Knowledgebase
necrosis and burnt leaves #752913
Asked May 30, 2021, 4:01 AM EDT
I noticed necrosis on a couple of blueberry plants on their leaves and it happens on only a few rows and a few plants.
This is a young plant that was planted in 2019, and the first crop is expected this season.
What could be the cause of this, is it perhaps a disease or a problem in the diet, or the impact of pesticides?
Here is some information that may be helpful in diagnosing you:
1. In addition to plantings, corn is grown 15 meters from the rows. Could the spraying of corn with herbicide and possible drift be the cause? Although the first rows to the corn have no symptoms.
2. Blueberries were fed with ammonium sulfate 20 days before the onset of these symptoms and fed daily through an irrigation system? Could the cause possibly be amosulfan fertilizer if thrown too close to the plant?
I am enclosing a couple of photos:
Midland County Michigan
Expert Response
Lesions shown on leaves do not correspond to injury symptoms by herbicide or fertilizer. These abiotic factors when they occur follow defined patterns in the field, for example rows of plants with similar symptoms. In the case shown in those pictures and based on the limited information provided with the pictures, the damage is like the damage caused by Anthracnose leaf infection. The infection is more frequent in highly susceptible blueberry varieties like Duke, Jersey, and Pender among other.
The disease is enhanced by hot and humid weather. The optimum temperature for fungal growth is 68 - 81º F, and about 12 hours of continuous wetness are required for infection.
Below is a description of the disease
Gloeosporium Leaf Spot or Anthracnose (Gloeosporium minus) can produce flecking, leaf anthracnose and stem lesions. Gloeosporium leaf spot was first described as a stem and leaf fleck disease of blueberry. Symptoms first appear as small reddish flecks on young leaves and stems of succulent shoots. Leaf and stem flecks do not develop further. The leaf anthracnose stage produces large (1/2 to over 1 inch across) brown to gray lesions that are the most common symptom observed in the field. Development of lesions results primarily from infection through hydathodes at the margins of the leaf, and to a lesser extent through wounds. Secondary stem lesions can develop from leaf infections by growing through the petiole into the stem, and from bud infections late in the season. Stem lesions first appear on current season's growth as dark red circular to elliptical lesions around leaf scars. As the lesions enlarge, the affected stems turn brown and eventually become gray and die. On highly susceptible cultivars such as Duke, Jersey, and Pender, the disease can result in severe dieback.
The control of this disease is with early season fungicides applications and before harvest. Recommended fungicides are Abound, Switch and Pristine. For doses per hectare check with your local Extension Agent
In addition to the potential Anthracnose infection. Herbicides applied directy to the planst for weed control can cause similar symptoms. You need to review the type and dose of herbicide applied to these plants to have a better picture of the causes that could damaged those plants.
