Blight or Insect Damage on Blackberry Bushes
Dear Sir or Madam, In the last week or so, I have been noticing significant discoloration of leaves on my year-old blackberry bushes. The problem started at the base of the plant, leaves initially developing some yellowish coloration, then turning grayish-purple, then dying. Photos are attached. The white spots are remaining Sevin dust (I was dealing with a Japanese beetle infestation). The plants have already developed significant numbers of berries, and these seem to be maturing as normal. There seems to be a lesser case of the same thing on the neighboring red raspberry bushes, though I also saw a bit of white film in a few of the leaves (aphids, maybe?) Any advice you can provide would be most appreciated.
This does not look like a disease or insect issue and are not usually a problem on one year old plants. You can always look for mites on the undersides of the foliage. They are a sucking insect and like hot dry conditions. If so, dislodge with a forceful stream of water. https://extension.umd.edu/hgic/spider-mite-vegetables
It is possible that you may be dealing with spacing, poor soils, etc. Take a look at our website for planting information, care, and common problems https://extension.umd.edu/growit/fruit-profiles/raspberries-and-blackberries#blackberries
We do not recommend Sevin to control Japanese beetles. Sevin is a broad spectrum insecticide that kills all insects including beneficials that help
keep pest insects in check. As soon as you notice the beetles, handpick and drop into a bucket of soapy water.
Send us more photos, if you notice additional symptoms.