National Invasive Species Awareness Week — Hemlock Woolly Adelgid

Posted on: February 27th, 2018 by Samantha Kahl

Nation­al Inva­sive Species Aware­ness Wood, Day 2! 

Today we are look­ing at the Inva­sive Hem­lock Wool­ly Adel­gid (HWA), and small aphid-like insect that attacks North Amer­i­can Hem­lock Trees. Often, the HWA look like white wool­ly mass­es (or, ovisacs) found on the under­side of branch­es at the base of Hem­lock nee­dles. Ovisacs con­tain up to 200 eggs and will remain on the tree through­out the year. Native to Asia, the HWA was first found in the U.S. in 1951 and has spread north ever since. These inva­sive insects cur­rent­ly infect 43 coun­ties with­in New York State.

White Woolly egg ovisacs.

White Wool­ly egg ovisacs.

So what do Hem­lock Wool­ly Adel­gids do to Hem­lock trees that make them so invasive?

HWA’s hatch from the ovisacs and insert very long mouth parts into the tree, at the base of the nee­dles. The insects will remain in the same spot for the rest of their lives, con­tin­u­al­ly feed­ing on the starch­es stored with­in the tree. This process neg­a­tive­ly affects the trees by tak­ing in the nutri­ents meant for the tree limbs and nee­dles. With this process affect­ing the tree, mor­tal­i­ty of the tree occurs with­in 4 to 10 years of a HWA infestation.

Hemlock Woolly Adelgid attached to the base of a needle on a Hemlock tree.

Hem­lock Wool­ly Adel­gid attached to the base of a nee­dle on a Hem­lock tree.

How do we con­trol these pests?

There are a vari­ety of meth­ods the State and oth­er orga­ni­za­tions have col­lab­o­rat­ed togeth­er to do in order to save our native Hem­lock trees. Through the suc­cess­ful intro­duc­tion of non-native, but non-inva­sive species for pre­da­tion, the HWA has been con­trolled. Insec­ti­cides have also been used to treat a tree that has already been infest­ed or as a pre­ven­ta­tive method in a high-risk area. Though insec­ti­cides have been use­ful in treat­ing indi­vid­ual trees, large forest­ed areas are not ideal.

What hap­pens if you think you’ve found Hem­lock Wool­ly Adelgids ?

The New York State Depart­ment of Envi­ron­men­tal Con­ser­va­tion (NYS DEC), sug­gests tak­ing pic­ture of the infes­ta­tion includ­ing a coin or ruler for scale, make a note of the loca­tion, fill out the HWA sur­vey form, and send over the report, plus the pic­tures you take, to DEC For­est Health You can also report the infes­ta­tion you find on the iMap­In­va­sives map and con­tact the New York Inva­sive Species Infor­ma­tion (NYIS).

Decrease the spread of HWA and oth­er inva­sives by clean­ing any gear or equip­ment that has been in or near an infest­ed area!

For more infor­ma­tion regard­ing HWA, check out this neat video by Cor­nell Uni­ver­si­ty!

Check back tomor­row for anoth­er inter­est­ing Inva­sive Species in hon­or of Nation­al Inva­sive Species Aware­ness Week 2/26–3/2 2018! AWSMP Pub­li­ca­tions & ResourcesFace­bookTwit­terInsta­gram