Managing Backyard Berries for Quality Harvests

— Written By Eli Snyder
en Español

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Managing Backyard Berries for Quality Harvests

While I have predominately focused on home vegetable gardening in this season’s articles, I wanted to cover a topic important for all home berry and small fruit producers- one that I have gotten several calls about recently. Birds and larger critters often come up in conversations about protecting fruit and berries during harvest. However, there’s a tiny menace that if left unchecked, could result in 20-100% losses.

The Spotted Wing Drosophila (Drosophila suzukii) is an invasive fruitfly first detected in California in 2008. It subsequently spread across the country, landing in North Carolina by 2010. The female Spotted Wing Drosophila has a saw-like ovipositor or egg layer and allows the her to deposit eggs in ripe or ripening fruit, such that it does not leave any sign or notable damage on the fruit. Eggs hatch in as little as two hours, and the larvae will feed inside the fruit until pupation, after which they will emerge as adults and repeat the cycle. The fastest recorded time for life cycle completion is 8 days and two hours, but can range from 8-25 days.

Often gardeners will notice larvae in fruit before they observe the adult fruitflies themselves. Once active inside the fruit, fruit may lose turgor, appearing dehydrated. If you cut open fruit showing these symptoms, you may encounter larvae. The larvae resemble native fruitfly larvae. They are white, tapered at each end, lack a clearly visible head or legs, and reach lengths of up to 3 mm. The adult fruitflies may be easier to distinguish, especially with the help of a hand lens. Male Spotted wing drosophila adults have a reddish body and black spots on their clear wings, hence the name. Females lack the spots on wings.

Spotted wing drosophila will lay eggs and reproduce on most soft skinned fruit, including blueberries, raspberries, blackberries, cherries, and grapes. They are not often a problem for early-season strawberry production because they are sometimes not active or only beginning to be active during that harvest. However, later harvest such as those from day-neutral or everbearing varieties may be susceptible. They will also lay eggs in and reproduce on native fruit including mulberries, pokeberries, and wild brambles.

To manage population, gardeners should remove all ripe fruit from the plant at each harvest and remove any ripe or over-ripe fruit from the ground or plant as well. Leaving the over ripe fruit will allow populations of the just off of a two multiply resulting in higher infection rates in the fruit. If any of these are fruiting close to your home fruit production, consider ways to manage populations on those wild fruit to avoid population buildup in your home fruit. If you know you are removing infested fruit, and you’re not interested in eating it, place that fruit in plastic bag and deposit in the trash.

Gardeners with multiple types of home fruit production that ripen over the season are at greatest risk of having populations build up. It is very important to keep populations under control to preserve later harvests, especially. Japanese studies have shown that there can be as many as 13 generations in a year. With each unchecked generation, the populations will increase.

Once larvae begin developing, the berry may become very soft and collapse, or be very watery near the cap. If you are not sure if you have this fruit fly, you can place 50-100 fruit into a plastic bag 1 tablespoon salt in 8 oz warm water. Let it sit for 10 minutes. If present, the larvae will emerge in the solution. You can also place a trap near your fruit to monitor populations. Mix 4 Tbsp. sugar with 2 Tbsp yeast in 32 oz water, or a smaller batch of this, and place in a quart sized container with small 3/16th of an inch entry holes drilled in at the top. Use 5 fl oz of the bait solution, and hang near the fruit. Check and change the solution frequently.

Once harvested, immediately place fruit in the refrigerator or freezer. Or, use it immediately in cooking or processing. This will slow down the development or stop the development of the larvae that may be inside of the fruit, or even prevent eggs from hatching.

Managing to reduce Spotted Wing Drosophila is relatively simple, but it requires good eyes for detecting all ripe fruit, and dedication to pick every last one. Finally, consider sharing this information with your neighbor. The more unpicked, infested fruit there is close by, the more fruitflies we will all have in our berries.