Question: June 9, 2006

Hello - I am Dr. Mary Menard (an OSU grad) and a camelid veterinarian.  We have been getting a lot of questions from clients about the possible reproductive effects of Eastern tent caterpillars on the pregnant females (we are in the upstate NY area and inundated with them!!!) We are well familiar with the tragic losses in the equine industry and did not know if we need to be equally concerned for the camelids.  Can you direct me to someone who may be able to help us?  Thank you for your help - your ICI articles are very helpful -keep 'em coming!

Mary C. Menard, DVM

Answers:

I work with 3 alpaca herds in the middle of the bluegrass horse farms and we have had no problems while the horses were experiencing devastation.

Norm Evans

No I have no idea if they can cause any harm. I would still caution about them because one of the mechanisms that is suspected in causing problems with these caterpillar is just the spead of infection from the gut.
Ahmed Tibary

I do not know if the same problem can occur in alpacas/llamas fed
caterpillars.  Their gi tract is different.  I was under the impression that
the toxicity was dose dependent and higher doses led to shorter times to
abortion.  The mares exposed also developed a fibrinous pericarditis which
was associated with exposure to the eastern tent caterpillar.  So to be on
the safe side, prevention of exposure would be prudent.  I have attached a
fairly scientific article about control.  Sounds complicated to me and the
best time is to treat the egg sacs before larvae emerge. 

Jeff Lakritz

(Only posting abstract and citation here)

Pest Management Science Pest Manag Sci 61:3–15 (2005) DOI: 10.1002/ps.958

Managing Eastern tent caterpillars Malacosoma americanum (F) on horse farms to reduce risk of mare reproductive loss syndrome†

Daniel A Potter,* Leslie Foss, Rebecca E Baumler and David W Held‡

Department of Entomology, S-225 Agriculture Science Bldg North, University of Kentucky, Lexington, KY 40546-0091, USA

Abstract:An equine disease now known as mare reproductive loss syndrome(MRLS) struck the Ohio Valley in 2001–2002 causing thousands of foal abortions and enormous economic loss. Evidence that pregnant mares’ exposure to Eastern tent caterpillars Malacosoma americanum (F) induces MRLS created an urgent call for control measures suitable for use on horse farms. We surveyed egg mass distribution and monitored emergence in wild cherry trees, and evaluated reduced-risk treatment strategies including foliage sprays, trunk injections, winter egg mass treatments and barrier sprays to intercept larvae entering pastures. Egg masses were concentrated in the lower canopy, on exposed sides of trees. Larval emergence began in mid-March. Emergence was prolonged (3–4weeks) in 2002, a typically cool spring, but more synchronized in warmer 2003. Winter treatment of egg masses with bifenthrin or permethrin in a penetrating solvent prevented emergence, but 3% horticultural oil was ineffective for that purpose. Insecticidal soap or oil sprayed directly on neonates gave relatively poor control. Bifenthrin and spinosad were effective as foliage sprays against all instars, their field-weathered residues active for at least 7 days. Bacillus thuringiensis Berliner var kurstaki controlled neonates within 3 days but was less active against late instars, with shorter residual action than bifenthrin or spinosad. Larvae did not avoid insecticide treated leaves. Trunk microinjection of cherry trees with dicrotophos was effective against all instars, where as microinjection with milbemectin or abamectin gave poor or inconsistent control. Trunk injection with emamectin benzoate also was effective. Dry permethrin residues controlled late instars crawling in pasture grass for at least 7 days. Factors complicating M americanum management on horse farms are discussed.

. 2004 Society of Chemical Industry

Keywords: Malacosoma americanum; Eastern tent caterpillar; microinjection; mare reproductive loss syndrome; pyrethroids; horse farms