Margaret Lauterbach

Margaret Lauterbach: Blights, bugs still a threat to gardens in our arid region

This tomato plant is infected with late blight.
This tomato plant is infected with late blight. TNS

We have many newcomers to the Treasure Valley and many Idahoans starting to garden for the first time. I’ve been asked by a reader to write about tomato resistance to blight, a topic I covered several years ago, but worth a repeat for new gardeners here.

First of all, our area is so arid we usually don’t have to worry about early or late blights if we start our own plants from seed or buy plants that were started in this general area, usually from locally-owned nurseries or garden centers. Some chain stores bring in seedlings from parts of the country that are subject to blights, and although they look healthy when you buy them, if they carry disease, they quickly deteriorate and infect healthy plants of potato, pepper and eggplant.

If we have a wet spring, we may get such blight, for spores are water-borne or may be blown in on wind. Early blight is the fungus Alternaria solani, and it may attack early or late in the season. Late blight is a different fungus, Phytophthora infestans, and it may attack earlier than “late.” A strain of P. infestans was responsible for the devastating potato blight in Ireland in the mid-19th century.

This splashing water that carries blight spores can be stopped from infecting your tomato plants by removing lower leaves of the plant and splash-absorbing mulch. It’s also the reason you should irrigate tomatoes, peppers and eggplants instead of using sprinkler water.

The disease enemy most apt to attack our vegetable gardens in this area is curly top virus. That disease is common in arid areas such as ours, and attacks Solanaceae (tomatoes, potatoes, eggplants, etc.) and squash, beans, beets, etc. This disease is spread by a beet leafhopper that can ride the winds for up to 200 miles, and then land and bite into a mature fruitful plant, killing it. These insects are tiny and transient, their visiting habit not conducive to control by spraying anything.

They are attracted to and killed by sticky yellow cards placed in the garden. They’re said to avoid plants in shade. But tomatoes, peppers, potatoes, etc., require full sun to grow, so shade is not a good idea. Some folks plant tomato plants with strong-smelling herbs such as dill to prevent leafhopper landings.

Another option is to grow tomato plants that are resistant to that disease. Researchers at the University of Idaho and the University of Washington years ago determined that these varieties of tomato were resistant: RowPac, Roza, Saladmaster, Columbia, Owyhee, Payette and Parma. These are all determinate plants, bearing salad-size tomatoes with moderate flavor. The only commercial source I know of for most of these tomato seeds is Sand Hill Preservation Center (www.sandhillpreservation.com).

Curly top virus is common in arid areas in the Middle East; the intermountain west in the U.S., from Canada to Mexico; and part of the east bay area of California and, when conditions are right, southern Colorado. Symptoms in tomatoes include top plant leaves that twist and turn upward; leaves feel leathery and thick; and veins on backs of leaves are purple. Leafhopper numbers are larger some years than others. They attack many garden plants, and some years have been destructive to the commercial chile crops in southern New Mexico.

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This is the month you should prune your grape vines to make sure the vine produces only enough fruit to ripen and be well-sugared. The difficulty in verbally describing how to prune grape vines stems from the different ways to train vines and their ages. You’ll prune differently if you have vines trained for spur production than cane production. Another complicating factor is the age of the vine. Is it one or two years old or older? There are excellent videos on YouTube if you search for “pruning grape vines.”

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The Open Source Seed Initiative (OSSI) is dedicated to maintaining fair and open access to plant genetic resources worldwide. OSSI (Open Source Seed Initiative) vendors include Nichols Garden Nursery, Adaptive Seeds, High Mowing Organic Seeds, Wild Garden Seed, Fertile Valley Seeds, Fedco, Bountiful Gardens, Victory Seeds, Sand Hill Preservation Center, Southern Exposure Seed Exchange and others.

Send garden questions to melauter@earthlink.net or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.

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