Pea Wilt: Field Identification and Varietal Resistance

New Zealand Journal of Agriculture, Volume 84, Issue 2, 15 February 1952, Page 144

Pea Wilt: Field Identification and Varietal Resistance

PEA WILT (Fusarium orthoceras Appel and Wollenw. var. pisi Linford) was first recorded in the United States of America by Linford in 1928 as a major disease of peas. Though the disease was first recognised in New Zealand in 1948 (I), the present distribution and amount of infection indicate that it has probably been present in the older pea-growing districts for at least 10 years. I. A. M. Cruickshank, Plant . Diseases, Division, Department of Scientific and Industrial Research, Christchurch, here describes the disease and gives the names of resistant and susceptible varieties of peas.

CROP surveys over the last 3 seasons (1948-51) have shown that pea wilt is a serious disease in North Canterbury and Blenheim. The most serious losses were observed in the Marshland-Belfast-Harewood and the Taitapu-Lincoln-Southbridge districts. Smaller losses were seen in the Rangiora district and in Blenheim. Field Symptoms Pea wilt appears in crops, at any stage of growth up to flowering, as circular patches' of brown, dead pea vines scattered through the crop. The patches may vary in diameter from a few feet to several yards, depending on the amount and distribution of infection in the soil. When crops of peas have been grown repeatedly in infected fields and soil infection has become, general complete crops may be destroyed.

Close examination of infected plants at different stages of disease development reveals at first recurving of the tips of younger stipules and margins of leaflets. This is followed by downward curling of leaflets upon their main vein, so that leaves assume a tightly rolled appearance. Stem and leaves are at first covered with a dull bloom. Later they lose their colour, becoming rigid while the joints of the leaflets become brittle. The vascular system of stem and root is commonly discoloured orange or brick red. No externally visible lesions occur on either stem or root, but the lower internodes of stems are usually greater in diameter than those of healthy plants. Infected plants turn pale, ■ yellowish green at first and death follows rapidly. Some diseased plants may reach the flowering stage, but very few set seed. Influence of Environment Soil temperature: Moderate soil temperatures are favourable for wilt development. The optimum temperature is 18 to 22 degrees C. (2) .

Soil moisture: Wet soils favour early development of symptoms, but drier soils favour the rapid death of infected plants (2). Soil reaction: Alkaline soils, pH 8.0, are most favourable to wilt development (3) ; however, the disease can also be severe in acid soils, as indicated by the serious losses due to wilt in the peat soils of the Marshland district near Christchurch, which have a pH of 5.2 to 5.4. Dissemination and Survival Transmission of wilt within the seed has been demonstrated (3). However, contamination of the surface of the seed is of more importance. Infected soil may also be spread by such means as cultivation practices, on farm implements, or by animals. Once wilt has been introduced into a field it spreads within the soil when peas are being grown and also when the field is fallow or in some other crop. The disease survives indefinitely m soil; a wide rotation merely-slows down its rate of spread. . . ' Resistance of Varieties Over the last 3 years trials have been carried out with local and imported varieties of peas to determine their resistance or susceptibility to local isolates of pea wilt. The results are as follows: Garden Varieties Resistant: Alderman, Bliss Everbearing, Climax, Director, English Wonder, Epicure, Giant Aiderman, Giant Stride, Glaciator, Hurricane, Kelvedon . Standby, Kelvedon Triumph, Laxton’s. Progress, Lord Chancellor, Major, Morse’s Market, Multipod, Progress, Quartermaster, Queen, Stratagem, Triumph, Yorkshire Hero. ■ Susceptible: Autocrat, Blue Bantam, Cambridge . Multipod, Charles I, Churchill, Confidence, Coronation, Duplex, Exquisite, First and Best, Foremost, Gladiator, Greencrop, Greenfeast, Hursthouse, Kelvedon Monarch, Kelvedon Paragon, Laxton’s Superb, Little Gem, Little Marvel, Meteor, Miracle, Onward, Phenomenon, Pilot, Pioneer, President Wilson, Radium, Spitfire, Superb, Thomas Laxton, Veitche’s Perfection, V.C., W. F. ' Massey, Wando, Witham Wonder.

Field Varieties Resistant: Blue Prussian, Gruno, Hala, Harrison’s Glory, Helios, Mammoth White, Marathon, Vinco, White Canada, Zelka I, Zelka 11. Susceptible: Austrian Winter, Conserve, Mammoth Blue, Mansholt, Parel, Partridge, Rondo I, Rondo 11, Unica, Victoria. Canning Varieties Resistant: Canner’s King, Canner’s Perfection, Commando 2685, Deep Green Perfection, Delwiche Commando, Delwiche 21, Early Badger, Horal, Merit, Penin, Perfected Whales, Perfection, Wisconsin Early Sweet, Wisconsin Perfection. Susceptible: Alaska, Canner’s Queen, Early Perfection. Sugar Varieties Resistant: Dwarf White Sugar, Mammoth Melting Sugar, Melting Sugar.. Control Measures 1. Seed for resowing should not be taken from diseased crops. 2. Before being sown seed should be treated with a certified fungicidal seed dressing, that is, a dressing which has been tested by the Plant Diseases Division, • Department of Scientific and Industrial Research, and found satisfactory. A list of certified therapeutants is published biannually. 3. Crop refuse should be destroyed. 4. A crop rotation of 4 to 5 years should be practised to slow down spread. 5. Fields known to be infected with pea wilt should be sown only with wilt-resistant varieties. References 1. “New Zealand Journal of Science- and Technology”, vol. 33, No. 4A, pp. 75-80, “Pea Wilt'in New Zealand”, I. A. M. Cruickshank (1951). 2. University' of.- Wisconsin Agricultural Experiment Station'Research Bulletin No. ■ 85, “A Fusarium Wilt of Peas in Wisconsin”, by M. B. Linford (1928). 3. University of Minnesota Agricultural Experiment Station Technical Bulletin No. 89, “A Study of Diseases of Canning Crops (Peas and Corn) in Minnesota”, by G. H. Starr (1932).