Question from Barbara:
My daughter called me last night, upset because she discovered that many of the cherries she and her son had been eating (from their own tree) contained little white worms.
They live in Pleasant Hill, CA (Contra Costa County) and have never had this problem before. The tree is several years old, located in her front yard which faces south.
We’ve searched IPM info, but can’t find any suggestions that would eliminate the problem for next year – except really serious pesticide spraying.
Is it possible to grow organic cherries? Do you have any suggestions?
Answer from Pat:
Tiny white worms are an increasing problem with home-grown cherries of both sweet and tart varieties. These worms are the larvae of the Western cherry fruit fly (Rhagoletis indifferens Curran), first discovered in Colorado in the late 1990′s. The first thing to do is to report this infestation to your local agricultural department or UC Farm Advisor. It’s important that these agenciest monitor this pest since it threatens commercial groves.
The larvae of Western cherry fruit fly don’t harm human beings who have accidentally ingested them since they are not adapted to living in human intestines, and they are mainly, after all, made up of cherry meat, but it is certainly a disgusting thought to know you have been eating worms. Western cherry fruit flies emerge in spring from pupa that have wintered over in the ground under the trees. As soon as they emerge they fly up into the tree. These black flies are tiny with striped wings are sluggish flyers. People seldom notice them, but yellow sticky traps can catch them and tell you of their presence. Most stay in the same tree but some are blown by wind to other trees. Their lifespan is about 15 to 35 days. They can lay eggs seven to ten days after first emerging when the temperatures are about 75 degrees Fahrenheit to 85 degrees in daytime. They eat aphids and honeydew. Once they mature, they mate and females pierce holes into fruit, laying one egg inside each cherry. The eggs hatch inside the cherry and tiny larvae commence munching. After the larvae mature and get fat inside the cherries they drop to the ground and bury themselves in the soil under the tree where they pupate and remain in dormant state until emerging as flies in spring. Then, once again the process repeats itself. Unless checked they will become worse every year and will spread to all other cherry trees in your area.
Unfortunately, the solutions given by experts are often to spray fruit repeatedly to kill the flies before they can lay eggs. Also with a pest that occurs in various stages experts may recommend attacking it with various specific products to kill the pest at different times of year. Otherwise you couldn’t possibly get them all.
The safe way to get rid of this pest would be to interrupt its life cycle in an organic or natural way without using pesticides, but I don’t have a cherry tree and cannot try out these controls. What I recommend is cleaning up fallen twigs and leaves under the tree, then spreading a layer of dry bagged earthworm castings now under the tree to kill the worms as they fall to the ground. Cover the ground from the trunk to the drip line and a foot or two beyond. Earthworm castings contain chitinase which destroys chitin, the exoskeleton of insects. Insects are killed when trying to burrow through a layer of earthworm castings. Renew the castings in late winter to kill any remaining flies as they emerge and keep it up from year to year. A few fruit flies will migrate into your garden but the castings will get them so they won’t be able to proliferate. This system works for giant whitefly on begonias which have a similar life cycle in the ground under the plants and then emerging to attack the foliage. If you try it please report back with your results.
The Colorado State Cooperative Agricultural Extension recommends putting yellow traps into trees to make sure when flies are first present, and then repeatedly spraying the trees with Spinosad every seven days to get the various generations of flies while they are present. Spinosad is an organic spray but harms bees if used where bees are found. Also, I fear that using it in great quantities will eventually destroy its efficacy.
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We have noticed these worms in our cherries for the past 2 years. We,too, live in Pleasant Hill and have 2 cherry trees. One is affected, the other is not. I didn’t realize that I needed to contact my local agricultural department but will do so ASAP. Thanks for the information about the earthworm castings. We will try that.
Good luck and hope it works! Another idea is to completely cover the cherry tree with netting. http://www.jgpress.com/inbusiness/archives/_free/001366.htmlThere is a woman who invented the nets. See this funny video. I hope it does not keep folks from buying the nets! Here is another way to net the tree: http://gardeningafterfive.wordpress.com/2011/06/16/gizmo-makes-netting-fruit-trees-easy/
I’d like to tell you about another way to prevent cherry worms. It’s a
fine mesh net that covers the whole tree and can be used year after year.
I’ve been using one for 6 years and haven’t had a single worm in any
cherry since then. The net is still very strong and stretchy, even though
I put it on an apple for a while in the fall to keep the turkeys out.
I’ve also designed a different type that comes in long (75 metre) lengths
to cover grapes and prevent wasp and bird damage. The people who have
used it say it’s saved their crops.
You can find more information at http://www.kootenaycovers.com or email me at
mroberts@kootenaycovers.com.
Thanks,
Marilyn
Thank you for creating a way for gardeners to grow unsprayed cherries free from worms and other pests. Recently while eating “organic” cherries with my family, I said, “I wonder how one grows such good cherries the organic way? Do you think farmers cover the trees with netting—like bird netting?” Now I find someone has invented just such a device.
Thank you also for writing to tell me about it. Now I can spread the word. This fall when I give my slide-illustrated lectures, I will tell folks about Kootenay Covers. The video on your website explained it well. If I had a cherry tree I would send for one of your “box-like” bags immediately.
Many many thanks for what you are contributing to agriculture worldwide. Your bag for grapes would save much heartache for many vineyard owners, including friends of mine. I will tell them also about the Kootenay Covers.
I have these flies in my cherries too and I live in Newport, WA. (About an hour and a half from the Canadian Border and also on the border of Idaho.
If I “can or freeze” these cherries with the little white worms in them will they be noticeable when I get the cherries out to bake a pie??? Will canning the cherries whole with the little larvae in them spoil the fruit. Will I notice them in my pies???
It is so much trouble to pick them out that I would rather cook the little buggers unless that would be unhealthy. Thanks Sharon Davison
Most fruit pie recipes begin by saying “First, inspect and pick over fruit and cut off any bruised or damaged portions. Before cooking your cherries, I suggest you phone your local UC Extension office and see if they have an official reply to your question, since it seems to be something many folks would like to know. Below is my personal opinion, based not on scientific inquiry but on common sense:
Many insects and worms are edible and are a good source of protein. We know that worms and maggots of various sorts were eaten by ancient man and are still consumed today in some countries. Various types of worms, locusts, and ants, though disgusting to most westerners, are prepared in special ways to make them delicacies in some countries. However some insects, most notably certain caterpillars, have a bitter flavor and a few tropical kinds are poisonous. Cherry worms are not poisonous and don’t seem to have a bitter flavor, nor do they harm humans who ingest them since many people say they’ve eaten them by mistake without realizing what they had done and they had no ill effects. The main problem is when the worms consume the insides of the cherry and render the fruit itself unpalatable. Also, we have to face the fact that the cherry, once consumed by a worm contains what has gone through the insides of a worm and come out the other end. If you picked the cherries early while they are still in good shape I think it’s okay to cook them, but if later in the season the cherries themselves will be spoiled and won’t taste good in pie. High heat necessary to cook a pie, will sterilized the damaged fruit, but I can’t guarantee that the flavor or texture or look of the pie will come out right. My suggestion: try it and see. A few worms won’t hurt but masses of them might.
I eat them all the time fresh off the tree; sorry we can’t market them as ‘protein plus’ .
for three years now. I eat about lb a day from July 1st
through July 21.
… it’s just a little protein and does no harm — initially
a speck; about the size of a pice of long grain rice when
full grown. Hardly worth sweating over … but we are so squeamish here.
They are very small … once picked, chill cherries
as soon as convenient; it stops their activity, and
they will remain edible for four or five days … or more.
in the fridge.
I do cut in half and remove worms (1 in 4) from any I plan to share with my squeamish friends and family.
I leave whole the ones I freeze for personal consumption.
NOTE: you can fit more in the freezer if they’re cut in half … and there is less air space so they keep longer.
I freeze enough for 10 months. This year I froze extra – hopefully enough for 12 months.
Thank you for your comment which I truly appreciate. Even though not everyone can adopt the same attitude, your healthy and down-to-earth views might help some folks to chuckle about this subject and not to feel quite so upset with an otherwise frustrating situation. As you say, many people are squeamish, and I am glad you wrote to share your experience and honest opinion and tell others how you deal with this problem including your useful tips on pitting, storage and freezing.
We live in a squeaky clean society and most folks don’t grow up in the country where a peck of dirt and a few critters thrown in is par for the course.
Look for little holes in the cherries first. If you miss some the lukewarm water rinse b4 canning and hot syrup will make them surface. If there are not too many I skim them off. I never had them b4 for many years then all of sudden they started up -one year I had to disgard the whole crop AFTER picking them. We are going to try the cherry bait next. Even though we can get rid of them b4 canning it is gross. I have never noticed any spoilage. Didnt realize I had them 1 year and dried some cherries & found them fried at the bottom of the dryer. Have read the worms won’t hurt you if accidently ingested.
Thank you for writing to us on this subject and explaining more ideas to folks, such as the the lukewarm water rinse and hot syrup to make the worms surface so you can skim them off. That will work if there are not too many. Yes, when cooked, the worms are not harmful to ingest but they are unpalatable and make the fruit mushy. At their worst they ruin the fruit.
You are amazing! If we had a designation akin to Japan’s National Treasures, I believe you would definitely be in that class for gardeners. Thanks so much. I’ve shared your message with my daughter and will surely let you know how things go.
What a lovely reply. Many, many thanks!
My daughter took your advice and took samples of her infested fruit to the Contra Costa Ag Department. The entomologist provided both her and our 4 year old grandson with a great illustration of science at work. The pest has been identified as Drosophilla Suzukii. The link to the UC Davis IPM page for information about this pest is: http://www.ipm.ucdavis.edu/EXOTIC/drosophila.html
Its potential is absolutely horrifying, and it’s likely they’ll make it down here sooner or later. Thanks once again for your willingness to help. I’m very glad you’re here for all of us.
Thank you so much for replying with this important update with the UC Davis IPM page about Spotted Wing Drosophila (Drosophila suzukii). Many thanks to your daughter for immediately acting on my suggestion and taking samples of the pest to the Contra Costa Ag Department. I thought from your descriptions that the pest was the Western cherry fruit fly but now we know it is not. This new exotic pest sounds even worse, but it is good news that there is some evidence that traps made from empty yogurt containers may provide one way of controlling it. I urge all readers who have cherry trees to read the information on the link you have so kindly provided.