Today I would like to talk to you about how Ottawa County Parks and others are working from preventing that from happening again. I will be talking about hemlock woolly adelgid and specifically how it might affect our water quality.
Although forest pests are always something us conservation biologists worry about, HWA will have a disproportionate effect on natural lands. In West Michigan this is because this is one of the only native evergreens. The hemlock needles effect thermoregulation by keeping water temperatures warmer in the winter and cooler in the summer.
This slight change in temperature can make a trout stream inhabitable to brook and brown trout. Studies have shown that water temperatures greater than 68 are stressful to brook trout. Another study increased the number of streams that fell below 68 by 15%
Another study that looked at the defoliation of an oak forest during an insect invasion increased solar radiation to these cold water creeks which resulted in an increase of algal productivity 35-80% Similar effects are predicted along these cold water creeks with the loss of the evergreen hemlocks.
Additionally we know that hemlocks transpire less in summer than broadleaf trees. This means that small streams and vernal ponds like this one at Port Sheldon Natural Area will likely dry up earlier in the year.
One very important factor that we are considering is the potential effects of treating hwa using an insecticide on a landscape level. Because some of us are concerned that if the insecticide label is not followed, there is potential to contaminate groundwater, we are working with the local CISMA to coordinate the treatment efforts. We have been successful in receiving a 60000 grant from Great Lakes Restoration Initiative to begin survey and treatment efforts. We will continue to seek funding to hopefully contain this forest pest before it spread further and minimize treatment efforts. We will also make sure the methods of managing for this forest pests takes into consideration all of our natural resources, especially our water resources.
HWA & Water Quality
Save MI Hemlocks!
Hemlocks effect on
1.8-3.6F cooler in summer
Warmer in winter
>68F stressful for brook trout
3% w/ hemlock vs. 18% w/o hemlock
(Ross and Bennett 1996)
Defoliation in stream canopy
Algal productivity 35%- 80%
(Sheath et al. 1986 )
Do not move infested limbs!
This is a very, very efficient way to
spread HWA all over town.
Trim your trees!
Your vehicle can become a
vector when infected branches
brush its roof or sides.
We have a documented account of spread
from Muskegon to Zeeland this way.
Remove bird feeders during active months
Birds as known vectors. HWA is only active April-
August. Birds easily spread HWA. Remove bird
feeders that are near hemlock trees.
Step 1. Educate yourself
Step 2. Educate your friends, family & neighbors.
Step 3. Check out hemlocks-even healthy looking ones!
Step 4. Prevent the further spread.
Step 5. Report It!
Step 6. Treat infested trees.
Photo credit: Great Smoky Mountains National Park Resource Management
Heed label laws!
We want to help you with
treatment, but if you are
treating on your own,
heed the label laws. The
insecticide that effectively
treats HWA can
if not used appropriately.