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.

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  1. Thank you so much for your clear, comprehensive and precise advice!

    • Thanks for feedback! When I first came to California in 1944, there were no budworms. It was geranium heaven. Folks grew geraniums instead of front lawns, and they bloomed non-stop, no fuss, no bother, no sprays. All that changed in the early 1950’s when budworms arrived to chew out the insides of flowers and drive gardeners wild.

      • I overlooked part of your question, the query you had about little wasps. These are beneficials and you are lucky to have them and wise to watch them. There are a multitude of variously sized beneficial wasps, some tiny, others larger. Some of them even help with pollination of flowers. Many eat pollen and they like some moisture. I hope that Spinosad, if you use that, doesn’t harm them but fear it might do so but Bt does not.

        Most beneficial wasps are predacious in one way or another or their young are parasites of pests. In most cases the beneficial wasps, including trichogramma wasps (which are almost microscopic and you can purchase and release), lay eggs on pests such as caterpillars and then their young larvae eat out the interior of the caterpillar. The wasps you saw sitting on leaves might have been looking for prey, mainly loopers and perhaps they are controlling many caterpillars in your garden, but most of them work in the daytime, not at night and can’t get inside the flower buds once the budworms get inside.

        Small striped yellow wasps that don’t bite people but can pinch skin, are a bother sometimes at outdoor picnic table, but when they are at my house I am always telling people not to fear them. They are good. These small wasps love salmon. I give them a little and they pull pieces off and carry it away to put in with their eggs so when larvae hatch the young have something to eat. I once saw one of these small wasps carrying a tiny caterpillar that looked bigger than itself. They also scraped wood off my pergolas which I took to be used for building tiny nests. But most of these tiny wasps lay eggs directly on pests and their larvae kill the caterpillars. People are not always as observant as you who have been trying to figure out what they’re doing. Larger, mud-daubing wasps are beneficial also and kill many pests, but since they bite people, the public mistakenly thinks they are bad.

        • thank you so much for your commentary on the wasps – in fact, in view of your comments, Im wondering if they were attracted by the budworms and perhaps are controlling them

          in fact, since the appearance of the wasps (which are of the yellow-jacket variety, with long legs and about 1″ long – fairly big) it seems like I have fewer buds with holes — although it could just be a coincidence

          I found the following picture of budworms:


          and following your advice, I spent yesterday evening (and then again at night with a flashlight) looking very carefully all over for caterpillars but found only one well-camouflaged green grasshopper.

          I’ll hold off on the Spinosad to avoid harming the wasps — especially if they’re keeping the budworms at bay!

          There’s something interesting about the bug excrement that I find on the geranium leaves: it appears only on a few leaves, but those leaves are littered with maybe 25-50 of those tiny dots — as if the bugs were having a picnic on those leaves! Under a microscope, I do see the color of my red and pink geraniums..

          The geraniums in question are in four long window boxes, so easy to inspect. I figured I could just manually remove the budworms. Now that I see what their moths look like, it does ring a bell — I recall seeing many of them around the geraniums in the spring.

          Im thinking that next year (I live in NYC, so the geraniums die over the winter) I’ll plant zinnias there instead — my zinnias have done very well (except they are so sensitive to watering: miss a day and they droop; too much and their leaves develop a white powder; nonetheless, with adjustments, they spring right back; and this has been such a brutal summer).

  2. Spinosad will kill the budworms. Once the moths that lay the eggs that hatch out into budworms have discovered your geraniums they will probably keep returning. If you use Spinosad each year just before the first full moon in April, you will stop the worst of the budworms for the year. If it pours with rain that night you get a one-month reprieve until the next full moon. The full moon is when the moths fly and lay their eggs, beginning in April. (This subject of budworms is covered on page 158 of my organic book.) Last spring it did not rain that night but was very cold the night of the full moon and that cold night worked the same way. They didn’t fly until May. Don’t use Spinosad on anything that attracts bees since it kills them or harms their offspring. You are very wise not to go killing those tiny, golden, black-striped wood-dawbing wasps! Spinosad would kill them too and they are good guys who are going after your caterpillars in order to carry them away and shove them into their nests and lay eggs on them. Their babies will then hatch out and eat the caterpillars—poor caterpillars! You are a really good reader if you found all this in my book. Yes, it is there and maybe I told how I actually saw one of those tiny wasps flying away with a small green budworm or tiny green caterpillar in its grasp. This happened one day in late summer while I was having lunch under my rose arbor, an amazing sight!

  3. Just removed about half a dozen of these hateful things from my Easter geranium that I just got last week. Given the life cycle of these villains and the size of the worms (caterpillars) that I removed, I suppose that the plant already had been visited before I got it. I also cut off a developing flower head that had the characteristic holes, just in case there were larvae inside of it. It wouldn’t have opened anyway, so no real loss… there are many new heads developing, so it will be quickly replaced. I’ll treat with Spinosad liquid since the bees aren’t really too interested in the geraniums… they’re more interested in my spiderwort and blackberries at the moment! Liquid would probably be the better route since it would be more likely to seep up into the buds and kill the ‘worms’ than a powder would. If I see bees coming, I’ll switch to Bt(k) liquid. There is something cruelly satisfying about picking and smashing the little hateful things, though!

    • Thank you for your comment. I sympathize with you. When I first came to California there were no budworms and many folks had geraniums instead of front lawns. We humans are the ones who have upset the balance of nature and carried pests around the world. Gardeners have to find organic ways to deal with pests and problems and the very best ways are those that create a balance of pests and predators in our own environment. But with budworms, spraying with BT around the first full moon in April is the only option. You have evidently already read what it says in my organic book page158. Full moon this month was April 15 yet you and I both forgot or were too busy to spray just before and after that date, so now we have budworms. I noticed them on my geraniums a few days ago. It is difficult for grown ups not to hate the things like budworms and Argentine ants and our common (and edible) garden snails that cause us problems. But then I see my great grandchildren stroking caterpillars, making pets of snails, delighting in the mysterious ways of ants and loving all these creatures for beauty and peculiarity without regard to how annoying they might eventually be to them when they grow up to become gardeners.

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