Why Do I Have Caterpillars All Over My Trees?
As professional arborists, we often get asked “why do I have caterpillars all over my trees?” Here’s the answer.
What is it?
Gypsy Moth is an invasive pest that attacks a wide range of trees, including Oak, Maple, Birch, as well as certain deciduous trees. In some years this pest can reach outbreak levels and many trees can be defoliated completely in summer. Adding to this dramatic effect is the raining debris of caterpillar droppings, followed by swarms of white moths in late summer. The overall experience can be quite distressing for tree owners.
When are they active?
The egg masses are visible on tree trunks and branches from late summer through the following spring. Caterpillars emerge in April and can be observed feeding through June. This is the stage of development that causes defoliation.
Pupation can be seen between June and July. This is followed by the swarms of white moths in July and August.
Is it a serious problem?
Generally, healthy trees can withstand the damage and defoliation caused by Gypsy Moth. Populations rise and fall over the years, with some years being worse than others. Although unsightly, the health risk to host trees is relatively low.
Repeated defoliation in peak years can become more serious. With leaves being the ‘food factories’ for trees, a prolonged period of defoliation year after year can start to affect overall health and vigour.
What can you do?
Managing Gypsy Moth infestations is multifaceted. Destroying egg masses will reduce the overall population of moths for the next season. Egg masses can be carefully scraped off and destroyed. Dispose of the eggs in soapy water, or by burning.
Some egg masses can be dislodged or damaged by spraying water at them. Use caution if using a pressure washer, as bark can be damaged by the high pressure.
Burlap skirts installed around tree trunks provide a place for caterpillars to hide from the heat of the day. Collect the sheltering caterpillars and dispose of in the same way as the egg masses.
What can Maple Hill do?
Maple Hill Tree Services offers several services for reducing Gypsy Moth infestations.
In addition to burlap skirt barrier installation, we are available for the maintenance of these shelter traps, offering regular collection and disposal of the caterpillars within. Additionally, we offer clients Pheromone Traps later in the summer that attract and trap male moths and reduce the number of fertilized female moths. In this way overall populations can be reduced for the next year.
Biological controls are also available and can be quite cost effective and successful. This is done via micro injection into tree trunks and is non-toxic to the environment. Note: The application timing for this option is critical and any interest in this treatment method should be inquired about immediately if planning for use in 2021.
Long term health and vitality is critical for trees surviving repeated pest attacks. Improving the cultural conditions for host trees is integral.
Maple Hill can provide deep root Compost Tea applications to tree soils to improve organic nutrient content. We can further improve site conditions by the addition of well composted, high organic content wood chip mulches.
Both these strategies help to provide trees the best possible growing conditions, and in turn the best pest tolerance. Remember a healthy tree is a happy tree!
Traditional fertilizers can also be applied as needed for short term encouragement of new leaf development.
In the off season (September to April) egg masses should be effectively removed wherever possible. Most egg masses will be high in the canopy and removing these can be dangerous without the proper training and equipment. Maple Hill can access the parts of the canopy that are out of reach and safely remove the eggs, either through rope access or using aerial bucket trucks.
Tree pruning should also be considered where needed. Many traditional host trees affected by Gypsy Moth tend to have other regular pests as well. Sanitation pruning to eliminate these additional pests can help reduce the burden on host trees, and therefore the severity of the impacts from Gypsy Moth.
Are there other options?
Maple Hill also offers our clients monitoring through our Tree Management Program. With two annual inspections of the complete property pest and disease issues can be identified early and addressed as necessary. The inspections also provide detailed information about pruning needs, general tree health, and identified future tree care requirements to help you better plan and budget for any needed maintenance of your property trees.