Reduce Damage from the Codling Moth
is a codling moth?
Codling moths are small gray and brown insects
considered to be the greatest threat to many fruit and
nut growers. Their primary targets are apples and pears,
but they have also been known to attack English and black
walnuts, plums, and quince, a fruit used in jellies, preserves
Codling moths spend the winter primarily
under loose bark as mature larvae in a silken cocoon. In
some areas, they emerge as adults in the spring, starting
in mid-March, but later generations emerge from June through
September, depending on the area and the crop.
The earliest codling moths land on the leaves
and spurs of fruit trees, where they lay eggs. The eggs
then hatch into small larvae that may chew into the leaves,
but mainly move to the fruit. Later generations lay eggs
directly on the fruit. After exiting the fruit, the larvae
crawl down the side of the tree under loose bark, develop
into cocoons, and the process begins all over again. The
codling moth produces two to three generations each year.
|Codling moths start out as larvae inside cocoons
that develop in tree bark over the winter months. In
the spring, male moths mate with female moths, which
lay eggs that hatch into more larvae on fruit. Without
proper monitoring, codling moth larvae can cause widespread
damage to various fruit and nut crops. (Photo courtesy
of Jack Kelly Clark, UC Statewide IPM Project)
types of damage can the codling moth do?According to the United States Department of
Agriculture (USDA), if left unchecked, the codling moth
has the potential to destroy 80 percent of the apple crop
in the Northwest and 50 percent of the pear crop. The destruction
is caused by larvae that tunnel into the core of the fruit,
expand the seed cavity, then eat the seeds, making the
fruit unfit for human consumption. That means reduced profits
for growers and fruit packinghouses.
The larvae will often leave a mass of chewed
material or excrement outside the entrance known as "frass." Some
pieces of fruit may have more than one entrance hole with
each one surrounded by frass.
The larvae may also cause another type of
injury known as a "sting." A sting is a place where the
larvae chewed just a small amount, then either died inside
the fruit or entered at another place.
|Growers should discard fruit marked with "stings," which
are small entry wounds caused by codling moth larvae.
(Photo courtesy of Jack Kelly Clark, UC Statewide IPM
steps can be taken to reduce codling moth damage?
There are some non-chemical methods that can
be used to control the codling moth so that damage to fruit
crops is minimal. One is called "mating disruption." This
involves the use of dispensers containing pheromone, a
synthetic copy of a scent emitted by female moths to lure
males when they are in the mood to breed. Males that are
attracted to the pheromone scent become confused when they
can't find their female companions and fly away. This means
the female moths are unable to lay the eggs that ultimately
lead to damage.
One type of mating disruption dispenser in use in orchards
in California is called the "puffer." This brown rectangular
box emits pheromone equal to the scent of seven to 10 million
female months into the air every 15 minutes.
You can also control the spread of larvae by immediately
removing fruit containing worms from your trees and picking
up infested fruit that has fallen to the ground. Fallen
fruit should be buried underground six to 12 inches or
placed in a black plastic bag in the sun for at least four
weeks before it can be used as compost.
|These brown rectangular boxes, known as "puffers," release
commercially made pheromone, which attracts male codling
moths. The puffers are used to disrupt the mating practices
of the moths and subsequently reduce fruit damage.
(Photo courtesy of Jack Kelly Clark, UC Statewide IPM
Wrapping burlap or corrugated cardboard collars around
the tree trunks and main scaffolding branches may also
help prevent the development of larvae within the tree
bark. Place a 3- to 4 inch wide piece of cardboard around
the trunk 12 to 18 inches off the ground and secure it
with plastic flagging tape, string, or wire that can be
removed or retied. A burlap bag can also be used. Mature
codling moth larvae are attracted to these collars and
try to use them to spin cocoons. The collars are usually
more effective on trees with smooth bark, as opposed to
trees with rough bark that provide the larvae more places
to pupate. Be sure to check the collars frequently in early
June through September for larvae that may be starting
Try to limit the use of pesticides to control codling
moth. Some chemicals may kill beneficial insects, such
as wasps, spiders and predatory bugs that prey on codling
moth. Always use traps for monitoring and degree-day models
before deciding if and when to spray.
|Stone fruits such as plums and peaches may suffer
extensive damage from codling moth larvae. This plum
is no longer fit for human consumption after larvae
bore their way to the pit. (Photo courtesy of Jack
Kelly Clark, UC Statewide IPM Project)
and Don'ts of Reducing Codling Moth Damage
- Remember that the codling moth is the greatest
threat to many fruit and nut crops.
- Wrap collars made of corrugated cardboard or
burlap bags around tree trunks and scaffolding
branches to reduce the number of codling moths.
- Consider using mating disruption devices that
emit pheromone to prevent male moths from mating
- Don't allow fallen infested fruit to lie beneath
your trees. Pick those pieces off the ground so
codling moth larvae will not develop inside of
them and spread to your trees.
- Don't forget that "beneficial" insects such as
spiders and wasps feast on the codling moth. Therefore,
try to limit the use of pesticides that may kill
those insects as well.
- Don't hesitate to quickly remove fruit that's
been infested by codling moth larvae from your
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