Kansas State University


Extension Entomology

Tag: eastern tent caterpillar

Eastern Tent Caterpillar

–by Raymond Cloyd

The larvae (caterpillars) of the Eastern tent caterpillar, Malacosoma americanum, have hatched from eggs are feeding on the leaves of trees and shrubs (Figure 1).


Fig 1. Eastern Tent Caterpillar Feeding On New Leaves (Auth–Raymond Cloyd, KSU)

After caterpillar’s hatch from eggs, they create a distinct white, silken nest (or tent) in the branch crotches of trees and shrubs (Figure 2)

Fig 2. Eastern Tent Caterpillar Tent or Nest (Auth–Raymond Cloyd, KSU)

including: birch, crabapple, hawthorn, mountain ash, poplar, willow, and flowering cherry, peach, and plum. The nest protects caterpillars from cold temperatures.

Caterpillars are black with a distinct light stripe that extends the length of the back and there are blue markings on the side of the body (Figure 3).

Fig 3. Eastern Tent Caterpillar (Auth–Raymond Cloyd, KSU)


There are five instars (stages between each molt). Eastern tent caterpillar is one of our earliest caterpillar defoliators, feeding on newly-emerged leaves, which reduces the ability of trees and shrubs to produce food by means of photosynthesis. Although feeding damage may not directly kill a tree or shrub, a decrease in photosynthesis can predispose plants to secondary pests such as wood-boring insects. Leaf quality can influence tree and shrub susceptibility to feeding. For instance, black cherry trees grown in the shade are less fed upon by Eastern tent caterpillars due to lower leaf nutritional quality.

The young or early instar (1st through 3rd) caterpillars are active during the daytime and reside in the silken nest at night. During the day caterpillars emerge from the silken nest and feed on plant leaves. On over-cast or cloudy days, caterpillars will remain inside the silken nest. The final instar (5th) caterpillar only feeds at night. The length time of time that caterpillars spend feeding increases 4-fold between the 1st and 5th instars. However, feeding activity is contingent on temperature with caterpillars feeding longer under warmer temperatures than cooler temperatures. Eastern tent caterpillar overwinters as an egg mass attached to the branches or small twigs (Figure 4). There is one generation per year in Kansas.

Fig 4. Eastern Tent Caterpillar Egg Mass Attached To Branch (Auth–Raymond Cloyd, KSU)

The silken nests can be physically removed or disrupted by hand. You can destroy, disrupt, or open-up the silken nest using a rake or a forceful water spray. The young exposed caterpillars are susceptible to consumption by birds whereas the later instars are less fed upon because the hairs on the body deter birds from feeding on them.

Spray applications of the bacterium, Bacillus thuringiensis subsp. kurstaki, or spinosad are effective in killing small (young) caterpillars and suppressing minor infestations of Eastern tent caterpillar. These insecticides are stomach poisons so caterpillars must ingest the material to be negatively affected. However, when caterpillars are mature and approximately 2 inches long, then pyrethroid-based insecticides (e.g. bifenthrin, cyfluthrin, and lambda-cyhalothrin) will need to be applied. It is important to apply insecticides when caterpillars are active during the daytime to increase exposure to the insecticide. For more information on managing Eastern tent caterpillar populations contact your county or state extension specialist.


The Kentucky Derby = Finish Line Winner: ??? Kansas Insect Newsletter???

—Dr. Robert Bauernfeind

Yes —- there is a connection (although admittedly I may streeeetch the rubber band thin). The Kentucky Derby is held the first Saturday of May (tomorrow – May 2) and the winning horse will cross the finish line making some bettors and owners HAPPY!!! Coinciding with this Annual Run-for the-Roses are Eastern tent caterpillars and European pine sawflies which also are fast approaching the finish line for their yearly foraging activities.

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ETCs are nearly mature. I expect that by next week, they will have begun transitioning into their pupal stage. This begins with caterpillars creating their silken cocoons which are coated with a whitish/yellowish powdery substance (which can be irritating to a person’s skin and eyes).

Caterpillars may remain on the host plant, their cocoons being exposed (A) or somewhat concealed/wrapped in a leaf (B). Sometimes caterpillars may go “walkabout”, leaving their tree host to make an individual cocoon, or sometimes gathering and making cocoon clusters (C). After formation of cocoons has been completed, caterpillars transition into their pupal stage (D).

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By late May/early June, moths (A) will emerge and mate. Egg masses will then be deposited on twigs (B). A hard shellac-like coating (C) protects the eggs through the summer heat and rigors of winter. Their cycle will be renewed with egg hatch and caterpillar emergence in March of 2016.

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Regarding EPS, one has but to approach a heavily infested pine to know that the larvae are nearing the end of their feeding stage. The sparse/bare branches (a result of increasingly large larvae satisfying their ravenous appetites) signal an approaching end to their feeding cycle.

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Within a week, larvae will begin forming their thin-walled papery and somewhat leathery cocoons. Like eastern tent caterpillars, some larvae will form cocoons while remaining on their host (A). However, most will leave their host to form cocoons elsewhere. Cocoons may not be obvious because they will be camouflaged with particles of dirt and debris. When cocoons are formed under their host tree, the dirt/debris consists mostly of fecal pellets (B) which dropped to the ground by larvae as they fed.

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Unlike the rather immediate appearance of adults/mating/egg production of eastern tent caterpillars, European pine sawfly larvae aestivate (period of “rest”/decreased metabolic activity in response to higher temperatures) during the summer months. Actual pupation occurs in the fall followed by the emergence of adult sawflies (A) at which time mating occurs and overwintering eggs are inserted into needles (B). Their cycle will be renewed with egg hatch and larval emergence in late March/early April of 2016.

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Eastern Tent Caterpillar (ETC) and European Pine Sawfly (EPS) Update

—by Dr. Bob Bauernfeind

While recent cool temperatures have had people wondering when warmer temperatures will prevail, both ETC and EPS have thrived —– not surprising because these are cool-season insects.

Currently, Eastern Tent Caterpillar “tents” are of sufficient size that they can be easily detected. If people object to the presence of webbing and caterpillars, and if within hands-reach, the easiest remedy is to use your fingers to “rake-out” the web. Preferably do this during daylight hours when most (if not all) caterpillars are “resting” within. Do not fret if several caterpillars fall to the ground —- individually, the few escapees are of no concern. If a person is skittish about touching web masses (and the caterpillars and frass within), that portion of the branch can be pruned and disposed of.

Eastern Tent Caterpillars

European pine sawflies require a different approach because it is impractical to prune out each infested terminal. Fortunately, EPS are highly susceptible to insecticides. There are numerous products registered for use in Kansas against EPS. Horticultural oils and soaps are very effective against the “soft-bodied” larvae. A single thorough application will eliminate EPS larvae. But do so NOW before they become thoroughly destructive.

European pine sawfly