Burnley where he undertook research in a range of problems in commercial agricultural and horticultural crops.He always insisted that research

Effect of Soil Moisture on Decline of Pinus radiata

The longevity of conidia of S. fructicola was determined in an orchard environment. Less than 1 % of conidia remained viable after exposure or 8 days in the tree canopy. In addition to reducing viability, exposure reduced both germ tube length and infection of mature fruit. Conidia prepared in a suspension in sterile water, to simulate those that are dispersed in rain, lost viability more rapidly on exposure than conidia that remained dry. When conidia were in contact with unsterilized soil for 24 hr they also lost viability.

The dispersal of conidia of Sclerotinia fructicola (Wint.) Rehm. was studied in a peach orchard and in the laboratory, with the use of traps for water-borne spores and an automatic volumetric spore trap. In the orchard, little aerial dispersal was detected by using a trap less than 10 ft from the nearest trees, but large numbers of spores were dispersed by rain falling on sporulating blossoms. In the laboratory, splash droplets from a drop of water falling onto a sporulating fruit or glass slide dusted with conidia were recorded at distances of up to 36 cm. More than two-thirds of the droplets contained spores, the numbers ranging from 3 to more than 7000 per droplet. Aerial dispersal was detected in the laboratory when sporulating peach fruits were placed 3 ft from the volumetric trap. Dispersal was greatest at minimum humidities and maximum air temperatures. The results of the experiments suggest that splash dispersal is more important than aerial dispersal of conidia of S. fructicola in the epidemiology of brown rot of stone fruits.

An infection of immature peach and apricot fruits by Sclerotinia fructicola (Wint.) Rehm. is described. Since infection results in macroscopically visible lesions it is proposed that this type of infection be known as "quiescent" rather than latent. Symptoms have been induced in immature apricots by inoculation with conidia of the fungus and, after a period of quiescence, progressive rots developed from such infections as the fruit ripened. The fungus was re-isolated from surface-sterilized material bearing quiescent infections. Cultural evidence, together with field observations, indicate that a quiescent infection occurs naturally in the orchard, particularly in a season of moderate to severe blossom infection. Fruit losses during a dry harvest period are ascribed in the main to the activation of quiescent infections during fruit ripening. The histology of the lesion is described. The response of the host to infection is variable, but always includes a more or less extensive collapse and necrosis of the epidermis and of one or more layers of the hypodermis. Periderm formation may be associated with the necrogenic reaction. The results of a spray trial demonstrate that some measure of control of quiescent infection can be achieved by applying eradicant sprays during blossoming, and thus provide circumstantial evidence that a proportion of such infections can be established during this period. The quiescent infection is compared with other host-pathogen combinations in which infection is followed by a period of latency or quiescence, and suggestions are put forward as to the factors governing quiescence. The concept of "latent contamination" is re-evaluated in the light of the evidence presented in the present paper. It is argued that conidia alighting on the fruit surface during the growing period are more likely to give rise to a quiescent infection than to survive to produce an infection of the ripe fruit.