Hawthorn (Crataegus)

Leaf Feeders

Hawthorn leafminer
Lance S. Risley, William Paterson University, Bugwood.org
Hawthorn leaf miners are small flat caterpillar-like larvae that feed inside leaves, producing irregular brown splotches. Heavily mined leaves may drop prematurely but general tree health is usually not affected.

Japanese beetles
Lee Townsend, University of Kentucky
Japanese beetles can feed on about 300 species of plants ranging from roses to poison ivy but basswood is one of their favorites. They usually feed in groups, starting at the top of the tree and working downward, and prefer plants that are exposed to direct sunlight. A single beetle does not eat much; it is group feeding by many beetles that causes severe damage. Adults feed on the upper surface of foliage, chewing out tissue between the veins. This gives the leaf a characteristic skeletonized appearance. For more information, see Entfact 451.

yellownecked caterpillars
Gerald J. Lenhard, Louisiana State University, Bugwood.org
Yellownecked caterpillars are black caterpillars with thin longitudinal yellow stripes and some fine white hairs. The head is black and a plate just behind the head is yellow-orange. Eggs are laid in clusters of about 100 so there may be many individuals on a single tree. YNC caterpillars feed for about 4 weeks and tend to remain together. Mature larvae are about 2 inches long. Most of the damage is done in August and September. These caterpillars also feed on oak and other hardwoods. YNC overwinters in the soil as pupae.

Fall webworms
Milan Zubrik, Forest Research Institute - Slovakia, Bugwood.org
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.

Forest tent caterpillar
Steven Katovich, USDA Forest Service, Bugwood.org
Forest tent caterpillar is a brown caterpillar with a row of conspicuous keyhole-shaped whitish spots down the middle of the back; there is a blue and a yellow-brown line along each side. Eggs are laid in masses of 100 to 300 so there can be extensive feeding damage on heavily infested trees. Newly hatched larvae begin to feed at about the time of bud break. Groups of caterpillars tend to cluster in masses on lower trunks of infested trees. The first signs of infestation may be thinning crowns and a steady rain of pelleted caterpillar waste.

Eastern tent caterpillar
Robert F. Bassett, USDA Forest Service, Bugwood.org
Eastern tent caterpillar is a hairy black caterpillar with a white stripe down the back, brown and yellow lines along the side with a row of oval blue spots along the top line. The larvae live communally in silken tents. They feed for 4 to 6 weeks and may defoliate small trees. When mature, they wander to protected site to spin a cocoon. These tent caterpillars are active during April and May, there is one generation each year.

Leaf crumpler larva
Copyright © 2018 John van der Linden, bugguide.net, used with permission
The Leaf crumpler larva is around an inch long, with a green-grey color with purple markings at each segment. The adult is a small moth with brown and white stripes along its wings. The caterpillars build web tubes on twigs which incorporate leaf fragments as they feed. The tube can be 1.5-2 inches long by the time the caterpillar is mature. Damage and nests are at their peak in July and August.

Pear slug sawfly larva
Lesley Ingram, Bugwood.org
The name, Pear slug, is a misnomer; these are not true slugs but sawfly larvae. The shiny, green to orange larvae can be up to a half inch long and feed by skeletonizing leaves. Larvae feed on the lower surface of pear, cherry and plum. There are two generations per year with overwintering occurring as a pupa. Adults emerge in early summer and lay eggs which mature, pupate and emerge as adults by August-September. New larvae from the summer generation will feed then pupate for the winter.

Fall cankerworm larvae
A. Steven Munson, USDA Forest Service, Bugwood.org
Fall cankerworm is a looper caterpillar that can vary from light green with yellow stripes to green with a dark stripe down the back. Overwintering masses of about 100 eggs hatch in later April or early May; small caterpillars chew small holes in young leaves at branch tips. Larger loopers leave only the midrib and major veins. Fall cankerworms are about an inch long when full grown. Mature larvae descend from trees on silk threads to pupate in the soil. They emerge as adults during periods of freezing temperatures to mate and lay eggs on host plants. There is one generation each year.


Sap Feeders

John A. Weidhass, Virginia Polytechnic Institute and State University, Bugwood.org
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.

Calico scale
Raymond Gill, California Department of Food and Agriculture, Bugwood.org
Calico scale is a white and dark brown soft scale about 1/4 inch in diameter. It produces a large amount of honeydew in the spring so twigs, branches, and leaves may be covered with sooty mold. This scale can severely weaken trees, making them more vulnerable to drought and other stresses. Egg hatch occurs in May and the crawlers move to leaves to feed for the summer. Nymphs move back to bark for the winter.

oytershell scale
Whitney Cranshaw, Colorado State University, Bugwood.org
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.

Hawthorn lace bug
Jim Baker, North Carolina State University, Bugwood.org
Lace bugs are 1/8 to 3/16 inches long sap-feeding insects with clear, ornate, lacy wings; nymphs are spiny and wingless. Both stages live on the lower surface of leaves. As they feed, they leave tiny yellow to white spots on leaves and dark, varnish-like waste spots on the under sides.

These lace bugs spend the winter as eggs under bark or in leaf litter. The eggs hatch in early spring and the nymphs begin to feed on plant sap. There are several generations each season. Initially, numbers are so small that feeding symptoms are not noticed until the population peaks in late summer. When abundant, feeding can make plants unsightly and may cause premature leaf drop.

Susan Ellis, Bugwood.org
Leafhoppers are small, active insects live on the underside of the leaves. They use sucking mouthparts to feed on plant sap and leave tiny spots on leaves similar to those caused by lace bugs. Usually large numbers are present by the time the injury is obvious. Heavily damaged leaves may drop early but this insect usually does not cause serious problems.

San Jose scale
United States National Collection of Scale Insects Photographs,
USDA Agricultural Research Service, Bugwood.org
San Jose scale is one of the most destructive scale species. Infested stems, twigs or branches may be killed and heavily infested trees may die. These small circular brown armored scales have a series of dark concentric rings on their waxy covering. There are several generations each year. First crawlers are active from late May to early June, a second generation appears in late July and a third in late summer or early fall. Heavily infested plants may have a crusty covering of scales.

Twospotted spider mites
David Cappaert, Bugwood.org
Twospotted spider mites are tiny (1/50 inch) arthropods with a dark spot on each side of the oval, light green to yellow body. They live on the underside of leaves and use needle-like mouthparts to remove the contents of individual cells. This produces tiny white to yellow spots on leaves, sometimes called flecking or bronzing. These mites produce fine silk-like webbing that often covers infested plants. Infestations are usually most serious during hot, dry periods.

European red mite eggs on apple tree
University of Georgia Plant Pathology, University of Georgia, Bugwood.org
The European red mite female is brick red, while the male is a pale yellow-green. They are small and globular. Some individuals may "balloon" to new locations, creating new infestations. They can feed on many different species of plants and cause leaves to become pale and eventually bronze. There can be 6-8 generations per year depending on the weather and they overwinter as eggs that are laid in the bark and near buds (red spheres in image at left). For more information, see Entfact 205.


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