Plant and Insect Diagnostic Clinic Update - May 6, 2016

The following are highlights and updates about samples and questions recently received in the Plant and Insect Diagnostic Clinic. Visit the PIDC's Facebook page to ask questions and for updates and more pictures.


Spruce needleminer is a caterpillar that feeds on spruce. The needleminers eat inside and hollow out needles as they grow.  A small round hole at the base of the needle is a characteristic symptom.  The caterpillars clip the hollow needles and weave together small mats of needles with silk. Spruce needleminers are generally more of a cosmetic problem and do not kill trees. Adult moths will emerge in June, lay eggs, and the new caterpillars will mine into needles and feed until fall. Partly grown larvae overwinter in the needles and resume feeding in the early spring.

Clover mites are common accidental invaders and are common around homes. They do not breed indoors. Clover mites live outdoors where they feed on grasses and weeds. They commonly wander indoors, especially in the fall and spring.  A perimeter spray of insecticide on and next to the foundation may reduce invasion.  Clover mites already inside should be carefully vacuumed to avoid crushing and staining.  Plant & Insect Diagnostic Clinic website.

Cigarette beetles feed on a wide variety of items including tobacco (hence the name) and dried fruit, spices, seeds, flour, meal, nuts, dried flowers, and many other items.  They can be a challenge to eliminate. The best thing to do is go through any possible food items in the rooms where you see them inspecting for beetle activity (live and dead beetles, larvae, etc). Infested items can be discarded. Insecticides are not necessary for control and should not be sprayed in areas where you store food.

Close-up of a bad spruce needleminer caterpillar infestation. Shows dead needles covered in webbing and frass.
Spruce needleminer caterpillar with mat of dead needles, webbing and frass.
Close-up of adult cigarette beetles
Adult cigarette beetles are about one-eighth inch long, oval, reddish brown, and have a downward-facing head.


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