American plum borer
Euzophera semifuneralis (Walker)
From: Solomon, J.D. 1995. Guide to insect borers of North
American broadleaf trees and shrubs. Argic. Handbk. 706. Washington, DC:
U.S. Department of Agriculture, Forest Service. 735 p.
Hosts. Plum, peach, cherry, Chinese plum, pear, mountain-ash,
persimmon, apple, white mulberry, sycamore, apricot, walnut, pecan, olive,
basswood, poplar, sweetgum, yellow-poplar, gingko, elm, oak. Although this
bore has a wide range of hosts, plum and other drupe and pome fruit trees appear
to be favored. However, pecan and sweetgum are sometimes heavily attacked
all along the Gulf Coast region.
Range. Generally distributed throughout the United States,
Canada, and parts of Mexico (Heinrich 1956).
Description
Adult. Gray moth with wingspan of 17 to 28 mm (Blakeslee 1915,
Forbes 1890, Heinrich 1956). Forewings grayish brown with broad, wavy
bands of black and brown markings across outer third. Hindwings smoky with
black marignal lines fringed with white. Head, thorax, legs, and abdomen
dusky gray with bright bronze reflections.
Egg. Oval, measures, about 0.59 by 0.42 mm and opaque white and
coarsely punctate. Mature egg dull red, but about 24 hours before hatching
changes to dirty white with larval head plainly visible through the chlorin and
slight depression appearing in center (Blakeslee 1915).
Larva. White with dark brown head when newly hatched; reddish
color of alimentary tract clearly visible through integument. Mature larva
with dark brown head, thoracic shield, plate, and tubercles, and reaches about
25 mm. Body color varies from dark pink or reddish gray to dusky gren
(Blakeslee 1915, Forbes 1890, Sanderson 1901b).
Pupa. Ten to 12 mm long, possesses stout, hooked spines on end
of abdomen and enclosed in white silken cocoon. Newly transformed pupa
pale olive green but gradually changes to light brown, then to dark brown, and
finally almost to black.
Biology. Moths in southern range emerge form April through
September (Blakeslee 1915, Pierce and Nickels 1941). Females deposit 12 to
74 eggs singly or in small groups in cracks, crevices, or wounds in bark, and
under bark scales; in the absence of such niches, eggs are loosely glued to
smooth bark surfaces (Blakeslee 1915). Moths live 1 to 3 weeks but deposit
most eggs during the first 2 to 4 days. Egg incubation requires 8 to 14
days. Larvae bore into bark at scars, wounds, or crevices where bark
scales offer concealment and protection. Larval mines are very shallow and
irregularly shaped, cave-type burrows between wood and the outer bark.
Galleries usually are loosely packed with frass. Considerable frass is
expelled from larval entrance holes (Sanderson 1901b). Larval feeding
lasts 30 to 38 days. In the South, larvae of all sizes may be present
throughout most of the growing season (Blakeslee 1915). They pupate in
burrows under the bark in loosely spun silken cocoons partially surrounded by
dark excrement pellets. The pupal stage lasts 24 to 33 days for the
overwintering brood but may be completed in as few as 10 days for summer
broods. Up to five generations occur annually in central Texas (Pierce and
Nickels 1941), but only two generations in Virginia (Blakeslee 1915), Delaware
(Sanderson 1901b), and Michigan (Biddinger and Howitt 1992).
Injury and Damage. New attacks can be detected by oozing sap or
"weepy spots" on tree trunks (Kelsey and Stearns 1960). The most
obvious signs of infestation are accumulations of dark brown or black frass on
bark at attack sites (Blakeslee 1915, Pierce and Nickels 1941). The frass
typically consists almost entirely of black excrement pellets that stick or
adhere loosely together with sap exudate and silken threads. Attacks are
limited largely to trees with mechanical wounds, frost damage, sunscalds, disease
cankers, pruning wounds, and recent grafts and buds. Disease cankers and
other diseased patches of the cambium or partially girdled stem are sites
favored for invasion. Lifting dead bark killed by disease or other injury
exposes accumulations of frass, larvae, and larvae burrows extending into the living
tissue. The presence of one or more loosely woven cocoons of white silken
threads is characteristic. White silken cocoons distinguish this bore from
Synanthedon scitula and other sesiids, which have dark brown or black
cocoons usually covered with dark frass. It attacks trees and
branches of all sizes but most commonly the lower trunks, especially just above
groundline. Usually not of widespread economic importance, but it can
seriously damage trees in some localities. It is a major pest of cherry
orchards in Michigan (Biddinger and Howitt 1992). In the late 1950's and
1960's, it seriously damaged many London plane trees in eastern cities. It
prefers trees in poor health, particularly those with mechanical injuries and
fungal diseases (Blakeslee 1915). Larvae on pecans may injure or destroy
either grafts or patch-buds; in a Texas orchard, it destroyed two-thirds of
1,200 grafts and one-third of 3,000 patch buds (Pierce and Nickels 1941).
Also, it girdles the base of sprouts that previously have been patch-budded; in
a Texas pecan grove, it infested 322 of 616 sprouts on 24 top-worked
trees. Deadening and felling trees and cutting back branches before
top-working lower vitality and lead to maintenance of high populations of this
borer (Pierce and Nickels 1941).
Control. Because eggs and first-stage larvae occur at or near
the bark surface and later stages develop just under outer bark, this borer is
subject to considerable parasitism and predation. Hymenopterous
parasites--including Idechthis nigricoxalis (Cushman) and Mesostenus
thoracicus (Cresson) in Virginia and Itoplectis marginatus (Prov.), Mesostenus
gracilis Cresson, and Pimpla sp. in Georgia--destroy upwards of 14%
of the larvae (Blakeslee 1915, Carlson 1979). Woodpeckers, ants, and
larvae of Tenebrodies corticalis Melsh. effectively reduce populations.
Use of recommended pruning, grafting, and cultivation procedures and good
cultural practices in general help to prevent infestations. Tree shakers
used on nut-and-fruit-producing trees should be properly adjusted or padded to
avoid bruising and breaking the bark. Prompt trimming and painting of bark
wounds with tar-based tree paint provide some control (Wiener and Norris
1983). Pesticides give mixed results but have provided control when
properly timed and carefully applied (Kelsey and Stearns 1960, Pierce and
Nickels 1941, Wiener and Norris 1983).
Larva(e) (note mine cavity with larvae and silken cocoons). James Solomon,
USDA Forest Service. |
Adult(s). James Solomon,
USDA Forest Service. |
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