What is happening?
Have you noticed the caterpillars with blue dots on their backs crawling up and down your trees? You are not alone! Ontario is experiencing an infestation of Gypsy Moths this season and this means that your trees are at risk of being quickly defoliated!
These caterpillars feed on deciduous trees at an alarming rate; one caterpillar can eat its way through a square metre of leaves as it grows into its adult form. Maple, beech, birch, ash, poplar, oak and more are all appetizing to these ravenous insects. They will also move on to some of the evergreen trees when their deciduous buffet is exhausted!
Gypsy moths are currently at a stage in their life cycle that makes them susceptible to control. Safer’s BTK is a biological insectide that can be effective when applied while caterpillars are in their crawling stages. Joining the ranks of many products that have been in demand during the pandemic, this may be difficult to acquire. Try your hardware store if they have it available.
Life cycle of the Gypsy Moth
What can you do?
Fortunately, there are natural controls!
While awaiting the arrival of more BTK, there are several natural controls that you can use to eliminate the caterpillars.
1. Pressure wash the trunk and main branches of your trees to dislodge the caterpillars.
2. Hand remove any visible caterpillars.
3. Apply a band of caterpillar tape or duct tape inside out on the tree trunks. Caterpillars travel up and down the trunk and will become stuck on the sticky tape. **If using this method, please add a layer of chicken wire or mesh to the outside of the duct tape as birds may also accidentally become trapped.
4. Create a burlap trap on trees with heavy caterpillar traffic:
Wrap a piece of burlap around the trunk and tie a string tightly at the halfway point of the fabric.
Allow the top half of the burlap to drape down over the string, creating a fold.
Check the burlap trap regularly as the caterpillars will use this as a place to retreat from the hot sun. They won’t be able to navigate their way upwards and become trapped.
Remove the trapped caterpillars and allow them to drop into a bucket of soapy water. They cannot swim.
Keep an eye out in the coming months for the pupa and moths; pupa can be removed by hand and moths can be attracted to traps. Next January/February, add the removal of egg masses from tree trunks to your list of ‘things to do in the garden’.
Healthy trees can naturally handle a season or two of defoliation and they’ll leaf out the following spring as they normally would. Weakened or vulnerable trees plus several seasons of defoliation are detrimental to the health of your trees, and we encourage you to help keep them strong!