Wednesday, October 28, 2009

Powdery mildew has been found - UPDATE 28/10/2009

The first signs of Powdery Mildew for Vintage 2010.
The first signs of Powdery mildew have been seen in the last 10 days.So far these have been minor, however small Powdery mildew infections before flowering can turning into large problems at harvest.

Powdery mildew doesn’t need rain to spread - mild temperatures (20 – 29oC) & cloudy conditions favour the disease. In these conditions powdery rapidly produces spores and spreads on to unprotected leaves and bunches.

Be careful this season as weather conditions this spring have been favourable to the disease. Based on what we have seen in vineyards we feel Powdery mildew pressure is higher than last season.

Powdery has been found in two commercially monitored blocks, one block has a history of the disease, the other has been very clean up until now. The good news in most vineyards no Powdery has been found. On blocks with a bad history of disease, where growers have been running good protective spray plans for a few season vineyards the vineyards seem clean.

Powdery mildew prevention has effects over many seasons. Good control last season makes control easier this season. Good control this season makes future control easier by reducing the amount of disease that survives winter in the vineyard.

No Downy mildew - UPDATE 28/10/2009

Downy mildew needs rain to start its lifecycle.

No rain = no downy.

Weather conditions for the next week are not predicted to be favourable to Downy Mildew.

Monday, October 26, 2009

Junk Bugs - Predators in your vineyard.

Richard McGeachy has photographed these Junk Bugs. Junk Bugs are predatory insects found in your vineyard. They are the larval stage of Lacewings.

Lacewings go through complete metamorphosis (egg, larva, pupa, adult) and have at least two generations per year. The life cycle takes about 4 weeks depending on temperature. A female Lacewing can deposit over 200 eggs. In 4 to 5 days, the eggs will hatch into small junk bug larvae.

Lacewing larvae are brownish and can have dark reddish-brown stripes and spots (as shown).

They have large jaws for grasping prey and injecting a paralyzing venom. Lacewing larvae, sometimes called aphid lions, typically feed on soft-bodied insects such as aphids, mealy bugs, thrips, and Light Brown Apple Moth. The larvae develop three instars in to 3 weeks, and are 9.5 mm long when full grown. Larvae will spin a silken pale cocoon that is loosely attached to foliage. During the pupal stage they develop wings and reproductive organs.

After 5 to 7 days the adult will emerge from the cocoon and begin to mate. Adult lacewings have chewing mouthparts, are about 18-19 mm long, and feed mostly on nectar and pollen. They can survive for about 5 to 6 weeks.

Thursday, October 22, 2009

Vine Stress & Poor Nutrition.

Over the last three weeks many vineyards have not been growing through the wet weather. Also they have shown symptoms of nutrient deficiency including iron as shown by pale leaves (above).

The reason for this slow growth and poor nutrition is a lack of root growth.

Talking with Stoller USA agronomist - Guillermo de la Borda he offer the following advice.

As a rough rule of thumb if your vines shoots are not growing neither are your vine roots. Vine roots pick up the nutrients for growth at this time of the year.

Several stress events which limited vine growth have occurred in including;

- Hail damage
- Wind damage
- Salinity
- Cold soils.

All of these stresses upset the vines hormone production and normal growth. Waterlogging and cold soils slow down root growth. Physical damage including hail, wind and frost cause the plant hormone Ethylene to be produced. Ethylene interferes with the plants growth hormones Auxin, Cytokinin and Gibberellic Acid. With an imbalance of these growth hormones root growth is stunted, this in turn stunts shoot growth.

Many growers apply fertiliser to improve shoot growth, but without active root growth the vines will not pick up the fertiliser and growth will not improve.

The good news is, as vines experience good weather, they should grow out of this ‘stress damage’ and grow new roots on their own accord.

See Stoller's frost recovery programme here.

Friday, October 16, 2009

Leaf Botrytis - UPDATE 16/10/2009

Botrytis seen on leaves, shoots and inflorescences this week. Pictured bottom is severe hail damage in Blewitt Springs.

No Downy mildew 10:10:24 a near miss - UPDATE 16/10/2009

CropWatch McLaren Vale and CropWatch Adelaide Hills report the weather was not suitable for Downy mildew this week.

In McLaren Vale windy conditions assisted in drying vineyards out creating conditions that stopped the 24 hours of leaf wetness that Downy mildew needs to start its lifecycle. While Downy mildew can survive short gaps of leaf wetness, the computer disease models shows the canopy dried out enough to halt the Downy.

Analysis of the weather data shows that the Adelaide Hills has had a near miss for a 10:10:24 Downy Primary Event.

Fortunately overnight temperatures were less than 10oC on the wet nights of the 12th/13th, 13th/14th and 14th/15th. High wind speeds also aided drying out canopies and breaking the 24 hours of leaf wetness Downy mildew needs.

Wednesday, October 14, 2009

Grapevine Nutritional Deficiencies

Due to a cold and wet start many vineyards have been slow to grow. Vineyards on black cracking clays (Biscay Soils) have a naturally high fertility. In most seasons vines are healthy and yields are good. Sometimes, due to the alkaline limestone rock underneath, grapevines can have some nutritional problems but these are generally fixed once the weather warms up.

Look out for these symptoms particularly if your vineyard is on heavy black clay.
Currently in the vineyard nutritional disorders are easily seen on this soil type including Magnesium as shown (upper and lower left).

Above and Below: Iron Deficiency shows up as pale leaves.

Thursday, October 8, 2009

CropWatch Adelaide Hills

Adelaide Hills Crop Watch 091009

Rust Mite - UPDATE 8/10/2009

Rust mite are slowing down some vineyards and restricting early shoot growth. This damage seems to be the most severe in blocks that were pruned late this season.

This is seen as shoots with slow and perhaps stunted shoot growth with distorted leaves. It is too late for spraying to be effective this season. The stunting effects of Rust Mite are limited by the application of Sulfur at bud-burst.

With warm weather and good growing conditions, these any distorted shoots will begin to grow normally and the damage becomes difficult to detect by flowering.

Blister Mite- UPDATE 8/10/2009

Some blister mite have been seen in monitored vineyards this week.

Friday, October 2, 2009

Light Brown Apple Moth - UPDATE 2/10/2009

The first signs of the second Light Brown Apple Moth generation have been seen this week. Lookout for their eggs. Egg Masses are not easy to see because they appear clear. These take a few weeks to hatch.

At first the grubs (caterpillars) are found only in leaves but will begin to move into bunches when flowering begins.

Pay close attention to you vineyard if you have had LBAM problems in the past. Where present, the grubs feed for a week or two before moving during flowering to feed on bunches. If you detect larvae on more than 10% of shoots, it may be necessary to apply an insecticide such as BT’s, Mimic®, Prodigy®,Avatar®, Proclaim®, Entrust® or Success2® during the flowering period.