Enough to Kill...... 2

Nematodes in vineyards

Nematodes are microscopic, worm-like organisms that live in soil. They attack roots of susceptible crops, leading to poor health, reduced productivity and even death. Four groups of nematodes damage grapevines:

                                                         Root-knot nematode (Meloidogyne spp.)

  Root lesion nematode (Pratylenchus spp.)

  Citrus nematode (Tylenchulus spp.)

  Dagger nematode (Xiphinema spp.)

The root-knot nematode is the biggest problem in vineyards and can cause substantial economic loss. Nematodes are widely distributed in most  soils and are particularly prevalent in the sandy soils of the Granite Belt. They are often present in re-plant sites following previous vineyards or other susceptible crops, especially tomatoes. You are likely to have nematodes present if planting a vineyard on land previously used for agriculture. The density of nematode populations correlates with the potential extent of economic loss.

If nematodes are present or are introduced into a vineyard and are left untreated, their numbers will tend to increase by infesting vines and susceptible weeds. DPI&F recommends the use of nematode tolerant rootstocks for all  vineyards because nematodes are widespread in the state’s soils and they are difficult to control in established vineyards.

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Grapevine Leaf Rust (GLR) is a disease of grapevines caused by the wind-borne fungus, Phakopsora euvitis. GLR is common throughout South-East Asia and other parts of the world. In 2001, the disease was detected in Australia for the first time in backyard vines in Darwin in the Northern Territory, and resulted in a National Grapevine Leaf Rust Eradication Program being established. It involved implementation of a quarantine zone, extensive surveys, removal of diseased vines and monitoring of healthy plants, and has been successful in eradicating GLR. Following the Northern Territory detection, surveys were conducted throughout Australia in at-risk rural and urban areas but GLR was not found outside the Darwin area.

Enough to Kill.....

Phylloxera..........?      

Phylloxera (Daktulosphaira vitifolia) is a small aphid-like insect native to north America. Phylloxera spread to Europe and then to many of the grape-growing regions around the world in the late 1800s.

Symptoms and damage

There are several types of phylloxera; those that affect the roots, those that affect the leaves and those that affect both the roots and the leaves.

The initial signs of a possible phylloxera infestation include a small area of weakened vines and showing premature yellowing in an otherwise healthy vineyard. By the time these symptoms show, the insect may have been present for 2-3 years, but at a level that is difficult to detect. The best time to look for phylloxera is when populations are likely to be at their peak during mid to late summer (November to March).

Phylloxera reproduces most successfully on healthy root systems; dead and weakened vines will often have low populations. When searching for a suspected phylloxera infestation in your vineyard, it's best to look for the pest at the border of the damaged area on vines just showing the first signs of decline.

One of the most important on-farm prevention measures is to exclude visitors, vehicles and other equipment from vineyard areas, unless appropriate disinfestation procedures have been observed or plant health certification provided. Signs at the property's entrance outlining the basic biosecurity requirements are helpful in reminding visitors and staff of their obligations.

On-farm prevention

Check that any grape plant, machinery, equipment or grape material from interstate is accompanied by appropriate certification. If a certificate is not provided with the item, don't allow it onto your property and report it to Biosecurity Queensland. Any equipment, machinery or footwear should have soil and vegetation removed before use in your vineyards.

By carefully digging up a number of roots within 50 cm of the soil surface, you can inspect new fleshy growth on fine, feeder roots for galls (small swellings), which result from phylloxera feeding. Root tips infested with phylloxera are often club-shaped or form hooks. Galls may initially be white or yellow, turning brown later. A 10X hand lens or greater will be needed to see the small (0.7 - 1.0 mm), oval-shaped, soft-bodied adults, which can vary in colour from green to brown or orange. A female can lay up to 400 eggs that, when newly deposited, are lemon-yellow, oval, and about twice as long as they are wide. Nymphs resemble adults except they are smaller.

Galls are formed when adult phylloxera lay their eggs into the leaf surface. Evidence of leaf galling may be found on both the upper and lower leaf surface.

                             

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Powdery mildew is caused by the fungus Erisiphe necator. It is endemic in Australia and one of the major fungal diseases infecting grapevines. The disease is characterised by white to ash-grey powdery fungal growth capable of infecting green vine tissue. Severe infection can lead to high crop losses and may also be detrimental to final wine quality. In Queensland, many of the commercial Vitis vinifera varieties are susceptible (particularly verdelho). 

Leaves
Yellow-green blotches (2-10 mm diameter) appear on leaves. Progresses to produce ash-grey to white powdery spores on upper and lower leaf surface. Often confused with downy mildew, which only produces spores on the lower surface of the leaf.

Berries
Produces ash-grey to white spores on immature berries and bunch stalks. Diseased berries may become distorted and split, causing them to shrivel or rot.

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