As the spring months fall upon us, you’ll be thinking about getting into the garden. Well one thing to watch out for this year is tent caterpillars. This guide goes through what you can do to protect your trees.

The larvae of numerous moth and butterfly species combined are referred to as tent caterpillars. You can see tent caterpillars distributed throughout many parts of Canada and the United States, and they may multiply while defoliating several species of shrubs and trees in a relatively short amount of time. They may also be responsible for webs that protect caterpillars from predators. However, these “tents” are aesthetically unpleasing in tree branches. Neglected orchards and roadside trees are where you will most commonly see them.

A tent caterpillar doesn’t usually threaten the lives of trees, but infestations of them can be unsightly, so when they occur, you can use a professional service like Mr. Tree to eliminate the infestation for you. However, before you can eradicate tent caterpillars, you must first be able to identify them, which means knowing everything possible about the four most common types of tent caterpillar.

1. Forrest Tent Caterpillar

Malacosoma disstria

Malacosoma disstria

The forest tent caterpillar is usually located in areas of Canada and the United States where hardwoods can be found. Notwithstanding the name, this is a pest that does not spin a true tent. Rather, it creates a silken mat on top of the surfaces of branches.

Larvae look a lot like M. americanum but have a bunch of keyhole-shaped white spots that run down the back rather than a solid line. Adults of the species are light yellow to tan-colored moths that are just over one inch long with forewings containing two dark bands. Host plants consist of aspen, maple, wild cherry, oak, and hawthorn.

2. Fall Webworm

Hyphantria cunea

Hyphantria cunea

The fall webworm lives most often in parts of North America and can feed on over 85 species of trees. Different from tent caterpillars that build nests in trees, webworm webs are generally positioned at the outer ends of branches.

These caterpillars are coated with long hairs in a variety of colors, with a yellow stripe on each side and a black stripe on the back. They are roughly one inch long. Their heads are black or red, and adults of the species are pure white and often have dark spots on their wings.

3. Eastern Tent Caterpillar

Malacosoma americanum

Malacosoma americanum

Eastern tent caterpillars are usually located east of the Rocky Mountains and north into the southern part of Canada. Full-grown caterpillars are roughly two inches long, are black in color with pale blue spots on the side, and have a little bit of hair. They bear a white stripe down the center of their backs, which makes them easily identifiable.

Adult moths of the species are reddish-brown with two white bands running diagonally across each forewing and are just over one inch long. Host plants include cherry, crabapple, apple, and crabapple, but can be seen on an array of shade trees too.

4. Western Tent Caterpillar

Malacosoma californicum

Malacosoma californicum

Located primarily in northern and western areas of Canada and the United States. These caterpillars are roughly two inches in length, hairy, and yellowish-brown with blue spots on their backs and orange spots scattered in-between.

Adults of the species are orange-brown with two slim yellow lines on the wings. Willow, poplar, cottonwood, birch, apple, oak, cherry, plum, and roses are preferred host plants.

Life Cycle of the Tent Caterpillar

Once you’ve figured out how to identify a tent caterpillar, the next step is to understand life cycles. Many species of tent caterpillars hibernate in the egg stage. Dark brown to gray egg hordes comprising of 150 to 400 eggs are connected throughout the small twigs of trees and shrubs. Hatching occurs roughly when leaf buds start to evolve, typically in early spring. Caterpillars are convivial and quickly create silken tents, which operate as shelter throughout the early morning and evening hours and throughout rainy spells. They abandon their tent and eat only during the day, leaving a silk trail as they crawl in order to find a way back to their sanctuary.

Roughly six weeks after hatching, and five instars later, the larva develop into being fully grown with hair, and they’re up to two inches in length. Pupation happens in silken cocoons, which are usually located on fences, tree trunks, or leaf litter. Around two weeks after, adults of the species come to light and quickly lay the hibernating eggs. One generation per year is the frequency with which this process occurs.

Defense Measures

So now that you know how to identify a tent caterpillar and what its life cycle involves, you’re ready to attempt controlling them. There are many things to consider when attempting to do this, including:

  1. Get rid of and scrape away hibernating egg hordes and remove the protective tents with your hands prior to the beginning of the feeding of the larvae.
  2. Constrain caterpillar movement and restrict access to eating areas via the use of Tree Tanglefoot Pest Barrier or Sticky Tree Bands.
  3. The organic, soil-inhabiting bacterium Bacillus thuringiensis or Bt-kurstaki is especially useful when used on inchworms of all kinds. Employ easily used spray to hit worms and defend the leaves at the first signs of harm. You should also keep in mind that Btk sprays do not impair honey bees or birds and are not dangerous to use close to children and pets.
  4. Spinosad, a biological agent that originated from fermentation, is also highly efficient. It’s the active ingredient in Monterey Garden Insect Spray, an organic product, as listed by the USDA, and recognized for organic use by the Organic Materials Review Institute. Note that Spinosad is toxic to bees, so apply late in the evening and only to plants that aren’t producing blossoms or pollen.
  5. AzaMax contains azadirachtin, the crucial insecticidal ingredient in neem oil. This useful spray disturbs the growth and development of pest insects and has repellent and antifeedant properties. Most importantly, it’s safe for honeybees and several other useful insects.
  6. Fast-acting botanical insecticides must be utilized as a last-ditch option. Originating from plants, they have insecticidal properties, have fewer dangerous side effects than synthetic chemicals, and break down more rapidly.

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