Figure 1. Oak trees defoliated by oak
leaftier. |
Introduction
Oak leaftiers
and oak leafrollers defoliate oaks throughout the northeastern United
States and adjoining Canadian provinces and as far south to Texas.
In recent years, scattered but severe outbreaks of oak Leaftier have
occurred in Connecticut, Massachusetts, New Jersey, New York,
Pennsylvania, and West Virginia. In 1978 more than 100,000 acres were
defoliated in these states. Outbreaks of the oak leafroller complex
have been reported in Michigan, Pennsylvania, and West Virginia, and
continues as far south into Texas.
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Two or more years of
moderate to severe defoliation by tiers and rollers usually results in
twig and branch dieback, loss of diameter growth, and tree decline
(Figure 1). Tree mortality has occurred in many areas. Trees with half
of the twigs and branches dead are often subsequently attacked by wood
borers. especially the twolined chestnut borer, Agrilus bilineatus
(Weber), and the shoestring root fungus, Armillariella mellea
Vahl. ex Fr.
What are Leaftiers and
Leafrollers?
Although
oak leaftiers and leafrollers resemble each other in the larval
stages, the two insects differ in the way they web leaves and in
larval characteristics. |
Figure 2. A leaf rolled by a leafroller. |
Leaf webbing
habits
The leaftier larva (caterpillar) binds two or more leaves together
with strands of silk and then feeds and rests between them. The larva
is found by separating the tied leaves (cover photo). After feeding
ceases, the larva drops to the ground and pupates in the litter or
duff. The leaftiers of oak include a small group of tortricid moths
and three other minor families
The leafroller larva rolls or folds one leaf, then binds it with
strands of silk. It feeds and rests within the rolled or folded leaf
(Figure 2). The larva is found by unrolling the partially folded leaf.
Although some larvae may pupate in folded leaves, most pupate on the
ground. The leafrollers of oak are comprised of more than 15 species
of moths in 5 families. Of these, about 60 percent are tortricid
moths. |
Larval characteristics
Oak Leaftiers
Head:
Both, dark area around the eye and a broad dark brown to black bar on
side of head always present Figure 3).
Prothorax
(front of thorax): Legs dark brown to black. (Figure 3)
Go to Oak Leafrollers
page
Head: Either dark area around the eye or
broad dark bar on side of head, or neither present; never both.
(Figure 4)
Prothorax (front of thorax): Legs
not dark brown to black. (Figure 4) |
Figure 3.
Head and portion of body of oak leaftier larva, Croesia
semipurpurana (Kearfott). Dark area around the eye and a broad
dark brown to black bar on side of head; legs dark. (Magnification
150X). |
|
Figure 4.
Head and portion of last larval instar of oak leafroller, Archips
semiferanus (Walker). Either dark area around the eye or broad
dark bar on side of head, or neither present; legs not dark. (Other
larval instars of this species have black heads and prothoracic
shields.) (Magnification 150X) |
Important leaftiers and leafrollers on
oaks
An important oak leaftier is Croesia
semipurpurana (Kearfott). The larva of C. semipurpurana is
an early defoliator of northern red oak, black oak, pin oak, scarlet
oak, and scrub oak (Figure 5). It feeds on unopened buds and
developing foliage in early spring, resulting in severe stress on food
reserves. Rarely are chestnut and white oak attacked.
The most important oak leafroller is Archips semiferanus
(Walker) (Figure 6). Other leafrollers of oak such as A.
argyrosplilus (Wlkr.) and Choristoneura fractivittana
(Clem.) are not known to cause serious damage but are abundant on oak
and feed with A. semiferanus and C. semipurpurana. Most
leafroller larvae hatch about a week later than oak Leaftier larvae.
This group of insects may also feed on other hardwoods. |
Figure 5.
Larva of oak leaftier, C. semipurpurana. |
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Figure
6. Last larval instar of oak leafroller, A. semiferanus.
(Other larval instars of this species have black heads and
prothoracic shields.)
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Leaf
roller eggs on branch
Photo Jack Kelly Clark |
Leaf
Roller damage
Univ. of California
|
Pupae
Washington State Univ.
Adult Moth
Washington State Univ.
|
Author
Parker
Snowden, Entomologist
NA State and Private Forestry
Portsmouth, NH 03801 |
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