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Plum pockets, caused by the Taphrina fungus, led to this young plum tree developing deformed fruits. Special to Forum News Service

'Plum pockets' could be cause of browning fruit

Q: I have a question about several of our young plum trees. Some of the fruit are all brown and shriveled up. Any idea what is happening? — Lisa Rakowski, Mayville, N.D.

A: Thanks for the great photo, which would make a classic show-and-tell picture of the disease called plum pockets. Caused by the Taphrina fungus, it begins as small blisters on developing fruit a month or two after blossoming. Infected fruit becomes unusually large, puffy, spongy and eventually hollow. As the disease progresses, the deformed fruits become dry, brown mummies, covered with spores and clinging to the tree.

North Dakota State University says "Taphrina diseases have only one infection cycle per year and infection sources include spores that lay dormant on or near buds plus mummified fruits that disseminate spores via rain splash and wind." For control, the university recommends removing and destroying mummified fruits, and applying Bordeaux mixture or fungicides containing chlorothalonil to all parts of the tree in early spring when temperatures are above freezing but before buds begin to swell.

Q: What's the best time of year to transplant rhubarb? Are there any special instructions? — Larry Graf, Mapleton, N.D.

A: Rhubarb re-locates successfully in spring, as new sprouts are just beginning to peek through the soil. A second successful time to move rhubarb is September, after foliage has been lightly frosted. These are the two preferred options for moving rhubarb, dividing it to make more plants, or rejuvenating an old plant whose center has become open and woody.

Dig rhubarb by starting far enough from the plant so large roots can be saved. The entire plant can be dug, divided and reset. Or leave a healthy portion in place, and just remove the extra portions.

Once the plant is lifted out of the soil, divide with a sharp knife, saw or shovel. Replant at the same level, no deeper, which can adversely affect rhubarb. The "eyes" or buds that are located in the crown between the above-ground stems and the roots should be covered with no more than 1 to 2 inches of soil. Water well after planting.

Q: We struggle every year with leaf blight on our tomatoes. By harvest, there are barely any leaves left. We have spread newspapers around the plants and are thinking of spraying with a copper fungicide. We always watered with overhead sprinklers when we lived in North Dakota and never had a problem. Any suggestions? — DuWayne Schwindt, Bemidji, Minn.

A: Most tomato leaf blights are caused by fungi. Prevention is the key, because once foliage is yellow and brown-spotted, it won't revert to normal appearance. Some tomato varieties are more disease-resistant, so check descriptions when choosing tomato types next year.

Mulching plants as you've done helps create a barrier between the vines and fungus-infected soil. Keep the foliage dry when watering to prevent splashing and spread of fungal spores. Irrigate in the morning so any water that gets on the foliage can dry before nightfall. Remove any leaves that show blight symptoms to reduce spread. Protect healthy foliage with a fungicide containing the active ingredient chlorothalonil. An organic option is the copper product you mentioned. Staking can help by maximizing airflow around plants. After frost, remove all tomato vines to reduce fungal problems next year.

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