The effect of five rootstock cultivars and two pruning methods with two crop loads each on Botrytis cinerea Pers. rot of Vi tis vinifera L. cv. Chenin blanc was investigated. The effect of these factors on bunch compactness, berry skin strength, pedicel strength, total soluble solids and nitrogen content of berries was also investigated to determine the correlation between these parameters and botrytis rot. The most rot occurred with Chenin blanc on Ramsey, 110 Richter and 101-14 Mgt when spur pruned, while the least rot occurred with Chenin blanc on 99 Richter when cane pruned. Rootstock cultivar had a significant effect on bunch compactness, berry skin strength, pedicel strength, cane mass and crop mass while rootstock cultivar and pruning method had a significant effect on total nitrogen and total soluble solids of berries. Except for bunch compactness none of the other parameters appear to have any direct effect on botrytis rot. Control of bunch rot of grapes caused by Botrytis cine-rea Pers. is achieved mainly by chemical means. This is an expensive operation; the total cost in South Africa for wine and table grapes is estimated at R2,0 million per season. As a result of the rise in cost of chemical control as well as the fact that strains of B. cinerea resistant to some of the fungicides have occurred, it is unlikely that practical control of botrytis bunch rot can be achieved by the use of fungicides alone. It is known that many cultivation practices which are likely to increase vine vigour, e.g. excessive nitrogen fertilisation, vigorous rootstocks and irrigation, will increase the susceptibility of grapes to B. cinerea (Bra-nas, 1960; Champagnol, 1969; Delas, 1972; Dry & Smart, 1982). Christensen (1981) found that by increasing the number of nodes per vine from 40 to 60 in the case of Chenin blanc, a significant decrease in botrytis bunch rot occurred. Practical experience in European viticultural areas has shown that choice of rootstock and scion cultivar as well as fertiliser application level, are very important factors with regard to control of bot-rytis bunch rot (Dry & Smart, 1982). The present study was carried out to determine the effect of certain cultivation practices, viz. the use of certain rootstock cultivars, pruning method and crop load on the incidence of botrytis rot of Chenin blanc. The effect of these factors on bunch compactness, as well as pedicel strength, berry skin strength, nitrogen and sugar content of berries was also evaluated in order to determine if a relation exists between these parameters and botrytis bunch rot. MATERIALS AND METHODS A fourteen-year-old vineyard at Robertson, consisting of five rootstock cul ti vars viz. Ramsey, 99 Richter, 110 Richter, 101-14 Mgt and Jacquez with Chenin blanc as scion, was used in this study. Vines were trellised ac'cording to the Perold system as described by Zeeman (1981). A randomized block design in which each rootstock cultivar was replicated four times was used. Each plot consisted of four rows with seven vines per row. Two prunin...

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Boron-arsenic and boron-phosphorus films have been grown on Si, sapphire, and silicon-on-sapphire (SOS) by pyrolyzing Group III alkyls of boron, i.e., trimethylborane (TMB) and triethylborane (TEB), in the presence of AsH3 and PH3, respectively, in a H2 atmosphere. No evidence for reaction between the alkyls and the hydrides on mixing at room temperature was found. The films were predominantly amorphous. The film growth rate was found to depend on the concentration of alkyl boron compound and was essentially constant when TEB and AsH3 were pyrolyzed over the temperature range 550~176The films were found to contain mainly carbon impurities (the amount varying with growth temperature), some oxygen, and were highly stressed and bowed on Si substrates, with some crazing evident in thin (2 ~tm) B-P and thick (5 ~m) B-As films. The carbon level was generally higher in films grown using TEB as the boron source. Films grown from PH3 and TMB showed a higher carbon content than those grown from AsH3 and TMB. Based on their B/As and B/P ratios, films with nominal compositions B,2 ~6As2 and Bl.l-l.3P were grown using TMB as the boron source.

Single-spore colonies of Diplodia natolensis P. Evans originating from individual pycnidia were compared with each other and with those from different pycnidia from the same grape cane, different canes from the same vineyard, and different vineyards, to evaluate the natural range in variation and stability of taxonomic characters currently used to delimit this species. Distinct colony types were recognized-in some cases as many as four originating from an individual pycnidium. Colony type per se is not considered to be useful for taxonomic purposes. Results suggest that several genera now recognized in this group are congeneric, and indicate a great need for determination of the inherent variation that these fungi are capable of exhibiting.

Little leaf of gra.pevines is corrected by applying zinc to the vine (1, 2,3,4,5,6 RESEARCH EXPERIMIENT 1: A dlormant cane was prepared and the amount of water in the vessels of a 1.5-m section was determined by sucking the water out into a trap with a vacuum. This section of grape cane yielded 3.5 ml of water by this method. A 1-ml aliquot of the low activity Zn65SO4 solution was diluted to 4 ml with distilled water and placed in the glass tubing attached to the base of another cane. This amount of solution would just approximately displace the solution in the cane. The tip of this cane was cut off at 1.62 m andl the solution allowed to flow through it. The exudate, 3.8 ml in all, was collected in 1 ml lots and examined for radiation. The cane was then pushed through a cylindrical sample chamber having 5.7 cm thick lead walls for radioactivity measurements (Tracer Laboratory). The Geiger-MIuller tube was an end-on type having a thin mica window of 2.54 cm diameter (Tracer Laboratory), and of about 1.8 mg/cm2. The