Cause Although both Rhizoctonia solani (teleomorph: Thanatephorus sp.) and Cladosporium sp. have been associated with affected leaves, the causal agent has not been determined. The disease is severe in the 'Jade' variety.
Symptoms Symptoms generally are not noticeable until late in the growing season when sprouts are quite mature. The first symptoms are small, black lesions, which, with high humidity and warm weather, rapidly expand and coalesce, completely rotting outer leaves on the bottom sprouts. The entire leaf tissue of the infected sprouts may rot, yet the main stalk, stem, and core of each sprout do not become diseased. Rotted leaves do not fall from the plant and remain rather tough and pliable until badly invaded by secondary organisms.
Cultural control Avoid 'Jade', and plant current varieties that have a more open growth habit.
Biological control Efficacy unknown in the Pacific Northwest.
- Double Nickel LC at 0.5 to 4.5 pints/A on 3- to 10-day intervals. Can be applied the day of harvest. 4-hr reentry. O
Reference Siemer, S.R., Vaughan, E.K., and Newburg, W. 1971. Studies on the cause of basal sprout rot in 'Jade' variety Brussels sprouts. Plant Disease Reporter 55:297-301.