ISBN 0-662-20745-9 Cat. No. Fo 29-6/1-1993E 1 FOREST Balsam Woolly Adelgid Pest R. Turnquist and J.W.E. Harris LEAFLET Pacific Forestry Centre Introduction Tikwalis Creek on the west side of the quarantine zone established by Fraser Canyon near Hells Gate. On provincial Order in Council. Some The balsam woolly adelgid, Adelges Vancouver Island, infested trees are highlights of the regulations piceae (Homoptera: Adelgidae), was found in east coast drainages from accompanying the revised zone are: accidentally introduced to North Victoria to Qualicum Beach and just annual permits are required to grow America from Europe and has become south of Port Alberni. Infested and and sell Abies spp. in British an important pest of true firs in the damaged trees have also been found Columbia; the movement of Abies Maritime Provinces, the Northeastern on Lasqueti and Hornby islands. spp. from within the zone to outside and Northwestern States, and southern Several of these locations were the zone is prohibited, only logs British Columbia. The adelgid can beyond known infestations and the transported and stored in water and damage and sometimes even kill a 1976 regulation zone. As a result, on processed promptly are exempted; significant proportion of the true fir in a October 22, 1992, new boundaries the selling or movement of cut trees stand after a few years of infestation. were drawn up and a revised or foliage of Abies spp. anywhere in In B.C., its impact on local B.C. between January 31 forest economies has and November 1 of a depended upon the Balsam woolly adelgid calendar year is prohibited. significance of Abies sp. in quarantine zone The revised quarantine forest stands. zone, related to present distribution, lies mostly Distribution within the southern part of In British Columbia, the PORT HARDY the Vancouver Forest adelgid occurs up to Region (Fig. 1). PEMBERTON about 1000 m elevation in The insect does not lower Fraser Valley CAMPBELL RIVER FRASER R. appear to have spread drainages east to Agassiz rapidly to adjacent stands, COURTENAY and, in patches, up the which is, in part, attributable mainland coast to West PORT ALBERNI VANCOUVER HOPE to the quarantine restricting Thurlow Island, north of NANAIMO the movement of host Powell River. Positive 0 40 80 km material within the samples in young Province. Presumably it is amabilis fir have also VICTORIA capable of spreading over been collected from Lizzie Figure1. Quarantine zone (1992 Order in Council) for balsam woolly much of the range of its Creek on the east side of adelgid in British Columbia. hosts, as demonstrated in Lillooet Lake, and at Idaho where the adelgid, mouthparts and remains at the interaction with the tree. This results chosen location for the in a breakdown of normal remainder of its life. It translocation processes and becomes a black, flattened, eventually in abnormalities at the resting form with a feeding sites. Twigs swell or "gout" at b characteristic pattern of white the nodes (Fig. 3) and the cambium wax exudations along the midline, produces wide, irregular annual between the body segments, and in a growth rings consisting of reddish, fringe around its body (Fig. 2b). This highly lignified, brittle wood, similar to is the overwintering form. Feeding "compression wood," which reduces a begins after several weeks, or after the quality of lumber and pulp. Heavy overwintering, and the body becomes attacks on the bole or stem (Figs. 4,5), Figure 2. Balsam woolly adelgid: (a) Adult more rounded, resembling the adult. often results in tree death after 2 or 3 with waxy "wool" covering omitted from After three months, it becomes an years, but it is not unusual for trees to drawing, (b) first-stage resting or adult and begins laying eggs. Eggs, recover. Gouted trees may survive for overwintering form. young crawlers and adults are present many years, but growth is curtailed. from as early as February in coastal Crowns become distorted and thin as areas until October. There are two to old needles are gradually shed and no first found in 1983, has spread four generations each year. At low new growth is added, while chronic throughout much of the state. It was population levels, detection is very attack can result in top-kill. Previous recently detected in lower elevation difficult and requires microscopic infestations in B.C. in the 1950s and grand fir and also in alpine fir stands examination of branch nodes. '60s have caused extensive damage up to 1800+m elevation. Although it is and mortality in amabilis and, to a generally believed that the adelgid Damage lesser degree, grand fir. In Idaho, does not survive temperatures below - The insect inserts its mouthparts into approximately 16 000+ ha of recent 34°C, unless protected by snow at the the living cells of the bark, introducing grand fir mortality were recorded lower parts of tree boles, the Idaho substances that produce an during aerial surveys in 1989. experience with high elevation grand fir mortality suggests the adelgid may be able to survive lower temperatures than previously suspected. Description and life history Adult balsam woolly adelgids are aphid-like, wingless, oval, purplish- black insects (Fig. 2a), less than 2 mm long, covered with white, a woolly, wax threads. The female (there are no males) may lay as many b as 100 red-brown eggs in a cluster about her body. These hatch into tiny, red-brown first-stage nymphs or "crawlers," the only motile stage. After selecting a feeding location on thin bark, branch nodes, leaf or cone buds, the adelgid Figure 3. Abies amabilis foliage showing swellings Figure 4. Medium stem attack on Abies amabilis. inserts its tube-like or gout at nodes: (a) Branch with light gout, (b) close-up of twig showing heavy gout. 2 Host susceptibility areas of infested branches may be British Columbia, and microscopic more or less pronounced, and is examination is necessary to positively All species of true fir (Abies sp.) are usually greatest in the upper crown distinguish it from Adelges piceae. susceptible, but some are less where growth is most rapid. This species does not cause resistant to injury than others. Alpine In summer, tufts of adelgid wool significant damage to Abies. fir (A. lasiocarpa) is the most readily can be found by experienced Lepidopteran borers also cause nodal damaged of the British Columbia searchers on the nodes and buds swellings, but this damage can be species, but attacks on this host are even when branches show no signs of identified by cutting through the node not yet widespread in the province, injury. In winter, much less wool is to expose the larval mine. although widespread damage and present so the most practical method mortality has been found in high is to collect branch tips and have elevation stands in Idaho. Amabilis fir Dispersal experienced examiners search for (A. amabilis) is the second most Spread of the balsam woolly adelgid aphids under the bud scales with a affected host and heavy mortality has occurs during the egg and newly microscope. Gouted seedlings and occurred at certain sites on the B.C. hatched nymph or crawler stages. mainland. Grand fir (A. grandis) is Experiments have shown crawlers the least susceptible to damage of to live over 8 days and to be the major B.C. species, but can capable of crawling more than 30 suffer appreciable deformation m. Eggs and crawlers fall or are and mortality. blown from infested crowns during Trees of all ages and vigor, the spring, summer and fall and on all growing sites, may be may be carried on clothing, attacked. Some trees are more vehicles, tents and other resistant than others, but trees equipment. They have been apparently free of attack for many found in traps 90 m from infested years may suddenly develop a stands and are probably capable heavy population of adelgids and of being carried many kilometres die. by wind currents. They are also carried by birds and animals. Detection Movement of infested logs, nursery stock and seedlings are Balsam woolly adelgids may other means of spread. attack any part of the crown and bole but they are difficult to detect Prevention of spread until symptoms of injury are well and control advanced. Stems with as many as 100 Figure 5. Close-up view of medium stem attack on bark. Direct control of the balsam adelgids per square cm of bark, Each spot of white wool covers an aphid. woolly adelgid in forest stands is although the most easily detected impractical by methods known at are infrequently found. The presence understory trees are an indication of present. Because the adelgids are of live individuals may be confirmed infestation in the main stand above. protected by their woolly covering and by brushing the wool-covered bark Persistent crown infestation feed in protected sites, direct control and finding purplish streaks on the results in visible thinning of the foliage, (with pesticides, for example) is not fingers. Stem attack occurs most top-killing, broken tops and the practical. frequently on smooth thin-barked eventual death of the tree (Fig. 6). Losses in forest stands can be trees, but is sometimes found in bark Secondary enemies, such as bark- minimized by selective and intensive crevices of thicker-barked trees. It is beetles, may hasten tree mortality. cutting of Abies before serious tree most frequent on moderately exposed Trees experiencing damage may show mortality occurs and before dying boles along roadsides, trails, edges of thin crowns with strong growth on the trees become unsuitable for salvage. logged areas, natural stand openings extreme top, so infested crowns may Preliminary results from studies in and in parks.