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There cherry tree fly it is a parasite present in cherry growing areas in Italy and in much of the world. Particularly aggressive, the cherry fly larva can develop into ripening cherries and, if left unchecked, can ruin almost any fruit on a tree. Even poor control can have serious consequences on the harvest, considering that most of the cherry trees present in Italy do not tolerate any form of infestation by these insects.
It should also be noted that the behavior of cherry tree flies it ensures that adults are poorly migratory and therefore will not go beyond what is necessary to find a host tree. For this reason, infestations between various cultivation areas tend to be very sporadic, while infestations within an orchard, where the trees are close, can spread rapidly.
The stages of the life of the cherry tree fly
The egg of the cherry fly is yellowish and elongated, with a stem at one end. It is about 0.8mm long and settles under the cherry peel.
There larva instead it appears as a creamy white worm, without legs, tapered in the head and blunt in the back. It goes through three instants of life and grows to about 8mm in length. The worms found in cherries can be those of the cherry fly or they can also be larvae of the Drosophilidae family. Drosophila fruit flies do not attack fruit unless the skin has been physically damaged, allowing an opening for spawning. This usually happens when the cherries are bruised due to damage caused by wind or rain or bird feeding or are rotten. The larvae of the cherry fly, and other species of Rhagoletis, can be distinguished from the Drosophila species by examining the posterior end of the larvae. The rear end of the cherry fly larva is rounded and the spiracles each have three darker lines that extend laterally from the midline. The back of the Drosophila larva has two protuberances on which the spiracles are located.
Then we arrive at the state of pupa. The pupa is yellowish to dark brown in color and resembles a large grain of wheat, approximately 4 mm long. Finally, there is the adult state: the adult has a black body with white bands on the abdomen. The wings are transparent with a distinctive dark stripe pattern. It is easily distinguished from other fruit flies precisely because it appears on the wings. The cherry fly is about 5mm long. The female is slightly larger than the male.
The evolution of cherry tree flies
The cherry fly completes only one generation a year. It overwinters as a pupa in the ground, affected by the temperature of the soil. Adults begin to emerge in May, about 5 weeks before harvest, and are active for up to 3 or 4 weeks after harvest. The peak emergence often coincides with the harvest.
Adults live 16 to 35 days, depending on temperatures. They feed on leaf deposits such as honeydew and pollen. Adult females undergo a pre-ovition period of 7-10 days before reaching sexual maturity. After mating, they lay their eggs under the peel of the fruit. Females often feed on fruit juices oozing from the sting made during spawning.
Each female can lay 50 to 200 eggs over a 3 week period. The eggs hatch in 5-8 days and the larvae burrow into the fruit pit where they are unreachable by most pesticides. When they are fully developed, 10 to 21 days after hatching, they dig their way out of the cherries and fall to the ground. Within a few hours they dig a tunnel in the ground to pupate. Most develop into adults in the following season, although some remain dormant for two years.
Cherry fly defense: remedies and treatments
The cherry fly is difficult to monitor, as it is not strongly attracted to traps. The most effective trap is a yellow panel covered with adhesive with a bait of ammonium carbonate. These traps should be placed in the crown of the tree, with fruit and foliage removed around this element.
However, it is not good to take the effectiveness of this tool for granted, considering that even if there are no cherry flies trapped, the orchard may not be safe.
In order to reduce the risk of infestation, we therefore proceed with the application of chemical sprays, with a frequency that will depend on the interval of first spawning, usually from 7 to 10 days. Applications of products with a very short residual life are repeated every 7 days. Emergence and spawning continue after harvest, making it important to maintain a control program through the harvest.