Sweet cherries of a variety called Géant.Most of the windfalls showed evidence of being attacked by Common Cherry Fruit Fly Rhagoletis cerasi (Mouche de la cerise). I'm not surprised, as I found one walking about the kitchen in early May. Cherry flies can infest cherries at all stages of development, from when the fruit is an unripe green marble, to soft and fully ripe. The later maturing varieties are much more prone to severe infestations than the early varieties. This year our latest bearing sweet cherry was all over and done with by 29 May - at least a month to 6 weeks early - so the cherry fly problem has not been very severe.
Sour cherries.Affected fruit shows characteristic twin puncture marks where the maggot has entered and exited. When inside the fruit the maggots liquidise the flesh and suck out the nutrients, leaving a bruise which turns the fruit rotten. Once mature these larvae drop to the ground to pupate in the soil.
Common Cherry Fruit Fly.Those fruit that have been infested are more prone to falling, which is why so many of my windfalls show the signs. I'm not too bothered - if the fruit has not actually gone rotten, they taste fine and the maggots disappear if you cook them. They are not like plum sawfly maggots, which leave large amounts of unappealing frass around the stone. The ripe cherries I have picked from the tree are perfect, showing no signs at all of damage, and the windfalls are a fairly low percentage of the total crop. But the total crop of sweet cherries this year was 1.5kg, compared to tens of kilos the last two years.
Our orchard neighbours are obviously much fussier. They have a huge old yellow fruiting cherry, which they tell me they only keep because it is a beautiful tree. They never eat the fruit as they are always full of les asticots.