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Aphids are small insects (1-4mm) that suck plant sap. They transmit many plant diseases as well as causing leaf curling and other symptoms on plants. Most overwinter as eggs in Idaho and have summer hosts that are different from the winter host plant. They are characterized by having a pair of cornicles that project upward from the rear of the abdomen. Adelgids are aphid-like but do not have cornicles. Their life histories can be quite complex. Dormant oil sprays are good control measures for these insects. They are also frequently attacked by parasitic wasps and other natural enemies.

Coming soon   Leaf curl ash aphid

These large aphids start feeding on leaves of ash trees soon after leaf expansion. Their feeding causes leaf curling that persists after the aphids have left or been controlled.

  Spruce aphid

Several species of Cinaria will attack spruce. They feed on needles close to the bark.

They are some of the larger aphids.

  Honey suckle witches broom aphid

This small green aphid attacks honeysuckle in southern Idaho. It can become quite abundant in a short period of time.

  Witches broom

A "witches broom" symptom appears on honeysuckle shortly after the aphids start feeding. These symptoms stunt the growth of the plant and last all season.

  Rose aphid

This red or green aphid stays on roses all season. The eggs overwinter on the canes and the aphid hatch as soon as buds begin to swell.

  Wooly elm aphid adult

Examining the underside of curled elm leaves reveals this black aphid that secretes a wool-like wax.

  Giant willow aphid

The bark of willows is oftentimes covered with these black aphids. They sometimes look grey because of hairs on the body. Damage is usually minimal with people being mostly curious about the insect. Other large rust brown aphids will also colonize willow.

  Bean aphid

Bean aphids occur on euonymous and snowball bushes. The black eggs can almost cover the bark of snowball branches. Affected leave curl badly but the aphids move to beans, sugarbeets, and other hosts for the summer.

  Wooley apple aphid

The wooley apple aphid attacks limbs, trunk, and roots of apple and several ornamentals. They are purplish in color and hide in white cottony masses. They can overwinter in several forms on different hosts.

  Parasitized wooly apple aphids

Above ground the wooley apple aphid can be heavily parasitized. Most damage to trees is done by feeding on the root

Balsam twig aphid

Pine and spruce are attacked by the balsam twig aphid. The aphids are pale green and covered with white wax. They cause curling of twigs on these evergreen tree.

  Balsam wooly adelgid

Balsam wooly adelgids attack balsams and other firs. The small blue black body is covered with waxy filaments and infested trees appeared to be covered with white wax. The saliva is toxic and causes swelling of twig tips and reduced needle growth.

Coming soon   Elm leaf aphid

Elms are infested the elm leaf aphid. These insects are yellow to green and secrete abundant honeydew which can coat the leaves and areas under the tree.

Coming soon   Elm with honeydew

Elms heavily infested and covered with honeydew appear very shiny and are sticky to the touch.

  Cooley spruce gall adelgid "pineapple"

Feeding on spruce by the cooley spruce adelgid causes enlarged growths on the end of spruce brances. The saliva of the insect causes the abnormal growth.

  Adelgid adult and egg mass

The adult overwinters on the spruce tree and lays eggs in a cottony mass at the base of the needle bundles. As the needles break out of the bundle, the new insects hatch from the egg and start feeding. These insects can have 5 different forms and infest douglad fir as well as spruce.

  Pine bark adelgid

Pines infested with the pine bark adelgid appear to have bark covered with snow. Needles and small twigs are also infested. This insect is most abundant on trees over 10 years old but younger trees are also infested.