Pasmo

a serious infectious disease of flax, caused by the fungus Septoria linicola. It was first discovered in Argentina in 1911. Pasmo, which is common in many countries, appears sporadically in the USSR in the Far East, Krasnodar Krai, Rostov Oblast, and the Crimea.

Brownish spots with black dots—pycnidia (the spore-bearing organs of the fungus)—appear on the leaves during flowering; the spots later appear on the stems, buds, and fruits. Severely infected plants are entirely covered with spots, and their leaves, buds, and pods wither and fall. The quality of the fiber and the yield of seed from an infected plant decrease drastically. The causative agent of pasmo reproduces by means of spores, which are spread during the vegetative period by wind, rain, and insects. The spores retain their viability through the winter and sprout in the spring, forming infectious hyphae that penetrate the healthy plant tissues. Pasmo occurs most often in moist places and lowlands when the air temperature is relatively high (about 21°C). Infected seeds and the remains of diseased plants in the soil may be sources of infection.

Control measures include multiple-field crop rotation, in which the flax is cultivated in a given field once every six or seven years. Quarantine measures should be implemented, and the seeds and soil should be treated with fungicides.