Dung Beetles

Dung beetles have significant beneficial effects in cattle pastures. By breaking down and burying dung pats (Figure 1) they clear the pasture of dung accumulation, return nutrients to the plant root zone and reduce compaction. They also reduce parasite challenge to cattle by removing breeding areas for bushflies, biting midges and buffalo flies.

• Dung beetles disrupt parasite life cycles that rely on dung (bushflies, biting midges, buffalo flies and worms).
• They are negatively affected by some parasite control chemicals (some MLs and SPs).
• Populations are especially vulnerable during their early breeding season (spring months in winter rainfall regions, October to March in northern Australia).
• The product label should be checked for risks to dung beetles and it is critical to use the dose rates specified on the label when treating cattle.
• Treatment by injection, pour-on, oral and dipping has a greater risk of effect on dung beetles.
• Treating cattle with ear tags has the least effect on dung beetles, followed by backrubbers.
• Ongoing and repeated use of dung beetle–active chemical treatments have the worst effect on dung beetle populations.
• Minimise treatments with high risk chemicals when dung beetles are most active.
• Chemicals should be applied strategically, and only when economic thresholds for parasites have been exceeded, to reduce the number of treatments required.

The adverse effects of some parasite control products can include death of adult beetles, eggs or larvae, reduced breeding capacity of adults and retarded growth of larvae. Heavy chemical usage may lead to local extinction of some dung beetle species. Populations are especially vulnerable during their early breeding season. In some situations, there may also be a short-term indirect effect on the rate of earthworm colonisation of dung pats.

Not all chemical treatments affect dung beetles and whether or not tick, fly, lice and worm treatments are damaging to dung beetles is determined by a number of factors. Harmful effects can be avoided with careful choice and use of chemicals.

Factors determining effects of chemical treatments on dung beetles

Chemical type: The different chemical groups and chemical actives registered for application to cattle and their likely effects on dung beetles are listed in Table 1. The two main groups implicated in undesirable effects on dung beetle populations are synthetic pyrethroids (SPs) and macrocyclic lactones (MLs), although the effects of chemicals from other chemical groups, particularly some more recently registered products are less clearly defined. In addition, there are marked differences in the degree to which the different types of MLs impact dung beetles and these are listed in order from highest to lowest in Table 1. Where there is a risk of effects on dung beetles, this is usually listed on the product label.

Method of chemical application: The likely effect of a chemical treatment method is determined by the amount of chemical absorbed. Most chemical is absorbed from injection, pour-on or oral and dipping treatments, less from over-sprays, even less from backrubbers and least from ear tags. However, this is also influenced by the type and concentration of the chemical used. Depending on the chemical contained, slow release capsules (only registered for sheep not cattle in Australia) can have severe effects against dung beetle populations because of their prolonged release of active compound. Less persistent formulations have less severe effects.

Mode of excretion from the animal: Chemicals where a significant proportion of unaltered chemical or toxic breakdown products are excreted in dung represent the greatest hazard for dung beetles. Synthetic pyrethroids (SPs) and macrocyclic lactones (MLs) and some insect growth regulator compounds (IGRs) are excreted mainly in the dung whereas most organophosphate compounds (OPs) are excreted principally in the urine and therefore have less effect on dung beetles.

Frequency and timing of chemical application: The worst effects on dung beetles occur when there is ongoing and repeated use of dung beetle–active chemical treatments, or where there is extended release of chemicals such as with controlled release capsules. Repeated or long-term use of dung beetle active chemicals can have significant and persisting impacts on populations. Effects can lead to local extinction of some dung beetle species in severe instances.

In northern Australia, dung beetles are most active from October to March and most susceptible to the effects of chemicals during this time. In winter rainfall regions it is in spring months. Treatments with high risk chemicals should be minimised during these periods.

Strategic applications, and application only when economic thresholds for parasites have been exceeded, can reduce the number of treatments required. Have a worm egg count done and seek advice before treating for internal parasites. Information on the effect of different chemical groups on dung beetles is provided on the chemical groups and actives pages.

Some animals are more susceptible to parasites and treating only the animals that really need treatment can reduce chemical use. For example, weaners and young cattle are most susceptible to worms; bulls usually carry the heaviest populations of buffalo flies. Bos indicus cattle are generally more resistant to parasites and require less treatment. Look at the treatment sections in TickBoss, WormBoss, FlyBoss and LiceBoss for the best advice on when, what and how to treat cattle for the different parasite groups.

Concentration: It is critical to use the dose rates for parasite treatment products specified on the label. Even chemicals considered low risk to dung beetles can have damaging effects if used at higher than recommended dose rates. Beware that using lower than the label-recommended dose rates can also have undesirable impacts by leading to rapid resurgence in pest numbers, requiring more treatments, with ultimately greater effect on dung beetles.

Table 1. Chemical groups and chemical actives contained in cattle parasite treatments and their likely effects on dung beetles

For more information on dung beetles refer to the Dung Beetles Australia website.