My dhan nursery and young plants have many small brown spots shaped like a sesame seed, and the older leaves look pale and weak.
3 Answers
Many small oval reddish brown spots the size of a sesame seed, especially on a pale weak looking crop, point to brown spot, a disease that often shows up when the plants are stressed or short of nutrients, particularly on poor or sandy soils. Unlike blast, the spots are more rounded with a brown centre rather than spindle shaped with a grey centre, but please confirm with a photo to your KVK or agri officer. Because brown spot is closely linked to poor plant nutrition, the first step is to correct the deficiency: get the field or nursery soil checked and apply the balanced nutrients your officer recommends, as potassium and micronutrients are often involved. Use healthy certified seed with a seed treatment for the next nursery. If the disease is severe on the standing crop, fungicide actives such as mancozeb may be advised, but follow the label dose, the pre-harvest interval and the local KVK recommendation. Fixing the underlying nutrition usually makes the biggest difference with brown spot.
In my poor sandy plot this was bad until I corrected the nutrition as advised. The new growth came much cleaner.
Soil testing showed my field was low in potash. After correcting it the brown spots reduced a lot the next season.