BacterioFiles 334 - Measuring Mycelial Moth Muncher Management

Gypsy moth caterpillar
By CharlesC, CC BY-SA 4.0

This episode: Figuring out the best way to study the spread of a fungus that kills an invasive tree-eating caterpillar pest!

Download Episode (8.2 MB, 8.9 minutes)

Show notes:
Microbe of the episode: Pasteurella aerogenes

News item

Journal Paper:
Bittner TD, Hajek AE, Liebhold AM, Thistle H. 2017. Modification of a Pollen Trap Design To Capture Airborne Conidia of Entomophaga maimaiga and Detection of Conidia by Quantitative PCR. Appl Environ Microbiol 83:e00724-17.

Other interesting stories:

Studying the whale microbiome

Gut bacteria help herbivorous ants get enough nitrogen

Environment factors can affect our microbes apart from genetic factors

Fiber could encourage gut microbes to help with type 2 diabetes

Gut microbes can affect parasitic worm infections

Post questions or comments here or email to bacteriofiles@gmail.com. Thanks for listening!

Subscribe: iTunes, RSS, Google Play. Support the show at Patreon, or check out the show at Twitter or Facebook.

Episode outline:

• Background: Invasive species can be incredibly harmful, no matter what size
• Kudzu in US south
• Rabbits in Australia
• Aedes albopictus mosquito all over the place
• Whenever they can get plenty of resources
• And lack of predators or disease
• Another problem species in US is gypsy moth, Lymantria dispar
• Introduced from Europe long time ago
• Caterpillars eat tree leaves, create bags of webbing
• Can defoliate whole trees and kill them
• Many different trees affected: oaks, birch, willow, etc
• Sometimes called “bagworms”, can get so abundant almost dripping from trees
• Top 5 costliest invasive insects in world, $3.2 billion yearly in US
• How to control? Could try introducing biocontrol
• Disease or predators
• Doesn't always work, like myxoma virus in Australian rabbits
• Parasitoids tried, also fungus called Entomophaga maimaiga from Japan
• What’s new: Now, scientists publishing in Applied and Environmental Microbiology have looked at how this fungus spreads through the air to infect and kill these invasive insects!
• Methods: Set up sampling near fields with known infected caterpillars
• Tested different ways of sampling to see which was best
• Just flat pieces of plastic
• Fungus DNA detected in 15/22 samples
• But didn’t last too long; DNA signal had decreased after 2 days, gone by 7
• Dry surfaces don’t maintain well
• So set up another type: wet traps modified from kind used for pollen
• Like jar with cup in bottom, topped by lid like lampshade (sloped) with screened opening
• Worked better
• So detected fungal DNA in PA through June
• Peak at mid-June; no more larvae after June
• Less fungus farther from defoliation; limit to spread
• But spread can be up to ~40 miles (64 km)
• Most 6-12miles, ~10-20 km, 
• Killed up to 86% of caterpillars around, but often not that much
• Applications and implications: Better understand fungal spread
• Predict how bad caterpillars will be in a given year
• Then modify pesticide spraying programs as needed
• One spore can make 1 million more from caterpillar
• Could try to help more spread
• Fungus seems spreading at same rate as caterpillars are, but 3 years lag
• What do I think: Not clear why DNA didn’t last long on dry surface
• Could be degrading, or getting washed off by rain, or fungus launching more spores
• Wet traps work better
• Overall biocontrol doesn’t seem super-effective, but better than nothing
• If too effective, resistance probably develop quickly
• This way can limit spread somewhat and use other methods of control in addition
• Resistance less likely
• Important that it is specific to these caterpillars, not likely to get out of control
• Still a long way from solving problem of invasive species