The Hemlock Wooly Adelgid: 



Attracting Attention South of Our Border 

 Robert D. Childs 



The Hemlock Wool- 

 ly Adelgid, Adelges 

 tsugae, is an aphid- 

 like insect, most 

 probably from Asia, 

 that was acciden- 

 tally introduced into 

 the USA in 1924, where it began 

 feeding on Western Hemlock in Or- 

 egon. Damage to this host is usually 

 very insignificant; but this pest has 

 since invaded Pennsylvannia (in the 

 1960's) and southern Connecticut (in 

 1985) where it now feeds on Eastern 

 Hemlock, T<;uga canadensis. Infesta- 

 tions on this host usually result in 

 death of the tree within two years; 

 even on healthy specimens in good 

 growing sites. Thousands of trees 

 have already been killed in Connec- 

 ticut. It is not yet known if the pierc- 

 ing-sucking damage alone causes 

 tiee mortality or if a toxin in their 

 salvia aids in the rapid decline of the 

 host. 



The presence of the Hemlock Wooly 

 Adelgid (HWA) can be easily recog- 

 nized by the white, cottony, spherical 

 eggmasses that are lined up along 

 the twigs at the base of the needles. 

 The HWA is atypical of most insects 

 by being active during very cold pe- 

 riods of the year and mostly inactive 

 throughout much of the summer. 

 Therefore, the best time to find new 

 eggmasses is in January and Febru- 

 ary. Eggs hatch over a staggered pe- 

 riod between February and June in 

 Connecticut. These will mature and 

 produce eggs which quickly hatch; 



and by July the new immatures will 

 settle down on the twigs, at the base 

 of the needles, and become inactive 

 until (approximately) mid-October. 

 There immatures can only be seen 

 with a good hand lens but the rem- 

 nants of their cottony eggmasses 

 will still remain. Activity resumes in 

 mid to late October and new 

 eggmasses start appearing by Janu- 

 ary. Research has shown that even 

 on extremely cold days in winter they 

 are still developing. This ability to 

 thrive in cold temperatures suggests 

 that the HWA has the potential to 

 move northward through all of New 

 England. 



The HWA was first reported in Mas- 

 sachusetts in 1988 in a residential 

 area of Springfield, as well as the 

 adjacent wooded town property 

 known as Forest Park. Another re- 

 port that same year came from 

 Waltham (just outside of Boston) on 

 Carolina Hemlock. 



The reason for these two apparently 

 unrelated, yet coincidental, infesta- 

 tions in Massachusetts is due to sev- 

 eral factors. The HWA is primarily 

 moved from one geographic region to 

 another (and tree to tree) by: 



Wind. This is how it invaded Con- 

 necticut; by being carried northward 

 on prevailing storm winds. 



Migrating birds. It is strongly rec- 

 ommended that bird feeders not be 

 placed in hemlocks. Visiting birds 

 will pick up the eggs and/or insects 



in their feathers and transport them 

 to new locations. 



Humans, Transport of contaminat- 

 ed hemlock logs or equipment, such 

 as chippers, can introduce this pest 

 quickly into new areas. 



Given these methods of transmission 

 it is important to note that one the 

 HWA has invaded an area (and 

 hopefully has been controlled) one 

 must always be on the alert for new 

 reinfestations. 



Virtualy all of the research done on 

 the HWA in New England has been 

 carried out by Dr. Mark McClure of 

 the Connecticut Agricultural Sta- 

 tion. Along with deciphering the 

 very complex life cycle and methods 

 of dispersal, he has also experiment- 

 ed with controls. These experimental 

 controls include insecticidal soaps, 

 dormant oils, various chemical in- 

 secticidal sprays, and insecticidal 

 tree injections. Most of the com- 

 pounds used as sprays work very 

 well, but the key to control is com- 

 plete coverage of the entire ti'ee. 

 Trees only sprayed on one side still 

 suffered unacceptable damage. The 

 preferred treament is a dormant oil 

 spray when possible. Currently, this 

 is the only labeled control for this 

 pest in Massachusetts. 



Dr. Robert D. Childs is a member of 

 the University of Massachusetts at 

 Am herst Department of Entomology, 

 Fernold Hall, Amherst, MA 01003. 

 For further information, call Bob at 

 (413) 54.5-2283. '* 



Caring Nurseries 



Lining Out Stock 



Million of Seedlings 

 High Quality Reasonable Prices 



Over 100 selections for Christmas trees, ornamentals, windbreaks, limber, soil conservation, wildlife cover. 

 Free Catalog: Carino Nurseries Box 538, Depl. CC, Indiana, Pensylvania 15701 



PHONE: 412-463-3350 or 463-7480 



Fkhkuaky/March 1991 23 



