Ask Maine Audubon: Invasive insects pose a threat to hemlocks

Ask Maine Audubon: Invasive bugs pose a menace to hemlocks

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An entomologist examines a department of hemlock infested with hemlock woolly adelgid. The invasive insect plunges its needle-like mouth deep into the branches of hemlock bushes and slowly sucks out the vitamins and kills the plant. John Bazemore/Related Press

Over the previous yr, I’ve written about a number of invasive species, a few illnesses, and whether or not or to not take down your chook feeders to cease the unfold of illness. I used to be shocked to comprehend that I’ve by no means lined hemlock woolly adelgid and have been requested about it once more not too long ago. So this week, let’s ensure we all know what they’re and what you possibly can, or can’t, do to assist fight this invasive insect.

First, whereas hemlock woolly adelgid (HWA) is a brand new subject to my column, this damaging insect has been in Maine since 1999, when it was inadvertently shipped right here on an untreated inventory of crops arising from Connecticut. HWA took its first leap (through human cargo) from its native vary of east Asia to the US again in 1951, close to Richmond, Virginia. HWA are a “true bug” within the order hemiptera, or “half-winged” bugs, like aphids, leafhoppers or mattress bugs. Chances are you’ll be acquainted with the frequent trait of this order, their “piercing-sucking” mouth components – consider aphids biting crops in your garden, or (hopefully not) mattress bugs biting you.

That is the issue with HWA: the adults will use their stylet – the flamboyant title for his or her straw-like mouth components – which is 3 times the size of their physique, to pierce right into a hemlock’s tissue and extract the vitamins. Discovering the small, 0.8mm adults is troublesome, however the egg sacks they depart on the underside of hemlock branches is far simpler to detect. These patches, typically with tons of of eggs, appear to be white tufts of cotton alongside the branches.

Within the spring, the larvae emerge from these eggs after which will look to unfold to new bushes. And right here’s our query for this week. A couple of readers are questioning if having chook feeders up will increase the unfold of HWA. The velocity HWA is spreading, and the quantity of harm they depart behind, is a serious explanation for concern given how vital hemlocks are to a wholesome forest. The tiny HWA larva are identified to unfold by blowing within the wind, transferring round on the fur of mammals, and even being carried lengthy distances by catching a journey on birds’ feathers. A paper printed in January 2019, by researchers on the College of Connecticut and the U.S. Forest Service, confirmed that the nymph stage of HWA – known as “crawlers” – are most frequently picked up (passively) by birds throughout their northward spring migration, and that they’re able to settling into new hemlocks.

This examine confirmed how a small, comparatively motionless insect was capable of journey and increase its vary so rapidly within the U.S., above and past the unlucky human-caused unfold. It is very important understand the explanation for the unfold right here for instance that chook feeders don’t play any function within the unfold of HWA. The seed you might be placing out in your feeders does entice birds, however solely to your feeder, making them simpler so that you can see. The hopefully wholesome hemlock forest could be internet hosting so many native bugs that it will be a better attraction to the birds.

I’ll take this chance to remind you that conserving your chook feeders clear is vital to forestall unfold of illnesses, particularly avian conjunctivitis. Use a diluted bleach resolution (or vinegar) and let it dry utterly earlier than placing it again out. Relating to coping with HWA, I like to recommend checking the Maine Forest Service’s web site on HWA, which incorporates a number of management strategies and a kind the place you possibly can report areas the place you discover HWA in Maine.


Roost or nest? What’s the distinction? It’s develop into more and more widespread to place out roosting containers within the winter to supply shelter for birds. I wish to thank Maggie from Topsham for writing in with questions on roosting containers, and ensuring there shall be locations for her wrens to nest come subsequent spring. Let’s make clear precisely what they do, how and why they assist birds within the winter, and the way they’re completely different from the birdhouses we offer in the summertime.

Whether or not they’re roosting or nesting containers, the premise is identical: We’re including supplemental shelters to the surroundings for birds to extend their probabilities of survival or profitable nesting. The dearth of snags, or outdated useless bushes, within the panorama signifies that many species that use cavities don’t have sufficient of these shelters, thus we’re serving to with these synthetic choices.

A few key variations between roosting and nesting containers is of their dimension and building. Relating to dimension, nesting containers are typically smaller and solely want to carry the nest a chook will construct, and that nest solely must be massive sufficient to carry its eggs. The chicks from that nest will typically fledge earlier than they’re even full grown. Roosting containers, alternatively, have to be bigger since you’ll typically have a number of grownup (or a minimum of full grown) birds all roosting collectively: extra our bodies equals extra heat. Most constructed roosting containers may even have perches inside for these birds to sit down on, whereas nesting containers are in any other case empty (leaving area to assemble a nest). The doorway gap, or cavity for coming into the field, is usually on the high of a nesting field, so the birds can drop down into the nest, whereas roosting field makers typically put the holes on the backside to assist preserve heat air trapped inside.

Each roosting and nesting containers make for fascinating yard observations and make nice items. Whether or not you purchase them ready-made or construct one your self, preserve these in thoughts as we head into the vacation gift-giving season. They’re certain to deliver a smile to the receiver and the birds.

Do you have got a nature query for Doug? E-mail inquiries to [email protected] and go to to be taught extra about birding, native crops, and packages and occasions specializing in Maine wildlife and habitat. Doug and different naturalists lead free chook walks on Thursday mornings, 8 to 10 a.m., on the Gilsland Farm Audubon Sanctuary in Falmouth.

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