Cottonwood (Populus deltoides)

Leaf Feeders

Poplar tentmaker caterpillar and damage
Stanton Gill, University of Maryland Cooperative Extension,
Poplar tentmakers are light brown to nearly black caterpillars with 4 light yellow lines along the back and a bright yellow and several indistinct lines along each side. There are black tubercles on the back of the first and eighth abdominal segments. The larvae live together protected by leaves pulled together and secured with silk. Small larvae feed on the leaf surface, large larvae leave only the petiole. Full grown larvae are about 1.3 inches long.

redhumped caterpillar
Copyright © 2006 tom murray
At its largest, the Redhumped caterpillar is 1-1.5 inches long. The head and first abdominal segment are red, the rest of the body is yellow with black and white stripes. Black tubercles extend from the back. These caterpillars initially feed as a group on a single leaf, skeletonizing it, and use a collective warning display to ward off predators. As they grow, they will spread out as individuals and consume entire leaves. Mature larvae overwinter in the soil and pupate in the spring. Adults fly from June till July and caterpillars feed July to September.

Fall webworms
Milan Zubrik, Forest Research Institute - Slovakia,
Fall webworms are small hairy white caterpillars that live communally in thin silken webs at the ends of branches. They may leave the tent to feed individually as they get larger. While the webbing is unsightly, feeding damage is usually limited to limbs around the tent. Large established trees are not seriously affected by small to moderate infestations. The larval stage feeds for 4 to 8 weeks and may be found on a variety of hardwoods. The first generation occurs in late May and early June, the second generation is usually larger and active from July through September. For more information, see Entfact 424.

Cottonwood leaf beetle adult and larvae
Lacy L. Hyche, Auburn University,
Cottonwood leaf beetle is a pest both as an adult and as a larva. The larvae will feed by skeletonizing leaves, while adults feed along veins and the midrib. Larvae are black when they first emerge and lighten in color as they age; they can also produce a pungent odor from spots along their back. Adults are yellow-orange with black stripes and spots along the back. They overwinter as adults and emerge in the spring to lay eggs on host plants. There are multiple generations per year, with damage occurring throughout the growing season.


Sap Feeders

oytershell scale
Whitney Cranshaw, Colorado State University,
Oystershell scales are about 1/10 inch long and resemble crusty accumulations of oyster shells on the bark. Their drab, bark-like appearance makes them easy to overlook, even on close inspection. Heavy infestations can kill twigs or branches. This scale overwinters in the egg stage under the waxy covering of the female. The eggs hatch and the crawlers are active from late May to early June.

John A. Weidhass, Virginia Polytechnic Institute and State University,
Aphids are soft-bodied insects that use their piercing sucking mouthparts to feed on plant sap. They usually occur in colonies on the undersides of tender terminal growth in the spring. Heavily-infested leaves can wilt or turn yellow and senesce prematurely because of excessive sap removal. While the plant may look bad, aphid feeding generally will not seriously harm healthy, established trees. Some plants are very sensitive to feeding by certain aphid species. Saliva injected into plants by these aphids may cause leaves to pucker or to become severely distorted, even if only a few aphids are present. Also, aphid feeding on flower buds and fruit can cause malformed flowers or fruit.

Aphids produce large amounts of a sugary liquid waste called "honeydew". The honeydew that drops from these insects can spot the windows and finish of cars parked under infested trees. A fungus called sooty mold can grow on honeydew deposits that accumulate on leaves and branches, turning them black. The appearance of sooty mold on plants may be the first time that an aphid infestation is noticed. The drops can attract other insects such as ants, flies, and wasps that will feed on the sticky deposits. For more information, see Entfact 103.



twig pruner larvae
James Solomon, USDA Forest Service,
Twig pruners are the larvae of small beetles that tunnel in twigs and small branches. Female beetles lay their eggs about the time of bud break in the spring. Eggs are laid in small holes which are chewed into the bark. The larvae that hatch from these eggs bore into and tunnel toward the base of twigs. In late summer, they chew concentric circles outward toward the bark then move toward the tip. The twig eventually snaps and falls to the ground. The larva pupates in the fallen twig and emerges as an adult in the spring. Collecting and destroying fallen twigs can help to reduce infestations.

James Solomon, USDA Forest Service,
Carpenterworms are reddish pink caterpillars that tunnel into the bark and wood of oaks, especially red oaks and a number of other hardwoods. Their damage causes unsightly scars on ornamental trees and degrades rough sawn lumber. Eggs are laid in bark crevices or under vines and lichens. Small larvae feed into the phloem and cambium but soon chew into the sapwood. Fine frass mixed with sap is ejected from the entrance hole in the bark and builds up at the base of the tree as larvae hollow out galleries beneath the bark. Infested trees usually are not killed but long term attacks may weaken trees structurally.

Cottonwood borer adult and larva
Jim Baker, North Carolina State University, (adult)
James Solomon, USDA Forest Service, (larva)
The Cottonwood borer is a large (nearly 2 inches long) black and white longhorn beetle. It is occasionally mistaken for the Asian longhorn beetle due to similar coloration. Females lay their eggs in August at the base of host plants and larvae will bore into the tree. Larvae are legless roundheaded borers that are up to 1.5 inches long. Development takes between 2-3 years beneath the bark. Damage is rarely threatening to the tree, though girdling can occur.

Loepard moth larva and adult
Petr Kapitola, Central Institute for Supervising and Testing in Agriculture, (larva);James Solomon, USDA Forest Service, (adult)
Both the caterpillar and adult of the Wood leopard moth are very distinctive. The caterpillar is the damaging stage, feeding under the bark of host trees. It is a white-orange color with numerous spots on its body. The adult is white with six black dots on the thorax and black markings on the remainder of the body. Adults may be active June-September and larvae feed inside of plants for 2-3 years.



Poplar petiole galls
Herbert A. 'Joe' Pase III, Texas A&M Forest Service,
Poplar petiole gall is a growth caused by small gray aphids with a waxy appearance that live inside the gall. The hard galls are green, eventually turning red. Aphids leave the galls in mid-summer and move to another host plant. The leaves are not damaged by galls. Ants are often seen around the galls.


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