As vines spring back to life with green shoots, it’s an ideal time to look for pests and diseases. Some simple checks now can assist greatly in ensuring vines start healthy and stay healthy.
Soon after dormancy is a good time to peel back some bark on trunks and cordons to check for scale and mealybugs. Having scale and mealybug present is not concerning if numbers are low. However, scale and mealybug are vectors for viruses.
Where scale, mealybugs and resulting sooty mould have historically been a problem, remove several spurs, seal in a jar and keep close for easy monitoring. Watch for the emergence of crawlers when temperature rises and time treatment for soon after crawlers emerge, typically closer to flowering.
Snails, slugs and earwigs can all cause damage to small immature leaves when young. Until vines start to grow quickly, damage appears to be severe but it is unlikely to impact the crop. Monitoring for numbers typically results in small pockets of outbreaks and control options are available.
During early growth, keep a vigilant watch for powdery mildew flag shoots which is a whole shoot covered in powdery mildew. These arise from infection of the buds late last season and as the new shoot grows this season, carries the powdery mildew in the growing tip, infecting the whole shoot. These infected shoots can be spotted, marked and removed to avoid infection of neighbouring shoots and vines. A good powdery mildew preventative spray program can help to keep powdery mildew at bay for the following season. Tagging of the flag shoot location allows monitoring throughout the season on nearby vines.
Watch for mite (bud, bunch, rust and others) damage as shoots grow. Crinkling of leaves and what looks like absent early internodes are good giveaways. Mites can burrow into the dormant bud causing slow growth. A good sign is the bunches/inflorescence appearing at internodes 3-5 rather than being almost on the cordon/base of the shoot. Having good basal internodes before the bunch can ensure bunches have good airflow and spray penetration to avoid more serious problems later in the season. Using IPM friendly pesticides throughout the season can help to reduce bud mite numbers for next year.
Blister mites appear as cups, or blisters, on leaves. Blister mites tend to form cups that bulge out on the upper surface of the leaf, opening to the underside of the leaf, with mites living inside the cup. This is not to be confused with phylloxera that form a similar cup, bulging on the lower side of the leaf.
Eutypa lata and other trunk diseases will appear as yellow stunted shoots that tend to crop far lighter than uninfected shoots on the same vine. Wine Australia has some fantastic images and resources on grapevine trunk diseases. It is always good to identify the infected wood by removing the cordon and treating/sealing the wound to avoid reinfection. By cutting through the cordon, infected wood will have the pie section of dead/dying wood indicating the infection remains in the vine. It is recommended to remove infected cordons back to 10 cm below any visible infection. Remove infected wood from the vineyard. Remedial work to rejuvenate the vineyard is best to occur during dormancy and it’s best to cut as low as possible, allowing for dieback that will occur when cutting back
Spring is also a good time to check vine roots on poorly performing vines. New root growth occurs just before budburst, so do this any time after budburst. Look for white feeder roots indicating healthy vines. If roots appear black and dead, it may indicate poor soil conditions or structural roots close to the trunk. Root nodules or lumps can be signs of nematodes, or phylloxera, and you should ask for advice from a trusted source, and have the roots and soil tested.
Yellow leaves and shoots are not uncommon, particularly in cold conditions. Vines struggle to take up nitrogen in cold weather and once the temperature increases, vines will green up. If vines continue to remain yellow, seek advice from your chemical reseller or winery. It could be other underlying nutrient deficiencies causing the symptoms.
Having a strong preventative spray program from budburst to flowering is the best way to keep many pests and diseases at bay. Applying the first fungicide at flowering is fraught with danger, as spray penetration and coverage is poor. Early and frequent fungicide sprays on rapidly growing new growth are best. Refer to the AWRI Agrochemicals Booklet (Dog Book) for seasonal changes and pesticide application periods.
If adjoining vineyards are being rested or poorly managed, having a strong spray program on your vineyard next to your boundary is the best approach. You cannot spray over the fence into your neighbour’s vineyard as this is chemical trespass. If your neighbour is facing hardship and is unable to spray, reach out and ask if you can spray boundary rows for them. Vinehealth Australia has written a great article on the options for growers in this situation.
Finally, if you spot something unusual, ask. As an industry, we have a wealth of skilled people including chemical resellers, vineyard consultants, winery representatives, regional associations/networks, the AWRI help desk and Vinehealth Australia. If you see something unusual or concerning, you can also call the Exotic Plant Pest Hotline on 1800 084 881.