DOI: 10.5061/dryad.44j0zpcp4
title: Data from: Rising temperatures may increase fungal epizootics in northern populations of the invasive spongy moth in North America

description: Insect pest species are generally expected to become more destructive with
 climate change because of factors such as weakened host tree defenses
 during droughts, and increased voltinism under rising temperatures;
 however, responses will vary by species due to a variety of factors,
 including altered interactions with their natural enemies. Entomopathogens
 are a substantial source of mortality in insects, but the likelihood of
 epizootics can depend strongly on climatic conditions. Previous research
 indicates that rates of infection of the spongy moth (Lymantria dispar) by
 its host-specific fungal pathogen, Entomophaga maimaiga, increase with
 environmental moisture and decrease as temperatures rise. High
 temperatures may have direct and indirect (due to the associated drying)
 effects on the fungus, but the interactive effects between temperature and
 moisture level on larval infection are unclear. Here, we test the
 hypothesis that warmer, drier conditions will decrease rates of infection
 of spongy moth larvae by E. maimaiga. We evaluated the effects of
 precipitation and temperature on larval mortality caused by E. maimaiga
 with a manipulative field experiment, conducted in one of the northernmost
 and coldest parts of the spongy moth’s nonnative range in North America.
 We caged laboratory-reared spongy moth larvae in experimentally warmed
 open-air forest plots, exposing the larvae to soil inoculated with E.
 maimaiga resting spores during two consecutive trials. Caged larvae were
 exposed to three temperature treatments—ambient, +1.7 °C above ambient,
 and +3.4 °C above ambient—and either supplemental precipitation (+173 mm
 per trial) or ambient precipitation. Opposite of our hypothesis, there was
 no significant effect of supplemental precipitation, nor an interaction
 between precipitation and temperature. There was, however, a significant
 positive effect of increasing temperature on the number of larvae
 infected. On average, in each respective trial, larval infection increased
 by 44% and 50% under the elevated temperature treatments compared to
 ambient temperature. Experimental warming may have increased infections
 because ambient temperatures at the field site were suboptimal for fungal
 germination. The results from this experiment suggest that in colder
 portions of the spongy moth’s invasive range, increasing temperatures due
 to climate change may enhance the ability of E. maimaiga to help control
 populations of the spongy moth.
description: # Data from: Rising temperatures may increase fungal epizootics in
 northern populations of the invasive spongy moth in North America
 [https://doi.org/10.5061/dryad.44j0zpcp4](https://doi.org/10.5061/dryad.44j0zpcp4) This dataset contains the results of this experiment, reported in the related article. The final results are raw counts of the number of spongy moth larvae infected by the pathogen, *Entomophaga maimaiga*. The general laboratory methods for obtaining these results are as follows: Following each field trial (trials 2 and 3), we transferred the larvae to the lab and secured them individually in lidded 1 oz. plastic cups containing a 0.20 g piece of artificial wheat germ diet. We maintained larvae at 18–22 °C and monitored them for 10 days or until death, whichever occurred first. Larvae that died within the 10-day monitoring period were placed on 1.5% water agar plates and checked daily for 3 days for conidial production. Although conidia are often visible without magnification, we noticed during the first trial’s observation period that conidia were sometimes only apparent under a dissecting microscope. We did not include trial one data in the statistical analyses because of the possibility that we missed conidia on cadavers that we inspected without a dissecting microscope. We examined cadavers from trials two and three under both a dissecting and a phase contrast microscope. For phase contrast microscopy, we macerated and smeared a larva onto a microscope slide and observed the specimen at 200–400× magnification. We counted a larva as infected by *E. maimaiga* if we saw conidia either externally or via phase contrast. It is also possible for larvae to have resting spores present instead of, or in addition to, conidia, but we did not expect this because previous research indicated that infections initiated by germ conidia from resting spores only produce conidia, not resting spores. ## Data-specific information for: Larval infection counts\_trials 2 and 3.csv: 1\. Number of variables: 5 2\. Number of cases / rows: 37 3\. Variables list (column headers): **block**: Unique identifier for a given experimental block **plot**: Unique identifier for a given experimental plot **temp_treat**: Temperature treatment     Temperature code           ambient: ambient temperature (no artificial warming)           low: low temperature treatment i.e., +1.7 degrees celsius warming above ambient           high: high temperature treatment i.e., +3.4 degrees celsius warming above ambient **precip_treat**: Precipitation treatment     Precipitation code           control: no supplemental precipitation added to cage with larvae           supplemental: cage received +173 mm additional (supplemental) precipitation during the trial **trial 2 infections**: number (count) of infected larvae in trial 2 for a given block, plot, temp_treat, and precip_treat    combination (i.e., cage). Infected larvae were those larvae that we identifed as being infected with Entomophaga maimaiga. **trial 3 infections**: number (count) of infected larvae in trial 3 for a given block, plot, temp_treat, and precip_treat combination (i.e., cage). Infected larvae were those larvae that we identifed as being infected with Entomophaga maimaiga.