Choristoneura freemani
| Choristoneura freemani | ||||||||||||
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Choristoneura freemani |
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| Scientific name | ||||||||||||
| Choristoneura freemani | ||||||||||||
| Razowski , 2008 |
Choristoneura freemani ( English Western spruce budworm ) is a North American species of butterfly from the genus Choristoneura within the family of the winder (Tortricidae). It is considered a major forest pest in its homeland.
description
Adult moths reach a body length of around 12.7 millimeters and a wingspan of 2.2 to 2.8 centimeters. The wings are gray or orange-brown in color and have banding or stripes. There is a noticeable white point on the wing edges. Males and females are similar in appearance, with the females being a bit more robust.
The oval, light green eggs are around 1.2 millimeters in size. They are placed in groups and overlap like shingles .
The caterpillars go through a total of six larval stages. Freshly hatched caterpillars are yellowish-green in color and have a brown head. From the second to fourth instar they are orange to cinnamon brown with a black head and collar. In the fifth stage, they have a pale olive-brown body with small white dots, a black collar and a reddish-brown head with black triangles. In the sixth larval stage, the olive to reddish brown caterpillar is 2.5 to 3.2 inches long and has a light brown to light chestnut brown head and collar. There are also large, ivory-colored areas on the body. The 1.3 to 1.6 cm large pupa is initially brownish yellow or green and later turns a reddish brown.
distribution
The distribution area of Choristoneura freemani is in western North America. It stretches along the Rocky Mountains of Alberta and British Columbia in the north, through Washington , northwest Oregon , Idaho , Montana , Wyoming , Utah and Colorado to Arizona and New Mexico in the south.
Way of life
Food crops
The caterpillars feed mainly on the Colorado fir ( Abies concolor ), the coastal fir ( Abies grandis ), the rocky mountain fir ( Abies lasiocarpa ), the West American larch ( Larix occidentalis ), the Engelmann spruce ( Picea engelmannii ), the white spruce ( Picea glauca ), the blue spruce ( Picea pungens ) and the Douglas fir ( Pseudotsuga menziesii ). They also eat less frequently the purple fir ( Abies amabilis ), the white-stemmed pine ( Pinus albicaulis ), the coastal pine ( Pinus contorta ), the flexible pine ( Pinus flexilis ), the western white pine ( Pinus monticola ), the Yellow pine ( Pinus ponderosa ), the West American hemlock ( Tsuga heterophylla ) and the mountain hemlock ( Tsuga mertensiana ). The caterpillars are often found on the common spruce ( Picea abies ) and forest pines ( Pinus sylvestris ) that are planted for ornamental purposes .
development
In most of the distribution area the species goes through all stages of its development within 12 months. The fully formed moths hatch from their pupae from early July to early August, depending on their location. 7 to 10 days after hatching, the female lays around 150 eggs on the underside of the needles of the forage plants and then dies. The eggs are deposited in one to three-layer piles of up to 130 eggs.
After about 10 days the caterpillars hatch from the eggs. The caterpillars do not eat, but immediately start looking for a sheltered place under the bark or under lichens, where they can spin to hibernate. In early May to late June the caterpillars leave their winter hiding places and start looking for food. They mine annual needles and closed buds. They often leave silk residues and excretions at the entrance hole. When new shoots sprout, the caterpillar spins a loose web over it and begins to feed on the fresh needles. When the shoots begin to grow in length, they tie up neighboring needles to feed on them. The young needles are preferred to be eaten. On some food plants, it also affects the male cones and the as yet undeveloped seed cones .
The caterpillars are fully grown around 30 to 40 days after leaving their wintering places. They mostly pupate in their feeding places. The fully developed butterflies hatch after around 10 days.
Harmful effect
Choristoneura freemani is classified as one of the most important pests in the western coniferous forests of North America. When the population in Douglas fir stands is high, eating the needles can cause the crown area to die off. In addition to the leaves, the caterpillars also eat the flower cones and the as yet undeveloped seed cones of the food plants, which can lead to a collapse in seed production. This has particularly negative effects in stocks for seed production as well as in locations with already little natural regeneration. Due to the weakening of the tree, this can last for several years. An infestation on seedlings and young trees can lead to de-needles, deformities and death. Old trees are usually weakened and growth is inhibited.
Trees weakened by an infestation with Choristoneura freemani are susceptible to secondary pests such as Dendroctonus pseudotsugae and Scolytus ventralis .
swell
- David G. Fellin, Jerald E. Dewey: Western Spruce Budworm . In: US Department of Agriculture Forest Service (Ed.): Forest Insect & Disease Leaflet . tape 53 , March 1982 (English, online ).
Individual evidence
- ↑ a b c d e f g h i j David G. Fellin, Jerald E. Dewey: Western Spruce Budworm . In: US Department of Agriculture Forest Service (Ed.): Forest Insect & Disease Leaflet . tape 53 , March 1982 (English, online ).
