Upon visiting a project of mine, which was done last year, I discovered insect problems on a Quince and a White Pine.  I had a notion what could be bothering the Quince, but was not sure about the White Pine’s ailment.  In addition, I know that good diagnosis takes into account numerous factors, and it’s critical to get the “whole picture” so that treatment is quick and effective.

The home was quite a distance from our normal working area, so I photographed the symptoms and showed them to Michael Hirsch, plant health care specialist.  These are his findings:

Quince: fall web worm and/or tent caterpillar

  • Tent caterpillar lay eggs in summer which hatch early the next spring; in mid to late summer they appear as brown moths.
  • Fall web worm build similar nests to tent caterpillars in early summer and pupate at the soil. As many as four generations may occur June through September.
  • Control can be systemic injection in early spring or a variety of spray chemicals can be used when caterpillars are present.  A more organic approach would be to hand pick egg masses or use sprays such as horticultural oil or soap-based sprays.

White pine: pine bark adelgid

  • Under the white sugary mass is an insect that feeds off the tree. Under severe infestations it tends to look as if the tree is covered in snow.
  • I have found that many trees with heavy infestations of adelgid are stressed in some manner; possibilities include: girdled roots, trees still tied from time of planting or possibly over watering.
  • Control methods can be a variety of chemical sprays or systemic injections. A more organic approach would be horticultural applications or manual hosing or washing of the trunk; remember to alleviate original source of stress.

Mike was correct with his thought that the White Pine could be stressed.  I found the soil to be too wet and discovered the automatic sprinkler system was cycling on too frequently.

Both insect problems will now be treated and the irrigation program will be adjusted.

  • Catherine
    11:36 AM, 3 June 2012

    Is it alright to spray it with horticultural oil. My pine tree is in the middle of my yard. It seems like it isn’t overwatering that causes this white mass but it does look exactly like adelgid. I bought it when it was about two feet and now is is about twelve feet.

    • Roger
      1:10 PM, 3 June 2012

      It’s hard to say exactly why your pine has adelgid. It’s good you’re conscious of not over-watering though. Check to make sure there isn’t too much mulch piled up on top of the root system and on the neck of the plant. I’d have to see the plant and the conditions it’s in to offer other suggestions of potential causes.

      With regard to the horticultural oil, you’ll want to wait until the soft new growth has hardened-off before applying. Starting in August would be a safe time. Also, choose a day that’s not humid and when temperatures are below 90 degrees F.

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