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The effect of fruiting on carbon fixation and retention in leaves was monitored by measuring net photosynthesis (Pn) and total non‐structural carbohydrates (TNC) on a seasonal basis on mature fruiting and non‐fruiting sweet cherry trees (Prunus avium L. cv. Bing). Pn was also measured diurnally during stages II and III of fruit development. Pn rates increased to between 18 and 20 mg CO2 dm‐2 h‐1 during stage II of fruit development and were maintained until harvest. Diurnally, Pn increased in the morning to 20 mg CO2 dm‐2 h‐1 and this rate continued until sunset. Leaf carbohydrate levels decreased in both fruiting and non‐fruiting trees beginning at the equivalent of stage II of fruit growth. Carbohydrates were lower in leaves and woody portions of current, 1‐ and 2‐year‐old shoots of fruiting trees. Although differences were found in levels of non‐structural carbohydrates, no differences in Pn were found in fruiting vs non‐fruiting plants on either a seasonal or a diurnal basis. Pn rates in swet cherry in the field were primarily affected by ontogeny and environment and not by sink strength.

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Phytophthora ramorum (Pram) is a pathogen of regulatory concern in the USA, and accurate diagnostics is a key component in the response to potential pathogen outbreaks. Although the molecular diagnostic protocols used in regulatory programs have been evaluated using regulatory samples, to date, no direct comparison of these methods has been analyzed within a nursery setting. A block of 300 camellia plants within a California nursery known to be infested with Pram was simultaneously assayed for visual symptoms, growth medium pH, and moss presence as well as culture isolation and molecular analysis prior to plant destruction. Disease symptoms such as foliar lesions and leaf drop were recorded for each plant prior to foliar and growth medium sampling. All diagnostic assays were highly correlated with one another and disease symptoms, with nested PCR having the best correlation with symptoms, followed by Real-Time PCR then culture. No correlation with disease or diagnostic assays was observed with moss presence or medium pH. Analysis of results allowed diagnostic sensitivity and specificity of the assays to be determined and the performance of each method for diagnosis of Phytophthora spp. or Phytophthora ramorum in camellia tissues and associated potting medium could be compared. Accepted for publication 12 July 2006. Published 16 October 2006.