Abortion research funded by TBQA

Thoroughbred Breeders Queensland is funding research regarding the link between processionary caterpillars and mares aborting.

Nigel Perkins from AusVet is one of the key researchers in the project and there have been plenty of developments since it began in 2005-06.  There has been some anomalies discovered between properties in New South Wales and Queensland, in that most of the caterpillar nests at NSW studs are found at the base of wattle trees, yet there are limited numbers at elevated levels in gum trees.  The situation appears to be the reverse in Queensland.

Researchers have conducted various experiments and found a clear link between mares ingesting caterpillars and caterpillar exo-skeletons and abortion or birth of compromised foals at term.  Abortions can occur from three to four days of the caterpillars being eaten, but in most cases it is between one to five months later, depending on the amount of time it takes for bacterial infection to develop in the foetus and placenta and result in abortion.

Researchers believe the caterpillars are accidentally ingested by the horses, possibly as they travel through paddocks from one tree to the next.  The caterpillars are native to Australia and may be found right across the country, therefore every stud has the potential to be affected.  While many affected studs will only have relatively small numbers of losses due to caterpillars (one to three abortions in a year for example), there are a small number of farms that have suffered heavy losses in particular years (as high as 40-60% of pregnant mares losing their foals).

There is no insecticide that is registered specifically for processionary caterpillar control though anecdotal information suggests that products registered for control of other caterpillar species are likely to be effective.

Current recommendations for caterpillar control are based on detecting nests and removing them from paddocks where pregnant mares are likely to be kept.  Inspection and removal should occur where possible between December and January to ensure that caterpillar material is removed before the caterpillars can pose risk to pregnant mares (thought to be from February on).  Nest material may be disposed of by burial or burning under suitably controlled conditions.

The thoroughbred breeding industries in Queensland and New South Wales and researchers from the University of Queensland are working together on this matter and have applied for various State and Federal grants to help fund further research to assist breeders in developing improved risk management strategies for controlling caterpillars on breeding farms.

General information on processionary caterpillars (Ochrogaster lunifer) including photographs of nests, caterpillars and moths, can be found on various web sites such as:



Nigel Perkins has prepared a report into his research relating to processionary caterpillars on property visits conducted during October & November 2012.  View his findings here:


Management of processionary caterpillars is relatively easy but you do need to be thorough.  Click here for what you can do: