Pests & Diseases of Grapevines in Marlborough, N.Z.

A tool for Pest and Disease Monitoring.

1. Fungi.

1.1. Powdery mildew Uncinula necator (syn. Erysiphe necator).

flag shoot

The disease Powdery mildew originates from inoculum that overwinters in infected buds. Flag shoots carrying the disease are produced in the spring and subsequently infect adjacent tissue. Flag shoots can be identified by their stunted growth and cupped leaves which are coated with a film of grey mycelium.

powdery on leaf

Powdery mildew spreads onto grapevine leaves in the late spring. The light grey spots of mycelium can be hard to detect.

p0wdery 0n berries

Powdery mildew spreads slowly but will infect bunches if not treated. Early symptoms on grapevine berries can be difficult to detect.

bad mildew

Very bad Powdery mildew.

1.2 Phomopsis Phomopsis viticola and Black Spot Elsino ampelina

phomopsis

Phomopsis is a fungal disease that can occur during wet weather in the spring. Symptons are small, dark spots with yellow halos on the basal leaves, black fissures and cracking on basal internodes and bleaching and black scaring on canes from the previous season.

blackspot

Black spot is caused by the the fungal organism Elsinoe ampelina. Similar to Phomopsis the disease spreads during wet spring weather.Shoot and leaf symptoms are also similar, however cankers on shoots are more severe and leaf spots lack the distinctive yellow halo characteristic of Phomopsis infection.

1.3 Botrytis Bunch Rot Botrytis cinerea.

botrytis

Botrytis bunch rot caused by the fungus Botrytis cinerea is the most damaging of all grapevine diseases. Assessment of the disease's severity can be subjective and difficult: visit www.bunchrot.co.nz to view the BRAT- Bunch Rot Assessment Trainer.

spor

Botrytis cinerea spores survive over winter on rachis left behind after harvest.

bot on rachis

Botrytis rot can occur early in the season on dammaged tissue on young shoots and rachis.

bot

Botrytis bunch rot at bunch closure.

1.4 Trunk diseases.

E lata

Eutypa dieback is caused by the infection of vine xylem vessels by the pathogen Eutypa lata. The spores of the fungus spread in rainy conditions and often invade recent pruning wounds.

Symptons are dieback along cordon (Dead arm), devigoured shoots with leaves with downward cupping plus chlorotic and necrotic margins and wedge shaped zones of dead wood in trunks or cordons.

black goo

Other trunk diseases found in Marlborough vineyards are Petrie Vine Decline (Phaeoacremonium spp.), Black Foot (Cylindrocarpon spp.) and Botryosphaeria Dieback (Botryosphaeria spp.).

 

2. Pests.

2.1 Erinose mite Colomerus vitis.

mite

Erinose mite is also known as Blister mite. Infested foliage can be identified by the presence of blister like galls on the upper surface of the vine leaf.

rear mite

The mites colonise the underside of emerging leaves and the white, furry, basal zones of the galls are caused by enlarged leaf hairs.

2.2 Mealy bug Pseudococcus longspinus

M bug

Longtailed mealy bugs in Pinot noir cluster. These sap sucking insects excrete honeydew which leads to the growth of black sooty mould which has the potential to reduce the value of the grape crop. More significantly the organism is a vector for Grapevine Leafroll -associated Virus Type-3. (GLRaV-3).

m bug debris

Colonies of Mealy bug under the bark can be identified by the presence of white webbing. With warm temperatures in summer Mealy bugs migrate into the grapevine foliage and then into the grape clusters.

2.3 Grass grub beetle Costelytra zelandica.

beatle

Brown beetles are the adult stage of the New Zealand grass grub. They emerge from the soil at night in late October/early November and can cause extensive damage to grapevine foliage, especially around the edges of the vineyard.

beetle on inflorescence

Brown beetles can damage inflorescences also.

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3. Bacteria and Viruses.

virus p noir

Pinot noir vine with symptoms of Grapevine Leafroll -associated Virus Type -3. Note the red interveinal zone and downward cupping of leaves.

virus_chardonnay

GVL-aV-3 in Chardonnay. Symptoms are not as distinctive as in red grape varieties: there is a bronzing of the lamina and doward cupping of the leaf margin.

yellow virus

Symptoms of the Yellow speckle viroid in Pinot blanc.

fanleaf

Yellow mosaic symptons of Fanleaf virus in pinot noir.

crown gall

 

 

Causal organisam for Crown gall is the bacterium Agrobacterium vitis. The disease is usually transmitted from infected rootstock, however the bacteria can be tranmitted from an infected vine to an adjacent one through the soil. Galls develope on the roots and lower trunk area of infected vines.