downy mildew of lettuce

africa agricultural agriculture agriculturer agronomy algeria are attacked bacteria blight branch bremia chlorosis color conidia country countryside covered curling disease downy feed field foliar food fungi fungus gall green horticulture lactucae leaf leaves legume lettuce line mediterranean microogranims mildew mycelium natural nature necrosis new north oomycete pannosa pathogen pathogens pattern phytopathology plant podosphaera powder powdery reprezenting rose roses seen stem tissue vegetables white wilt wilting zoospores