Tomato. Fresh tomato with drops isolated. With clipping path.

Central Oregon gardeners may complain about having to be more selective of tomato varieties to grow, limiting the maturity time to approximately 90, but the weather keeps fungi down.

It’s time for a head’s up. Now isn’t the time to get caught napping in the tomato patch. My tomatoes may have gotten off to a slow start as a result of the extreme heat. Tomatoes prefer and grow best when temperatures are under 90 degrees Fahrenheit. For weeks the plants just seemed to sit there.

The word “comatose” came to mind as I was doing my morning walk-about, I just wanted to shake them.

Now that we are into August I think the tomatoes have gotten the message that it is time to produce and are showing signs of aggressive production. Now is also the time for gardeners to be watchful for tomato problems.

Blossom-end rot is the first problem you might see developing. Blossom-end rot shows up as a gray to black spot on the blossom end of the tomato, the end opposite the stem. It can affect green fruit as well as ripe fruit.

The two major causes of the rot are deficiency of calcium availability in the plant, moisture stress either from very wet or very dry conditions contributes to how the calcium, which is in the soil, is delivered to the plant. According to an Oregon State University fact sheet, excess nitrogen, magnesium, potassium or sodium had been applied as fertilizer. Again, another reminder that more, is not necessarily better. Tomatoes are not heavy feeders. Fertilizer that is low in nitrogen (the first number) is applied at planting time and then again when tomatoes start to set fruit and need the extra energy.

More water produces less

Tomato splitting or fruit cracks is associated with rapid fruit development and wide fluctuations in water availability. Perhaps during the extreme days of high temperatures, we felt we had to water more. The sudden uptake of water causes internal fruit tissue to grow faster than the skin causing the skin to crack or split. The fruit is still edible, just less visually appealing.

The bane of all tomato growers is the discovery of the dreaded tomato hornworm, the caterpillar of the five-spotted hawkmoth (Manduca quinquemaculata) also known as the hummingbird or sphinx moth.

Hornworms are up to 5” long, bright green with a black horn on its posterior. They feed on tomato leaves and can defoliate an entire plant. They can also feed on the fruit. A telltale sign that an attack is under way is their black frass (droppings) on the leaves. Look under the leaves, they are masters of camouflage. The control measure is to hand-pick and destroy.

Hot, dry weather may cause a symptom called physiological leaf roll. This is a self-defense response, where leaves curl slightly to prevent further water loss. Some tomato cultivars display leaf rolling as a normal growth habit. Mild leaf roll generally does not lower yields or quality. Severe symptoms may cause flowers to drop and fewer fruit to set.

Tomato variety can be limited

Herbicide drift can also damage tomato plants. Tomato plants are extremely sensitive to herbicides and can be injured by concentrations as low as 0.1ppm. Wind speeds as low as 5 mph can move herbicides up to a mile. Being aware of herbicide drift may answer problems you are having in parts of your landscape.

Central Oregon gardeners may complain about having to be more selective of tomato varieties to grow, limiting the maturity time to approximately 90. Perhaps we can’t grow the big beefsteaks but we do have a plus side.

Our gardens are generally not plagued with fungi, viruses or bacterial wilt damage such as the mid-west and southern states experience. I raise my tomato plants in my greenhouse and in the open garden. The greenhouse does have its issues in trying to control the temperature and the air circulation. A new greenhouse variety for me this year is “Big Juicy.” The growth is very prolific and I need to do some pruning of lower branches to increase the circulation and eliminate the possibility of fungus diseases.

The plants in the open garden are maintaining slow but healthy growth with BeaverLodge from Territorial doing exceptionally well this year. Midnight Roma, the new variety released by Dr. Meyers from Oregon State University is fascinating. The tear-shaped, dark purple paste tomato has an 80 day maturity. Harvest occurs when the base of the fruit turns deep red.

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