Diagnosis - Apple Tree Problems on Leaves
Holes in Leaves or Parts of Leaves Missing

Cankerworms

Cankerworms or Paleacrita vernata and Alsophila pometaria

  • Chews smalls holes between veins at first, later chewing leaf tissue except for major veins, and eventually chewing all of the leaves except midvein
  • Defoliation typically light to moderate, although it can potentially be severe
  • Smooth-bodied, light green to brown, 1 1/3 inch long when fully grown; moves in a characteristic looping motion
  • Occurs late April/early May until June
Photo by J. Hahn, University of Minnesota
Photo by James B. Hanson, USDA Forest Service, bugwood.org

Cankerworms (inchworms) cause defoliation in shade trees. They are found on elm, apple, hackberry, basswood, oak, boxelder, maple and ash trees as well as shrubs growing beneath heavily infested trees.

Young, newly transplanted, or weak trees have more chances of injury from defoliation.
If a tree is defoliated for three consecutive years, the branches of the tree can die, making the tree very weak.
Pesticides can be used when the caterpillars are small (around the second week of feeding), for two reasons: to protect trees and; to eliminate the presence of cankerworm moths around homes.

Spring and fall cankerworms feed at the same time of year on the same trees causing the same kind of damage.  Feed on buds and expanding leaves right after egg hatch in the spring.  These creatures create small BB-sized holes (about 4.4 mm) in the leaves.  As the larvae grow, holes get bigger until all the tissue between the veins is eaten up.

Information source: https://extension.umn.edu

Cecropia

Cecropia or Hyalophora cecropia

  • Chews entire sections of leaves; defoliation typically is minor
  • Light green body with a double row of reddish-orange knobs on thorax behind head; also series of smaller yellow and blue knobs on abdomen; grows up to 4 inches long
  • Becomes a large, attractive moth
  • Occurs in August and September

Information source: https://extension.umn.edu

Photo by Herbert A.
Photo by J. Hahn, University of Minnesota

Eastern Tent Caterpillar

Eastern Tent Caterpillar or Malacosoma americanum

  • Larvae feed on leaves, sometimes defoliating trees
  • They make a web or “tent” in the fork of the branches
  • Larvae are hairy with blue, black, and orange markings, and a white stripe down the back, almost 2 inches when fully grown
  • Present during May and June

Information source: https://extension.umn.edu

Photo by Terry Price, Georgia Forestry Commission, bugwood.org
Photo by J. Hahn, University of Minnesota
Photo by Robert L. Anderson, USDA Forest Service, Bugwood.org

Fall Webworm

Fall Webworm or Hyphantria cunea

  • Produces silken webbing that covers the ends of branches
  • Chews entire sections of leaves, leaving major veins
  • Yellowish or greenish with long, fine white hairs with two rows of black spots down its back
  • Occurs from late July through September

Information source: https://extension.umn.edu

Photo from Ministry of Agriculture and Regional Development Archive, bugwood.org
Photo by J. Hahn, University of Minnesota
Photo by Lacy L. Hyche, Auburn University, bugwood.org

Forest Tent Caterpillar

Forest Tent Caterpillar or Malacosoma disstria

  • Chews entire sections of leaves, often leaving some major veins; defoliation can be severe
  • Hairs along sides of the body, blue and black with characteristic footprint shaped white markings on top of the body, almost 2 inches long when fully grown
  • Occurs in May and June
Photo by Kenneth E. Gibson, USDA Forest Service, bugwood.org
Photo by Steven Katovich, USDA Forest Service, bugwood.org

Feeding by forest tent caterpillars generally does not kill deciduous trees, as they can produce another set of leaves during the same season.

Healthy trees can tolerate two to three consecutive years of heavy defoliation.

Trees may die or be killed if the same tree has been heavily defoliated for four or more years or when trees become stressed, such as during a drought.

Information source: https://extension.umn.edu

Obliquebanded Leafroller

Obliquebanded Leafroller or Choristoneura rosaceana

  • Early season larvae feed on the undersurface of a leaf along the midrib or other large veins
  • Early season larvae feed inside bud clusters and developing fruit, resulting in fruit drop or corky scars on the fruit
  • Late season larvae can scar the fruit
  • Larvae are yellow-green and 1” in length when mature
  • The adult moth is reddish-brown with brown bands on the wings

Information source: https://extension.umn.edu

Photo from USDA Forest Service, bugwood.org
Photo from Minnesota Department of Agriculture
Photo by J. Hahn, University of Minnesota

Redbanded Leafroller

Redbanded Leafroller or Argyrotaenia velutinana

  • Larvae skeletonize leaves from the underside, folding and webbing the leaves together
  • Fruit injury is usually shallow with ragged edges and thick, corky tissue over the damaged area
  • Larvae are green with a green head and reach about ½” at maturity. Larvae are yellow-green and 1” in length when mature.
  • Larvae are present early May – June
  • Adults have distinct red-brown bands on the forewings that form a V-shape when at rest and are about ¼” in length

Information source: https://extension.umn.edu

Photo from Minnesota Department of Agriculture
Photo by Clemson University
Photo by J. Hahn, University of Minnesota

Redhumped Caterpillar

Redhumped Caterpillar or Schizura concinna

  • The larva will eat the entire leaf, leaving only the midvein
  • Redhead and a wavy black, yellow, and white striped body with a red projection (hump) on the thorax behind the head, 1 1/3 inch long when fully grown
  • Occurs in August and September

Information source: https://extension.umn.edu

Photo by Lacy L. Hyche, Auburn University, bugwood.org
Photo by Jerry A. Payne, USDA Agricultural Research Service, bugwood.org
Photo from Department of Entomology, University of Minnesota

Yellownecked Caterpillar

Yellownecked Caterpillar or Datana ministra

  • Small larvae skeletonize undersides of leaves; Larger larvae consume all but leaf petioles
  • A black head and a black body with yellowish stripes and a yellowish rectangle behind its head, it is almost 2 inches when fully grown
  • Occurs in August and September

Information source: https://extension.umn.edu

Photo by J. Hahn, University of Minnesota
Photo by Lance S. Risley, William Paterson University, bugwood.org
Photo by J. Hahn, University of Minnesota
Don't see what you're looking for? Ask us...
[gravityform id=”6″ title=”false” description=”false” ajax=”false”]