Late blight and gray mold are important diseases that seriously affect the yield and output value of tomato in spring eel in North China. Early detection and accurate identification are prerequisites for effective prevention and control. The field symptoms often vary with species and environmental conditions, are easily confused with one another, or are confused with other diseases, causing growers to be confused. The symptoms of the two diseases and the precautions for identification are described below in order to provide some incentive for growers. help.
Late blight
Symptoms: The whole growth period, leaves, stems, and fruits can be affected. The damage to leaves and green fruits is serious. The incidence of seedlings usually begins with dark green water-stained lesions on the leaves, and then spreads toward the stems, with dark brown rots near the petiole. As the disease progresses, the base of the young stems is constricted and the plants wilting fold. At the adult stage, the onset of disease progresses from the lower leaf to the upper leaf. The leaf tip and leaf margin begin to produce dark green water-spotted lesions (like water scalding) that gradually turn brown. When the disease is heavy, the leaves of the whole plant dry up; the lesions on the stem are Brown or dark brown water stains, a little sunken; fruit lesions are initially dark green, gradually dark brown to brown (yellow) color, mottled lesions, rough hardened. During the wet period, the white mold layer can be produced at each affected site.
Note: (1) Sometimes leaves lesions appear V-shaped from the tip of the leaf, or when the conditions are not appropriate disease Department dry, can not see the mold layer, in the simple leaves of the disease easily confused with gray mold. (2) When the environmental conditions are particularly suitable, the onset is rapid, and there are no obvious lesions in the leaves, but there are obvious white molds. (3) Simple leaf disease is easily confused with freezing injury, but frost damage occurs from the upper leaves. (4) Improper fertilization can also lead to leaf dryness similar to late blight, which also occurs from the lower leaves, but is evenly distributed throughout the field.
Grey mold
Symptoms: The leaves, stems, flowers, and fruits can be infected, and the incidence of fruit, especially green fruits, is heavier. The incidence of fruit is mostly from the petals, tobras and stigma remaining on the green fruit, spread to the fruit and fruit stalk, and the peel is gray and white and soft-rotated. The diseased fruit is generally rigid and does not fall off; the disease of the leaf begins from the tip or edge of the leaf. The "V" shaped inward expansion, the lesions are brownish, with a dark and light ring pattern or no burrs; the stem infection is a small, water-soaked spot, and later develops into an elliptical or irregular shape. On the surface of the diseased parts, brownish brown mold layer was generated on the surface.
Matters needing attention: (1) In recent years, atypical symptoms known as ghost spots are often seen. The appearance of fruit appears white, green in the middle, and a round spot of 3 to 10 mm in diameter. Occurrence of hard-skinned tomatoes in foreign countries is relatively easy. Confused with ulcer disease, scab disease. (2) The lesions on the leaves vary, with V-shaped, nearly circular, irregular, etc., with or without ridges. (3) mold layer is easy to produce after the onset of disease, but mold layer is sometimes not seen.
According to field symptoms, distribution, combined with meteorology and water and fertilizer management and other factors to make a preliminary diagnosis to help emergency control, but due to the diversity of symptoms, complexity, if necessary, should ask a professional to conduct indoor microscopy to confirm the diagnosis, and then Control measures have been amended.
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