Effects of Pratylenchus vulnus and Xiphinema index singly and combined on vine growth of Vitis vinifera.

Inoculation of 'Thompson Seedless' grapevines with 500 Xiphinerna index or 1,000 Pratylenchus vulnus alone or in combination suppressed vine shoot and root growth under greenhouse conditions. Pratytenchus vulnus caused greater stunting of roots than X. index. Each nematode species inhibited top growth about equally. Concomitant inoculations caused greater stunting of tops and roots than did inoculations of either nematode species alone. Differences in growth between inoculated and control plants increased with exposure time. Pratylenchus vulnus competed with and gradually superseded in numbers an established population of X. index. Both species reproduced on 'Thompson Seedless' roots, but P. vulnus increased to a much higher level than did X. index. The increase of P. vulnus, together with extensive damage, proves its pathogenicity to grapevines.