Potato fungicides11/29/2023 Tuber infection results in small black pits forming on the tuber surface. Tuber symptoms of brown leaf spot are commonly referred to as Black Pit. alternata may infect tubers late in the season or during harvest. As they grow, surrounding tissue becomes chlorotic, and lesions turn brown and disintegrate, causing leaf edges to curl up. Brown leaf spot lesions are not restricted by large veins. Severe infection of foliage by the early to mid-bulking period can result in smaller tubers, yield loss and lower tuber dry matter content.įigure 2. Severely infected leaves eventually wither and die but usually remain attached to the plant (Fig. Elongated, superficial brown or black lesions may also form on stems and petioles. Furthermore, as the lesions coalesce, they are not restricted by large veins as in early blight and the whole leaf may become chlorotic, with infected areas turning brown and disintegrating, causing the edges of the leaf to roll up (Fig. However, brown leaf spot lesions never develop the dark, alternating concentric rings characteristic of early blight. On young leaves, lesions may be confused with those of early blight, which are also small, circular lesions initially. Brown leaf spot can occur throughout the growing season and is usually seen before early blight. Symptomsįoliar lesions appear as small, irregular to circular, dark brown spots on lower leaves, and range in size from a pinpoint to 1/8 inch (Fig. Spots range in size from a pinpoint to 1/8 inch. Brown leaf spot lesions first appear as small, irregular to circular dark brown spots on lower leaves. In Michigan, intensive fungicide treatment has restricted losses to less than 5 percent.įigure 1. Though losses rarely exceed 20 percent, if left uncontrolled, the disease can be very destructive. This is reflected by the fact that leaf lesions are usually smaller and darker in color than early blight lesions. The fungus is considered to be a weak pathogen. The disease occurs over a wide range of climatic conditions and disease severity depends in large part on the frequency of foliage wetting from rainfall, fog, dew or irrigation, on the nutritional status of foliage and on cultivar susceptibility. Although it occurs annually to some degree in most production areas, the timing of its appearance and the rate of disease progress help determine the impact on the potato crop. solani) and the two pathogens are closely related. It is often confused with early blight (caused by A. Brown leaf spot is a very common disease of potato that is found in most potato-growing areas.
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