Frequently
Asked Questions
What is Apple Maggot?
Apple
maggot (Rhagoletis pomonella Walsh) is a native
pest of the Eastern United States and Canada. In 1979 it was discovered
in Oregon and has since moved into California, Washington, and
other Western states.
Commercial
North Coast apple orchards under conventional pest management
are less likely to have problems with apple maggot, because pesticides
used for codling moth and aphids will control it. The presence
of apple maggot in backyard orchards is considered a serious threat
to organic apple production because organic growers would be adversely
affected. The pest is capable of destroying fruit in organic commercial
orchards. It is of the utmost importance to be able to identify
the pest as early as possible, so that management strategies are
more likely to succeed.
Fruit
from backyard trees should not be moved offsite. Please, do
not give away fruit from your orchard. Early stages of apple
maggot damage are difficult to detect, as apples appear normal.
They may be transported and discarded in apple growing areas where
they will threaten commercial production. Apples are fit for consumption
after discarding the damaged parts. Throw the damaged parts in
the trash, do not compost unless you make sure that the maggots
are dead (disposed of by cooking (over 160 Degrees F.), freezing
or any method that will ensure the death of any larvae in the
fruit).
When should I see apples damaged by apple
maggot?
As
early as mid-June. From late June through early July, female apple
maggot adults deposit eggs singly under the apple skin. After
2-10 days, a small maggot hatches from the egg and starts burrowing
and eating through the flesh, leaving a brown, thread-like trail.
(Figure 1).
As the maggot grows, the burrows increase in size and bacteria
associated with the maggot cause the fruit to rot internally (Figure
2).
How do I know if I have maggots in my apples?
Cutting
the apples in half will tell you if the apples are rotten or not.
See figures 2 and 3
How
do I know if my apples have apple maggots or codling moth worms?
If
you find maggots or worms, look for the presence of legs. Apple
maggots are leg-less, cream-colored cylindrical-shaped, and with
a blunt posterior and a tapered front end that contains two black
mouth hooks. Codling moth worms have a distinct brown-colored
head, and several pairs of legs.
If
maggots or worms are not found, the flesh of the fruit damaged
by apple maggot has a mushy, brown appearance (Figure 2) while
the apple core is left untouched. In contrast, codling moth worms
tunnel and reach the apple core, where they feed actively, leaving
behind abundant frass (i.e. fecal pellets that look like saw dust)
(Figure 3).
Figure 3. Codling moth damage in apples.
The larvae penetrate the fruit skin, bore
to the core, and feed in the seed cavity.
Why
do I have apples dropping under the tree?
All
the fruit found under the tree is likely to be damaged by apple
maggot or codling moth. See figure 2.
How
do I control apple maggot?
There
are several choices, depending if you want to apply insecticides
or not.
Non-Chemical
Control :
DISCARD
FALLEN AND/OR WORMY APPLES. Fully grown maggots leave the apples
to pupate in the soil. Very few maggots leave the apples while
they are still hanging from the tree. After the fruit drops, maggots
spend a few days inside the apple before leaving it to pupate
in the soil. Usually a few days elapse between the time an apple
maggot-infested apple falls to the ground and the maggots leave
it. Clean up fallen fruit regularly so that larvae don't have
a chance to burrow into the ground and pupate, becoming a problem
the following season.
If
dropped apples are collected and disposed inside plastic bags
, the cycle will be interrupted and fewer flies will survive.
Composting the fallen apples may not be sufficient to kill the
maggots.
TRAP
ADULT FLIES: Adult apple maggot flies are attracted to red sticky
plastic spheres or yellow sticky panels. Flies get trapped in
the sticky substance (Tanglefoot®) and die. The red spheres
mimic ripening apple fruits to which flies are attracted for mating
and egg laying while the yellow traps mimic apple leaves. Both
types of traps may be improved with the addition of attractants
( i.e. apple volatile lures or ammonium acetate). Traps can be
used to attract and kill adult flies or for monitoring when flies
are present to time an insecticide application. Around mid June,
place one to three apple maggot traps in the trees, about head
height, surrounded by fruit and foliage, (but not obstructed from
view).
CHEMICAL CONTROL: If you can not tolerate any damage, a spray
program with Imidan® (phosmet) or Diazinon® will control
apple maggot flies. Do not target the application to control maggots,
the pesticide will not kill them while they are inside the apple.
You should use at least one monitoring trap and only apply pesticides
when the monitoring traps indicate the presence of apple maggot
flies. WAITING TIME BETWEEN SPRAYING AND HARVESTING: When using
an insecticide on edible fruits, a period of time must be observed
when no spray is applied to prevent excessive residues of the
insecticide on the harvested fruit. Examine your pesticide label
to determine these day limitations.
WARNING.
Pesticides are poisonous and must be used with caution. READ THE
LABEL BEFORE OPENING A PESTICIDE CONTAINER. Follow all label precautions
and directions, including requirements for protective equipment.
Apply pesticides only on the crops or in the situations listed
on the label. Apply pesticides at the rates specified on the label.
If
you need more information, please contact the U.C.C.E. Master
Gardeners at the Cooperative Extension office, (707) 565 2608.
Codling
moth control information is available in the following references:
Integrated
Pest Management for Apples and Pears, UC ANR Publication 3340;
pgs 77-89;
Pests
of the Garden and Small Farm; A Grower's Guide to Using Less Pesticide,
UC ANR Publication 3332, pgs 53-57
Pest
Note 13. Codling moth
Lucia
Varela, Phd
North Coast IPM Advisor
