An Overview: Botrytis Cinerea || Gray Mould || Viticulture

The fungus that causes botrytis bunch rot and gray mould on grapevines is called botrytis cinerea. A decline in output and a decline in fruit quality in disease-prone years can result in significant economic loss. Due to the multiplicity of circumstances that can lead to infection and disease progression, managing botrytis can be difficult. It is necessary to be aware of these factors and ways to lessen their impact.

Factors influencing grapevine susceptibility:

A variety of environmental and managemental elements have an impact on a vine's vulnerability to botrytis infection.

• Weather: Botrytis cinerea is a pathogen that is influenced by the weather. High humidity or lengthy rain combined with cool or mild temperatures that leave berries with persistent wetness encourage the growth of illness and infection. A soggy spring followed by rain just before harvest is the worst-case seasonal scenario.
• Microclimate/Canopy architecture: Vines with closed, dense canopies retain moisture and create favourable circumstances for botrytis for a longer period of time. Closed vine canopies also hinder the effective application of pesticides and restrict spray penetration.
• Stage of grapevine development: Grapevine flowers, right after capfall, and berries following veraison are especially prone to botrytis infection. Green, hard berries can also contract the disease, though. The cap's abscission near the bottom leaves a wound that serves as a point of entry for the fungus. Berry swelling and softening start after veraison, as sugar levels increase and acids level out. Any fungus inside the berry left over from an earlier infection may be encouraged to flourish as sugar levels rise. Sugar leakage through the berry skin might support the growth of B. cinerea on the berry surface.
• Varietal susceptibility: Thin-skinned, densely packed bunches from vines are more likely to split and absorb moisture, which favours botrytis. Chardonnay, Chenin Blanc, Grenache, Muller Thurgau, Pinot Gris, Pinot Noir, Riesling, Sauvignon Blanc, Semillon, Traminer, and Sultana are the varieties most at risk. Botrytis can affect any kind.

Life-cycle of Botrytis Cinerea:

Fig. Life-cycle of Botrytis Cinerea

Infection: 

The first step in controlling the virus is to recognise it in all of its forms. Early-season symptoms suggest that the conditions have been favourable for disease development, and measures to limit future development should be made to lessen the severity of botrytis during harvest.

Both types of the fungus generate spores in moist or humid environments. These can sprout on harmed green tissue and are dispersed by the wind or water splashes. Damaged tissue is naturally found in flowers. A common infection location is where the bloom cap has come off and left a wound.

Fig. Botrytis infected Grape Leaves

Fig. Botrytis infected Grapes

Symptoms of Botrytis (Gray mould):

1. Young leaves have a distinctive V-shaped dead tissue region that spreads towards the major veins and have yellowing leaf edges.
2. Soft brown rotting spots appear on shoots that have sustained injury and are diseased.
3. At the moment where the caps abscise, it is typical for individual blooms to get an infection, yet there are no obvious symptoms.

Management of the disease Botrytis Cinerea/ Gray mould:

Botrytis control necessitates the fusion of cultural and chemical management techniques. Although even the finest attempts be aggravated by the weather circumstances are favourable to the development of illness near to harvest, there may be a chance of crop loss be decreased by taking measures early in the season.

Cultural practices:

Cultural practises that make flowers and bunches more accessible should be employed to boost spray effectiveness and to produce conditions that are unfriendly to the illness.
When planting in high-risk locations, choose types that are the least sensitive. These can be identified by the thicker-skinned berries and loose bunches they produce.
To lessen bunch zone congestion and limit bunches around trellis posts, use pruning and bunch thinning.
To hasten the decomposition of inoculum and the amount carried over from the previous season, cultivate prunings into the soil or manage the vineyard floor for elevated microbial activity.
Fruit can be collected deliberately and diseased fruit can be avoided for crops that are manually harvested. Pickers must be able to identify botrytis bunch rot and be aware of which rotten bunches need to be thrown to the ground.

Chemical control strategies:

A fungus called botrytis has the potential to seriously harm grape vines. The disease can be treated with a variety of medicines, and protectants work on the surface of the vine to stop spore germination. Spraying in advance of infection is advised to prevent fungicide resistance since it is more effective than spraying after illness. Eradicants, or curative chemicals, penetrate the vine to kill the fungus that is forming. When it's challenging to get a good spray coverage, translaminar fungicides, which can migrate within the leaf, provide protection. Botrytis's resistance to specific herbicides and the withholding periods imposed on grapes intended for export must be taken into account in any spray programme. In order to ensure that control alternatives are available at the conclusion of the season if necessary, chemicals must be utilised carefully.

Considerations for spraying at various growth stages:

To manage Botrytis infection, spraying grapevines should take into account conditions including early-season disease levels, early flowering, 80% capfall, pre-bunch closure, and veraison. If there are significant disease levels or vineyards are prone to leaf and shoot damage, fungicides can be used to protect young shoots and leaves. When the bloom caps come off, grapevine flowers are susceptible to Botrytis infection. If the weather is rainy and the flowering period is protracted, more spraying may be required. Translaminar sprays work best during the 80% capfall period because they target the wounds left by the fallen flower caps. The last chance to get chemicals within the bunch to safeguard more sensitive post-veraison berries as well as bunch and berry stems is during pre-bunch closure sprays. Spraying may be necessary during veraison to seven days prior to harvest, particularly at the first indications of berry damage or if a wet spell is predicted close to harvest. The selection of fungicides is constrained during this time due to market and winery constraints.

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Unmasking Downy Mildew || Downy Mildew || Viticulture

Downy Mildew

Downy mildew is a major disease of grapevines caused by the fungal-like oomycete Plasmopara viticola. This species is unique to grapevines and is established in all Australian grape growing districts. It is spread by wind and water and favourable conditions for infection and disease development occur in warm wet weather, especially in late spring and early summer. In most districts, vines are at greatest risk from 3–6 weeks after budburst until berries are pea-sized. Inadequate control of downy mildew can result in severe crop losses. Most commercial varieties are susceptible to this disease. Essential components for strategic management of downy mildew include prediction of infection based on weather events, monitoring the vineyard for symptoms of infection, knowing the disease cycle, and understanding how cultural management practices and registered agrochemicals affect disease control. This page provides links to help growers understand and manage this grapevine disease.

Understanding Downy Mildew:

Downy mildew, scientifically known as Peronospora and Plasmopara, is a group of pathogens that primarily affect plants. Although they resemble fungi, downy mildews are classified as oomycetes, which are more closely related to brown algae and diatoms. These insidious microorganisms thrive in cool, moist conditions, making them particularly problematic in regions with high humidity or during wet seasons.

Symptoms of Downy Mildew:

Look for symptoms of downy mildew after suitable warm wet nights particularly in late spring and early summer.

1. Yellow oilspots, initially with a chocolate-coloured edging, appear on upper leaf surfaces. On young leaves, oilspots can expand to around 50 mm diameter. ‘mosaic-like’ appearance of small angular yellow-brown spots confined by the leaf veins.
2. Oily brown patches spread along infected shoots, stems and tendrils.
3. Flowers, berries and whole bunches turn brown and have an oily appearance.
4. Younger berries harden and turn purplish if diseased, then brown before shrivelling and falling.
   
   

   

   Symptoms of Downy Mildew on Grape berry

   
   

   

   Symptoms of Downy Mildew on Grape Leaf

   
   

Different types of Downy Mildew:

1. Downy Mildew of Grapes:

Downy mildew (Plasmopara viticola), a fatal fungus that damages grapevines, is a frequent problem for vineyards and grape farmers. The disease damages the leaves, branches, and fruit, lowering the quality and quantity of the grapes. The growth of oily-looking patches on the leaves, which eventually turn dark and necrotic, is one sign of the disease. The use of disease-resistant grape types, regular pruning to increase air circulation, and the use of copper-based fungicides are just a few of the tactics grape growers use to battle this threat.

2. Downy Mildew of Maize:

Corn crops are seriously threatened by the pathogen Peronosclerospora spp.'s downy mildew of maize. The characteristic symptoms of this illness, which can swiftly spread throughout the plant, are white or greyish patches on the leaves. The plant's capacity to photosynthesize is hampered as it progresses, resulting in lower yields and limited growth. Farmers frequently employ fungicides and resistant cultivars of maize to battle downy mildew. In addition to crop rotation, effective field sanitation is essential for managing disease.

3.Downy Mildew of Cucurbits:

Cucurbit crops, including cucumbers, squash, and melons, are susceptible to the fungus Pseudoperonospora cubensis, which causes downy mildew. If this illness is not controlled, it might wipe out entire fields. Yellow lesions on the upper side of leaves and a characteristic, downy white growth on the bottom leaf surface are the early symptoms of downy mildew in cucurbits. When managing downy mildew in cucurbits, fungicides should be used sparingly along with cultural techniques including crop rotation and the establishment of resistant types.

Prevention and Control:

Preventing and controlling downy mildew in crops is essential to ensure healthy yields and economic viability. Here are some general tips and strategies for managing downy mildew:

        1.Weather Monitoring:

• It's crucial to keep an eye on the weather when deciding whether or not to use sprays. In some areas, downy mildew infection advisories are issued based on Bureau of Meteorology warnings. Sprays intended to prevent infection should be used as soon as feasible before an infection occurs.

        2. Viticulture Practice:

• Practises that promote air movement, sunlight penetration, and spray penetration into the canopy can lessen the likelihood of infection and the subsequent onset of disease.
• Utilising the prevailing breeze that moves along rows will help leaves dry out more quickly.
• Avoiding crowding and promoting open canopies through planting densities, trellising, and training techniques.
• The vine framework is made more accessible by canopy management techniques like leaf picking, shoot thinning, hedging, and skirting.

        3.Chemical Strategies:

There are two strategies for chemical control of downy mildew based on whether sprays are applied pre- or post-infection.

• The pre-infection technique entails applying a 'protectant' fungicide with enough coverage before climatic conditions that favour disease growth. The chemical functions as a barrier, preventing spores from reaching the vine tissue.
• In accordance with the post-infection strategy, an 'eradicant' fungicide must be sprayed right away after an infection event has taken place. If the necessary chemicals are applied within five days of the circumstances that made an infection more likely and before oil marks form, more spraying shouldn't be required until the circumstances that made an infection more likely to occur again.

Keep in mind that grapes are more than just a crop; they are a representation of history, culture, and delectable flavours. For many people, protecting their health and vitality is more than just a duty. You may protect the future of your vineyard and the calibre of your wine by putting into practise the best practises covered in this blog, from good pruning and canopy management to the prudent use of fungicides and the adoption of disease-resistant grape varietals.

Raise a glass in support of healthy, disease-free grapevines and the ongoing development of this traditional custom. A prosperous and abundant harvest is toast!

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Enemy of Vineyard or Grape vines: Phylloxera || Insect/ Pest || Viticulture

Grape Phylloxera

Spots Seen on Grape leaf by the pest

A little, yellowish bug with a 'aphid-like' appearance, Phylloxera (Daktulosphaira vitifoliae), is indigenous to North America. It is regarded as one of the worst grapevine pests in the world and causes significant harm to vines of European ancestry (Vitis vinifera). After several years of infestation, its presence on Vitis vinifera's roots causes the vine to deteriorate, produce less, and eventually die. Replanting Vitis vinifera vines grafted to tolerant or resistant rootstocks is the only way to control the pest once it has taken hold in a vineyard. Phylloxera is only now found in a few locations in Victoria and New South Wales. As most Australian grape plantings are own-rooted Vitis vinifera, which is particularly sensitive to phylloxera, it is crucial to stop the spread of the disease to areas that are now unaffected. There are strict biosecurity control measures in place to prevent spread to other wine regions, with areas classified as Phylloxera Infested Zones (PIZ), Phylloxera Interim Buffer Zones (PIBZ), Phylloxera Risk Zones (PRZ) and Phylloxera Exclusion Zones (PEZ).

Phylloxera Insect

Lifecycle of Phylloxera:

The phylloxera lifecycle involves egg, nymph and adult stages. Adult phylloxera are 1mm long, yellow to brown in colour and predominantly reproduce asexually in Australia. Phylloxera feed on leaves and/or grapevine roots causing death of the European grapevine, Vitis vinifera, within 5-6 years on average, dependent on which endemic strain is present. Phylloxera have been found to survive for up to 29 days without food. Adults can lay around 200 eggs per cycle and are capable of several breeding cycles per season, depending on the virulence of the phylloxera strain, nutrition and environmental conditions. Populations peak between November and March.

How does Phylloxera spread:

Phylloxera can quickly transferred to neighbouring vineyards, grapevines and regions, causing extensive damage, through clothing, footwear, tools, and vehicles (including harvesters), as well as in soil and vine material (leaves and shoots). In nature, crawlers can move from vine to vine by moving along the soil's surface, via the tree canopy, or by moving from root to root underground. They have a potential spread of 25 metres in the wind as well. A vineyard's natural spread is thought to be between 100 and 200 metres every year.

Cure on the vineyard infested by phylloxera insect:

Use of a resistant, or tolerant, rootstock, developed by Charles Valentine Riley in collaboration with J. E. Planchon and promoted by T. V. Munson, involved grafting a Vitis vinifera scion onto the roots of a resistant Vitis aestivalis or other American native species.
Not all rootstocks are equally resistant. Between the 1960s and the 1980s in California, many growers used a rootstock called AxR1.
The use of resistant American rootstock to guard against phylloxera also brought about a debate that remains unsettled to this day: whether self-rooted vines produce better wine than those that are grafted.

Facts that seen on the grape vine that survived Phylloxera insect:

most Chilean wine has remained phylloxera free. It is isolated from the rest of the world by the Atacama Desert to the north, the Pacific Ocean to the west, and the Andes Mountains to the east. Phylloxera has also never been found in several wine-growing regions of Australia, including Tasmania, Western Australia and South Australia.

Another vineyard unaffected by the phylloxera is the Lisini estate in Montalcino in Italy, a half-hectare vineyard of Sangiovese with vines dating back to the mid-1800s. Since 1985, the winery has produced a few bottles of Prefillossero (Italian for "before the phylloxera").

Until 2005, three tiny parcels of ungrafted Pinot noir that escaped phylloxera were used to produce Bollinger Vieilles Vignes Françaises, one of the rarest and most expensive Champagnes available.

It's vital to remember that phylloxera can be quite difficult to entirely remove once it has infected a vineyard. As a result, the use of resistant rootstocks and grapevine varietals is the major strategy for long-term management and prevention of phylloxera damage to vineyards.

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White Fungus on Plants: Powdery Mildew || Viticulture

Powdery mildew on grape leaf

Powdery mildew on Grapes

White fungus on plants, also known as powdery mildew, is a common and troublesome issue for gardeners and farmers. By understanding the causes, conditions favoring its growth, and preventive measures, we can better protect our plants from this fungal menace. Regular vigilance and proper care can go a long way in maintaining the health and beauty of our gardens and crops. Whether you're dealing with mangoes, peas, roses, wheat, or cucurbits, taking action against powdery mildew is essential for a thriving garden or farm.

Early in the season, when fungus-friendly circumstances are less ideal, the disease's progression may be gradual. The period right before blooming to fruit set is when powdery mildew is most susceptible to growth. The disease can persist from one growing season to the next in infected buds or as chasmothecia, or "resting spores" (formerly cleistothecia). Powdery mildew may infect several species and cultivars of economically significant grapevines. To stop the disease from spreading, it's crucial to manage it early in the season.

Gardening enthusiasts and farmers alike are no strangers to the challenges that can arise when it comes to plant diseases. One common problem that often plagues various plant species is powdery mildew, a type of white fungus on plants. In this blog post, we'll explore the phenomenon of powdery mildew and its impact on different plants, including mangoes, peas, roses, wheat, and cucurbits.

What is Powdery Mildew?

Powdery mildew is the common term for a group of plant diseases. In grapevines the disease is caused by the fungus originally named Uncinula necator, now renamed Erysiphe necator. Infection and subsequent disease development is influenced by many factors including the presence of infected grapevine tissue, spores, and the occurrence of particular weather conditions.

Powdery mildew is a fungal disease that affects a wide range of plants. It derives its name from the powdery, white, or grayish coating that it forms on the leaves, stems, and sometimes even the flowers of infected plants. This unsightly fungal growth can weaken the affected plants and reduce their overall health and productivity.

Common Types of Powdery Mildew:

• Powdery Mildew of Mango (Oidium mangiferae): Mango trees are susceptible to powdery mildew, which can hinder fruit development and reduce yield. The white fungus on mango leaves can be quite conspicuous and may lead to premature leaf drop.
• Powdery Mildew of Pea (Erysiphe pisi): Peas are often affected by powdery mildew, which can negatively impact the pea pods and reduce crop quality. Gardeners need to monitor their pea plants closely to catch the early signs of this fungus.
• Powdery Mildew on Roses (Sphaerotheca pannosa): Roses are prized for their beauty, but they are also susceptible to powdery mildew. This disease can mar the appearance of rose bushes, affecting their aesthetic value.
• Powdery Mildew of Wheat (Blumeria graminis): Wheat is one of the staple crops affected by powdery mildew. The fungus can reduce the yield and quality of wheat grains, which has implications for food production.
• Powdery Mildew of Cucurbits (Various species): Cucurbits, including cucumbers, pumpkins, and squash, are highly susceptible to powdery mildew. The fungus can affect both leaves and fruits, leading to reduced crop yields.

Causes and Favorable Conditions:

Powdery mildew is caused by various species of fungi, each with its own preferred host plants. It thrives under specific conditions, including:

• High Humidity: Powdery mildew tends to develop in areas with high humidity and poor air circulation.
• Moderate Temperatures: It prefers moderate temperatures, typically between 60°F and 80°F (15°C to 27°C).
• Dormant Spores: Fungal spores can survive on plant debris, waiting for the right conditions to infect new plants.

Prevention and Control:

Preventing and managing powdery mildew requires a proactive approach:

• Choose Resistant Varieties: Whenever possible, select plant varieties that are resistant to powdery mildew.
• Prune Regularly: Pruning can improve air circulation, reducing humidity around plants.
• Monitor and Inspect: Regularly inspect your plants for signs of powdery mildew. Early detection is key to managing the disease effectively.
• Fungicides: In severe cases, consider using fungicides labeled for powdery mildew control, but use them according to the manufacturer's instructions.
• Cultural Practices: Remove and dispose of infected plant material to prevent the spread of spores. Additionally, avoid overhead watering, as wet foliage can promote the growth of powdery mildew.
• Sulfur Dust: Sulfur is a traditional and effective treatment for powdery mildew on grapes. It acts as a fungicide and can also reduce mite populations. However, avoid sulfur applications during high temperatures to prevent vine damage.

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Iron Deficiency || Chlorosis || Viticulture

Iron deficiency, sometimes known as "iron chlorosis," is a frequent issue in the production of grapevines. For grapevines, iron is a key micronutrient since it is vital to several physiological processes, such as the production of chlorophyll and photosynthesis. Iron deficiency in grapevines can have a negative impact on the health of the plant, the quality of the grapes, and the overall production of the vineyard. Key elements of iron shortage in viticulture include the following:

Iron deficiency signs and symptoms:

1. Interveinal Chlorosis: One of the most obvious signs of iron shortage is interveinal chlorosis, where the veins of grapevine leaves stay green but the tissue in between the veins becomes yellow.
2. Reduced Growth: Grapevines with low iron levels sometimes have shorter shoots and smaller leaves.
3. Smaller Grapes and Poor Fruit Set: Iron deficiency can result in smaller grapes and poor fruit set, which can affect yield and grape quality.
4. Weak Vines: Affected vines might grow weaker and be more vulnerable to other illnesses and stresses.

Iron deficiency causes:

Iron insufficiency is frequently connected to the amount of iron present in the soil. The capacity of the plant to absorb iron might be restricted by high pH values, alkaline soils, or calcareous soils.

1. Competition: Other soil constituents, such as too much calcium or magnesium, may compete with iron for grapevines' ability to absorb it.
2. Excessive moisture: Because it hinders the vine's capacity to absorb iron from the soil, poor soil drainage or soggy circumstances can worsen an iron deficit. 

Management and prevention:

Iron chelates or iron sulphate can be put to the soil as soil amendments to make up for an iron deficit. The grapevines may easily get iron from these sources.

• pH Modification: Bringing alkaline or high pH soils into a more neutral range can help with iron absorption.
• Irrigation Management: Effective irrigation management can help reduce iron shortage by enhancing drainage and preventing waterlogged situations.
• Selecting the right grape kinds for your soil conditions might be helpful since several grapevine cultivars are more tolerant to iron shortage than others.
• Monitoring: Regular soil testing, leaf tissue analysis, and grapevine health monitoring can all assist identify early iron deficiency and direct corrective action.
• Foliar sprays: To quickly treat severe instances, foliar sprays of substances containing iron can be given directly to the leaves. However, this is typically a stopgap measure and does not take the place of dealing with the underlying soil problems.
• Organic methods: Organic viticulture techniques frequently concentrate on enhancing soil health and microbial activity, which may help grapevines more readily absorb iron.
• Professional Advice: Due to the vast range of local circumstances, it is advised to speak with a viticulture specialist or agricultural extension agency in your area for particular advice on controlling iron deficiency in your vineyard.

Wine quality and grapevine health may both be significantly impacted by iron deficiency. For a vineyard to be successful, this problem must be addressed by correct soil management and fertilizer supplementation.

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