Leaf yellowing
Older leaf~ Normal for bottom leaves to yellow and drop as plant ages
Plant becomes yellow and stunted: small nodules cover roots- ..... reduce the impact of nematodes on vegetable plants.
Root knot nematode~ Plant becomes yellow and stunted: small nodules cover roots-
Verticillium~Leaves yellow, wilt and curl upward
Fusarium wilt~Slow yellowing of foliage; wilting of upper leaves
Aphids~Chlorosis and leaf drop from severe infestations
Whitefly ~Small, transparent oval insects on leaf undersides. Tiny, white
insects fly up when plant is disturbed
Spider mites~Yellow stippling; leaves may appear dirty on undersides
Nitrogen deficiency~Lower leaves yellow
Magdropnesium deficiency ~Interveinal chlorosis of lower leaves
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A majority of diseases in plants are caused by fungi. Some examples commonly encountered in home gardens and landscape trees are: brown rot of cherries, apple scab, black spot of rose, snapdragon rust, corn smut, powdery mildew of rose, peach leaf curl, sycamore anthracnose, early blight of
potato, Verticillium wilt of tomato, damping-off, and root rot of vegetables.
Plant Disease Terms
Curly top/leaf curl/leaf roll—Rolling and curling of leaves and growing point (curly top of sugarbeet, tomato, bean, etc.; peach leaf curl; potato leaf roll).
Root knots—Swelling and deformation of roots (tomato root knot).
Blight—Rapid death of leaves and other plant parts (fire blight of apple, early blight of tomato).
Use of Disease-Resistant Cultivars
Where available, use of disease-resistant cultivars is the most cost-effective, safe, easy, and environmentally desirable option for the gardener. In fact, for some diseases (such as curly top of tomato), resistant cultivars offer the only practical control option available. Varieties resistant to one or more
diseases are available in several vegetables and fruits (e.g., tomato cultivars with resistance to Fusarium wilt, Verticillium wilt, nematodes, and tomato mosaic virus; and apple cultivars resistant to fire blight).
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Bacterial spot
Leaf spots can be caused by either bacteria or fungi. They come in a variety of colors, shapes, and sizes. Leaf spots caused by bacteria has a water-soaked appearance. Fungi cause leaf spots with a small black dot in the center. One of the most common leaf spots encountered in the garden is a bacterial leaf spot, which is 1/16 to one inch in diameter and dark to tan in color. Crop rotation will help to discourage the problem. Also, select treated seed or resistant varieties. Remove any infected leaves promptly and apply Maneb or chlorothalonil fungicides. An organic approach is to dust the leaves with lime.
Blossom end rot
Tomatoes are the most commonly affected plant of blossom end rot, but the problem can happen to other plants as well. The blossom end of the fruit will become brown when the fruit is one third to one half mature. The affected area of the fruit may become depressed or concave. Blossom end rot is basically a deficiency of calcium. Too much or too little water is what causes the plant not to acquire the proper amount of calcium. Also, too much nitrogen fertilizer can cause the plant to grow too fast and not get the calcium that it needs.
Bacterial spot
Leaf spots can be caused by either bacteria or fungi. They come in a variety of colors, shapes, and sizes. Leaf spots caused by bacteria has a water-soaked appearance. Fungi cause leaf spots with a small black dot in the center. One of the most common leaf spots encountered in the garden is a bacterial leaf spot, which is 1/16 to one inch in diameter and dark to tan in color. Crop rotation will help to discourage the problem. Also, select treated seed or resistant varieties. Remove any infected leaves promptly and apply Maneb or chlorothalonil fungicides. An organic approach is to dust the leaves with lime.
Blossom end rot
Tomatoes are the most commonly affected plant of blossom end rot, but the problem can happen to other plants as well. The blossom end of the fruit will become brown when the fruit is one third to one half mature. The affected area of the fruit may become depressed or concave. Blossom end rot is basically a deficiency of calcium. Too much or too little water is what causes the plant not to acquire the proper amount of calcium. Also, too much nitrogen fertilizer can cause the plant to grow too fast and not get the calcium that it needs.
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