The Dispersal of Phylloxera Crawlers and Spread of Phylloxera Infestations in New Zealand and Australian Vineyards

Abstract

The dispersal of phylloxera crawlers and alates, the rate of spread of phylloxera infestations, and the pattern of vine decline were studied over three to four years in New Zealand and Australian vineyards. Emergence patterns of crawlers and alates were similar in both countries with a peak in February/March. The crawler stage was trapped on the trunk, canes, and leaves of vines and recovered from a grape harvester, demonstrating the potential for dispersal on machinery. Crawlers were also taken in traps after wind dispersal, up to 20 m from the nearest vine, illustrating the capacity for dispersal by wind. Repeated systematic sampling of three vineyards in New Zealand and one in Australia showed rapid increases in the proportion of sampled vines infested with phylloxera, with an annual increase in the number of infested vines ranging from 1.2x to 3.8x. Patterns of spread consistent with wind dispersal were noted in some vineyards. Measurements of spread showed that within-vineyard phylloxera migration of 15 to 27 m per year occurred, but distances of up to 100 m may be covered. Decline in vine health in New Zealand vineyards was very slow. Less than five percent of vines had depressed vigor in one vineyard where over ninety percent of vines were infested with phylloxera. In contrast, vines in the Australian vineyard showed a decline in vigor one year after infestation and were usually uneconomic in the second year. The significance of those findings on spread of phylloxera infestations to areas with large contiguous plantings of ungrafted Vitis vinifera vines is discussed.