Date of Award

Spring 5-5-2023

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Entomology

Advisor

Angela Mech

Second Committee Member

Philip Fanning

Third Committee Member

Allison Gardner

Additional Committee Members

William Livingston

Abstract

Browntail Moth (BTM; Euproctis chrysorrhoea) is a non-native species currently outbreaking in Maine. BTM are polyphagous folivores and feed on a variety of woody plant species, including many economically and ecologically important ornamental and forest trees such as oaks and apples. Human health is also a concern as BTM larvae produce urticating hairs that can cause severe dermatitis in people. New monitoring and management programs are urgently needed, with the current population densities reaching a 100-year high.

The Maine Forest Service monitors BTM populations by visually assessing winter nest densities and defoliation patterns, both time and labor intensive. This research investigated the optimization of BTM sex pheromone monitoring traps in field trials during the adult flight period in 2021 and 2022. Trials in 2021 tested lure purity and two trap types, bucket style and delta style sticky traps. Results indicate that male moths were more attracted to lures with > 95% purity and bucket-style traps. Trials in 2022 tested additional trap styles and color variations. Results from 2022 indicate that white traps were significantly more attractive than green or multicolored traps. The Pherocon 1C trap caught the most male BTM; however, it was not significantly different from the other white traps, indicating that any white trap could be recommended for use in future long-term monitoring programs for BTM.

In addition to monitoring evaluations, management strategies were tested for the control of BTM. Current control is the responsibility of municipalities and landowners, and broad-spectrum insecticides are commonly used due to the limitations of alternative control methods. Trials developing methods and testing the efficacy of more targeted biopesticide were conducted to determine if they were effective at reducing BTM populations. Initial trials observed BTM behavior in bioassay studies. Differences were found in the amount eaten and mass of larvae depending on the number of larvae present in bioassay cups (10, 25, 50 larvae, or the whole winter nest), which indicates that the amount of larvae present can impact lab experiment results.

Treatment bioassay trials testing the efficacy of different commercially available Bacillus thuringiensis (Bt) products were conducted in 2021 and 2022 on pre-diapause larvae. Survival and defoliation rates were determined for the various Bt treatments, both alone and including the use of spider peptides, which have the potential to increase the longevity and compound efficacy of Bt treatments. Results indicate that Bt products significantly reduce the amount eaten by larvae from control (water) treatments. Deliver (Bt kurstaki) used with peptide products was not significantly different from the current industry standard biopesticide product, Entrust (spinosad), a broad-spectrum insecticide. Peptide treatments alone did not significantly reduce the amount eaten from control treatments, but there were inconsistencies in the results of Basin and further testing is needed. The results of this research provide evidence supporting the adoption of new monitoring approaches and the potential use of less broad-spectrum biopesticides to manage BTM.

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