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HEMLOCK WOOLLY ADELGID FREQUENTLY ASKED QUESTIONS

Table of Contents

1. If my neighbors do not treat their trees, won't they re-infest mine?
2. How often do I need to treat?
3. My trees were treated last year, but I still see woolly masses!
4. My heavily infested tree still looks terrible, even after two years of treatments!
5. Are these treatments harmful to my family pets or garden?
6. Why are some of the needles, twigs, and entire branches turning yellow in the fall?

If my neighbors do not treat their trees, won't they re-infest mine?

As long as your neighbor's trees are infested, they will produce more adelgids that will spread into your trees.  However, the residual activity of the soil and stem injections will make your trees immune to HWA, and they will be fine unless you stop treating.  If they do not treat their trees, your neighbor's trees will die and the dead trees may become a threat to your property and property value.  Depending on the time of year, if you use soap or oil your trees are vulnerable to re-infestation within hours after a treatment.

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How often do I need to treat?

Only as needed.  Soil and some stem injections should last for XXXseveral yearsXXX, and then should be repeated only as needed.  Soap spray must be done no less than every year.

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My trees were treated last year, but I still see woolly masses!

If they were treated with a soil or stem injection- don't worry!  Imidacloprid is a potent insecticide, but it takes time- up to a year on some trees- to take effect.  Do not retreat until one year after initial application.  Trees treated in the fall will usually have maturing HWA in the following spring.  This is because the adelgids have to feed to ingest enough insecticide to die.  Fall treatments do not have enough time to kill adults and any eggs already laid.  Be patient- we have never been failed by imidacloprid!

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My heavily infested tree still looks terrible, even after two years of treatments!

Hemlocks are slow to respond- but they do.  One of the reasons the lower limbs die first is the tree senses that the limbs are unproductive and begins to shed them.  This same process can also restrict transport of imidacloprid into those limbs.  Expect to lose some limbs or significant portions of them, especially on the lower part of the crown.  Given time, the tree will once again become green and full, but not overnight!  A soap spray of the lower crown may be advisable on heavily infested trees to try to get a jump on the adelgids before buds are killed.  This may reduce the severity of needle loss.  For best control, don't wait until you see a heavy infestation to treat!

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Are these treatments harmful to my family pets or garden?

Not if applied correctly.  Soil and stem injections leave no visible or contactable residue.  Imidacloprid is in fact the same active ingredient used in some flea and tick control for dogs and cats.  Soap and oil residue is non-toxic in properly applied dosages.  you would not want to eat fruits or vegetables within the drip line (crown tips) of a hemlock treated by soil injection.

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Why are some of the needles, twigs, and entire branches turning yellow in the fall?

Although hemlocks are conifers, they shed old leaves and twigs in the fall just like other trees.  Shaded limbs or twigs hat are not producing sugars for the tree will be shed as the tree grows new ones.  This is normal, and since HWA kills new growth, the yellowing is not caused by HWA activity.  However, HWA infestation can contribute to premature needle loss, but it will start on the end of the twigs, not within the canopy of the tree.

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