Seasonal development
and life cycle—Raspberry horntail
Beginning in April, female horntails insert their eggs just under the epidermis, about 2 inches below
the tips of the canes, causing pronounced swelling inside new shoots. Eggs are pearly white and oblong,
with a curved point at one end. The eggs hatch into very small larvae a few days after being laid. The
young larvae spirally girdle the tips of the canes and cause wilting. The cane becomes weak in the area
of the crook and often breaks at this point during pruning and training. The larvae later feed throughout
the terminal portion of the cane, which often causes dieback. When mature, larvae burrow down the canes
in the pith and spend the winter in silk-lined cells in the burrows. In spring they pupate and the adults
emerge through a round hole cut in the sides of the canes. In some locations they may have two generations
per year.
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Wilting
of foliage due to horntail feeding
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