Fall is a great time to do a quick scouting outside the greenhouse for any unusual leaf-mottling symptomology on weeds. The weeds are typically larger and with the heat stress of summer, symptoms are more likely to be noticeable. By taking control measures now, it curtails the possibility of infecting next year's crop.
Outside our greenhouse, there is a large landscape bed with annuals and perennials. It also contains some pokeweed (Phytolacca americana) plants. Pokeweed fruit are a bird's favorite and seeds get dispersed by the droppings. Once established, the perennial pokeweed with its extensive taproot will survive for years. Several pokeweed plants were observed with mottled leaves (Fig. 1). Last year some annuals in the bed also developed virus-like mottling and necrosis. This situation brings up the need to scout for broadleaf, perennial weeds outside the greenhouse and eliminate any potential source for overwintering problems.
We did not test any plants last year and therefore we do not know if the infected
annuals were infected with the two most common greenhouse viruses, Impatiens
Necrotic Spot Virus (INSV) or Tomato Spotted Wilt Virus (TSWV). This year the
pokeweed was tested, and neither of the Agdia ImmunoStrips were positive for INSV
nor TSWV. So the pokeweed has another undetermined virus.
Click here to read the full e-GRO Alert