What is eating my geraniums?
Question from Bob:
The sides of many of the flower buds have pin-head-sized smooth, round holes as if something is eating into them; the affected buds die without blooming, and the inside of the bud (cutting it opened) is either empty or whithered.
Some of the leaves are littered with tiny black “grains” – under a magnifying glass, they look like droppings: amorphous, compacted matter (they’re not bugs).
I’ve looked carefully all over the plants for the culprits, but found nothing. Except, Ive noticed that these geraniums have attracted a lot of attention from wasps — could they be the culprits? Ive watched them closely: they land on the flowers, bee-like; they seem to like to alight on the leaves, although Ive never caught one defecating there; and mainly, Ive never caught one eating a bud.
What do you think of Spinosad as an insecticide? is it innocuous, or does it have a dark side?
Answer from Pat:
What you have described is the activity of budworms. These begin as night-flying moths. They lay eggs on geranium flowers and other flower buds, the eggs are tiny, hatch into tiny larvae that drill round holes into flower buds and devour the interior, blasting the flower. There are several kinds of bud worms. You have the tiniest and most difficult to see without a magnifying glass.
Budworms first fly in spring the night of the first full moon in April. Spray before and after with fresh (not old) Bt. (Caterpillar killer. Bacillus thuringiensis.) If this doesn’t seem to work, spot treat with Spinosad® but don’t use where bees visit. Yes, contrary to what one might think there is a dark side to Spinosad®. Please see the posts on this blog dealing with Spinosad® and bees. http://patwelsh.com/wpmu/blog/bees/please-help-save-the-bees/ Please also read about budworm in my book page 158.
If there is heavy rain the night of the first moon in April then wait another month for the next full moon. Continue monthly but you will have gotten rid of most of them.