An assessment of fungicides for the control of wilt and dieback caused by phytophthora cinnamomi in container grown chamaecyparis lawsoniana u cultivar ellwoodii
Annals of Applied Biology 94(2): 225-234
In fungitoxicity tests against P. cinnamomi on C. lawsoniana cv. Ellwoodii, a drench of furalaxyl (1000 mg a.i.[active ingredient]/l) applied to the compost in which 1 yr old plants were growing, 1 wk before they were inoculated with 650,000 zoospores, controlled disease for at least 12 mo. With an inoculum dose of 650 zoospores/plant, furalaxyl at 500 mg a.i./l controlled disease even when inoculation was 12 wk after fungicide treatment. Aluminum tris (ethyl phosphonate) (2000 mg a.i./l) applied as a drench 1 wk before inoculation with 650,000 zoospores/plant did not prevent root infection but delayed foliar symptoms for 9 mo.: the same treatment, using etridiazole (500 mg ai.i/l) only slightly reduced disease incidence. When applied as a single drench 2 days before inoculation, prothiocarb (2000 mg a.i./l) and cuprammonium compounds (200 mg a.i./l) were much less effective than furalaxyl (1200 mg a.i./l), sodium ethyl phosphonate (1500 mg a.i./l), aluminum tris (ethyl phosphonate) (1500 mg a.i./l) or etridazole (500 mg a.i./l). However, a drench of furalaxyl at 1000 mg a.i./l, aluminum tris (ethyl phosphonate) at 2000 mg a.i./l or etridiazole at 500 mg a.i./l did not eradicate P. cinnamomi from compost containing infected root debris. Pre-planting drenching of the compost was ineffective. All fungicide treatments were non-phytotoxic to 1 yr old C. lawsoniana cv. Ellwoodii. These results are of special relevance to the control of P. cinnamomi on container-grown woody ornamentals.