Sooty Mould in Olive Trees

At this stage of the season black olive scale can be seen on olive trees. The adult females are very easy to recognise on the olive tree stems. They are dome shaped dark black in colour and 2-5mm in size. Note also the co-responding sooty mould. 

Olive black scale and co-responding sooty mould.

During spring use copper fungicides to reduce the amount of sooty mould.

At this point of the season scale are dormant underneath their protective shell where they lay egg.

During the December and January cream coloured 'crawlers' hatch from these eggs and move up the stems. They usually settle along the veins of  young leaves. At this stage they don't have the impervious shell of the adult and can usually be killed with one or two applications of insecticidal oil about two weeks apart. It puts an oil film over the young 'crawler' and suffocates it. 

Spray oil during December to stop the crawlers.

If the crawlers are allowed to live, they will moult after about one month and then migrate to the young stems and twigs of the tree. Here they will mature and lay more eggs and their protective brown shells will be impervious to sprays.

Olive black scale. Squash the scale between your fingers to see if it is alive. If it is alive, then your fingers will be wet from the juices squeezed out. If it is dead  then your fingers will be dry and dusty.

Bad infestations of live mature scale may need spraying with an insecticide.

As the scale feeds they excrete is a sweet, sticky, 'honeydew'. A  fungus known as sooty mould feeds on this food and multiplies until the entire tree may be covered with the black sooty mould.

The leaves are coated with the black deposit so the sun's light can't  penetrate the leaves properly. Therefore photosynthesis can't take place efficiently. This results in a stunted  and unhealthy tree with poor crops.

To make the problem worse, sweet 'honeydew' on the leaves also attracts large  numbers of ants. Ants constantly move over the scale, they frighten away the small wasp parasites which in normal cases would  keep the scale under control. 

The good news is that healthy olive trees don't get the scale, sooty mould and ant infestation to any great extent. More good news is that heavily infested  trees are easily fixed.

Map of CropWatch Weather Stations

the 2017/18 CropWatch season is beginning. These are the approximate locations for Langhorne Creek & McLaren Vale, with the BOM & NRM weather locations for Kuitpo, Currency Creek and Noarlunga.

Rust Mite Spray Timings

Rust Mite levels were seen to be significant in some vineyards last season. Rust mite are microscopic mites that enter into grapevine buds during early spring and affect the growth of early season shoots.

The significant level of Rust Mite’s last spring has made us re-think our recommendation regarding Rust Mite control. It is likely that a high percentage of vineyards monitored last season will benefit from a controlling sulphur spray.

We have been advising our clients regarding whether they should apply a controlling sulphur spray, or not for this season. If you would like specific advise please contact DJ’s.

Recommendations for prevention of Rust Mite symptoms are:

When Rust Mite symptoms in spring are stunted & uneven shoot growth.

• Application of wettable sulphur @ 500g/100lt (include non ionic wetter at label rate if not adding oil).

• Water rates of 600 – 900 lt of water per hectare - do not use less than 500 lt/ha - increased water rate should be used if worried about coverage.

• Make sure coverage of the cordon and all spur wood is thorough.

• Inclusion of Canola oil or Mineral oil at 2% (2lt per 100 lt) may improve control (10-15%) but should only be applied if the variety being sprayed is fully dormant (eg. Cabernet). Need to be aware that some Canola oils may contain GMO’s.

• A period of 2-3 fine days and 15 degrees C or higher on the day of spraying is ideal.

• Chardonnay is the indicator variety for timing of spraying in each region. Spraying should be done on all varieties when Chardonnay reaches 10% green tip (ie most buds woolly bud). Look for services like McLaren Vale CropWatch to advise of this timing.

McLaren Vale - Valley Floor.

Our feelings are that spraying should occur from the last week of August to the end of the second week of September on all varieties/blocks that require rust mite treatment.


Currency Creek & Langhorne Creek.
Spraying should occur from the last week of August to the end of the second week of September on all varieties/blocks that require rust mite treatment.

Blewitt Springs & Clarendon.

Spraying should occur from the first week of September to the end of the third week of September on all varieties/blocks that require rust mite treatment.

Adelaide Hills.

Mid-September through to the end of September. To get ideal timing find a block of Chardonnay in within your mesoclimate for exact timing.

Rust Mite symptoms in spring, cv. Cabernet Sauvignon, Blewitt Springs McLaren Vale GI. 

Bud Dissection Q&A

Hi, 

I am curious about looking at grapevine buds under the microscope. Could you also please let me know how many buds you can dissect in an hour, as I have a uni project to do on yield analysis and the number would be of assistance.

Many thanks, Andrew

Dear Andrew,

Almost anyone can learn to dissect buds, but not everyone has the patience to sit down and complete many samples. We use a compound microscope with to eye lenses that give a stereoscopic view of the inside of the bud.  This allows us to assess the internal bud structure and look at the inflorescence primordia which are the structures that develop into grapevine flowers.

Bud Dissection.

We would average two to three buds a minute, therefore it takes us between one and one and half hours to complete a vineyard (30x; 5x bud canes).  We would generally limit ourselves to three vineyards per day to keep our eyes fresh.

 

The time it takes to dissect buds under a microscope varies from variety to variety. Sauvignon Blanc has small buds and small inflorescences which make it the slowest variety to assess. Grenache has large buds and large inflorescences which are the quickest to assess.

Low bud fruitfulness and high primary bud necrosis is linked to vigourous vineyards.

 

Internal bud structure.

We perform dissections to look for low fruitfulness and assess the level of primary bud necrosis.

If we find problems with fruitfulness eg. levels below 1 bunch per bud (inflorescence primordia per bud), or high levels of bud death from primary bud necrosis, we advise growers to change their pruning in the short term and look at their management in the long term.

It is when you find blocks like these bud dissections come into their own as a vineyard tool.

DJ's agronomist Matthew Wilson says,  

"Vineyards with high levels of lateral shoot growth can show low levels of fruitfulness. Primary bud necrosis is often common in vigorous vines and this is contributing to low fruitfulness. If you can catch this before pruning you can take action to prevent correspondingly low yields at harvest."

Primary Bud Necrosis (PBN) note how the centre bud has died but the two secondary buds are viable. This would indicate that secondary buds will burst in place of the larger primary bud.

For more information refer to bud dissection and primary bud necrosis.

Assessing Vineyard Canopies

James Hook shows Assessment of Vineyard Performance cv. Shiraz to predict grape quality. 

Vintage 2017 Summary

2017 Vintage seasonal summary with James Hook.

Vineyard Update: Grapevine fungal diseases in 2016/17

James Hook on fungal disease identification. Vintage 2017. 

Downy Mildew explained in less than 5 minutes.

James Hook explains a Downy Mildew Primary Event 10:10:24 event in laypersons terms.