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

The research paper discusses the measures taken to control Eastern Tent caterpillars on horse farms in order to reduce the incidence of Mare Reproductive Loss Syndrome, a disease causing foal abortions and financial losses. The team investigated various control methods, including various sprays and treatments, and determined their effectiveness and impacts.

Exploration of Caterpillar Distribution and Emergence

• The researchers began by investigating the distribution and emergence of the caterpillars to better develop their approach. This included recording emergence times, location of egg masses, and the duration of the caterpillar lifecycle.
• They found that the caterpillar egg masses mostly dwelled in the lower canopy and exposed sides of trees, where larvae emerged around mid-March. The emergence time varied, lasting for 3-4 weeks in cooler spring months, but was more simultaneous in warmer weather.

Efficacy of Different Control Strategies

• Various control methods were tested, including spraying of foliage with different insecticides, winter egg mass treatments, trunk injections, and barrier sprays to intercept larvae entering pastures.
• Winter treatments with bifenthrin or permethrin proved effective to prevent larvae emergence, but 3% horticultural oil was ineffective. Direct sprays of insecticidal soap or oil on larvae offered poor control levels.
• Bifenthrin and spinosad sprays were identified as beneficial against all stages of the caterpillars, and remained active in weathered conditions for about a week. Bacillus thuringiensis var kurstaki was active against young larvae within 3 days, but proved less effective against mature larvae.
• Trunk injections with dicrotophos were effective but the ones with milbemectin or abamectin were inconsistent. Injections with emamectin benzoate were also effective.
• Residues of permethrin effectively controlled mature caterpillars in pasture grasses for a week.

Complicating Factors in Caterpillar Management

• The article concludes by discussing the multiple factors that complicate the management of the caterpillars on horse farms. It does not, however, clarify these complicating factors.

The research presented in this article outlines the ways in which farmers can control the Eastern tent caterpillar population on their lands, with the goal of reducing the prevalence of MRLS among horse populations. It provides vital information for farmers, advising them on the best times and ways to act to minimise the impacts of these damaging insects.