Are our trees in trouble?
Natural predators and pathogens are the main reason the gypsy moth outbreak in North America is collapsing. Nuclear polyhedrosis virus (NPV) is a viral infection known to kill gypsy moth larvae once the virus builds up in a population. It can spread quickly from infected larvae to non-infected larvae, killing them.
Entomophaga maimaiga is a fungus known to cause gypsy moth populations to collapse. Cool, wet conditions provide an ideal environment for the spread of this fungus.
Birds, mammals and other insects are also known to prey on gypsy moth. A species of wasp called Ooencyrtus kuvanae is known to parasitize gypsy moth eggs and can reduce gypsy moth populations.
Canada’s cold winters are also an effective method to control Gypsy Moth. Overwintering egg masses experience a 90% mortality rate when exposed to temperatures below -24 °C for a period of 5 or more days.
Will Gypsy Moth kill my tree?
Gypsy moth is unlikely to be the primary factor that causes a tree to die unless there is significant repeated defoliation. Defoliation of the leaves will reduce annual growth and create a higher risk for other health issues including, drought, secondary pests, and poor growing conditions. If you have a healthy mature tree the risk from gypsy moth is minimal. Young, newly planted trees are most susceptible to gypsy moth damage. They are also easy to treat due to their height allowing you to reach the caterpillars easier.
If your tree does lose leaves due to gypsy moth, don’t panic, your tree will produce new leaves in 2-3 weeks, and it is most likely not dead.
Can I use sticky tape or duct tape to prevent gypsy moth on my tree?
Sticky tape or duct tape can be used as a tool to prevent caterpillars from neighbouring trees or properties from infecting your healthy trees. Sticky tape or duct tape is only effective at stopping small caterpillars when they first emerge and is not an effective tool at reducing caterpillar populations on an already infected tree. Placing sticky tape or duct tape on your tree at this time will capture and do more harm to other beneficial insects and wildlife than gypsy moth caterpillars.
I’ve been told to put burlap on my trees; how does it work?
Placing burlap on your trees is an effective way to congregate gypsy moth caterpillars in one location that makes their removal and disposal of easier. To place it on your tree cut a band of burlap approximately 45cm wide that will wrap around the trunk of your tree. Place a string in the center of the band to secure it to your tree and fold the top over the string to create a skirt. This pocket within the burlap provides an area for the caterpillars to hide during the day and avoid the sun. Check the burlap by lifting it twice a day and remove any gypsy moth caterpillars that you see by placing them in soapy water or squishing/crushing them.
Example video Gypsy Moth Burlap trap for caterpillars - YouTube
Burlap bands are not allowed on public trees at this time so please refrain from installing them on boulevard and park trees.
What is BtK?
The use of BtK is a cosmetic pesticide approved by the Health Canada Pest Management Regulatory Agency and is permitted for applications on private trees. According to Health Canada, BtK poses no threat to human health through either handling products directly or being exposed to them indirectly during a spray program.
BtK is a bacteria which occurs naturally in soil. The bacteria is poisonous only to a certain group of insects when ingested during their larvae or caterpillar stage. BtK does not affect adult moths or butterflies or other beneficial insects such as honeybees, or pets, birds, fish, or mammals. Learn more about BtK on Health Canada's Btk Fact Sheet and on Natural Resources Canada's website.
You can pick-up BtK from most garden centers and hardware stores for private use. BtK lasts for approximately 3-5 days on the foliage of trees and degrades overtime with UV exposure. Caterpillars must ingest the bacteria for it to be effective. BtK will also kill other caterpillars so it’s important to only spray when gypsy moth caterpillars are present and have at least 90% emergence from the egg masses as it can harm monarch caterpillars among others. Thankfully, their life cycles don’t overlap. Always read and follow the instructions and regulations when applying pesticides.
Will the Township of Centre Wellington be spraying trees with pesticide to remove gypsy moth?
The Township of Centre Wellington will not be spraying trees with a pesticide to aid in the removal of gypsy moth caterpillars in 2021. The Township is monitoring the situation and will be conducting an inventory and assessment of egg masses following protocols established in neighbouring communities in the fall to determine if spraying will be an appropriate response for 2022. The county is also looking into spray applications, you can find more information on that here.
I’m noticing a rash or irritation after removing gypsy moth caterpillars.
The fine hairs of the gypsy moth caterpillar can cause a rash or irritation that appears similar to an insect bite. Some individuals are allergic to the hairs but not all. Wear gloves to help minimize contact with the caterpillars. If you notice a rash or irritation it will go away shortly, if your problem persists contact a medical professional for assistance.