Why raspberries droop and die
Q: What is wrong with my red raspberries? The tips of some canes are drooping and dying. What can I do?
— Dave from Salem
A: Dave sent us photos of his raspberry plants. About 7 inches from the tip, the branch started to bend downward, and the leaves on the tip turned brown.
At first look, this very much looks like a disease is infecting the raspberry cane at that point because the cane is dark and shriveled. At this point on Dave’s canes, the cane turned a dark purple color, with brown and grey edges.
At first, that was all we saw. But when it comes to diagnostics, the magic is in the details. We need to look at each problem with several sets of eyes to catch what might not be obvious upon a first look.
Upon closer inspection, there were two perfect lines of dots encircling the cane — one near each end of the discolored section of the cane.
Aha! These dots are the tell-tale sign of the raspberry cane borer (Oberea perspicillata). This damage is done by the female when she lays her eggs. She chews the two lines just over a half inch apart and lays an egg between them. These lines girdle the cane and cause the tip of the cane to droop and wilt.
The egg hatches after several days. Then, the white-colored larvae emerges and tunnels through the cane, traveling toward the base — very slowly. Most of the research states they end up just an inch or two from the girdling site at the end of the season.
If left unchecked, it will travel to the base of the cane early in the next growing season. Then, it emerges as an adult beetle in June of that next year to complete the cycle and lay eggs for another generation.
The adult is slender and black with an orange colored thorax and long black antenna. These adults will feed on the fresh growth of young canes and start the cycle all over again.
Getting rid of this insect is exceptionally simple. The best method for control is to cut the canes just below the two girdles and get it away from the raspberry planting. This will remove the next generation from the cane. Presto — an easy way to get rid of this insect.
Continue watch the patch for the next week or two to ensure you have gotten all of the canes with eggs in them removed from the planting. This insect will not cover the entire patch — just a cane here and there.
Each season, watch for the signs and remove any cane tips with signs of egg laying. These insects can reinfest each year with the presence of wild brambles in the area. They also have been reported on azalea, oak and roses.
To learn more about this insect and to see pictures of the damage, go to: http://go.osu.edu/caneborer.
Barrett is The Ohio State University Extension educator for Agriculture and Natural Resources in Mahoning County. Submit questions to the office at 330-533-5538. Regular clinic hours are 10am-noon on Thursdays or visit go.osu.edu/virtualclinic.