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Results

Site descriptions

The following describes some of the 24 sites and indicates the abiotic measurements taken. All trials were carried out I 1998.
 

Site 1
This crop was planted in August and soon after establishment had a high plant count (86.4/m2). The incidence of Asteraceae and Compositae weeds was minimal (< 1%) and the majority of plants appeared large and healthy. A small proportion of plants exhibited ray blight symptoms.. Pyrethrum paddocks were less than 50 metres to the north west and approximately 1 km to the east. This crop was positioned on the top of a hill and in an established pyrethrum growing district.. Unfortunately, no soil nutrition information prior to planting was available for this crop.

Site 2 

This crop was planted in October , and soon after establishment plant density was assessed as 29.0/m2. Soil nutrition results from samples taken prior to planting indicated an adequate pH (6.5) and phosphorus (Alson – 52 ppm), marginal levels of potassium (280 ppm), whilst levels of exchangeable calcium and magnesium were adequate.The incidence of Asteraceae and Compositae weeds was approximately 10%, and the majority of species were Sonchus oleraceous and Taraxacum officinale. Pyrethrum paddocks were situated less than 50 metres to the south-west and approximately 500 metres to the north. The paddock was situated in a low lying area with a slight northerly aspect in an established pyrethrum growing district. Disease symptoms included ray blight, leaf and stem lesions, and plant death. Examination of dead plants failed to detect infection by Sclerotinia spp. The majority of plants were medium in size and severely affected by disease (>50%) 

Site .3.
This crop was planted in June and soon after plant density estimates were 36.4/m2. Soil nutrition results from samples taken prior to planting indicated an adequate pH (5.8), low levels of phosphorus (Alson – 13 ppm) and potassium (160 ppm), and adequate levels of exchangeable calcium and magnesium The incidence of Asteraceae and Compositae weeds was low (<5%), and the dominant weed species were Cirsium vulgare and Taraxacum officinale. One paddock of pyrethrum was 200 metres to the north west. This crop was situated on the crest of a hill with a hawthorn and blackberry hedge on the northern and eastern sides. Disease symptoms included leaf and stem lesions, and high levels of ray blight in both small and large plants. The majority of plants were severely affected by disease (>50%). Almost 15% of plants were small and had died from a cause other than infection by Sclerotinia species. No plants at this site were found without some level of disease . 

Site.4.

This crop was planted in August Soon after establishment, plant density was measured at 49.2/m2. Soil nutrition results from samples taken two months prior to planting indicated an adequate pH (6.6), and sufficient levels of phosphorus (Alson – 28 ppm), potassium (360 ppm), and exchangeable calcium and magnesium (Ca:Mg = 14.1). The incidence of Asteraceae and Compositae weeds was minimal (<1%) and the dominant weed species present was Cirsium vulgare. One pyrethrum paddock was immediately adjacent to the north east. This crop was positioned on a moderate slope with a northerly aspect. Low levels of disease were identified, and the majority of symptoms were ray blight. The majority of plants were large and either healthy or had less than 25% of leaf area was diseased.

Site.5

This crop was planted in July and soon after establishment plant density was estimbated at had 31.9/m2. Soil nutrition results from samples taken three months prior to planting indicated an adequate pH (6.7), and adequate levels of phosphorus (Alson – 44 ppm), potassium (330 ppm), and exchangeable calcium and magnesium (Ca:Mg = 9.85) (A. Salardini, pers. comm.). The incidence of Asteraceae and Compositae weeds was minimal (<5%), and the only weed species was Taraxacum officinale and Hypochaeris radicata. This crop was in the centre of an established pyrethrum growing district and established crops were immediately to the north west, less than 500 metres to the south west, approximately one kilometre to the north, and 500 metres to the south east. The paddock was positioned on the crest of a hill with a slight north-westerly aspect. The crop had low levels of disease, and symptoms included leaf and stem lesions, and ray blight. A small proportion of plants were infected by S. minor. Healthy regrowth after slashing in the irrigator runs suggested the majority of damage from fungal infections occurred earlier in the season. All plants were large and disease levels were less than 25%.

Site 8
This crop was planted in October.. Assessments of plant density soon after establishment indicated 33.5 plants/m2. Soil samples taken for nutritional analysis prior to planting indicated an adequate pH (6.2), adequate levels of phosphorus (Alson – 32 ppm), potassium (440 ppm), and exchangeable calcium and magnesium. The incidence of Asteraceae and Compositae weeds was relatively high (approximately 25%) and the dominant weed species were Cirsium vulgare, Taraxacum officinale, Sonchus oleraceous, and Leontodon taraxacoides. This crop was in an established pyrethrum producing area and crops were situated 100 metres to the south east, and approximately two kilometres to the south and north east. The majority of plants were medium in size and over 50% of the foliage was affected by disease. No plants were identified as healthy in any size category Symptoms included leaf and stem lesions and ray blight.

Site 16

This site was planted in October, and soon after plant density was 29.0 plants/m2. Nutritional analysis on soil samples taken four months prior to planting indicated an adequate pH (6.1), very low levels of phosphorus (Alson – 10 ppm), adequate levels of potassium (290 ppm), and exchangeable calcium and magnesium (Ca:Mg = 16.4) The incidence of Asteraceae and Compositae weeds was low (<5%), and the dominant weed species were Sonchus oleraceous, Taraxacum officinale, and Hypochoeris radicata. This crop was on a southerly slope and a dam was also present in the paddock. The nearest established pyrethrum crop was approximately two kilometres to the south west. A high proportion of plants had died from causes other than Sclerotinia spp. Many plants were small or medium in size with over 50% of their foliage affected by stem and leaf lesions. When buds did form they were also affected by ray blight.

Site.18

This crop was planted in September 1998 and soon after plant density was 23.5/m2. Nutritional analysis of soil samples taken two months prior to planting indicated an adequate pH (6.8), phosphorus (Alson – 27 ppm), potassium (360 ppm), and deficient levels of magnesium (Ca:Mg = 3.9). The incidence of Asteraceae and Compositae weeds was approximately 10%, including Senecio vulgaris, Senecio jacobaea, Sonchus oleraceus, and Carduus tenuiflorus. No pyrethrum paddocks were in the vicinity. High levels of dead small and medium size plants, and small and medium size plants with over 50% of the foliage affected by disease were found. No healthy medium and large size plants could be detected. The small proportion of small size plants with no disease symptoms reflected healthy regrowth. Symptoms included stem and leaf lesions, and when buds had formed, they were affected by ray blight.

Site .23
.Nutritional analysis of soil samples prior to planting indicated an adequate pH (6.7), adequate levels of phosphorus (Alson – 32 ppm), potassium (530 ppm), and exchangeable calcium and magnesium No Asteraceae or Compositae weeds were identified at this site. This crop was on a very steep north east facing slope. No pyrethrum paddocks were in the vicinity. Plants were generally large and showed no signs of disease. Disease symptoms included leaf tip necrosis and necrotic stem lesions. Only a very small proportion of plants also exhibited ray blight. Infection by Sclerotinia sclerotiorum was responsible for the small proportion of dead medium size plants. The majority of plants were large in size and less than 25% of the foliage was affected by disease.

The following graphs shows the disease levels of plants assessed in the various categories.

Analysis of results

B) Survey of diseases
Observation
Questions
Experimental Design
Results
  Site descriptions
  Graph results
Analysis of results
  Site Comparisons
  Effect of Fungus
  Association of site factors
  Other factors
Discussion

C) Treatment of Fungal Diseases
Introduction
Observations
Experimental design
Results
Discussion

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