Pine tip moths in Georgia, USA

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Author: H.C. Ellis, University of Georgia

Contents

Tip moths are the most serious insect pests attacking Christmas trees in Georgia. Two species commonly occur; the Nantucket pine tip moth Rhyacionia frustrana (Comstock), and the pitch pine tip moth, Rhyacionia rigidana (Fernald). The Nantucket pine tip moth is the most common pest. They attack Loblolly Pine, Shortleaf Pine, Virginia Pine, and other pines except for Eastern White Pine.

Description

Adults are small (9 - 15 mm wingspread) gray moths with brick-red to brownish patches on their wings. Fully grown larvae are orange-brown and about 10 mm long.

Damage

Injury is caused by larvae tunneling in new growth, buds and shoots. Infested twigs die, resulting in loss of main-stem terminals, poor tree shape, and poor tree growth.

Life History and Habits

Tip moths pass the winter as pupae inside infested tips. Adults begin to emerge with the first warm days of spring. Emergence has been recorded as early as late January in south Georgia, but the first significant emergence is usually in late February or early March. It often continues through April.

Adults are rarely seen during the day, being most active at night, dawn or dusk. A few days after emerging, moths mate and begin laying eggs on needles, in needle sheaths, on developing tips or on buds. First generation eggs normally hatch 25 - 30 days after the moths emerge. Newly hatched larvae feed on the bases of needles (Fig. 3) and often construct delicate webs in needle axils or between buds and needles.

After molting, the second instar larvae bore into and consume buds. A bead of resin exuding from a bud is often the first sign of larval entry.

As they grow and develop, each larvae continues to feed within the bud and shoot, boring down the center of the shoot after it has consumed the bud. Eventually, infested tips turn brown and die.

The larval period lasts two to four weeks, and pupation occurs within infested tips. The pupal stage lasts one to two weeks; then moths emerge to begin the cycle again. There are usually four generations per year in south Georgia, and three in north Georgia. Developmental time depends largely on temperature.

Control

Tip moth suppression in commercial Christmas tree plantings requires chemical controls. Time sprays to kill the small, newly hatched larvae when they are exposed on the outside of shoots (before they penetrate the buds). Larvae are most vulnerable immediately after egg hatch. Sprays can best be timed by monitoring adult emergence with pheromone traps, recording daily maximum - minimum temperatures and predicting egg hatch using a temperature "degree-day" program. This technique was described by Gargiulllo, et.al. (1983, 1985). An alternative method is to monitor adult emergence from pupal cases. When empty pupal cases are found in terminals, moths have emerged and egg-laying can be expected within a predictable range of days.

First Adult Emergence Expected First Egg Hatch
Generation 1 25 - 30 days
Generation 2 10 - 20 days
Generation 3 5 - 10 days
Generation 4 10 - 15 days

This method of determining egg hatch requires careful, frequent, and accurate monitoring of adult emergence from pupal cases within the tips.

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