Peach Twig Borer

Peach Twig Borer major pest of peaches in the eastern region of the united states NY, NJ, Connecticut.

The peach twig borer it is present in the eastern portions of the State, it is usually of minor significance. The name of this insect should not be confused with that of the peach tree borer which attacks the trunks of peach and plum trees in East Texas.Early generations of the peach twig borer larvae feed in the twigs of peach and plum trees. Damage is similar to that caused by the oriental fruit moth. Later generations attack peach fruits, either penetrating to the pits or hollowing out areas beneath the skin up to 1/4 inch in diameter. Varieties which mature fruit late in the season are damaged most severely. Early maturing plums are rarely attacked.

The adults are dark gray moths with lighter gray markings. They have a wingspread of about 5/8 inch. The young larvae are light brown with black heads. Mature larvae average 3/8 inch in length and are reddish brown with yellow-white bands around the body.As an immature larvae, the peach twig borer passes the winter beneath the bark in a hollowed- out cell called a hibernaculum. The larvae become active in early February and feed on the bark until the trees are in the pink bud stage, usually early March, the larvae move upward to tunnel and mature in the developing shoots. First evidence of larval activity is the appearance of wilted shoots when early flowering varieties are in full bloom and foliage is beginning to emerge.

Life Cycle: The larva has a dark brown head and prothorax with distinctive alternating dark and light brown bands around the abdomen. The larva has 4 or 5 instars. A mature larva may grow to 1/2 inch long. The pupa is smooth, brown and does not reside in a cocoon. Pupae are usually found beneath bark scales or cracks in the bark.The adult moth is between 1/3 and 1/2 inch long. It is steel gray with white and dark scales.Peach twig borer adult Life history The peach twig borer has three complete generations in Washington in most years. It overwinters as first or second instar larvae in cells, known as hibernacula, under the thin bark in limb crotches or in bark cracks. To detect the hibernacula, look for small chimneys of frass and wood chips built up by larvae feeding under the bark.

During bloom and petal fall, overwintered larvae emerge from their cells, migrate up the small limbs and twigs and begin to feed on buds and young leaves. As terminal growth develops, a larva will enter a single shoot, boring down the center, causing the terminal to wilt or flag. When mature, the larva leaves the mined shoot in search of a protected place to pupate. Adults from overwintering larvae usually begin to emerge in mid- to late May. Females each lay between 80 and 90 eggs on fruit, shoots or the undersides of leaves next to veins. The eggs, which are laid singly, hatch in 5 to 18 days, depending on temperature.

Damage: Larvae damage both growing shoots and nuts, causing shallow channels and surface grooves on the nutmeat. Peach twig borer damage can be masked by navel orangeworm feeding, which often occurs on nuts previously damaged by peach twig borer.Some orchards will require a treatment for peach twig borer. Use past history or harvest samples to determine if your orchard will require treatment. Preferred treatment timing is at full bloom and petal fall.

Treatments during the dormant season with environmentally sound insecticides such as spinosad (Entrust, Success) and diflubenzuron (Dimilin) are also acceptable. Avoid applications of organophosphates during the dormant season as these applications threaten water quality when they run off during winter rainfall. At the beginning of bloom, monitor hibernacula to determine when larvae are emerging. Place pheromone traps out around April 1, and monitor for shoot strikes to catch any inseason problems.

Control: Peach twig borer has about 30 species of natural enemies. Among those commonly found in California are the chalcid wasps, Paralitomastix varicornis and Hyperteles lividus. Another commonly found parasite is Macrocentrus ancylivorus, which attacks both peach twig borer and Oriental fruit moth. In some years and orchards, these natural enemies destroy a significant portion of larvae, but they may not reduce twig borer populations below economically damaging levels. Ants, Formica spp., also can be found preying on peach twig borer larvae.

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