eprinomectin drenches (pour-on, oral or injectable), contain unsafe dung pats in a certain area or paddock (ideally away from your good dung beetle populations) by holding the cattle in that area for up to 1 to 2 weeks. Provide quality feed and water.
- (1) is especially important when you’re treating stock during periods of high dung beetle activity (see Life Cycle).
- If you aren’t able to hold cattle in a designated area after drenching, and want to have no effect on dung beetle larvae, use moxidectin based products.
If you would like to chat more about drenching regimes, or how drenching may or may not be affecting your dung beetle population, feel free to give us a call on 1800 243 683, or contact us.
References
Daeda, M., Schaefer, D., & Young, D. (n.d.). Investigating the Dung Beetle Population at the Beef Grazing Farm. Madison, Wisconsin, United States of America.
Dung Beetle Ecosystem Engineers | Euoniticellus intermedius
Dung Beetle Ecosystem Engineers. (2023). Managing dung beetles on your farm.
Floate, K. D., Wardhaugh, K. G., Boxall, A. B., & Sherratt, T. N. (2005). Fecal Residues of Veterinary Parasiticides: Nontarget Effects in the Pasture Environment. Annual Review of Entomology, 153-179.
Halley, B., Nessel, R., & Lu, A. (1989). Ivermectin and Abamectin. In Environmental Aspects of Ivermectin Usage in Livestock: General Considerations (pp. 162-172). New York: Springer-Verlag.
Holter, P. (2003). Particle feeding in Aphodius dung beetles (Scarabaediae): old hypothesis and new experimental evidence. Functional Ecology, 631-637.
Jacobs, C., & Scholtz, C. (2015). A review on the effect of macrocyclic lactones on dung-dwelling insects: Toxicity of macrocyclic lactones to dung beetles. Onderstepoort Journal of Veterinary Research, Art. #858.
National Registration Authority. (1998). Special Review of Macrocyclic Lactones. Canberra: NRA.
Wormboss | Dung Beetles in Cattle.