Spring has sprung, which means our gardens are starting to come to life, bringing beautiful new flowers that bloom into our beloved fruits and vegetables. For those who have the pleasure of enjoying home-picked cherries from their very own cherry trees, you may notice some of the cherries have a little extra bonus when you bite into them. You may notice some bugs in cherries when that was never an issue before.
Preventing pests from overtaking our gardens is a problem most gardeners will face at one point or another. With some research and a little effort, infestations can be halted for future bounties.
Insect Pests of Cherry Trees
There are numerous pests that could potentially infest a cherry tree. In the Pacific Northwest, there are two that are notable:
Western Cherry Fruit Fly
The western cherry fruit fly (Rhagoletis indifferens Curran) is a pest known to the western region of the United States. This pest was found in the Pacific Northwest area of North America in the early 1900s. The adult pests start to emerge in May and lay their larvae under the skin of cherries after mating. Each female can lay up to approximately 200 eggs in a season. Adults emerge about five weeks prior to harvest and are active until about four weeks after harvest.
The eggs hatch a week after being laid in the cherries, and the larvae burrow toward the pit of the cherry for protection. When fully grown in approximately two to three weeks, they bore their way out of the cherries and drop to the soil below, burrowing to mature underground until next season.
Spotted Wing Drosophila
The spotted wing drosophila (Drosophila suzukii) originated in Asia and was first discovered in our area in 2008 in California and 2009 in Oregon and Washington. Spotted wing drosophila differ from the common drosophila (Drosophila melanogaster) in that the spotted wing variety can pierce the skin of the fruit to lay its eggs, while the common drosophila must find damaged fruit where the skin is already broken to be able to lay their larvae inside.
The spotted wing drosophila use sweet cherries as their hosts but can also use other fruits, such as berries, grapes, and other stone fruits like peaches and nectarines. Adults live approximately 1 to 2 months, and adult females can lay from 200 to 600 eggs in their lifetime. The time from egg to adult is approximately one to two weeks.
Integrated Pest Management System
Now that we know what the pests are, how do we stop the infestation of bugs in cherries? The USDA advises using the Integrated Pest Management System in order to best treat the infestation. According to the USDA, the Integrated Pest Management System is defined as:
The implementation of diverse methods of pest controls, paired with monitoring to reduce unnecessary pesticide applications. In IPM, pesticides are used in combination with other crop management approaches to minimize the effects of pests while supporting a profitable system that has negligible negative effects.
To best utilize this method, the first step is to determine which pest has infiltrated the cherries.
Pest Identification with Traps
The best method to determine which bugs have infested is to monitor the trees by using traps. The western cherry fruit fly is more difficult to trap, as it isn’t typically attracted to most traps. The best traps for these pests have a yellow panel covered in adhesive and ammonium-carbonate, which is the bait. It is best to place the yellow panel among the fruiting canopy, and it’s best to remove the foliage around the panel for a foot and a half of clearance.
To trap the spotted wing drosophila, you can use a basic fruit fly trap, or make one at home using a clear plastic cup with some holes poked through and using apple cider vinegar as bait.
Baits need to be changed weekly to remain effective. Traps should be placed well before fruits begin to ripen. Cherries should still be green to straw-colored when placing traps to monitor pests. Once the pest is identified, you may use the appropriate chemical spray to try and stop the life cycle.
Once the pest is determined, pesticides can be used to spray the crop for prevention. The current crop is not salvageable once infested. The sprayed chemicals must cover the entire cherry and must be potent enough to kill the adults prior to laying their eggs. As stated above, both the western cherry fruit fly and the spotted wing drosophila mature in just one to two weeks, so a quick response is required to protect the next year’s crop.
Spraying should start in late May, once the first fly is trapped, and while the cherries are still green to straw-colored. Sprays should continue every week while the cherries are expanding to ensure complete coverage. Pesticides for yard use are typically sold at garden centers under many different brand names.
Many pesticides are lethal to bees. Review the pesticide label to determine if your product is harmful to bees. If it is harmful to bees, do not spray while bees are foraging or when there are blossoms on the tree. The PNW Handbook has an extensive list of pesticides best used for each pest. If you’re unsure of the spraying process or which pests you may have, contact the experts at Mr. Tree.
Though pests can infest our beloved cherry trees, it’s possible to stop the life cycle and enjoy next year’s crop if caught in time. Regular monitoring of trees with traps to identify any potential pests and spraying in a timely and regular fashion can make next year’s cherries enjoyable for all. If you have noticed bugs in cherries, don’t hesitate to ask the experts at Mr. Tree. Our professional certified arborists have been working in the Portland area for over 30 years.