Lettuces: how to grow plants of the genus Lactuca

Gray mold, caused by the fungus Botrytis cinerea, is a widespread necrotrophic pathogen affecting over 1,400 plant species. It thrives in cool, humid conditions and attacks weakened or aging plant tissues, causing soft rot and characteristic gray fuzzy growth.

Rhizoctonia solani is a soil-borne fungus that attacks stems, roots, and young seedlings. It thrives in warm, humid weather and in soil that stays wet or drains poorly. Typical signs include seedlings collapsing at the soil line (damping-off), sunken brown lesions near the soil on stems, brown rotting roots, wilting even when the soil is moist, and slow, stunted growth. In lawns, it can cause the well-known “brown patch” during warm, humid periods. Many plants are at risk, including vegetables (such as lettuce, beans, and brassicas), ornamentals, houseplants, and turfgrass.

White mold (Sclerotinia sclerotiorum) is a devastating fungal disease affecting over 400 plant species worldwide. The fungus produces black, seed-like structures (sclerotia) that can survive in soil for 5 or more years. The disease is favored by cool, moist weather (50-68°F/10-20°C), especially during flowering.

Calcium deficiency is a common plant disorder caused by insufficient bioavailable calcium in the growing medium or, more frequently, by low transpiration rates that prevent proper calcium transport to new growth. It manifests as necrotic leaf margins, curling of young leaves, stunted growth, and in severe cases, conditions like blossom end rot in fruits. The disorder primarily affects rapidly growing tissues where calcium demand is highest.

Mosaic virus is a group of plant viruses that cause mottled, patchy patterns on leaves and can affect a wide variety of plants. The virus creates characteristic yellow, white, and green mosaic patterns, often accompanied by stunted growth and deformed plant parts. This highly contagious disease spreads rapidly through insect vectors and contaminated tools.