Larch Wooly adelgid (Adelges laricis) and Sacchiphantes Abietis(L.)
From Bugwoodwiki
From: Kolk A., Starzyk J. R., 1996: The Atlas of Forest Insect Pests (Atlas skodliwych owadów lesnych) - Multico Warszawa, 705 pages. Original publication in Polish. English translation provided by Dr. Lidia Sukovata and others under agreement with The Polish Forest Research Institute.
Occurrence: Both species are widely spread throughout Europe in the range of the Norway spruce distribution. They have been introduced to the North America. Sacchiphantes abietis also occurs in Mongolia. In Poland these species are common in woodlands, also in parks and gardens.
Host Plants: These species usually occur on the Norway spruce. The larch woolly adelgid requires two hosts for its development. They are the spruce and larch. Sacchiphantes abietis develops on the spruce only.
Morphology: These are small insects, 1.5-3.0 mm long, with wings or wingless. Winged specimens of A. laricis are dark red, reddish brown or black, and those of S. abietis are yellowish. Wingless specimens of the former species are greenish brown, and those of the latter one are yellowish green. The egg is yellowish white, 0.3 mm wide.
Biology. Females of A. laricis (fundatrix) overwinter at the basis of spruce buds. In spring they sack on buds, and then lay eggs. Females become covered with long white waxed threads ("wooly"). A female lays approx. 100-180 eggs. Newly hatched larvae feed on buds. Their feeding causes the development of 1 cm wide, cone-shaped galls. Then larvae enter into the gall. Galls always are on the top of current year shoots. Galls are 1.5-3.0 cm long in the final developmental phase. After the development is finished in June or July, galls dry up and chambers open. Larvae leave chambers and after the last molting they become winged females. They move to larch trees, where reproduce parthenogenetically by laying eggs on needles. Hatched larvae (exulantes) feed on larch needles through late autumn. They overwinter in bark crevices or on shoots. In spring they become wingless females after short feeding. Females lay 100-150 eggs on needles. Hatched larvae feed (sack) on needles in their middle part. In the feeding place appears white wax secretion. Damaged needles become yellow and kneed. A portion of larvae develops into black winged aphids (sexupara) that move to a spruce where they give a bisexual generation (sexulantes). Mated females of sexulantes lay single eggs under bark scales of shoots. Young fundatrix emerges from the egg and overwinters. Another portion of larvae stays on a larch and develops into wingless females that parthenogenetically produce 2-3 generations of aphids (exulantes latentes). Biology of S. abietis and A. laricies is similar. However, wingless females of S. abietis unlike those of A. laricies develop from unfertilized eggs. Besides, winged females do not move from a spruce to a larch, but they stay on a spruce, where they cause new galls at the shoot base. Larvae feeding inside the gall causes its enlargement up to 3 cm in diameter.
Damage: Both species cause shoot deformation by creating galls, a decrease of the shoot increment, and weakening of trees by defoliation. Damages caused by both species are rather local.
Preventive measures: Planting of spruce and larch trees close together should be avoided.
Control measures: In small areas, like private gardens, green galls can be removed manually. Systemic insecticides can be used in large infested areas or at high population densities.
 Photo by Robert Dzwonkowski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |
 Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |
 Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |
 Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |
 Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |
 Photo by Stanislaw Kinelski, , Bugwood.org |  Photo by Stanislaw Kinelski, , Bugwood.org |
