Can’t wait for that first ripe tomato?

You go to pick it, and then you see it: blossom end rot.

Blossom end rot usually appears as a brownish, water-soaked spot which gradually increases in size and turns black and leathery. It usually occurs very early in the season and seems to progress with the season.

Blossom end rot is not a disease, but a physiological disorder caused by not enough calcium reaching the blossom end of the fruit.

As a result, the cells in this area die. Blossom end rot is worse after dry spells, as the plant may not have sufficient water to move the calcium to the plant cells.

To control, be sure there is sufficient calcium in the garden soil before planting tomatoes. A soil test can tell you if calcium levels are sufficient. Gardeners who lime their soil on a regular basis are usually not as affected by this condition.

When blossom end rot develops and the calcium supply is approaching the inadequate level, here are some suggestions:

Do not add additional fertilizer containing magnesium, potash, or nitrogen.

Make soil uniformly moist as possible. Apply a heavy watering (one or two inches per square foot), if possible.

Practice timely and uniform watering until soil moisture is restored by natural rainfall.

Avoid disturbing plant roots when cultivating.

Mulch may be used to help maintain a uniform and adequate water supply.

Research has shown that daytime temperatures above 90 degrees Fahrenheit or night temperatures above 70 degrees result in decreased flowering and fruit set.

There is strong evidence that night temperature is the critical factor in setting fruit, with the optimal range being 59-68 degrees. When night temperatures are out of this critical range, fruit set is reduced or absent.

Low temperatures reduce the production and viability of pollen. High temperatures (especially in conjunction with low humidity and moisture) can reduce fruit set because of pollination and-or fertilization failure.

Tomato hornworms are one of the garden’s largest caterpillars at nearly 3 to 4 inches long and about as big around as your little finger. They are green with diagonal white stripes with a black or reddish horn-like protrusion projecting from its rear end, hence hornworm. Don’t worry, it will not sting you.

Tomato hornworms eat your tomato plant stems and leaves and maybe even some of the fruit. They are difficult to see because their protective colorings blend in with the plant.

Most of the damage from the tomato hornworm is usually on the top half of the tomato plant. If you see large black or brown droppings on the plant’s leaves or on the ground around the plant, look hard because there is a tomato hornworm on that plant somewhere.

They are a little easier to spot if you see one with small white larvae attached to its back. They look like rice grains, but they are the larvae of the Braconid wasp which will eventually kill the hornworm.

The wasps are not a threat to humans. Once the parasitic wasp cocoons emerge, they will eat the internal organs of the hornworm, literally eating the caterpillar from the inside out.

They desiccate or dry-up the hornworm, so leave these hornworms on the plant if you choose because they will eventually die. The easiest way to remove them is to simply pick them off by hand. You can then either squash them or put them in a bucket of soapy water.

The Great Allentown Fair, Aug. 28-Sept. 2: Many home gardeners enjoy seeing the fruit, vegetable and flower displays at The Great Allentown Fair. Why not enter your own bounty? Entry deadline is July 29. For a Premium List of entry information: AllentownFairPA.org

“Growing Green” is contributed by Diane Dorn, Lehigh County Extension Office Staff, and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613