As you may already know, hemlocks are prey to a couple of different insects:
Woolly Adelgid: Looks like a white puffy substance on the underside of the needles. The adelgid is the white cottony substance on the branches and the actual scales are the brown oblong ovals on the individual hemlock needles. Click for an example.
Spider Mites: Tiny spiders (1/64 of a centimeter long) that feed on the juice from the cells on the underside of the needles. This insect will give the Hemlocks a grayish-brown hue. If your Hemlocks begin to look like this, contact us immediately to test for mites.
Spider mites can multiply rapidly in the absence of rain.
Tiny black circular or elongate insects on the undersides of needles. Due to the armored nature of this insect, pesticides must be targeted at crawler stages. Click for an example.
In order to control these insects, we recommend the following:
Spray Program: Have the hemlocks sprayed at least twice a year with a horticultural oil. This will take care of the majority of insect problems. If a major infestation occurs, we may recommend additional sprays.
Integrative Pest Management: During periods of drought in the summer months, hose down your Hemlocks with a garden hose in the morning or evening (avoid watering during the hottest part of the day). Spider mites reproduce exponentially during dry periods. A weekly hose-down will deter them from carrying out their feeding (they tend to fall off the needles during a rain or a hose-down).
MORE TIPS There are a few more tips we have gathered over the years that will help keep your hemlocks looking healthy:
Hemlocks are intolerant of heat. Once the temperature reaches 95 degrees, hemlocks are susceptible to burning. Do not shear or trim your Hemlocks on these hot summer days.
Hemlocks are intolerant of drought. Call us during times of drought so that we can draw up a watering schedule tailored to your property.
Hemlocks do not do well with road salt. Try not to plant your hemlocks too close to the street where they may come into contact with high volumes of salt during the winter months.
Hemlocks are sensitive to automobile emissions. Warming up one's car with the tailpipe directly blowing on the Hemlocks could cause a severe decline.
Trimming/Pruning: As a general rule of thumb, hemlocks that are thinned (so that they are kept light and airy) are more tolerant of shade than hemlocks that are sheared into hedges.
Planting: When you plant your hemlocks, make sure that the nylon string around the trunk is removed, and that the burlap is trimmed away from the top of the root ball.
When planting hemlocks, be sure not to plant them too deep. Lack of oxygen to the root zone can cause a decline in plant vigor. Also, do not plant them in areas where soil flooding may occur.
Thank you for choosing American Tree Experts, Inc. We feel that, working together with you the customer, we can help keep your hemlocks healthy. Feel free to call us any time with any questions (973) 744-6091.