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Tree root borers – Broad-necked root borer

Broad_necked_root_borer_JordiI believe the insect you brought in to the office is a Broad-neck root borer, possibly Prionus laticollis.  The female is much larger than the male, growing to two inches or more. The structure you see at the end of the abdomen is actually called an ovipositor, not a stinger. Ovipositors are structures on female insects in which they deposit eggs. This particular insect deposits eggs into the ground around trees and shrubs. The yellow eggs are about 1/8 inch long developing into larvae which then feed on the living roots of trees and shrubs. The larvae may be as long as 3 ½ inches with black mandibles (very scary).  Broad-neck root borers prefer deciduous trees of the forest but have been known to feed on fruit trees and shrubs such as peach, pear, apple, blueberries and even grapes. The complete life cycle takes about three years. Adults emerge from the ground between June and August eating the foliage of trees and, on some occasions, even damaging the fruit.  The smaller males are seen more often as they are attracted to light. Broad-necked root borer’s range is from Quebec and Ontario to Minnesota and as far south as Florida.  Because the larva of this insect feeds exclusively on the roots of trees, the only visible symptoms are limb die-back and the yellowing and/or thinning of foliage. Borers can completely destroy young trees and make older trees more susceptible to being blown over.  Prevention is the key – keep grass, leaves, mulch, bark and other litter cleared away from the bases of trees. This prevents the borer from having a place to hide and makes it more visible to predatory birds. In addition, avoid over pruning, over fertilizing and over watering trees – all of these can cause additional stresses.