Designing around a new pest

I’d like to ask for some help designing a guild around a cherry tree where we are also dealing with an insect pest which is new to our area.

The tree , a dwarf Stella cherry, is about 12 years old now. It’s pruned low and wide, about 15ft tall and 20ft wide. There are no perennials under it except a few spring bulbs. Out just beyond the dripline on the N side is a clump of lovage, a clump of fennel, and some more bulbs. Soil is sandy and acid but has had quite a lot of homemade compost added over the years, so the organic matter is fairly good. There’s a soaker hose looped around about 6ft away from the trunk all round. The tree is very dense and has a lot of leaves, it shows water stress sometimes in our summer drought period of mid June to mid Sep, even though we water it. There is currently about 4” of wood chip mulch out to the drip line. It’s planted near the front of our 35ft wide lot, near the road, with lots of kids going up and down to the local lake in the summer.

The pest is the Cherry Fruit Fly. This is a housefly sized beast whose larvae make a 3mm diameter exit hole in the fruit just before it ripens, causing us to lose a lot of fruit to rot. The pest lifecycle is that it pupates over winter in the soil, hatches in late spring and flies up to lay eggs on the developing fruit, eggs develop into larvae inside the fruit and eat their way out, dropping to the soil to pupate. It has no natural predators here yet. To break the cycle we lay mill felt over the soil in spring and leave it there till fruit harvest in June. Of course that makes planting perennials rather awkward, and it’s also not 100% effective.

The obvious answer is poultry under the tree. But we are on a bear trail and all our neighbors with chickens have had to resort to electric fencing to keep their chooks safe. The bears are smart and have learned to get through or past everything else. Electric fencing in that location would be difficult.

I’m especially interested in alternative ways to deal with the pest that don’t involve poultry or covering the soil, and/or ways of working around covering the soil if that’s what we have to do.

My immediate thought would rake in applications of DE throughout the spring. Actually my first thought was chickens, but DE would be my second choice. Or neem oil spray? Bio char to home potential predators? Just throwing out ideas, I'm sure there are more experienced permies. I really know nothing about these flies...Around my cherry I planted a ring of garlic to try to fence out ants.

A quick search tells me I should know! Traps are an option, which I'd be tempted to try some cherry juice traps hanging on low branches for a diy, or even on the ground for when they first appear. Looks like some sacrifice an entire harvest by picking while larva are still in the cherries, disrupting the life cycle. One site mentioned braconid wasps help in the home garden setting. That could be a good option for one tree.

Hope you find a good answer, keep us posted! I have a mature cherry in a two season old guild and haven't had much luck due getting cherries to unfortunate events. She seems a lot happier now and I'll be bummed if our first good harvest has maggots, will be keeping an eye out for the next few months.

I searched briefly as I am interested in the topic of caring for cherry trees, though I don't believe we have this pest in ohio. Not much turned up without citing the use of pesticides, except sticky traps  when the temperature is around 75⁰ the adults will emerge in the spring, although this was just used as an indication of when to spray. In the fall it was suggested to place landscape fabric to prevent the pupae from making it into the soil. I suppose this would be labor intensive as  you would need to remove them often? The article did not state and I'm not sure how mobile they are once on the ground.

As far as drought tolerance  of cherry it seems to be low and they should be deeply watered  the first three years of establishment. Perhaps switching to a tree spike watering setup could encourage deeper roots not sure at this point though.  All of the previous suggestions seem viable and I would imagine that it would take a regimen of actions  to reduce their numbers to an acceptable level, including coordinating with any neighbors in the area to take action as well. Do you moles in the area? Not sure if they would eat them, but then most folks consider those a pest as well.

Concerning guild plants to attract predators or increase the resistance of the tree I haven't any knowledge on that subject at this time. I would suggest reading Dr Redhawks Epic soil series, as I feel perhaps some EM and mycelium amendments might aid in the hydrology of the surrounding soil.

Ideally there would a BT bacillus thuringiensis that would affect these pests, but there doesn't seem to be.

Thanks Melonie, ben and William!

The DE is a good thought, I will have to do some digging and see if I can find anyone who's tried it. I also wish I could find info on how deep of a mulch would be needed to discourage the larvae from reach the soil on their way down, and the flies from reaching the air on the way up! Cherry juice traps, good idea. What a waste of cherry juice though! :)

re the landscape fabric... yes, that's what we are doing at the moment with mill felt (a waste product of the local paper mill, used for everything here!) and it's a nuisance to move back and forth. It goes on at or before flowering time, to stop the flies from coming up out of the soil, and stays till after harvest, to stop the larvae from going down to the soil. But at the moment we can't cover the entire area under the drip line so there are some places where the soil is accessible. It's also very hard to tell how much effect it's having.

From the point of view of underplantings that could work around the soil covering... spring ephemerals could do their thing before the cover goes on, and direct-seeded annuals and biennials could maybe be direct seeded (or even transplanted) after it comes off. Buckwheat would work. Any other ideas?

No moles here that I know of. Raccoons would probably eat the larvae/pupae if they found them, but they cause their own issues!

I will check out the Epic Soil Series.

Never noticed a raccoon digging for anything around here. I have noticed in late spring something comes through the yard and digs a few dozen small holes. I was thinking that it would be an opposum or a skunk. Doesn't do a ton of damage and heals quickly. I  imagine they are after grubbworms, unaware of what type though.  

Perhaps you could add some wild bird attractant during the times they would be emerging?

Are there any other cherry trees on neighboring property that will foil your efforts to reduce there population in the area?  

Hervé covez, agronomist in France found that the aphid predators also eat drosophila suzukii. His answer is to make sure you always have a aphid host plant for every period of the year for continuous food supply and to provide overwintering space for predators such as lacewing, hover fly, spiders etc.
De will kill all of them! It might be natural, but it is still a pesticide.
Among the plants he named were yarrow and elder.

Ben, the nearest cherry I have no control of, is about 100ft up the street. Most refs to this fly seem to say that it will fly to the nearest tree and not bother looking further, though I have my doubts... they must have moved to different trees in order to spread!

Susan, thank you, we do also have drosophila suzukii, the Spotted Wing Drosophila or SWD. That one has a different life cycle and is now all through the acres of wild blackberries here. I’m mostly just not looking too hard at the berries before I put them in my mouth! Extra protein.

About the DE... I’m thinking that most aphid predators are up on the plants. If I try some DE in the wood mulch below the tree it shouldn’t affect them too much.

I'm still not clear on the life cycle of this pest. I know that with apple trees, you have to catch all infected apples in a tarp and dispose of them far away. The point being to interrupt the air/soil cycle of the pest.  Does that make any sense here?

Douglas, you are right about destroying infected fruit, there can still be larvae in there. We haven’t done a great job with that in past years... ok about picking the tree clean eventually, but allowing too many infected fruits to fall onto the ground partway through the season.

The most important thing to do is to not invite there pests into your tree.  Set up traps away from your tree and between the one up the road and before the flies are due.  Any coming into your yard will be trapped.  It is ruthless but remove all the fruit to break the annual cycle.  Place into a black plastic bag and leave in the sun for two weeks to kill everything that is inside then throw in the trash or if you have a liquid compost maker, throw it in there to convert to really good liquid.  The other thing is that once the flies have hatched, with nothing on your tree, they will also go to the trap.  There are some great designs for traps so I will not dwell on the design but suffice to say, make sure that it (they) are away from the tree.  Having said I will not dwell on the design but there are yellow sticky traps - they like yellow or you can use a pheromone trap.  Again, the biggie is not to have the traps in your tree because you want to invite the flies to leave.
Good luck with your challenge

Thanks Paul, good advice!

What if... you planted a dense polyculture around the tree, and then did nothing?food always attracts something to eat it, prey attracts predators. You may even want to do things to increase their population, so that predators will move in faster. Canadian Permaculture Legacy on YouTube has a whole video about this “do nothing” method. He says it’s rocky for two or three seasons, but afterwards, 99% of pest problems just go away.