Pandora Moth Outbreak

Introduction:

Fremont-Winema National Forests' monitoring revealed a large outbreak of Pandora Moth in the spring of 2002 all over the Chiloquin District north of the Sprague River Road. Defoliation was significant on some of the larger ponderosa pine along Road 4584 south of the Silver Lake Highway. Many windblown larvae littered the road at one point. Mainly ponderosa pine was affected, but some lodgepole pine was also affected. The larvae were mainly affecting the upper crowns by chewing the needles to stubble. Some severely affected trees appear to have succumbed, or are close to it. 2005 was the 5th year of the local infestation. That year we saw some increase in the beetle killed trees, but not an alarming amount. Large numbers of pandora moths were found in Klamath Falls in 2005. Defoliation was mapped from the air during the week of June 12, 2006. Observers reported only some small areas of light defoliation. The winter of 2005-2006 was relatively wet and cold, which could have caused sufficient mortality in the overwintering caterpillars to account for the decline in defoliation, or a virus or bacterial infection could have reduced the population. Whatever the reason, the amount of damage done to forest trees declined dramatically from 2004 levels. Some levels of dead trees from defoliation followed by bark beetle attack were noted near the Klamath Marsh, but were not widespread. 2007 will be a mating year in the 2 year life cycle, and moths will be out in July through August. It remains to be seen whether the Pandora populations will rebound and cause more acres of weakened trees, or not, in 2007.

No, the photo to the left does not show a burned area. The outbreak continued into 2004. This June 2, 2004 photo, taken by Cam Richey, shows defoliation in the Wocus Bay area of the Chiloquin Ranger District. In combination with drought stress and other insects and diseases, these weakened trees may not survive. A situation much like that in 1918-1925, described below, seems to be developing.

	The photo to the left was taken on June 14, 2004. It shows a plantation on Solomon Butte (T33S, R8E). This area was planted after the Cave Mountain Fire several years ago. The photo above is of the same area taken from the air on June 15, 2004.

Additional impacts are shown in the following photos:

Lamms Camp area, with Silver Lake Highway visible across the marsh. T31S, R9E, the visible cinder pit is in SE 1/4 Sec 16	Southern slopes of Applegate Butte, T33S, R8E, Sec 24. Heavy defoliation in the lodgepole sink and in the ponderosa.
View from Kirk Road (T33S, R7E, SW 1/4 Sec 1) looking east toward Soloman Butte T33S, R8E, Sec 6,7,18.

In addition to the impacts displayed in the above photos, the defoliation is also very heavy on Yoss Ridge T32S, R9E, and east of Yoss Ridge; all along the Kirk Road from T32S, R8E Sec 31 to the north end of Yoss Ridge at T32S, R9E, Sec 2, both north and south of the road; Wocus and Little Wocus Butte appear totally defoliated as seen from miles away on the Silver Lake Highway. The north slopes of Solomon Butte don't appear as bad due to the un-eaten fir component, but the ponderosa and lodgepole pine have lost most of their needles. District personnel estimate about 80,000 to 100,000 acres are defoliated heavily on the Chiloquin Ranger District.

Defoliation is much heavier than the previous levels seen along the Williamson River Road. Many areas look like a fire went through and removed 100% of the needles. As of June 16, 2004, the caterpillars are dropping off the trees and burrowing 1-2 inches underground in preparation for pupation. The terminal buds have not leafed out yet, so the trees are almost devoid of needles.

Background: (by Kim Gillogly)

The pandora moth, Coloradia pandora Blake (Carolin and Knopf 1968), is an important defoliator of pines in western forests. The moth is recorded in the United States from the Rocky Mountains west, except Idaho and Washington. Outbreaks have occurred only on areas with soils loose enough for the larvae to bury themselves prior to pupation - chiefly pumice soils in Pacific Coast States and decomposed granite soils in Rocky Mountain States.

A destructive outbreak occurred on the Klamath Indian Reservation of southern Oregon in 1918-25 (Patterson 1929). Thousands of acres of ponderosa pine forest were heavily defoliated, with an accompanying serious loss of timber. Lodgepole pine in mixture with ponderosa pine was also attacked. Heavily defoliated trees died after 2 to 3 years. Others were greatly reduced in growth and recovered only after several years. The loss in growth throughout the defoliated area mounted to several million board feet.

In parts of the West, epidemics occur at intervals of about 20 to 30 years and continue 6 to 8 years. During periods of abundance, feeding may be fairly heavy without serious consequences. This is because the terminal buds are not eaten, and, since the insect has a 2-year life cycle and most of the feeding occurs in alternate years, the trees have an opportunity to recover. The more vigorous trees survive the attacks, and only during major outbreaks are losses likely to be heavy. In non-epidemic years, the pandora moth is scarce and seldom seen.

The adults are large, heavy-bodied, grayish-brown moths, with a wing expanse of 70 to 110 mm and a small dark spot near the center of each wing. The base and interior margins of the hindwings are clothed with pinkish hairs, which in the male shade to wine color. The males have large, feathery antennae, while the females have slender antennae. During epidemics thousands of these large moths will be seen fluttering over the tree trunks and flying through the woods. The eggs are globular, about 3 mm long, and are deposited in clusters of 2 to 50, usually on the needles or bark of pine. The newly hatched caterpillars are about 5 mm long, with shiny black heads and black or brownish bodies covered with short, dark hairs. When mature, the caterpillars are from brown to yellowish green and 60 to 80 mm long, with each segment supporting a few stout branched spines. The pupae are dark purplish brown, from 25 to 35 mm long, and are not enclosed in a cocoon.

The Pandora moth requires 2 years to complete its life cycle. Adults appear the latter part of June and in July, and the eggs hatch in August. The young larvae crawl up the trees and during the early molts feed in groups on the new foliage. At the end of the season they are about 25 mm long. These immature larvae spend the first winter hibernating in clusters at the base of the needles. They resume feeding the following spring, and the caterpillars reach full growth by the last of June. When mature, they crawl down the trees and enter the soil to a depth of 25 to 125 mm where they form elliptical cells in which they transform into pupae. Typically the pupal stage lasts 1 year; however some pupae remain in diapause for as many as 5 years before transforming into adults (Carolin 1971).

Epidemics of the pandora moth are controlled a by a number of natural factors. Perhaps the most important is a wilt disease that affects the mature larvae. Once this disease becomes established it runs rampant and few of the insects survive. Ground squirrels and chipmunks dig up and destroy large numbers of pupae. Birds, insect parasites, and high soil temperatures also exert some control. Direct control measures have not been devised specifically for this insect.

Information gathered from "Western Forest Insects", U.S.D.A. - Forest Service

What can be done? (by Kevin Moore)

There really isn't anything that we can do on the Forest scale to eliminate the pandora moth. In 2004, the defoliation was pretty severe on over 80,000 acres of Federal lands. There are no approved pesticides that we could use to spray for the caterpillars, especially at that scale.

In a yard, one can spray the moths, egg masses, and the tiny caterpillars. They will hatch in late summer from the eggs. Any insecticide that is approved for soft bodied insects in the garden or on fruit trees should work. If the label says it works on things like tomato hornworms and cabbage loopers, it will likely kill the pandoras.

To avoid insecticides, you may reduce the population somewhat just by spraying the eggs off the trees with water, or with soapy water. Watering yard trees and fertilizing will also increase the general health of pines in your yard, making them more able to shake off the effects of defoliation.

The eggs will hatch in late summer, and the small (1 to 2 tenths of an inch long) caterpillars will start crawling up the trees to the needles and feeding. They are pretty hard to notice at that size, and don't do a lot of apparent defoliation. They slow down and feed intermittently, depending on temperature, over the winter. Cold, wet winters will kill off a large percentage of them, and mild winters let many survive. In the spring of the following year they will start feeding in earnest, growing and molting several times. They only eat the older needles of the pines, and will reach full size, about 3+ inches long, in June. They then drop into the loose soil at the base of the tree and pupate, staying in the ground until late June-July of the following year. Then they emerge as moths. Defoliated trees look horrible for a couple of weeks, until the new growth needles emerge. The entire life cycle takes 2 years, and in the upper Klamath Basin the defoliation is taking place in even numbered years, and the moths are out in odd numbered years.

These moths are only found in any numbers in the Western US where there are pine trees and loose volcanic or pumice soils. They are an unusual forest insect, in that the population does not rise and fall on the condition of the trees. Most forest pests increase in numbers and in effect on the trees if the trees are old, or stressed by drought or overstocking, or scorched by fire. Pandoras come and go to some cycle that has not been determined definitively yet.

Usually pandoras last one or two cycles and seem to disappear. Most defoliators that occur in concentrated populations eventually "bust" due to bacterial or viral infections. Infected caterpillars blacken and turn to soup inside. 2005 is the 5th year of the local infestation, and we cannot really predict when it will end. We are seeing some increase in the beetle killed trees, but not an alarming amount as yet.

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