OFM Life Cycle

OFM Shoot Damage

Fruit Injury

Internal Damage

Other Caterpillars Causing Similar Damage

OFM Identification

Comparison of Other Larvae

Acknowledgements

OFM overwinters as a fully grown larva protected within a silk cocoon called a hibernacula located in tree crevices or in the orchard ground cover.

OFM pupates in the spring with this overwintering generation emerging around the time of peach blossom.

This first peak moth emergence is typically late April to mid-May.

Eggs are laid on foliage, usually on the upper side of terminal leaves. Females can lay up to 200 eggs. Incubation can take between 5 and 21 days depending on temperature.

After hatching, 1st generation larvae bore into growing shoots. The 1st instar larvae are very tiny and difficult to see. In the photo below the 1st instar larvae is visible only by first detecting the dark head capsule.

The 1st instar larvae will grow from 1.5 mm (1/16th inch) up to 8 to 13 mm (3/8th to 1/2 inch) as a 4th or 5th instar larvae, depending on generation.

First generation larvae reach maturity by mid- to late May, depending on temperature. The 1st generation moth flight is from early June through mid-July.

There are 3 to 4 moth flights per year in Washington state. (1 for each completed generation.)

Some 2nd, and most 3rd and 4th generation larvae attack fruit before seeking overwintering sites where they spin a silk cocoon (hibernaculum).

OFM larvae are typically cream to pink in color with a dark head capsule, except just after molting as seen with the larva pictured below.

Twigs infested with larvae usually have wilted leaves.

Upright twigs with one small wilted leaf usually means a larva has entered within the last day or two.

If a twig is dark or has dry leaves and gummy ooze, the larva has already exited.

First and Second generation larvae tend to mainly damage shoots.

Most of the fruit injury is due to Third and Fourth generation larvae.

There are two distinct types of fruit injury.
The first type is shown in the pictures above. The injury is caused by feeding on or entrance into small fruit early in the season. This is refered to as "Old Injury" because it is the oldest at harvest time. As the fruit grows, gum exudes from the wounded area.

As the season progresses and the fruit grows the exudate turns dark and a black blotch appears at the wound site at harvest time.

Active larval feeding may also be evident at harvest. This is refered to as "New Injury".

Internal Damage Type 1

Larvae can enter by way of making an entrance hole in the exterior part of the fruit. Here the larvae has tunneled into the fruit to feed.

However, larvae can also enter a fruit by way of borrowing into a stem and moving down into the fruit. This is called Type 2 damage.

Internal DamageType 2

The second type of fruit damage can occur when newly hatched larvae enter the side of a green stem and work its way down into the fruit without injuring the skin.

When the fruit is picked, the stem breaks off and any evidence of entry is left behind.

This is why fruit cutting is required during the inspection process.

Peach Twig Borer

PTB larvae may cause similar surface damage to fruit.

Look for alternating dark and light bands to identify the larvae as PTB.

However, the 1st instar PTB are very hard to differentiate from OFM and must be looked at under magnification.

 

Codling Moth

Codling moth infesting stone fruit is extremely rare.

The late instar CM larvae are much larger than OFM.

OFM larvae can be identified under magnification by the presence on a structure called an "anal comb". OFM lavae have 5 "teeth" in the comb.

Peach twig borer larvae have 6 teeth in the comb.

Codling moth larvae do NOT have an anal comb.

Lesser Appleworm Grapholitha prunivora Walsh (0.82mm)

LAW is not reported in peaches, apricots or nectarines.

Cherry Fruitworm Grapholitha packardi Zeller (0.89mm)

CFW only has peach reported as a possible host.

Oriental Fruit Moth Grapholitha molesta Busck (1.11mm)

OFM is found in stone fruit, but is rare in apples in Washington state.

Codling Moth Cydia pomonella Linnaeus (1.65mm)

CM has no anal comb (as mentioned above) and is rare in stone fruits.