A blackish spot develops on the bottom of my tomato fruit. What is the problem and how can it be prevented?
Blossom end rot is probably responsible for the blackish spot on the tomato fruit. Blossom end rot is a common problem on tomatoes. Blossom end rot appears as a brownish black spot on the blossom end of the fruit. Secondary organisms invade the affected area, causing the fruit to rot. Blossom end rot is most common on the earliest maturing fruit.
Blossom end rot is a physiological disorder caused by a calcium deficiency in the developing fruit. Wide fluctuations in soil moisture levels impair calcium uptake by the root system. Excessive nitrogen fertilization may also contribute to blossom end rot.
To reduce blossom end rot, water tomato plants on a weekly basis during dry weather to supply a consistent supply of moisture to the plants. Mulch the area around the tomato plants to conserve soil moisture. Avoid over-fertilization. Adding calcium to the soil is ineffective.
Pick and discard fruit affected with blossom end rot. The removal of the affected fruit will allow the tomato plant to channel all of its resources into the growth and development of the remaining fruit.
Blossom end rot may also occur on peppers and summer squash.
How can I tell when to harvest my watermelons?
Harvest watermelons when the underside of the melon (portion resting on the ground) turns from a greenish white to a buttery yellow or cream. This color change is especially pronounced on the dark-skinned varieties. In addition, the remaining portion of the fruit loses its slick appearance and becomes dull when ripe.
Several flowers on my purple coneflower are green and badly distorted. What is the problem? The purple coneflower probably has aster yellows. Aster yellows is a disease caused by a bacterium-like organism called a phytoplasma. Phytoplasmas live in the phloem or food conducting tissue of living plants. The disease is spread from plant to plant by leafhoppers.
Aster yellows affects a wide range of annuals and perennials. Susceptible plants include purple coneflower, monarda, aster, chrysanthemum, marigold, snapdragon, zinnia, tomato, squash and others. Symptoms of aster yellows include yellow foliage, stunted growth, proliferation of short stunted shoots and green leaf-like flower parts.
Plants infected with aster yellows can not be cured. Plants that exhibit symptoms should be removed from the garden. The prompt removal of infected plants will hopefully prevent leafhoppers from transmitting the disease to other plants.
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