do birds eat spongy moth caterpillars

Gypsy Moth CatapillarLymantria dispar (Linnaeus), the spongy moth, is one of North Americas most devastating forest pests. Etienne Leopold Trouvelot in 1868 accidentally introduced the spongy moth, a native specie of Europe and Asia, into the USA. By the 20th century, the spongy moth has spread over 20 states from its introductory state Massachusetts. In 1932 in Pennsylvania, the first spongy moths were detected in Luzerne and Lackawanna Counties. By the 1980s, the infestation advanced into Centre, Blair, Huntingdon and Clearfield Counties. Ever since then, heavy defoliation has occurred along the mountain ridges. Several successive years of defoliation on plants result in mortality of the plants.

Gypsy Moth LifecycleMost of the yearly cycle of spongy moth is spent in the egg stage. The life cycle consists of the egg, larva (caterpillar), pupa, and moth. Female spongy moths lay their eggs in large clumps called egg masses in July. The egg masses are covered by a dense coating of hairs from the abdomen of the female. As a result, the egg mass in the late summer and early fall appears to be a dark tan to light brown but as the egg mass weathers, later it looks light tan to gray in color. Each egg mass is around 0.5-1 inch long and contains between 500 to 1,000 eggs.

Eggs begin to hatch in late April through early May. The larvae of gypsy moth develop in stages known as instars. The male goes through five instars and the female six. First instars larvae that emerge from the eggs are mostly black and about 1/8 inch in length. The young caterpillars spin long silk threads and are covered with long buoyant hairs that are caught and carried by the wind. This method aids the caterpillars to disperse into new locations in search of food. Young larva feeds night and day.

Gypsy Moth Catapillar furryFifth and sixth instar larvae are about 2 inches long and are the most voracious feeders of any growth stages of the spongy moth. These feed only during the night and seek shelter during the day in bark crevices or other protected sites. Late instar larvae develop five pairs of blue dots and six pairs of red dots along their backs. Larvae feeders are most active from May to July. The larva (caterpillar) stage for gypsy moth lasts for about 40 days.

Pupation takes place in mid June to early July. They remain in this stage for 7-10 days and emerging as adult moths. Pupae are 3/4 – 1 1/2 inches in length and attach to tree bark, stones, buildings and other similar sites. Adult moths emerge mid July through mid August. Adult moths do not feed and may live for only a few days to several weeks. Females are larger than the males and have a white to cream color, and the males are dark brown.

Clusters of trees killed following gypsy moth defoliation in central PennsylvaniaTree damage is caused by larva (caterpillar), which feeds on the foliage of the plant. Depending on the density of the population, larva may cause tree defoliation. Defoliation makes trees more vulnerable to disease organisms and other insects. Affected trees will eventually die after 2-3 years. A series of successive defoliation results in the death of the tree. This in long term may result in deforestation and affects in weather changes. Since 1980, the spongy moth has defoliated over 1,000,000 acres (4,000 km2) of forest each year. In 1981, a record 12,900,000 acres (52,200 km2) were defoliated. This is an area larger than Rhode Island, Massachusetts, and Connecticut combined.

Clusters of trees killed following gypsy moth defoliation in central PennsylvaniaSpongy moth larvae prefer hardwoods, but may feed on several hundred different species of trees and shrubs. Some of which include; oaks, apple, sweet gum, speckled alder, basswood, gray and white birch, poplar, willow, and hawthorn.

Some of the trees they avoid are ash, yellow poplar, sycamore, butternut, black walnut, catalpa, flowering dogwood, balsam fir, red cedar, American holly, and shrubs such as mountain laurel, rhododendron, and arborvitae. This list may change with the availability of preferred plants.

Larvae infected by the nucleopolyhedrosis virus (NPV)Temperatures below minus 20°F or colder during the winter will destroy exposed eggs. Freezing temperatures in May may kill many larva (caterpillars).

Natural enemies include parasitic and predatory insects such as wasps, flies, ground beetles, and ants; many species of spiders; several species of birds such as chickadees, bluejays, nuthatches, towhees, and robins; and approximately 15 species of common woodland mammals, such as the white-footed mouse, shrews, chipmunks, squirrels, and raccoons. These play an important role during periods when spongy moth populations are sparse.

Diseases caused by bacteria, fungi, or viruses contribute to the decline of spongy moth populations, especially during periods when spongy moth populations are dense and are stressed by lack of preferred foliage.

Wilt disease caused by the nucleopolyhedrosis virus (NPV) is specific to the spongy moth and is the most devastating of the natural diseases. NPV causes a dramatic collapse of outbreak populations by killing both the larvae and pupae. Larvae infected with wilt disease are shiny and hang limply in an inverted “V” position. It is suggested to leave dead infected larva in this position to help the spread of the virus to other larva.

There are several ways to control the population of spongy moth without applying chemicals. Some of these include:

Wrap duct tape on a tree trunk at about chest height from the ground and smear tanglefoot, a very sticky substance in the center of the tape. When spongy moth larva tries to climb the tree, they will get stuck to the tape. One can remove the tape with the moth or remove the moth from the tape and destroy them by placing them in a solution of water and dishwashing detergent. Do not apply tanglefoot directly to the tree, because it may damage the tree.

Older spongy moth larva feeds during the night and hides during the day. Burlap makes the perfect hiding place. Wrap the burlap at about chest height on a tree trunk and during the evening lift up the burlap and collect all larvae and put them in a solution of water and detergent. This will kill them. Repeat this process until the population seems to decline.

When spongy moth reach the moth stage, the males can be trapped using a spongy moth trap. The traps contain a bait inside their lid that smells like female spongy moth pheromone, attracting males. Once the male gets into the trap they can not come out and they slowly die in the trap. This prevents the males from mating with the females, decreasing the number of eggs fertilized. As a result the next generation there will be fewer spongy moths.

The Spongy moth spends most of its yearly cycle in egg stage. These eggs could be found attached to tree bark. Scrape the eggs off the bark and place them in a solution of water and detergent for about 24 hours. This eliminates hundreds and thousands of larva from hatching and eating the tree leaves.

Many birds prey on spongy moth larva and birds feeding on the larva naturally decrease the population of spongy moth. Place water and other bird attractive supplies around the property that will help birds come onto the property and prey on these pests.

Given that caterpillars are active during bird nesting seasons and that fledglings are often fed caterpillars due to their high protein content, it stands to reason that the caterpillar life stage of the gypsy moth is the most significant to birds (Smith and Lautenschlager 1981). According to Gale, DeCecco, McClain, Marshall, and Cooper (2001), there are a variety of immediate effects of an influx of gypsy moth caterpillars on bird abundance. For instance, local abundance of the well-known caterpillar specialists Black- and Yellow-billed Cuckoos rose two years prior to the gypsy moth outbreak reaching epidemic levels, and they vanished as soon as the outbreak subsided. Prior to an outbreak, the population of Indigo Buntings increased similarly; however, it took approximately five years for the population to return to normal.

Gypsy moth damage has been observed in the eastern portion of the state following the significant defoliation of broadleaf trees like maple, oak, and elm caused by another introduced species, the winter moth (Operophtera brumata) (Elkinton and Boettner 2016). When gypsy moth caterpillars start feeding in May and June, trees and shrubs are usually just starting to sprout new leaves because winter moth caterpillars feed from April to early May. This implies that the same plants may attempt to produce three sets of leaves in a given season. This type of resource use puts the tree or shrub’s capacity to grow and survive in jeopardy. Caterpillars of the Gypsy moth will also migrate to less favored host trees, like pine and spruce, if they hatch in an area of the state where the winter moth has already stripped the leaves from most broadleaf trees. Since conifers do not produce new leaves every year and growing new needles requires a significant investment of the tree’s resources, defoliation of these species may have more severe and immediate effects.

A large, mature tree or shrub is unlikely to be killed by a single defoliation, even if it occurs completely. A broadleaf tree, e. g. , an oak or a maple, will usually produce new leaves in a few weeks in response to defoliation. However, if a tree is repeatedly stripped of its leaves over several growing seasons, it may eventually result in dead branches and even die entirely. This is especially likely to happen in environments where stress levels are already high, like during a drought. Complete defoliation of seedlings and small saplings can hasten the death of plants considerably.

As previously mentioned, the long-term effects of gypsy moth infestations on forest ecology are usually limited because the outbreaks last no more than one to three years, which limits the number of tree deaths and permits bird populations to quickly recover or to decline following any spikes in abundance. However, what would another year of defoliation mean for the future of Massachusetts’s forests? However, some areas of the state are about to enter what may be their third or even fourth year of extremely high gypsy moth populations. The repeated defoliations and resulting tree deaths could cause this pest to reverse the process of succession in some forests if drought conditions return in the summer of 2017 or in years to come (Bell and Whitmore 1997) The problem will only get worse due to the drought since a tree or shrub that has already been harmed by disease or defoliation may die more quickly from a lack of water. Because of the selective pressure that favors species that the gypsy moth dislikes to eat, hardwood forest ecosystems may be altered under such conditions (Twery 1991). These species would include shrubs like American holly, mountain laurel, and rhododendron, as well as trees like ash, butternut, walnut, dogwood, tulip poplar, and catalpa (McManus et al. 1979). Drought-resistant plants may also gain a competitive advantage.

Currently, there are areas in Cape Cod, Bristol, Plymouth, and Worcester Counties that have had severe tree defoliation and high gypsy moth infestations for at least two years in a row. The amount of egg masses on the trees in the outbreak areas suggests that 2016 was another excellent year for gypsy moth reproduction. In 2017, the Massachusetts DCR currently projects a third year of notable defoliations. Although the majority of Massachusetts has experienced relief from the drought thanks to early spring storms in 2017, the two dry years that preceded it suggest that there won’t be enough Entomophaga maimaiga spores this summer to significantly reduce the number of gypsy moth caterpillars (Massachusetts DCR 2017).

Microbial and Biological Pesticides

ThuricideMicrobial and Biological pesticides contain living organisms that must be consumed by the Spongy Larva. Microbials include bacteria, viruses, and other naturally occurring organisms; Biologicals includes manmade synthetics of naturally occurring organisms. These pesticides should be applied before the larvae reach the third stage of instar development. As they mature, larvae become more resistant to microbial pesticides and are, therefore, more difficult to kill.

Dipel Thuricide, which is approved for both aerial and ground application and contains the active ingredient Bacillus thuringiensis (BT), is an example of a microbial and biological pesticide. It comes in a range of brand names and is poisonous to other moth and butterfly larvae. It can be used safely near water.

A range of chemicals are available for the efficient control of spongy moths. This approach is advised for areas where the number of infections is very high. Applying should be done in accordance with label instructions once most eggs have hatched, which is in early to mid-May when the larvae are small. Verify that the tiny larvae have spread out and started feeding so that the host plant foliage has the recognizable shothole damage. Before significant defoliation happens, applications should be made to maintain good plant health.

Examples of Some Chemicals

  • Orthene: Sold under several brand names, this substance is registered for use both on land and in the air. It is often applied from the ground to treat individual trees, although it is known to be toxic to bees and some spongy moth parasites.
  • Sevin: Known by several different trade names, this substance is registered for both ground and aerial application. It is well known that this substance is poisonous to spongy moth parasites and bees. It was the most often used chemical in gypsy moth control programs at one point.
  • Dimilin is a pesticide with limited use that can only be applied by professionals. The same applies for other restricted chemicals.


What birds will eat gypsy moth caterpillars?

Bird species in the first group include the black-capped chickadee, blue jay, red-eyed vireo, rufous- sided towhee, scarlet tanager, northern oriole, catbird, and robin. These species are common residents and eat gypsy moths when the insect is at low population densities.

Do birds eat moth caterpillars?

“They’re nature’s hotdog,” he says. Human appetites aside, entomologists and ornithologists agree that caterpillars—the larval stage of both moths and butterflies—anchor the diets of many birds worldwide, especially those that dine in temperate forests and foliage.

What kills spongy moth caterpillars?

Birdhouses are magnets for female spongy moths looking to lay eggs. A few days after the eggs hatch, the spongy moth caterpillars can be controlled with applications of the biological insecticide Bacillus thuringiensis (Bt), a naturally occurring bacterium.

What eats moth caterpillars?

“Not only do birds and bats consume moths at every stage of the insects’ life cycle, so do lizards, small rodents, skunks and even bears,” Mizejewski says. Other insects, including hornets and ants, prey on moth caterpillars, and both spiders and beetles feed on moth pupae tucked away in their cocoons.