Here are five common forest insect pests most visible in the fall season.
Adult autumn Insects always make a come-back after the dog-days of late summer and during leaf fall. Fall wildflowers in open patches, for the most part goldenrod, are blooming and many insects are attracted to both the plant's pollen and nectar.
Entering an autumn forest will bring your close to the most available fall forest insects for viewing. Here are the five most common insect tree pest in larvae or adult form you might see this time of the year during a forest visit.
Adult cerambycids called long-horned beetles (in the Coleoptera family) have long antennae. They also have another name, roundheaded wood borer, probably originating from the fact that larvae borers make circular emergence holes. They do not have round heads.
The "horned" adult roundheaded wood borer is seen most often in the fall. The tree pest does attack living trees but rarely kills them. Longhorned beetles overwinter as larvae and bore out wood tunnels, most in dead wood (which quickly degrade salvageable logs) and a few in living trees (which can kill the tree very quickly).
The most destructive borer in North America is the emerald ash borer which attacks living trees. It is not considered a long-horned beetle.
Woolly alder aphids are insects in the family of woolly aphids (Eriosomatidae) and produce a waxy wool or cotton-like substance off their backs. They feed off the sap of alder, silver maple and other woody plants in the Eastern forest.
They may appear in the air as tiny tufts of cotton floating through the air. However they are very conspicuous on the stems of host plants, looking bright white and like sticky cotton surrounding the stems. Looking into the cottony material, you will see the insect which looks like little hand grenades.
They feed on leaf and twig sap and are minor defoliators. They are in the same insect category as the major tree defoliators, balsam woolly adelgid and hemlock woolly adelgid.
There are many species in the weevil family but very few have an effect on trees and forestry. The elephant-snouted acorn weevil (genus Curculio) is a very common one and attacks both white and red oak tree fruit. Look for a pinhead hole, crush the acorn and you will find a larvae and/or its damage.
You most likely will never see the weevil as they do their egg laying in the acorn while still attached to the tree. You will see the damage they can do to annual oak acorn mast crops by collecting fallen acorns for examination.
The larvae can eat out the entire nut inside an acorn (or hickory nut) but will not damage the tree. Squirrels will select good nuts early so you will have plenty of opportunity to see acorn weevil damage. A weevil outbreak can destroy an annual nut crop with dire short-term consequences.
Hyphantria cunea is the species name for the turn-of-the-season indicator insect fall webworm. This adult insect is a moth but the caterpillar larvae makes the web.
Look along roadsides and forest edges for masses of webbing enclosing both leaves and branch tips. Hatching caterpillars immediately start the web, usually at night, and can encompass several branches and extend for three feet. They only nest in deciduous trees and love persimmon, sourwood, pecan, fruit trees and willows.
Webworms eat leaves late in the season, the nests are generally concentrated to limited areas so little real damage is done to most trees. Nests can look very unsightly and multiple generations in long summers can lead to significant defoliation and an ugly host tree.
Sawflies are actually members of the Hymenotera family and are relatives of bees, wasps and ants. Adult sawflies look a little like fat wasps but their caterpillar stage is where damage to trees occur. Especially the conifer sawflies (Diprionidae) that are very destructive.
Sawflies overwinter as larvae in small parchment-looking cocoons that are attached to twigs on pines and other evergreens and the hatched larvae are easily located in fall. Look at the tips of young pine branches for caterpillar-like larvae (they will be about an inch long) feeding on the needles.
The redheaded pine sawfly is a major pest to commercial eastern pines and will deform young trees that are in stressful environments. You are most likely to see signs of sawflies in the fall on young pines less than 10 years old.
Entering an autumn forest will bring your close to the most available fall forest insects for viewing. Here are the five most common insect tree pest in larvae or adult form you might see this time of the year during a forest visit.
1. Long-horned Beetle
Adult cerambycids called long-horned beetles (in the Coleoptera family) have long antennae. They also have another name, roundheaded wood borer, probably originating from the fact that larvae borers make circular emergence holes. They do not have round heads.
The "horned" adult roundheaded wood borer is seen most often in the fall. The tree pest does attack living trees but rarely kills them. Longhorned beetles overwinter as larvae and bore out wood tunnels, most in dead wood (which quickly degrade salvageable logs) and a few in living trees (which can kill the tree very quickly).
The most destructive borer in North America is the emerald ash borer which attacks living trees. It is not considered a long-horned beetle.
2. Woolly Alder Aphid
Woolly alder aphids are insects in the family of woolly aphids (Eriosomatidae) and produce a waxy wool or cotton-like substance off their backs. They feed off the sap of alder, silver maple and other woody plants in the Eastern forest.
They may appear in the air as tiny tufts of cotton floating through the air. However they are very conspicuous on the stems of host plants, looking bright white and like sticky cotton surrounding the stems. Looking into the cottony material, you will see the insect which looks like little hand grenades.
They feed on leaf and twig sap and are minor defoliators. They are in the same insect category as the major tree defoliators, balsam woolly adelgid and hemlock woolly adelgid.
3. Acorn Weevils
There are many species in the weevil family but very few have an effect on trees and forestry. The elephant-snouted acorn weevil (genus Curculio) is a very common one and attacks both white and red oak tree fruit. Look for a pinhead hole, crush the acorn and you will find a larvae and/or its damage.
You most likely will never see the weevil as they do their egg laying in the acorn while still attached to the tree. You will see the damage they can do to annual oak acorn mast crops by collecting fallen acorns for examination.
The larvae can eat out the entire nut inside an acorn (or hickory nut) but will not damage the tree. Squirrels will select good nuts early so you will have plenty of opportunity to see acorn weevil damage. A weevil outbreak can destroy an annual nut crop with dire short-term consequences.
4. Fall Webworm
Hyphantria cunea is the species name for the turn-of-the-season indicator insect fall webworm. This adult insect is a moth but the caterpillar larvae makes the web.
Look along roadsides and forest edges for masses of webbing enclosing both leaves and branch tips. Hatching caterpillars immediately start the web, usually at night, and can encompass several branches and extend for three feet. They only nest in deciduous trees and love persimmon, sourwood, pecan, fruit trees and willows.
Webworms eat leaves late in the season, the nests are generally concentrated to limited areas so little real damage is done to most trees. Nests can look very unsightly and multiple generations in long summers can lead to significant defoliation and an ugly host tree.
5. Sawflies
Sawflies are actually members of the Hymenotera family and are relatives of bees, wasps and ants. Adult sawflies look a little like fat wasps but their caterpillar stage is where damage to trees occur. Especially the conifer sawflies (Diprionidae) that are very destructive.
Sawflies overwinter as larvae in small parchment-looking cocoons that are attached to twigs on pines and other evergreens and the hatched larvae are easily located in fall. Look at the tips of young pine branches for caterpillar-like larvae (they will be about an inch long) feeding on the needles.
The redheaded pine sawfly is a major pest to commercial eastern pines and will deform young trees that are in stressful environments. You are most likely to see signs of sawflies in the fall on young pines less than 10 years old.
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