Brown spots may be found on leaves, petioles, stem, sepals, and petals of the host plant. The fungus causes seedling blight and head rot disease. On the leaves, the lesions are dark-brown with a paler margin and a yellow halo. At the disease progresses, the size gets increased to about 2-3 cm diameter and eventually coalesce to produce an irregularly shaped lesion, causing blighting and withering of leaves. These will be surrounded by chlorotic zone with the grey-white necrotic center. Spots first appear on the lower leaves and subsequently spreads to middle and upper leaves. On the stems, lesions occur as circular, elongated or striated black spots. On the sepals and petals, the spots are similar to those on the leaves but are smaller (0.5-2 cm diameter) and coalesce. The consequences of infection are blight and defoliation, destruction of the flowers and seed-heads, wilting, cracking of the stem and ultimately death of the plant. Sometimes rotting of flower heads also occurs.
It is caused by fungus Alternaria helianthi. The pathogen survives on seeds and plant residues. The plants are susceptible to infection from the emergence stage to harvesting. The disease extensively spreads under warm, dry weather conditions with periodic rain. Excessive application of nitrogen fertilizers intensifies plant damage.
To enhance the self-cleaning capacity of soils after harvesting the precursor in autumn, it is recommended to apply biological products based on Trichoderma spp. or biological control agents of phytopathogens (Bacillus spp., Pseudomonas spp.).
Always consider an integrated approach with preventive measures and biological treatments, if available. For planting, use seeds treated with fungicides containing thiram, fludioxonil, iprodione (contact fungicides), imazalil, tebuconazole, and flutriafol (systemic fungicides). During the vegetation period, use of formulations containing famoxadon (contact fungicide), cymoxanil (locally systemic fungicide), boscalid, propiconazole, and tebuconazole (systemic fungicide) can control the disease.