T. V. Price

Stemphylium leaf blight of garlic (Allium sativum) in Australia

Stemphylium vesicarium was isolated from lesions on garlic (Allium sativum) leaves showing purple leaf blotch symptoms in commercial garlic farms at Tenterfield, New South Wales in 1994 and at Waikerie, South Australia in 1997 where an epidemic occurred. This is the first record of S. vesicarium on garlic in Australia. Isolates of S. vesicarium from garlic were pathogenic on onions and leeks. Disease incidence at Waikerie, on three commercially grown garlic cultivars, was 100% with severity of 10–30% leaf area diseased 1 week before harvest. The disease epidemic was influenced by prolonged periods (≥8h) of leafwetness. Most airborne conidia (950/m3) of S. vesicarium were trapped between 1100 and 1500 h. Under the same epidemic conditions five out of 26 garlic accessions grown in seed plots showed good resistance to stemphylium leaf blight.

Duration of control of stripe rust of wheat with foliar sprays

The duration of control (days after spraying that the mean percent leaf area affected remained less than 5%) of stripe rust of wheat with a single foliar spray of either propiconazole or triadimefon on wheat cultivars differing in susceptibility to the disease was determined. Both chemicals were equally effective, giving control for 21 days on susceptible cultivars (Avocet, Zenith, Halberd), 30 days on Olympic (moderately susceptible — moderately resistant) and 54 days on moderately resistant Condor.

Epidemiology of blind seed disease in perennial ryegrass (Lolium perenne) in Victoria

The epidemiology of blind seed disease (caused by Gloeotinia temulenta) of perennial ryegrass (Lolium perenne) and the relationships between disease incidence, apothecial populations, seed development, fertilisation and environmental conditions were investigated on commercial seed growers’ properties at Birregurra in southern Victoria and Mansfield in northern Victoria between 1987 and 1990. Mycelial growth of G. temulenta in culture was highest at 20C, while under controlled environmental conditions infection of L. perenne by G. temulenta was highest at 15C and declined at higher temperatures. Anthesis occurred from mid-to-late November in 1988, 1989 and 1990. Tissues were most susceptible at and just after anthesis and the proportion of available susceptible seeds over time followed a polynomial pattern in both fertilised and unfertilised plots. In 1987, the incidence of blind seed disease increased from <1% at anthesis to 86% at harvest. Apothecial numbers peaked on 18 November, 9 November and 8 November in 1988, 1989 and 1990, respectively. Nitrogen fertilisation significantly (P < 0.001) reduced the incidence of blind seed disease in irrigated plots. Blind seed incidence increased exponentially over the period 7–16 December 1988, and was significantly correlated (P < 0.01, R2 > 81%) with average daily mean temperature and cumulative rainfall over the preceding 7 days. In 1989, disease incidence was low (<15%). In 1990, disease incidence was significantly correlated (r = 80.2, P < 0.05) with average mean daily temperature. The monomolecular and Gompertz models gave the best fits of disease progress curves in 1987, 1988 and 1989 (R2 > 80%, P < 0.01). Spatial analysis indicated blind seed disease was randomly distributed through the 1990 crop. This work indicated that disease prediction models for blind seed disease should include the proportion of susceptible seed available, apothecial populations, and environmental conditions.

Victorian vegetable growers’ estimates of the incidence of downy mildew on brassica crops, crop losses and fungicidal control

Victorian vegetable growers were surveyed by mail-out questionnaires to quantify the importance of brassica downy mildew in 1992. Of the 59 respondents, 41 (70%) grew brassicas principally in Bairnsdale, Berwick, Cranbourne and Werribee shires. The main crops were cauliflowers, cabbage and broccoli. In 1992, downy mildew was reported by 78% of seedling producers and by 30% of growers. Downy mildew was considered more detrimental (moderate to serious) in the field (84%) than by seedling producers (50%), although all nurserymen ranked it as a serious problem and considered that more studies of it are required. Downy mildew occurred throughout the year and was most prevalent between July and October. Disease incidence was greatest in the shadehouse, although there was also a high incidence in the field. Fungicidal control was used by 66% of growers and most (74%) alternated their fungicides. Dithane was the most commonly used fungicide (85%), but mancozeb, other protectants, acylalanines and phosphonates were also used. The survey suggested growers required more guidelines on fungicide spraying frequency and application techniques. Problems with inadequate fungicide control were reported as early as 1970 and occurred mostly in the shadehouse with copper-based protectants, dithiocarbamates and acylalanines.

The effects of water stress on the incidence and severity of paspalum leaf blight and on Ascochyta paspali

The incidence and severity of paspalum leaf blight (PLB) and yield of infected plants in soil cores subjected to water stress under different irrigation and fertiliser regimes, and the effects of water potential on germination and growth of Ascochyta paspali, were investigated. Symptoms of PLB were produced more rapidly when paspalum plants infected with A. paspali were subjected to water stress, and disease severity (per cent diseased dry matter) was significantly higher in water-stressed plants compared to those subjected to basal or flood irrigation. The addition of NPK fertiliser had no effect on PLB incidence or severity but dry matter yields of uninoculated plants were significantly increased compared to inoculated plants. Yields of inoculated fertilised plants also differed significantly between irrigation treatments. Germination and growth in vitro of A. paspali declined at water potentials below −1.2 MPa and ceased at -4 MPa. Sporulation was inhibited at −1.9 MPa. The results indicate that pastures affected by PLB need to be well irrigated and fertilised to alleviate the loss of dry matter production caused by this disease.

Production of microsclerotia by Microdochium panattonianum

Microsclerotia of M. panattonianum were produced on cellophane sheets placed on potato-dextrose agar, corn-meal agar, water agar and purified agar, as well as directly on malt-extract agar, nutrient-pectin-cellulose agar and pectin-cellulose agar. The microsclerotia were 35–65 μm in diameter and composed of pseudoparenchymatous tissue of textura angularis and globulosa type. Microsclerotia were not observed in sections of unabscissed and abscissed anthracnose lesions on lettuce leaves.

Studies on fungicidal control of lettuce anthracnose

Fifteen fungicides, some recently developed, were screened for control of lettuce anthracnose under glasshouse and field conditions. Mancozeb, thiram, captafol and cupric hydroxide showed good protectant activity under glasshouse conditions, while flutriafol was the only fungicide that exhibited significant systemic activity. The best material overall was prochloraz Mn which exhibited protectant and translaminar activity, decreased field disease expression and increased yields. Prochloraz Mn and hexaconazole are recommended for further evaluation.

Lettuce anthracnose in Victoria: use of Field Runner to analyse spatial pattern of disease

The incidence and distribution of lettuce anthracnose (Microdochium panattonianum) was monitored at three sites at Werribee South, Victoria, in 1985 by means of Field Runner, a stratified random sampling program, installed on a portable microcomputer. The incidence on cv. Winterlake increased from 6.1% on 11 August to 25.5% on 9 September; the incidence on cv. Black Velvet increased from 5.3% on 20 August to 19.1% on 2 September. Disease severity on the majority of infected plants was light (1–30 lesions plant −1). The variance/mean ratios, Lloyd’s indices, K parameter of the negative binomial and Z scores measured by Field Runner confirmed that lettuce anthracnose was aggregated both within the fields and within rows and indicated epidemics commence from focal points. Field Runner was found to be a useful tool that allowed singlehanded assessment and analysis of disease incidence, severity, distribution in the field and monitoring of disease epidemics.

Dr Maurice Vernon Carter– plant pathologist and epidemiologist, 1926–2014

Dr Maurice Vernon Carter (Fig.1) was born at Victor Harbor in South Australia on 20 March 1926. He attended Scotch College, Adelaide as a boarder from 1935 to 1944 following which he enlisted with the RAAF as a Radio Operator, and was stationed at Wilson’s Promontory, Victoria and on an island north of Darwin, before being discharged in 1946. He then spent 2 years on the family farm in Western Victoria before enrolling at the University of Adelaide and graduating with a Bachelor of Agricultural Science degree with Honours in 1952. He then worked at CSIRO in Canberra for 2 years before joining the Waite Agricultural Research Institute of the University of Adelaide in 1953 as a Research Officer in the Department of Plant Pathology, and was appointed a lecturer in 1956. Maurice Carter’s early research concentrated on genes for resistance to barley powdery mildew (Pugsley and Carter 1953). In 1960 he spent a sabbatical leave at Rothamsted Experimental Station in the UK where he was greatly influenced by the expertise of Drs Philip Gregory FRS and Jim Hirst FRS on aerial and splash dispersal of fungal pathogens and worked with them on the development of spore trapping devices (Carter 1961). Maurice pioneered the use of spore traps to study the epidemiology of ascochyta blight in peas. This work contributed greatly to an understanding of the epidemiology of the disease. He established the pattern of ascospore release by Mycosphaerella pinodes (Carter 1961, 1963; Carter and Moller 1961), was promoted to Senior Lecturer in 1963 and was awarded a PhD for his work by the University of Adelaide in 1964. He contributed to the development of the Burkard Seven Day Recording Volumetric Spore Trap and the Burkard Quadruple Ascospore Liberation Tunnels. These traps are routinely used around the world by epidemiologists studying aerobiology, including collecting ascospores liberated from Mycosphaerella pathogens of eucalypt leaves. He built an open circuit wind tunnel to observe the liberation, dispersal and deposition of uredospores of prune and snapdragon rusts (Carter et al. 1970a, b) as well as spores of various fungal pathogens causing barley scald and leaf spotting of tree, ornamental and vegetable crops, and was responsible for establishing a Hirst spore trap at the South Australian Fig. 1 Portrait of Maurice Carter

Obituary: Professor H. R. Wallace—distinguished nematologist and plant pathologist 1924–2011

H.R. (Harry) Wallace was born on 12 September 1924, inLancashire, England. During World War II, he served in theRoyal Navy. Hesubsequentlytrained as azoologist andthenstudied wood-boring beetles for his Ph.D., which he re-ceived from the University of Liverpool. In 1952, he joinedthe School of Agriculture at the University of Cambridgeand began working on nematodes, studying seasonal emer-gence and the effects of soil structure, particularly aeration,on hatching in Heterodera schachtii. Whilst at Cambridge,Harry Wallace had extensive discussions with Sir JamesGray, Professor of Zoology, which led to his work onlocomotion in nematodes, commencing soon after he movedto Rothamsted Experimental Station (now RothamstedResearch) in 1955. However, Harry Wallace also contin-ued to investigate the effects of environmental factors onhatching and infectivity of juveniles, including attractionto roots, particularly in Heterodera spp. and Ditylenchusdipsaci. For some of these studies he worked collaborativelywith Audrey Shepherd and Jack Hesling. At Rothamsted healso supervised Cliff Blake’s Ph.D. project on Ditylenchus.In 1960, he was awarded a D.Sc. from the University ofLiverpool.In 1962, Professor W.R. (Buddy) Rogers visited Roth-amsted and encouraged Harry Wallace to move to Australia.He arrived at the then new CSIRO Division of Horticulturein Adelaide, where Alan Bird was already employed, in1963. There as Chief Scientist he concentrated his effortson Meloidogyne javanica and continued his work on envi-ronmental factors affecting movement of infective juveniles,studying the development, hatching and survival of eggs.He also became interested in factors affecting reproductionof M. javanica, and the effects of the nematode on its hosts.Seymour Van Gundy (University of California, Riverside,CA, USA) spent a sabbatical with Harry Wallace andAlan Bird in 1966, and collaborated with them on astudyofageingandstarvationinjuvenilesofM.javanicaandTylenchulus semipenetrans .In 1971, Harry Wallace was appointed to the Chair ofPlant Pathology at the Waite Institute, The University ofAdelaide. Whilst this meant he had to make contributions toundergraduate teaching and an increased administrative load(and hence less personal time for research), it also meantthat he had Ph.D. students and that he could broaden hisresearch interests. He continued his work on root-knot nem-atode and its effects on photosynthesis and nutrient demandin host plants. One major study, with Brian Stynes, involvedthe use of a synoptic approach to assess the relative impor-tance of various environmental factors on the growth andyield of plants. With Frances Reay he investigated thesusceptibility to and effects of M. javanica on various nativeplants and investigated the biodiversity of nematodes asso-ciated with the Australian bush.