Phylloxera - A problem or an opportunity?

4 February, 2008

Mart Verstappen, Corbans Viticulture

The destruction to New Zealand vineyards by phylloxera has once again been raised when Corbans Viticulture inspected a Central Otago vineyard towards the end of 2007 for possible infestation of this insect. This is not the first time that phylloxera has been found in the region but it highlights the spread and destruction of this insect in vineyards that have not been grafted onto phylloxera-resistant rootstock. By the time symptoms of vine decline are noticed, the vines may have been infested for up to two years or longer.

International studies have shown that up to 20 per cent of production can be lost in the first year of phylloxera infestation, with vines becoming uneconomic within three to 10 years of infestation.

Phylloxera attacks and feeds on the root system of Vitis Vinifera vines, destroying the root system and therefore preventing the uptake of moisture and nutrients. Due to this root degradation, it provides an entry site for the infestation of fungal diseases. It is often these diseases that cause more damage to the vine rather than the insect itself.

The yellow aphid feeds on vine roots and leaves and it is this feeding that causes galls to form on the roots and/or leaves. The aphid lives on the surface of these root galls or inside the leaf galls. Above the ground symptoms of phylloxera include weak shoot growth, premature yellowing of autumn foliage and a general decline in apparent vine health.

Fig.1 Phylloxera eggs and aphid on a vine root

The most reliable way to identify phylloxera is to examine roots for evidence of root galls. The best time for identification is between December and April when this insect is actively breeding.

Table 1. Seasonal development of Phylloxera

Phylloxera is mainly spread through soil particles present on machinery, cars and footwear.

So how damaging is this insect to New Zealand’s clean, green image and our reputation as a supplier of world class wines? And how can we rectify the problem to ensure grape growers and vineyard owners maximize profitability of their vineyard?

Step one involves acknowledging the problem:

• How severe is the problem – a few vines or an acre?
• How quickly is the infestation spreading?
• How much production may be lost and what is the potential impact to the bottom line?

Identifying these issues provides an array of opportunities to the vineyard owner:

• The selection of new and/or better clonal material
• Appropriate selection of phylloxera resistant rootstock best suited for the site (to manage vigour, bud burst and to assist in maturity dates)
• The selection of other varieties and clones in response to market demand.
• Possible redesign of irrigation systems and trellis reconstruction

In the short-term and until a replanting programme has been decided, minimising spread can be assisted through the:

• Quarantine of the infected area and vineyard
• Minimal use of machinery
• Minimising stress on the vine, laying less canes, managing the potential crop and providing a foliar feed
• Ensure only clean machinery enters and leaves the vineyard

The only way to manage this pest is to ensure that the grapevine varieties planted are grafted on phylloxera resistant rootstock.

Corbans Viticulture through their Total Vineyard Solutions consultancy service offers expert advice on selection of the best rootstocks for your vineyard. For more information please contact Mart Verstappen mart@corbansviticulture.co.nz or 0274 413 714.