Regional Gardening Reports :: National Gardening Association

In the Garden:
Northern & Central Midwest
August, 2011
Regional Report

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Blackberry anthracnose is not a pretty picture.

Blackberry Anthracnose

Several years ago I rescued some wild blackberry plants growing in the field next to my house. The wild stand was nice to have but hard to get to, so I brought some into my garden to make it easier to harvest. The berries are usually small but extremely tasty, and I've learned to increase the size of the berries by giving them plenty of water during berry development.

Cultivated Berries
Last year a friend of mine showered me with huge bowls of cultivated berries from her yard and offered me some shoots from her plants in the fall. I thought it would be nice to have some bigger berries that ripened earlier, in addition to my wild plants, so I added two plants to my blackberry patch.

Signs of Anthracnose
The berries have been developing side-by-side, with the cultivated ones much closer to ripening at the end of July than the wild ones. However, as the berries began to turn red, I've noticed that some of the leaves have irregular brown dry patches on them. And a few branches of the berries are drying out in spite of regular watering. After some searching, I've found that I have anthracnose, a fungal disease that affects blackberries and raspberries and resides in the canes.

Recommendations for Control
The interesting part about this is that I've never seen it on my wild blackberries. And at this stage in the summer, they are still quite healthy. The recommendation from the Extension Service is to avoid high nitrogen fertilization and to avoid overhead watering. They also recommend keeping the planting carefully contained in narrow rows so that there is plenty of air movement. Not exactly what I have going on in my garden.

Life Cycle
The fungus overwinters on live and dead tissue, so any pruning remains need to be destroyed so the new plants are not reinfected. You can also use a lime sulfur spray just as the plants break dormancy in the spring. All of which I will do this fall and next spring, but it doesn't help me now.

Cultivated vs. Wild Genetics
I do think I will have a good harvest this year, but I'm keeping close watch, especially on my wild blackberries. So far there are no signs of anthracnose on them, which is an interesting statement about the genetics of something that has had to survive in the wild versus a domesticated plant that was obviously developed for bigger berries.

Watch Those Trades!
All in all, this is just a gentle reminder to look carefully at the source of "friendly" trades. Be sure to check plants from friends as carefully as you would when purchasing from a garden store!

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