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The ultimate guide to fungal infections in succulents

1) Why does fungal infections occur frequently in succulents?

Fungal spores are spread by wind or air, infected soil or potting mixtures, infected plants, pruning wounds or contaminated water. These spores enter the stomata which are tiny openings in plant tissue that allows for gas exchange or through plant wounds

There are several environmental conditions that promote fungal growth, namely high humidity, slow drying of leaf surfaces, splashing rain and contaminated soil or garden tools as well as pests such as aphids and mealybugs

2) What are some common fungal diseases in succulents? How do I control such infections?

Sooty mold is a black or dark brown superficial fungal growth emerging on aerial parts of the plant. You can commonly spot them in the upper leaf surfaces. Sooty mold is spread by sap sucking pest such as mealybugs, aphids, whiteflies, and scale. Remove the pests and mold manually by washing it off using a hose or under a tap, dry thoroughly afterwards.

Grey Mold also known as Botrytis cinerea, this infection is easy to identify. Grey Mold form grayish brown spore masses on the surface of succulent leaves and flowers. Grey mold is most likely to spread when the weather is cool and wet. It commonly infects old, damaged or dying plant tissues and it spreads pretty quickly. Remove affected areas and dispose appropriately, avoid watering your succulent from the top, and allow the soil to dry out between watering.

Leaf spots are mostly harmless, but they can ruin your arrangements by disfiguring succulents pretty severely. Once the fungus dominates and takes over the control of the plant, the small spots will get bigger and will tend to look like a blotch. Eventually, the health condition of the plant will get worse. However, if you take precautions at the initial stage by removing affected leaves or areas, the condition will stabilise and the growth will not be affected.

Anthracnose is caused by fungi in the genus Colletotrichum. This infection affects a wide range of cacti and succulents. Sign of Anthracnose is moist tan coloured rot with red, orange or pink pustules on the surface. Spots spread quickly across leaves and crowns. When your succulent is infected with this fungi, you should remove affected leaves and dispose appropriately. This infection spreads through contaminated pots and soil, so you should avoid reusing the soil and make sure that your tools are perfectly clean. You should also use a copper fungicide to destroy the remaining spores and fungi.

Many cases of root and crown rots are caused by the fungal pathogens of genus Phytophthora. It’s very difficult to differentiate these diseases from the other fungal diseases in the early stages since their symptoms are not so specific. Affected plants become stressed, wilt, change colors and eventually die from a slow rot that develops upward from the soil level. Prevent crown and root rots by having a proper watering schedule and good ventilation to avoid overwatering and excessive moisture in the soil.

Fusarium wilt is caused by the pathogen called Fusarium oxysporum. Fusarium Wilt prevents succulent from taking up water. This causes heavy stress, wilting, yellowing and ultimately death. This fungus enters the plant through the roots and reproduces in the vascular tissues. This way tissues get blocked and succulent can’t absorb enough water. If you cut the leaf of the infected plant, you will see brown streaks. In order to prevent Fusarium Wilt, you should make sure your tools are properly sanitized when working with potted plants.

3) How do I prevent future infections from happening?

- Space plants adequately to increase air flow and ventilation, this also prevents fungal spores on infected plants to spread easily between pots

- Disinfect pruning or gardening tools after use, with rubbing alcohol or hot water

- Open windows or use a fan to blow your plants to increase ventilation and reduce humidity levels

- Always remove affected plant tissue and dispose properly

- Avoid reusing soil from infected plants and always sterilise contaminated soil with hot water or by baking it

- Apply non-systemic fungicides such as neem oil, captan, mancozeb or propineb regularly to kill fungi on the outside of the plant

- Apply systemic fungicides such as carbendazim, zagro stilt or fosphite through usual watering or on cut wounds to eradicate internal fungal infections

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