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Sometimes the number of pests and diseases that affect our plants is overwhelming, it’s a wonder we manage to grow anything.
Nature is a wonderful thing and disease is only part of the natural life cycle of our gardens. Every season we have to overcome whatever the environment throws at us. Sometimes we beat him, and other times he beats us.
Botrytis is one of those diseases that participate in the recycling of natural materials, but we don’t want it in our gardens on our flowers and our crops, thank you very much.
Contents
What is botrytis blight?
Botrytis blight is a common and serious fungal disease that affects many plants in the garden and greenhouse. Sometimes known as gray mold, it affects all parts of plants except the roots.
Damaged, diseased or otherwise stressed plants are more susceptible.
Caused by fungus Botrytis cinereait spreads quickly under the right conditions, generally cool temperatures around 50-60ºF combined with high relative humidity.
Botrytis is also severe at high temperatures and can cause major problems in greenhouses, where the humidity is often high.
Botrytis Blight Symptoms On Plants
Leaves, flowers, stems, buds and bulbs are affected by botrytis. It does not attack the roots. Here are the symptoms to look out for:
Flowers, stems and leaves
When a plant is infected with botrytis, the flowers and buds turn brown and develop abnormally. Spots appear on the flowers; the older the flower, the faster it rots.
Stems and leaves develop brown spots. Gray or silver mold can appear after cool, damp weather.
Berry Symptoms
Unfortunately, botrytis is quite common in berry plants like strawberries and blueberries, especially if the fruit or plant is damaged by insects.
With berries, young flowers are most susceptible and the disease often begins with the drying or browning of flower buds before they drop from the plant, known as bud burst.
In the early stages of fruit, the initial infection will appear as a rapidly enlarging dark spot. If you do not remove the infected fruits from the plant, a gray mold forms.
The disease can start on the fruit while it is still young and green, and as it matures the disease becomes more pronounced.
Depending on the fruit, however, the initial appearance may differ. On young or green pears, the spots appear light gray to green like a water-soaked spot. On brown pears and bright red apples, the spots appear dark brown to black.
On apples, you often see browning and softening at the stem bowl or calyx ends. This brown spot is growing rapidly. If you leave this fruit on the tree, it will eventually mummify and infect next year’s crop through spores.
As the fruit ripens and the infection develops further, you may smell a cider odor, accompanied by a gray growth that will quickly appear and spread quickly.
Sometimes you won’t notice the disease until the fruit is ripe and harvested. Allowing infected berries to touch others during the harvesting process will cause the disease to spread.
Under the right conditions, it only takes about 48 hours for a healthy fruit to become infected and become a rotting mass after harvest.
You probably saw this when you bought a container of strawberries at the store and realized that one rotted and formed gray mold, infecting anyone it touched in the container.
This disease is commonly seen in parts of the plant (or garden) with poor air circulation and high humidity. The disease can quickly spread to other plants and berries.
Affected plants
Botrytis can appear on fruits and vegetables, especially overripe fruits and damaged plants.
Pears and apples are susceptible, especially after harvest and at cooler temperatures such as cold stores or root cellars. This is why you should check your fruit stored in a root cellar often to prevent rot from spreading to all of your stored fruit.
Fruit trees that can be infected include (but are not limited to):
Vegetables that can be infected with botrytis include:
Some sensitive flowers include (but certainly not limited to)
Most berries can be infected, including:
Botrytis Life Cycle
Botrytis is what is called a filamentous necrotrope. Basically, this means that it is a fungus that survives on dead fruit tissue and plant material. Think of it in terms of prevention. Remove as many opportunities as possible for fungal spores to take hold.
The fungus survives on organic matter in the orchard or garden, such as mummified fruit left on trees or fallen to the ground, or infected material left where it falls.
If temperatures become low or high, the fungus produces sclerotia, which are food reserves, to survive until conditions become favorable again. A sclerotium is a compact mass of hardened mycelium with nutrients, allowing the fungus to wait out unfavorable conditions.
Once the conditions are right, with temperatures between 55 and 75°F, the mycelia (fungal threads) develop and the spores are dispersed by water, wind and rain.
Botrytis not only infects formed fruit or plant parts that have been punctured or damaged, it can infest a plant much earlier in the development process. The spores can infect the buds of ornamental flowers, fruits and vegetables before they fully develop.
The fungus can also cause infection at the flowering stage, while the fruit is developing, during harvest, or as a secondary infection when fruits stored with the fungus infect others stored.
Ideal conditions for Botrytis
Here are the ideal environmental conditions to create the perfect breeding ground for botrytis blight.
- Damaged, aging, or weak plant or fruit tissue
- Plant parts damaged by pruning, insects or pinching
- Temperatures between 55 and 75°F combined with high humidity
- Wet and rainy conditions
- Mummified fruits left on trees or where they fall
- Lack of airflow
- Poor garden and orchard hygiene
How to Prevent Botrytis
Prevention is much better than trying to treat the botrytis burn after an infection. Following simple rules in the garden and orchard can go a long way in preventing this fungus from taking hold.
Sometimes you can’t prevent it, but you can limit the growth and spread.
Cultural control
- Avoid watering overhead and wetting the leaves. Water at ground level or use an irrigation system like drip.
- Water early in the day to allow the foliage to get wet and the soil to dry out a bit as the day heats up.
- Reduce humidity where you can. Although you can’t control the environment, you can plant in open areas, promote good air circulation through pruning, keep the garden from being overcrowded, and reduce humidity in greenhouses where botrytis blight can spread quickly. Once in a greenhouse, it is difficult to eradicate it.
- Harvest at the right time. Some fruits like gala and honeycrisp apples start to split at the stem if left on the tree too long. The slit provides a convenient entry for botrytis blight.
- Minimize fruit damage or punctures when harvesting or when removing dead or diseased branches.
- Keep the floor clean. When debris falls to the ground, remove it as soon as possible.
- Spray with neem oil, which acts as a natural fungicide. Spray at dusk to avoid pollinators such as bees and follow package directions.
Treat botrytis
Timing is critical when using botrytis blight fungicides. Antifungal sprays are a good idea if you are battling this disease.
Bonide Fung-onil is a good all-rounder. Generally, you will need to apply it at four different stages:
- First to reduce spores on flowers and fruits, spray at the budding stage.
- At the young fruit stage, spray before the fruit becomes larger than two inches.
- The third should take place around mid-July.
- The last should be about seven days before harvest.
Of course, this only works if you harvest everything at once or if you know you will harvest most of your harvest in a short time. I have several fruit trees in a warm, humid environment that are ready to harvest at different times of the season.
To keep it simple, I finish the last spray at the same time.
Natural Remedies For Botrytis Blight
If you don’t like chemicals or store-bought remedies, try natural botrytis remedies. There’s no solid evidence that products like garlic or onion sprays work, but you can try them out and see if they work for you.
If you want more proven natural remedies, use a neem spray or a product that contains Bacillus amyloliquefaciens strain D747 as Southern Ag Garden Friendly Biological Fungicide.
Botrytis quickly becomes resistant to fungicides. This is why it is imperative to prevent it by keeping the disease away thanks to the hygiene of the garden and the orchard. Be sure to focus on:
- Cannabis control
- Collection of dead leaves
- Remove mummified fruit and vegetation
- Improve airflow
- Don’t overcrowd the plants
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