Brown Rot Of Stone Fruit Research Articles

Brown rot of stone fruits on the Murrumbidgee Irrigation Areas. I. Aetiology of the disease in canning peaches

In a typical season brown rot development in canning peaches on the Murrumbidgee Irrigation Areas was found to follow a basic pattern. There is little or no blossom blight or post-blossom infection. Infection of fruit is first seen in January and increases until harvest. Infections of fruit during the preharvest period are almost all initiated in injuries. Damage caused by larvae of the oriental fruit moth is the most important form of fruit injury. Infections of injured immature fruits may occur in dry weather and cannot be prevented by the application of fungicides. These injured rotting fruits produce inoculum which can start epiphytotics if rain falls when the fruit is ripe. Blighted blossoms are usually unimportant as inoculum sources at this stage, but they are important links in the infection chain since they can provide inoculum for the first infections of injured fruits. Dried fruit beetles were found to be vectors during the preharvest build-up of the disease, and there was some evidence that they may carry inoculum to blossoms in spring. Quiescent and latent fruit infections initiated in spring were noted, but they are thought to have little overall significance in the aetiology of the disease. Some infections occurring during the ripening period may exhibit latency. The implications of these findings for disease control and their relevance to brown rot aetiology in other, more humid fruit-growing areas are discussed.

Brown rot of stone fruits on the Murrumbidgee Irrigation Areas. II. Aetiology of the disease in Trevatt apricot trees

Blossom blight is of economic importance in apricots on the Murrumbidgee Irrigation Areas (MIA), but fruit rot is not. Monilinia fructicola generally does not overwinter effectively in apricot trees in the MIA, the inocula for primary infections coming from nearby peach plantations. Blighted blossoms in apricot trees, which flower a week before peaches, may provide inoculum for blighting of flowers in the latter crop. In apricot trees, unlike peach, there is a continuous infection chain from flowering till harvest. Inoculum may pass from apricot to peach in December and January, thus bridging a gap in the infection chain in peach. The infection chain in apricot is described. Latent and quiescent infections were observed. The implications of the exchange of inoculum between peach and apricot are discussed.

The dispersal of colidia of Sclerotinia fructicola (Wint.) Rehm.

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.

Sclerotinia laxa Aderh. & Ruhl: A cause of brown rot of stone fruits not previously recorded in Australia

A fungus with the cultural characteristics of Sclerotinia laxa Aderh. & Ruhl. has been determined as a cause of blossom and twig blight and fruit rot of stone fruits in southern Victoria. This is the first report of a brown rot species other than S. fructicola (Wint.) Rehm. occurring in Australia. European plum (Prunus domestica) is the host most severely affected, and there is evidence that the disease has spread from this host to adjacent cherry, peach, and apricot varieties. The distribution of S. laxa appears to be restricted to the Wandin, Tyabb, and Red Hill districts of southern Victoria. S. fructicola also is a cause of blossom blight and fruit rot in these districts, and is the only brown rot fungus which causes losses of stone fruits in the major canning fruit districts of northern Victoria.

A Comparison of the American Brown-Rot Fungus with Sclerotinia fructigena and S. cinerea of Europe

Is the American brown-rot fungus (Scierotinia fructigena) of stone fruits identical with the fungus bearing the same name and occurring throughout Europe, but there found exclusively upon pome fruits? That S. fructigena should occur in Europe only on pome fruits and in this country only on stone fruits appears unusual and to many improbable. If S. cinerea is the fungus attacking stone fruits in Europe, as all the European writers maintain, then the suggestion seems pertinent that our brown rot of stone fruits is caused by the same fungus. In fact, ADERHOLD and RUHLAND (5) assert that our species is S. cinerea. They came to this conclusion after an examination of a few preserved apothecia sent them by NORTON, and in the absence of a more extended study their evidence appears inconclusive. At the suggestion of Professor C. F. HODGE of Clark University, the writer has undertaken a comparative study of these two species. At first it was intended merely as a study in variation, but it soon of necessity became a problem in taxonomy. Our final interest was to determine as nearly as possible which one of the above species agrees more nearly with the rot of our stone fruits.