Monday, February 26, 2024

Streptocarpus: irregular or missing leaves

Question:  My Streptocarpus has irregular sections that are missing from the edges of the leaves, as if something had been eating them.  Any ideas?

Answer:  Actually, this is something one of our employees experienced with a plant she had taken home from the shop.  We’ve also been told similar stories by some of our violet-growing friends.  A week or so after telling us this, she brought in a small, black, insect in a plastic baggie (dead, of course).  She had found it on the plant and wondered whether it could have been the culprit.  As it turns out it was.  We couldn’t identify it, but knew who could.  It just happened that a large conference was being held by a group of entomologists and plant pathologists in Rochester.  Being only an hour’s drive away, they had scheduled a tour of our shop.  One of them quickly identified the insect as the “black vine weevil”, a black, wingless weevil about 3/8″ long.  All are female, do not fly, and disperse by walking or are transported by man or on infested material.  Adult weevils feed on foliage, chewing out notches.  Damage is usually not fatal, but often is unsightly.  As larvae, the grubs feed on roots and underground stems, and can be more damaging than adults.

These are most commonly found on outside plants, but they can become nuisance pests when found indoors.  Fortunately, infestations on houseplants are normally small, and control is best accomplished by removing adults by hand when found, even if the appear to be dead–it seems that the adults will “feign death” when disturbed!  In any event, this is not likely to be a widespread problem for violet growers, but this mysterious plant damage has been described to us before.  In this one instance, it was nice to have the mystery solved.

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