Potted grapevines of 140 Ruggeri (Vitis berlandieri × Vitis rupestris), a good Cl(-) excluder, and K 51-40 (Vitis champinii × Vitis riparia 'Gloire'), a poor Cl(-) excluder, and of a family obtained by crossing the two genotypes, were used to examine the inheritance of Cl(-) exclusion. Rooted leaves were then used to further investigate the mechanism for Cl(-) exclusion in 140 Ruggeri. In both ...

Leaves were sampled from Vitis labruscana Bailey cv. ‘Niagara’ and the interspecific hybrid ‘DeChaunac’ grapevines several times during a 2-year investigation of leaf area estimation. Linear measurements of leaf length and width were made and correlated with leaf area measurements made with a computerized image processing system. For each cultivar, nine regression equations were derived and com...

• Flower formation in grapevines follows 3 steps: 1) formation of uncommitted primordia, also called anlagen, within the latent buds; 2) differentiation of uncommitted primordia into inflorescence primordia; and 3) differentiation of inflorescence primordia into individual flowers . Steps 1 and 2 happen during the previous season, whereas Step 3 does not happen until budbreak of the current sea...

Concord grape (Vitis labrusca) plants were inoculated with Macroposthonia xenoplax at levels of 100, 1,000, and 10,000 nematodes. After 4 months, plants inoculated with 10,000 M. xenoplax were stunted, and root systems were darker and had fewer feeder roots than those in other treatments. The lower nematode inoculation levels suppressed top growth but did not affect root growth. M. xenoplax rep...

Three Cryptosporiopsis species have thus far been isolated from roots of woody plants. A fourth species, which was recently isolated from roots of Calluna vulgaris, Erica tetralix, Vaccinium vitis-idaea, and V. myrtillus in The Netherlands, is described here as new. Sporulation on the natural substratum has not been observed and the morphological description of this fungus is therefore based on...

Xylella fastidiosa (Xf) is the causal agent of Pierce’s disease in grapevines. The mechanisms of pathogenicity are largely due to occlusion of xylem vessels by aggregation of Xf and biofilm formation. Our previous work has documented the effects of xylem constituents on both Xf proliferation and biofilm formation. This current research utilizes 1) addition of xylem constituents to defined media...

The leafhopper Scaphoideus titanus is the vector of 'Candidatus Phytoplasma vitis', the causal agent of Flavescence dorée (FD) a key disease for European viticulture. In organic vineyards, the control of S. titanus relies mostly on the use of pyrethrins that have suboptimal efficacy. During 2016, three field trials were conducted to evaluate the efficacy of kaolin, orange oil, insecticidal soap...