Disease modelling and alerts

Downy Mildew Infection Check List

 

GrowCare Downy Mildew Infection Check List:

 

Primary Infection Check List:

 

Primary Infection
(Click right-hand tick-boxes only if answer is ‘Yes’).

 

The vines were unprotected ie not sprayed with a pre-infection fungicide in recent days?
This time will vary depending on the stage of season you are in: eg 5-7 days when growth is rapid and at flowering or 7-10 days until berries are pea-size.

Rainfall of more than 3 mm if soil was wet before the rain, or at least 5mm if soil was dry?

 

Temperature is above 10°C?

 

Oospore germination has begun

 

Soil continuously wet to at least 2 cm depth for at least 16 hrs?
- this means the palm of your hand is wetted when placed on the soil surface.

Soil did not dry for more than 3 consecutive hours?

Temperature remains above 8°C?

 

Oospores have germinated

 

Some rain fell after the 16th hour and leaves were wetted?

Zoospores have splashed and drifted to the foliage

 

The leaves then remained wet for 450C-hrs?
ie for at least 2 hr 15min at 20°C, or 3 hrs at 15°C, or 4.5 hrs at 10°C

 

All tick boxes are Yes?

 

If ‘Yes’, then Primary Infection is likely...

(see note below 1).

 

       ... and primary oilspots are expected in the next 5-7 days if the weather is warm (20-25°C) or in 10-14 days if the weather is cooler or hotter.

 

Is it at or near flowering and are berries less than pea-size?

 

If 'Yes'...

       ... apply a post-infection fungicide (eg Ridomil) before the new oilspots appear.

[These oilspots will be one or two every 50 m or so along the vineyard row - not easy to locate. If you find any, tag the spot!]

 

1  Please Note: This check list only provides a guide as to whether infection has occurred or not. It should not be relied upon when determining vineyard management actions. If needed seek expert advice on the complex interactions between the vine, the weather, the downy mildew organism and any previous spray cover you may have applied. All these factors determine if infection actually occurred or not.

 


 

 Secondary Infection Check List:

Secondary Infection
(Click right-hand tick-boxes only if answer is ‘Yes’).

 

Active oilspots are present in my vineyard?

 

The vines were unprotected ie not sprayed with a pre-infection fungicide in recent days?
This time will vary depending on the stage of season you are in: eg 5-7 days when growth is rapid and at flowering or 7-10 days until berries pea-size.

 

The conditions were warm and humid overnight and the leaves were wet in the morning?

 

Temperature was above 13°C and humidity was above 98% for at least 4 hours overnight?

 

Fresh white down will have appeared underneath active oilspots...

     ...Check any oilspots present for fresh, white down.

The spores drift in the wind to other places in the foliage.

 

The leaves then remained wet for 450C-hrs?
ie for at least 2 hr 15min at 20°C, or 3 hrs at 15°C, or 4.5 hrs at 10°C

 

All tick boxes are Yes?

 

If ‘Yes’, then Secondary Infection is likely...

(see note below 1).

 

       ... and secondary oilspots are expected in the next 5-7 days if the weather is warm (20-25°C) or in 10-14 days if the weather is cooler or hotter.

 

Is it at or near flowering and are berries less than pea-size?

If 'Yes'...

         ... apply a post-infection fungicide (eg Ridomil) before the new oilspots appear.

 

1  Please Note: This check list only provides a guide as to whether infection has occurred or not. It should not be relied upon when determining vineyard management actions. If needed seek expert advice on the complex interactions between the vine, the weather, the downy mildew organism and any previous spray cover you may have applied. All these factors determine if infection actually occurred or not.