The Roundup -

County Agent Update: Not Your Average Fruit Fly


January 30, 2019 | View PDF

Part 1: Identification and Biology

Most Drosophila species, commonly referred to as “fruit flies”, are a known nuisance in homes, especially around the banana bunch sitting on the counter. However, these flies typically feed on overripe or rotting fruit. There is another type of fruit fly, Drosophila suzukii, or commonly known as Spotted Wing Drosophila (SWD), that will also feed on fresh fruit. This fly has spread fast throughout most of the continental United States and was first reported in North Dakota in 2013.

Male SWDs can be identified by a prominent dark spot on the ends of their wings (hence the common name). Female SWDs do not have the spots, are slightly bigger than the males, and, if you look closely, have a darkened hind-quarter region with a saw-like ovipositor (egg-laying appendage).

The saw-like structure on the females is used to cut into the skin of ripe fruit so that eggs can be laid inside. Once hatched, the larvae feed on the inside of the fruit causing spoilage. The cutting of the fruit skin by the female SWD can also potentially lead to other problems such as diseases and attracting other fruit flies, ones that prefer rotting fruit. One female can lay up to 350 eggs during her lifetime. The SWD most prefers thin-skinned fruits such as raspberries (particularly fall-harvested varieties), tart cherries, everbearing strawberries, and blackberries as hosts for their eggs here in North Dakota. Typically, the population of SWD will be highest at the end of the season, so any host fruit crops that are harvested late-summer/fall are most susceptible to damage.

Other crops such as apples and tomatoes, if damaged, can also be hosts. Ornamental crops that produce late-season berries/fruit such as buckthorn, chokecherry, and nightshade, can sustain SWD population until a more preferable host is planted. It is unknown yet how well SWD can overwinter in North Dakota’s harsh winters, but adult SWDs have been shown to overwinter in other states in leaf litter, ready to infest next year’s crop.

Various control measures will be discussed in next week’s article.

Bovine TB Alert: Bovine Tuberculosis Identified in a Sargent County Beef Herd

From the desk of Michelle Mielke, Public Information Specialist, ND Dept. of Agriculture

“In late 2018, we were notified that two adult beef cows originating from the herd tested positive for Mycobacterium bovis at out-of-state slaughter plants,” State Veterinarian Dr. Susan Keller said. “The National Veterinary Services Laboratory in Ames, Iowa, confirmed the TB diagnosis in the cows.”

Tuberculosis is a disease that can be transmitted from cattle to humans and humans to cattle. Keller said that the bovine tuberculosis eradication program is a state-federal cooperative program. The North Dakota Dept. of Agriculture and State Board of Animal Health typically work with USDA-APHIS Veterinary Services on disease responses.

“An epidemiologic investigation is now underway, and further testing will be done to determine the source of the disease and to prevent its spread,” Keller said. “The herd owners are fully cooperating in the investigation.”

There are no other cattle herds which have direct contact with this herd. Animals which test negative for the disease may move direct to slaughter, but other movements are not allowed.  Meat from animals that pass inspection is safe for consumption.

For more information, please contact Dr. Susan Keller or Dr. Beth Carlson at (701) 328-2655. Any questions related to TB and human health can be directed to Dee Pritschet, North Dakota Department of Health at (701) 328-2377.


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