The cherry worm: what is it?
Appeared in France during the 2010s, the cherry worm is in fact the larva of either of the two flies that can attack the cherry tree. We present them to you here.
Adult, this small fly, or midge, measures on average 4 mm. Its black body is spotted with yellow on the thorax, as well as on its head. He has transparent wings on which are drawn 4 blue-black stripes.
The Drosophila suzukii is a little smaller than Rhagoletis cerasi, measuring on average 3 mm. In this species, the male is smaller than the female. This small fly is characterized by a yellow-orange thorax, as for his eyes, they are bright red in color. It has transparent wings on which 2 black spots are visible. This species of flies multiplies rapidly and attacks different fruits. It is very often the one that causes the most damage, especially since it resists cold quite well.
The larvae of these two species of flies are of little maggots which, at the end of their growth, are about 5 mm long. These maggots are creamy white in color and have dark mouthparts.
Their life cycle
Generally speaking, the flies that appear in the spring, when the weather is hot, come from the wormy fruits that have fallen from the tree the previous summer. Indeed, the worms had buried themselves in the ground to spend the winter there and metamorphose.
About ten days after having fledged and after mating, the females pierce the skin of ripening cherries to lay an egg under the skin of each. A female can lay eggs in sixty cherries. After about ten days, the larvae will emerge from the eggs. They will then be able to feed on the pulp of the cherries.
A month later, their growth ends and they fall to the ground. They bury themselves a few centimeters below the surface of the earth to turn into a pupa, a kind of chrysalis that protects the maggot during its metamorphosis. This stage, the second, of the life of these flies can last between one to 3 winters before the beginning of a new cycle.
Many differences in the life cycle of these flies cause them to cause much more damage than the previous species:
- The females choose ripe and healthy fruit in which to lay their eggs, and not just cherries.
- They can lay several eggs per fruit.
- the life cycle is similar to that of the midge Rhagoletis cerasi, but accelerated, since there can be up to 13 generations of larvae per year.
- L’life expectancy of these flies is only 9 weeks at most but during this time each female can lay up to 380 eggs.
- The entire life cycle can take place in the fruit, including metamorphosis in fly.
- The hotter it is, the faster the cycleswhich allows them to destroy many fruits both wild and cultivated.
Damage caused by the cherry worm
It is possible to see midges flying around the cherries from the end of May until the last cherries, depending on the species. When the sun is hottest, they can be seen on cherries or leaves. They will feed on the sugary secretions of the trees.
However, it is the larvae which, by consuming the pulp of the cherries, damage them. Generally, late or mid-late varieties of cherries will be attacked more often than early varieties which will reach maturity before the midges fly off and therefore before they lay eggs. Temperature having a direct impact on spawning, damage may vary from year to year and be greater when temperatures are very high.
Here is the damage you can see:
- When cherries are attacked by cherry worms it causes them to rotting.
- The wound caused to the fruit at the time of laying is a open door for fungi and bacteria. The fruit then becomes unfit for consumption and the contamination can spread to surrounding healthy fruit.
- You may also see attacks of Drosophila suzukii on all fruits with soft pulp such as strawberries, raspberries, peaches, figs, etc.
Recognize the presence of the cherry worm
When we see midges, they are difficult to recognize because of their small size. You can try to tell them apart using a magnifying glass. When the fruits are parasitized you can recognize an attack of Rhagoletis cerasi when only one maggot is present in the cherry, while if there are several, it is a Drosophila suzukii. But often rotting fruit is the only warning sign.
Prevent the appearance of cherry worm
You can take a few steps to limit the attacks of these pests.
- Prioritize early cherry varieties like the Napoleons, the Reverchons, etc.
- Near your cherry tree(s), avoid planting fragrant plantslike honeysuckle, for example, which will attract gnats.
- When fruiting is complete, don’t leave fruit on your cherry tree.
- During the winter, hoe the earth to expose the pupae and reduce the future midge population.
- At the beginning of April, you can set up sticky traps.
Cherry worm control
In the event of excessive proliferation of midges, it is important to favor mechanical techniques who are more environmentally friendly. To do this, there are different types of solutions that essentially aim to trap midges before they lay eggs:
- You can, for example, opt for sticky traps which you can find in garden centers among others. Then just hang them from the branches of your tree at the beginning of May. You can also make them yourself with yellow cardboard, reminiscent of ripening cherries, which you will coat with glue on both sides before hanging them.
- There are also pheromone traps funnel-shaped from which the gnats cannot get out once inside. They are commercially available.
- You can also manufacture a trap with plastic bottles, as for wasps. Paint them yellow or red. To attract gnats, you can put inside pheromones purchased in a sachet on the market or a mixture of water, cider vinegar, red wine, in equal quantities, and a drop of dishwashing liquid.