We are growing Green Globe artichokes with some success here, but recently found a couple of the fruits had been bored through to the heart. I did not find the insect, but ample evidence it had been there. Most of the outer leaves had been perferated, and there was a lot of detritus on the inner leaves, as well as a big hole going into the center of the fruit. Artichoke leaves are very tough. What garden pest can do this? What can I do to stop it?
Washington County Oregon
From your description, my best guess is that the pest is a caterpillar ~ most likely an army worm or a plume moth. However, it is possible that the pest could be a a weevil (a beetle). Whether it is a caterpillar or beetle will impact what type of chemical control(s) you can use to manage the problem in the future. Thus, correct ID is important. In the future, if you encounter the pest in the artichoke, please snap a photo that you can use to help us ID the pest.
Have you cut open the center of the fruit, to see if the culprit is still inside and feeding?
At this point, if the pest has already developed from caterpillar to pupa to adult ~ the adult moths have probably flown away from the artichokes. However, these adults may have mated and layed eggs on the artichoke. Thus, it is important to keep monitoring the plants, to see if you find any living, feeding pests. If you don't see the pests, and aren't sure they are there ~ applying an insecticide is likely to do you no good, and would be an unnecessary application of pesticide into the environment. ONLY if you find feeding caterpillars, will it be helpful to apply an insectide. Bt-k is a narrow-spectrum insecticide that only works against caterpillars. It is considered a 'least toxic pesticide', and is a good option if you adhere to organic production methods. Brand names that have Bt-k as their active ingredient include Dipel Dust or Thuricide. If the pest is a beetle, this insecticide will do you no good. Thus, once again, correct ID is important.
Do you grow your artichokes as a perennial crop? If so, practicing good sanitation ~ ~ cutting the plant off at the stalk 2-3" BELOW the soil surface ~ and shredding the plant material, can help cut down on future infestations. You can do this at the end of the growing season (fall).
Do you have weeds in the chenopod family growing in the area? These include Russian thistle, pigweed, lambs quarters. IF so, you may want to more aggressively manage these weeds, as they can serve as a source of insect pests on your artichokes.
I hope this helps. Please let me know if you have any additional questions.
Thank you for this information. I did see a small insect on one of the globes, and found a couple more inside after cooking. They were about the size of lady bugs but dark grey or black, and narrower of body.
In researching weevils i found out about the cribrate weevil attacking globe artichokes in California. The pictures look like the insect I found on our plants. I have not seen any catapillars so I suspect that the weevil is the culprit. One link I found:
http://triscience.com/Plant/the-cribrate-weevil-a-new-pest-of-the-globe-artichoke-in-california/docu... The pesticides are unfamiliar. What would be a fairly organic approach to dealing with these pests?
The pesticides listed are for commercial agricultural use, and are not available for home gardeners.
Unfortunately, with this weevil, there are few problems with control. First, the weevil is an internal feeder ~ so any chemical you would apply to the plant would not do much damage to the pest. The pest is protected and feeding inside plant tissues. Second, the chemicals you would need to use to effectively control the pest would make it unsafe to grow and eat the plant you're trying to protect.
So, you're left with cultural control as your primary option. Get rid of the infested shoots. Don't provide the weevils any place to overwinter in your garden. I've copied and pasted this text from a Texas A&M publication, regarding cleaning artichoke beds:
"Artichoke is a perennial plant so once the harvest is done in June, cut the plant back to soil level. This will put the plant crown into a dormant stage during the summer. The plant will send out shoots in the fall. The new shoots can be dug out to be replanted into a new location in the garden or left in place to produce another year. Make sure you leave only the most vigorous shoot on the old plant for production next spring."
Source = http://aggie-horticulture.tamu.edu/vegetable/files/2010/10/E-276_artichokes.pdf
I've had to take this same approach with my raspberries. I have a fly that lays eggs in the berries. I don't want to spray them, because I prefer unsprayed produce. So, I pick my berries as fast as I can ~ so that I get the best crop I can, before the fly invades my garden. Then, at the first sign of the fly, I strip all the berries off of my canes. I prunes back old canes. I rake up any fallen berries. And I wait until next year ~ to pick what i can before the pest re-invades my garden.
Hope this helps. Let me know if you have any more questions.