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University
of Rhode Island GreenShare Factsheets
Apple
Maggot Rhagoletis
pomonella
Diptera: Tephritidae
The apple maggot,
or "railroad worm," is one of the most serious pests of apples
in the fruit growing areas of the Northeast. All apple varieties
are
subject to apple maggot attack, but summer varieties and early
fall varieties are especially subject to injury. The insect also
attacks
certain varieties of European plums. The
adult apple maggot is a black-bodied fly slightly smaller than the
house fly. The female is larger than the male and has four white
bands across the abdomen, while the male has only three abdominal
bands. The wings of the fly are crossed by four dark bands. Signs of the
infestation on the fruit are minute egg punctures in the skin and
pitted areas on the surface. In late-season varieties the injury
usually appears as corky spots or streaks in the flesh. In the varieties
ripening during July, August and September open tunnels may occur.
Rot-producing organisms follow the maggots, causing rapid decay
of infested fruit. The adult flies
emerge from their overwintering puparia (cocoon-like structures)
in the ground during the latter half of June and continue to emerge
through the middle of August. After emergence, the flies feed, mate,
and, after 7-10 days, begin to lay eggs. During this time they may
be seen resting on the leaves or fruit of apples and other host
plants, lapping up drops of honeydew or moisture with their fleshy
mouthparts. The female has a sharp ovipositor with which she punctures
the skin of the apple and inserts her minute whitish egg into the
pulp of the fruit. A large number of eggs may be deposited in a
single fruit, and fruits of late varieties become dimpled and pitted
as a result. The eggs hatch in 4 to 6 days, young maggots beginning
at once to tunnel through the fruit, leaving brown trails. Severely
infested fruits often fall to the ground early. The numerous trails
in the fruit reduce the inside of the apple to a brownish, pulpy
mass and render it unfit for consumption. The full grown maggot,
which is about 10 mm (1/8 inch) long, leaves the fallen fruit and
burrows into the soil to a depth of 25-50 mm (1 to 2 inches). Here
it forms a puparium, the stage in which it overwinters. For backyard
apple trees, red sphere sticky traps can control the apple maggot
fly without the use of pesticides. A small amount of damage
may
occur, but not enough to warrant spraying. In mid- to late June,
place spheres within the canopy at about head-height. Set out
one
trap for every 150 apples (1 trap per dwarf tree, 2-4 per semi-dwarf
or 4-8 per full size standard tree). Traps may be removed at
the
end of August. For both backyard apple trees and orchards, picking
up and destroying fallen apples at weekly intervals from early
August
through harvest destroys the larvae within the fruit and reduces
the potential for maggot injury the following year. This is
most
practical where trees are isolated and wild or abandoned trees
are not nearby. For an overview of home apple tree management,
a list
of insect trap suppliers and sources of disease-resistant trees,
see "Home Tree and Small Fruit Pest Management Guide," or visit
the URI Apple IPM website at http://www.uri.edu/research/IPM Adapted
from the Cornell Cooperative Extension, 1999.
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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