Paraphoma Crown Rot of Pyrethrum (Tanacetum cinerariifolium).

Pyrethrum (Tanacetum cinerariifolium) is commercially cultivated for the extraction of natural pyrethrin insecticides from the oil glands inside seed. Yield decline has caused significant yield losses in Tasmania during the last decade. A new pathogen of pyrethrum causing crown rot and reduced growth of the plants in yield decline affected fields of northern Tasmania was isolated from necrotic crown tissue and described as Paraphoma vinacea.

Crop Damage from Sclerotinia Crown Rot and Risk Factors in Pyrethrum.

Sclerotinia crown rot, caused by Sclerotinia sclerotiorum and S. minor, is a prevalent disease in pyrethrum fields in Australia. Management involves fungicide applications during the rosette stage of plant development from autumn to early spring in fields approaching first harvest.

Minimizing Crop Damage Through Understanding Relationships Between Pyrethrum Phenology and Ray Blight Disease Severity.

The most damaging foliar disease of pyrethrum in Australia is ray blight caused by Stagonosporopsis tanaceti. The probability of growers incurring economic losses caused by this disease has been substantially reduced by the implementation of a prophylactically applied spring fungicide program. This has been traditionally initiated when 50% of the stems have reached between 5 and 10 cm in height.

Improving Fungicide-Based Management of Ray Blight Disease in Tasmanian Pyrethrum Fields.

Ray blight disease, caused by Phoma ligulicola var. inoxydablis, is a serious threat to the Tasmanian pyrethrum industry. The management of this disease relies upon the strategic application of fungicides in early spring.

Quantifying Loss Caused by Ray Blight Disease in Tasmanian Pyrethrum Fields.

The efficacy of newly implemented fungicide recommendations on reducing the intensity of ray blight disease caused by Phoma ligulicola to achieve site-specific attainable yield potentials in Tasmanian pyrethrum fields was quantified over two seasons in 46 and 51 fields during the 2003 and 2004 growing seasons, respectively. Disease intensity and yield in two plots (10 × 24 m), one following the commercial fungicide protocol recommendations and the second receiving no fungicide, were assessed in each pyrethrum field. The commercial fungicide protocol consisted of one application of azoxystrobin at 150 g a.

Seedborne Infection of Pyrethrum by Phoma ligulicola.

The incidence of Phoma ligulicola in Tasmanian pyrethrum seed and methods of managing seedborne mycoflora were determined. Fourteen different fungi were regularly isolated from seed, including Alternaria tenuissima, Stemphylium botryosum, and P. ligulicola, which have been documented as pathogens of pyrethrum.

Development of a Fungicide-Based Management Strategy for Foliar Disease Caused by Phoma ligulicola in Tasmanian Pyrethrum Fields.

The efficacy of a range of fungicides were assessed under in vitro conditions in four field trials over three seasons for the management of ray blight of pyrethrum, caused by the fungus Phoma ligulicola in Tasmania. Fungicides belonging to the demethylation inhibitor group, including prochloraz, tebuconazole, difenoconazole, and cyproconazole, produced the most significant reduction in mycelial growth in vitro compared with unamended controls. Significant reductions in germination of conidia resulted from low concentrations of azoxystrobin.