Temperature and Wetness-Duration Requirements for Grape Leaf and Cane Infection by Phomopsis viticola.

In 1998 and 1999, controlled-environment studies were conducted in growth chambers to determine the temperature and wetness-duration parameters required for leaf and cane infection of grape by Phomopsis viticola. Greenhouse-grown 'Catawba' (Vitis labrusca) and 'Seyval' (French hybrid) grapes were inoculated with P. viticola and incubated at constant temperatures of 5, 10, 15, 20, 25, 30, and 35°C and at wetness durations of 5, 10, 15, and 20 h for each temperature. Data from each cultivar were analyzed by nonlinear regression analysis to determine the relationship between disease severity and temperature and wetness duration. A generalized form of the Analytis Beta model was found to provide the best fit to the data. Disease severity on leaves and canes increased with increasing wetness duration at most temperatures. Minimum and maximum temperatures for infection were around 5 and 35.5°C, respectively. Optimum temperatures for leaf and cane infection were between 16 and 20°C. In the 2000 and 2001 growing seasons, the generalized Beta model was validated in 'Catawba' and 'Seyval' vineyards by inoculating vines during natural rain events. Average temperature and hours of wetness for each event and inoculation were recorded and used in the model equation to predict disease severity on leaves and internodes. Correlation coefficients between observed disease severities following field inoculations and predicted disease severities for both cultivars were between 0.71 and 0.81 and always significant (P < 0.01). These results indicate that the model reliably predicted leaf and cane infection on both cultivars over a wide range of wetness durations and temperatures. The model may be useful in developing disease-forecasting systems for Phomopsis cane and leaf spot on grapes.

Effect of Growth Stage on Susceptibility of Grape Berry and Rachis Tissues to Infection by Phomopsis viticola.

Intact 'Seyval' grape clusters in the greenhouse and 'Catawba' clusters in the field were inoculated with conidia of Phomopsis viticola at seven Eichorn-Lorenz growth stages between 12 (prebloom) and 35 (véraison) in 1998. Five pots (10 clusters) were used per inoculation, and the experiment was repeated three times. Also, 10 to 20 randomly selected Catawba clusters were inoculated in the field for each of three replications at each growth stage. Studies were repeated in 1999. In addition, Chambourcin clusters were also inoculated at four growth stages in the greenhouse in 1999. Results obtained in the greenhouse and field during both years and for all cultivars indicate that berry and rachis infections can occur at all growth stages between 12 and 35 with no evidence of decreasing susceptibility over time. Results disagree with some literature reports that indicate that berry infection occurs primarily during bloom and shortly after bloom, and susceptibility decreases as fruit matures.

Effects of an Apple Scab-Resistant Cultivar on Use Patterns of Inorganic and Organic Fungicides and Economics of Disease Control.

An inorganic (sulfur) and a conventional organic fungicide spray program were evaluated on an apple scab-resistant (Liberty) and a scab-susceptible (McIntosh) cultivar for control of scab and for cost effectiveness. Trees of both cultivars were either nontreated, treated with inorganic fungicides only, or treated with a conventional fungicide program. McIntosh trees received full-season fungicide applications and Liberty trees received only the summer cover sprays (after petal fall) for control of summer diseases. In 1991, the number of fungicide applications ranged from 0 for nontreated Liberty to 12 for the full-schedule inorganic program on McIntosh, with both treatments providing excellent scab control. All nontreated McIntosh fruit were unmarketable due to scab infection. Due to a dry growing season and lack of summer disease development, nontreated Liberty fruit was of high quality. In 1992, the number of fungicide applications ranged from 0 for nontreated Liberty to 14 for the full-schedule inorganic treatment on McIntosh, with both treatments providing good to excellent disease control. Results were very similar in 1993. Scab incidence was low for all treatments except the nonsprayed McIntosh over all years. Over 3 years of testing, the conventional fungicide program resulted in an average of 9 and 5 applications per year for McIntosh and Liberty, respectively, compared to 12.6 and 7 applications, respectively, for the inorganic fungicide program. The large reduction in the number of sprays for both programs was due to the elimination of all pre-petal-fall applications on Liberty; post-petal-fall applications are needed to control summer diseases such as flyspeck and sooty blotch. An economic analysis for total cost of fungicide applications for each spray program and cultivar was conducted for hypothetical 4.0-, 8.1- and 16.2-ha farms. Regardless of farm size, the cost of fungicides per ha varied among treatments and cultivars. The inorganic and conventional spray program for McIntosh had similar total costs. On Liberty, the inorganic and conventional programs had 73 and 57% less total cost, respectively, than on McIntosh. Fungicides for the conventional program on Liberty were 1.45 times more costly per ha than fungicides in the inorganic program, but the inorganic program required more applications, resulting in a small difference in total treatment cost per ha.

Reasons why kidneys removed for transplantation are not transplanted in the United States.

The Organ Center establishes by the South-Eastern Organ Procurement Foundation collected information on 575 kidneys procured but not transplanted in the United States. The greatest proportion, 393, were not transplanted because a crossmatch-negative recipient was not found. Of these kidneys, 260 were transported to at least one additional center and 115 were offered to an additional center within 24 hr of removal. In 18 instances, attempts to share kidneys were made too late. The blood group representation of these kidneys was 62% A, 15% B, 12% AB, 11% O. The SEOPF system of crossmatches enabling the donor center to perform crossmatches on immunized recipients from 42 other transplant centers still resulted in the loss of 98 kidneys. However, this loss was half that predicted from the national experience. Rather than discarding them, 272 kidneys were transported overseas where 183 were transplanted. Technical problems related to the deceased, organ size, anatomic abnormalities, expended or nonviable material for tissue typing, and perfusion failure led to discarding 182 kidneys. Only 15 kidneys were reported injured irremediably at the time of removal, while 12 had bacterial contamination. The data emphasize our national problem and demand collaboration and new systems for kidney distribution in recipients of non-O blood groups.

Effects of soil water stress and twospotted spider mites on net photosynthesis and transpiration of apple leaves.

Soil water stress and twospotted spider mites (Tetranychus urticae Koch) were tested for their influence on the content and activity of leaves of greenhouse grown Delicious apple trees. Soil water stress caused reductions in net photosynthesis (Pn), transpiration (Tr), and shoot growth. Leaf water potential was decreased by both water stress and mite feeding. Feeding of 15 adult mites/leaf for 28 days resulted in a 16% reduction in Pn while an initial population of 10 mites leaf/left to develop for 20 days reduced Pn by 27%. Mite feeding reduced leaf nitrogen and non-structural carbohydrate levels when sampled 20 days after placement on the leaf. There was no interaction between the changed physiology of the leaf due to soil water stress and mite feeding.