Whats Wrong With My Plants? - 5 plant diseases to look out for in July

As July’s warm sunshine brings growth to UK gardens they also bring several common garden diseases. If left unchecked these diseases can turn your lovely gardens into a war zone against the microscopic invaders.

Whether you’re an old hand or a beginner, knowing these potential threats and how to manage them is key to a healthy garden. Our Blog post looks at 5 garden diseases to watch out for this July and how to prevent and treat them.

Now you’re equipped to keep your plants strong and your garden blooming all summer.

1. Powdery Mildew

Powdery mildew is a fungal disease that shows up as a white or grey powdery substance on leaves, stems and buds. It’s caused by several species of fungi including Erysiphe, Podosphaera and Golovinomyces. Unlike many fungal diseases powdery mildew loves warm dry conditions so it’s a common problem in the summer, especially in July. The spores are blown by the wind and can infect plants quickly especially in areas with poor air circulation.

Powdery mildew can affect:

• Roses: One of the most common ornamental plants to be affected, often shows symptoms on leaves and flower buds.

• Cucumbers and Squashes: Cucumber and Squash plants are very susceptible, mildew shows up on the leaves.

• Grapes: Leaves and young grapes are affected, fruit quality is impacted.

• Apples: Apple trees show symptoms on leaves and fruit, reduced yield.

• Various Ornamentals: Many other garden plants including zinnias, dahlias and phlox are also affected.

Mildew on Cucumber Leaves

Mildew on Courgettes

Mildew on Tomato Plants

Mildew on Zinnias

Managing powdery mildew involves both prevention and treatment:

Prevention:

1. Air Circulation:

   • Plant spacing: Make sure plants are spaced well apart to allow air to circulate.

   • Pruning: Regularly prune plants to remove excess foliage and air to get in.

2. Watering:

   • Water at the base: Don’t overhead water which can create humid conditions for mildew. Water plants at the base to keep foliage dry.

3. Resistant Varieties:

   • Choose plant varieties that are resistant to powdery mildew.

4. Mulching:

   • Mulch around the base of the plant to retain soil moisture and prevent spores from splashing up onto leaves.

Treatment:

1. Fungicides:

   • Use fungicides specifically for powdery mildew. Organic options are sulfur-based fungicides and neem oil. Chemical fungicides can be used but as a last resort and according to the instructions on the label.

2. Remove Infected Parts:

   • Prune and dispose of infected leaves, stems and buds to prevent spores from spreading.

3. Milk Spray:

   • Some gardeners have found success with a milk spray (a mixture of milk and water) as a natural treatment. Spray the solution on affected plants every 7-10 days.

4. Baking Soda Solution:

   • A mixture of baking soda, horticultural oil and water can also be used as a treatment. This solution changes the pH on the leaf surface making it inhospitable to the fungus.

Regular monitoring and early intervention is key to managing powdery mildew. By following these prevention steps and acting fast when you see the first signs of infection you can keep your plants healthy and have a bountiful beautiful garden all summer.

2. Blight (Late Blight)

Affected Plants:

• Tomatoes: Foliage and fruit. Infected fruit shows dark, greasy looking spots which can spread fast and rot the entire fruit.

• Potatoes: Foliage and tubers. Infected tubers develop brown, dry rot which extends into the flesh making them inedible.

Blight on Tomatoes

Late blight is a deadly plant disease caused by the pathogen Phytophthora infestans. It affects tomatoes and potatoes and can cause big crop losses if not managed well. Late blight thrives in cool wet conditions and spreads fast, so it’s a big problem during rainy July. Symptoms start with water soaked spots on leaves which quickly turn into large dark brown lesions with a greenish edge. In humid conditions a white fuzzy mold appears on the underside of leaves and stems which is the spore producing structure of the pathogen. If left unchecked late blight can kill entire plants and infect tubers making them inedible.

Prevention and Treatment:

Managing late blight involves monitoring, cultural practices and resistant varieties and fungicides:

Prevention:

1. Resistant Varieties:

   • Choose tomato varieties that have been bred for late blight resistance. Some resistant tomato varieties are ‘Consuelo’, ‘Crimson Crush’ and ‘Orangeto’.

2. Air Circulation:

   • Space plants well and prune excess foliage to allow air to circulate and reduce humidity around plants.

3. Watering:

   • Don’t overhead water to keep foliage dry. Use drip irrigation or water at the base.

4. Mulching:

   • Mulch around the base of the plant to prevent soil from splashing onto the leaves which can spread the disease.

5. Crop Rotation:

   • Rotate crops and don’t plant tomatoes or potatoes in the same spot for at least 3 years to reduce soil borne pathogens.

Treatment:

1. Remove and Destroy Infected Plants:

   • At first sign of infection remove and destroy infected plants, including fallen leaves and debris. Don’t compost infected plant material as it can spread the disease.

2. Monitor and Act Fast:

   • Regularly check plants for early signs of blight and act immediately if you see symptoms.

3. Sanitize Garden Tools:

   • Clean and disinfect garden tools after working with infected plants to prevent the spread of the disease.

More:

• Barrier Methods:

  • Use row covers to protect young plants from spores during early growth.

By following these prevention and treatment methods gardeners can reduce the risk of late blight. Monitoring and acting early is key to managing this nasty disease and a healthy garden.

Blight on Potatoes

Late blight is a devastating disease caused by the oomycete pathogen Phytophthora infestans. It affects both tomatoes and potatoes and can cause significant yield loss and crop failure if not managed. It’s most prevalent in cool, wet weather so is a big problem during summer, especially in July when the weather is variable.

Symptoms in Potatoes:

1. Foliage and Stems:

   • First symptoms are dark, water soaked spots on leaves.

   • Lesions enlarge quickly and turn dark brown or black with a greenish edge.

   • White, fuzzy mold (sporangia) appears on the underside of leaves and stems in humid conditions.

   • Infected foliage will collapse and die within a week of infection.

2. Tubers:

   • Tubers develop firm, dark brown or purple lesions.

   • Under the skin a reddish brown, dry rot extends into the flesh often with a foul smell.

   • Secondary infections by bacteria and other fungi can cause soft rot and total tuber decay.

   • Infected tubers may look healthy at harvest but develop symptoms later in storage.

Prevention and Treatment:

Prevention:

1. Resistant Varieties:

   • Plant potato varieties that are resistant to late blight. Some resistant varieties are ‘Sarpo Mira’, ‘Cara’ and ‘Orla’.

2. Planting:

   • Don’t plant potatoes in low lying areas where water can collect.

   • Use certified disease free seed potatoes to prevent introducing the pathogen.

3. Crop Rotation:

   • Rotate crops and don’t plant potatoes (or tomatoes) in the same spot for at least 3 years.

4. Watering:

   • Water early in the day so foliage can dry quickly.

   • Don’t overhead water; use drip irrigation or soaker hoses to keep leaves dry.

5. Mulching:

   • Mulch to reduce soil splashing onto foliage which can spread spores.

6. Spacing and Air Circulation:

   • Space plants so there is good air circulation around them which helps reduce humidity around the plants.

Treatment:

1. Remove and Destroy Infected Plants:

   • At the first sign of blight, remove and destroy infected plants and tubers to prevent the disease spreading. Don’t compost infected material.

2. Fungicides:

   • Use fungicides as a preventative measure especially during wet weather.

   • Follow the label instructions and make sure to cover all plant parts.

3. Regular Monitoring:

   • Check plants regularly for early signs of blight. Early detection is key to management.

4. Sanitise Tools and Equipment:

   • Clean and disinfect tools and equipment after working with infected plants to prevent the pathogen spreading.

Storage Tips for Potatoes:

1. Harvest Timing:

   • Harvest potatoes as soon as they mature. Delaying harvest increases the risk of tuber infection.

2. Curing:

   • Cure potatoes in a dry, cool, well ventilated area for about 10 days to toughen the skin before storage.

3. Storage:

   • Store cured potatoes in a cool, dark, well ventilated area at 4-10°C (40-50°F).

   • Check stored potatoes regularly for late blight and remove any infected tubers immediately.

Late blight is a big threat to both tomato and potato crops but with regular monitoring, good cultural practices and resistant varieties, gardeners can manage and reduce its impact. By knowing the symptoms and using the right prevention and treatment methods you can protect your garden from this disease and have a good harvest.

3. Black Spot

Black spot is a common and serious fungal disease caused by Diplocarpon rosae. It affects roses mainly and shows up as round black spots with fringed edges on the upper surface of the leaves. The spots can cause the surrounding leaf tissue to yellow and turn chlorotic. Severely affected leaves will drop off which weakens the plant over time. Black spot loves warm and humid conditions and spreads through water splashes from rain or irrigation so it’s a big problem during summer.

Affected Plants:

• Roses: Main target, severe infestations will cause significant defoliation and reduced plant vigor.

• Other Ornamentals: Occasionally affected, but roses are the most susceptible.

Prevention and Treatment:

Prevention:

1. Spacing and Air Circulation:

   • Space plants far enough apart to allow good air circulation which will reduce humidity and dry leaves quickly.

   • Prune plants regularly to remove overcrowded growth and improve air circulation within the plant canopy.

2. Watering:

   • Water at the base of the plant to keep the foliage dry.

   • Water early in the day to allow any moisture on the leaves to dry quickly.

3. Mulching:

   • Mulch around the base of the plant to prevent water splashes from the soil which can spread fungal spores to the leaves.

   • Organic mulches like wood chips or straw also retain soil moisture and reduce weeds.

4. Sanitation:

   • Remove and dispose of fallen leaves and plant debris especially those showing signs of infection to reduce source of fungal spores.

   • Don’t compost infected leaves as the spores can survive and reinfect the plant.

5. Resistant Varieties:

   • Choose rose varieties bred for black spot resistance like ‘Knock Out’, ‘Carefree Wonder’ and the ‘Flower Carpet’ series.

Treatment:

1. Fungicides:

   • Apply fungicides as a preventative or as soon as you see the disease. Organic options are sulfur or neem oil and chemical fungicides like myclobutanil, chlorothalonil or trifloxystrobin.

   • Follow the label instructions for application rate and frequency.

2. Monitoring:

   • Check plants frequently especially during warm and humid weather for early signs of black spot.

   • Early detection and quick action can reduce the spread and severity of the disease.

3. Pruning:

   • Prune and dispose of infected leaves and stems immediately to prevent the disease from spreading.

   • Make clean cuts back to healthy tissue and sterilize pruning tools between cuts to avoid spreading the spores.

4. Fertilization:

   • Keep your plants balanced. Avoid over nitrogen fertilization which can promote lush and susceptible growth.

   • Use a balanced fertilizer to keep your plants healthy and more disease resistant.

More:

• Regular Care: Good care of your plants will make them healthier and more disease resistant.

• Weather Awareness: Check the weather forecast. Extended wet weather requires more vigilance and possibly more fungicide applications.

Black spot is a tough disease for rose growers but with regular preventative measures and timely treatment its impact can be minimized. Good garden hygiene, resistant varieties and fungicides when needed will keep your rose bushes healthy and blooming all season. Monitoring and quick action is the key to managing black spot and keeping your garden a vibrant and disease free haven.

4. Grey Mold (Botrytis Blight)

Botrytis on Tomatoes

Botrytis on Strawberries

Grey mold caused by the fungus Botrytis cinerea is a common and devastating plant disease. This pathogen can infect many plants and appears as fuzzy grey mold on flowers, leaves, stems and fruits. Grey mold thrives in cool and damp conditions especially when temperatures are between 15-21°C  and humidity is high. Spores are spread through air and can cause extensive damage if not managed properly.

Commonly found on:

• Strawberries: Infected fruit develops soft brown spots that spread rapidly and cover the berries in grey mold.

• Grapes: Berries develop brown or grey mold and bunch rot.

• Tomatoes: Grey mold on fruit, stems and leaves causing rot and decay.

• Ornamentals: Many ornamental plants like geraniums, peonies and begonias are susceptible to Botrytis blight showing symptoms on flowers, leaves and stems.

Treatment:

Prevention:

1. Air Circulation:

   • Space plants well to allow good air flow around them.

   • Prune plants to remove crowded growth and improve ventilation.

2. Watering:

   • Water at the base to keep foliage and flowers dry.

   • Water early in the day so any moisture on the plants can dry quickly.

   • Avoid overhead watering especially during cool and wet weather.

3. Sanitation:

   • Regularly remove and dispose of dead or decaying plant material as Botrytis cinerea can overwinter in plant debris.

   • Clean up fallen leaves and plant debris around the garden to reduce sources of infection.

4. Mulching:

   • Mulch around the base of the plant to prevent soil from splashing onto foliage and flowers which can spread spores.

5. Resistant Varieties:

   • Choose varieties that are resistant to Botrytis blight where possible.

Treatment:

1. Remove and Destroy Infected Plant Parts:

   • At the first sign of infection remove and destroy infected plant parts to prevent the disease from spreading.

   • Dispose of infected plant material in the trash not in the compost pile.

2. Fungicides:

   • Apply fungicides as a preventative measure especially during cool and wet weather. Organic options are neem oil and sulfur based fungicides. Chemical fungicides like chlorothalonil or iprodione can also be used.

   • Follow label instructions for application rates and frequency.

3. Monitoring:

   • Check plants frequently especially during cool and wet weather for early signs of grey mold.

   • Early detection and quick action can reduce the spread and severity of the disease.

4. Environmental Controls:

   • In greenhouse or indoor settings use fans and heaters to reduce humidity and improve air circulation.

   • Avoid dense planting and ensure good spacing between plants to improve air movement.

More:

• Disease Resistant Varieties: When planning your garden choose varieties of plants that are resistant to grey mold.

• Proper Fertilisation: Avoid over fertilising with nitrogen as it promotes lush growth which is more prone to disease.

Grey mold (Botrytis blight) is a big problem in the garden and can cause damage to many plants. But with regular monitoring, good cultural practices and timely intervention gardeners can manage this disease. By improving air circulation, good sanitation, proper watering and fungicides when needed you can protect your plants from grey mold and have a healthy garden.

Regular checking and quick action is key to keeping this pesky pathogen away and overall garden health.

5. Clubroot

Clubroot is a serious soil borne disease caused by Plasmodiophora brassicae. It affects the roots of brassicas (cabbage family) causing them to swell and distort into club shapes. The disease prevents the plant from taking up water and nutrients, resulting to stunted growth, yellowing leaves and overall poor health. Clubroot thrives in acidic and wet soils making it a big problem in poorly drained gardens. Infected plants often wilt during the day and recover at night, a sign of root dysfunction.

Affected Plants:

• Cabbage: Infected roots swell and distort, resulting to stunted growth and poor head formation.

• Broccoli: Plants are stunted and yellowing with reduced or deformed heads.

• Brussels Sprouts: Affected plants produce smaller and deformed sprouts.

• Cauliflower: Infected plants are stunted with small and misshapen heads.

• Kale and other Brassicas: All members of the cabbage family can be affected, showing root distortion and stunted growth.

Clubroot on Brussel Plants

Clubroot on Chinese Cabbage Plants

Prevention and Treatment:

Prevention:

1. Crop Rotation:

   • Don’t plant brassicas in the same area for at least 7 years to reduce clubroot spores in the soil.

2. Soil Drainage:

   • Improve soil drainage by adding organic matter like compost or well rotted manure.

   • Consider raised beds if you have heavy and waterlogged soils.

3. Soil pH Management:

   • Raise soil pH to 7.2 or higher by applying lime (calcium carbonate). Clubroot spores are less active in alkaline conditions.

   • Get a soil test to know the current pH and follow the recommended liming rates.

4. Hygiene:

   • Clean tools and equipment after working in infected soil to prevent spreading of spores.

   • Don’t move soil from infected areas to uninfected parts of the garden.

5. Resistant Varieties:

   • Plant clubroot resistant brassica varieties when available. Some examples are Kilaton cabbage and Crispus Brussels sprouts.

Treatment:

1. Remove Infected Plants:

   • Uproot and destroy infected plants including the roots to reduce spore spread.

   • Don’t compost infected plant material.

2. Soil Solarization:

   • Use soil solarization during summer to kill clubroot spores. Cover the soil with clear plastic and leave it in place for 6-8 weeks to heat up the soil and reduce pathogen levels.

3. Disease Suppressive Amendments:

   • Add organic amendments like compost and green manure crops which can increase soil microbial activity and suppress clubroot.

4. Transplant Management:

   • Start brassicas in sterile, disease free potting mix and transplant them to the garden once they have established strong root systems.

Disease Management Tips:

Regular Check-ups:

1. Check Plants Often:

   • Check plants regularly especially during warm and wet weather when fungal and bacterial diseases are more common.

Cultural Practices:

1. Spacing and Pruning:

   • Plant with enough space between plants to promote good air circulation and reduce humidity and disease development.

   • Prune plants to remove excess foliage and improve air flow.

2. Watering:

   • Water in the morning so leaves dry up quickly.

   • Use drip irrigation or soaker hoses to keep foliage dry and prevent water borne pathogens.

Sanitation:

1. Clean Up Plant Debris:

   • Remove and dispose of fallen leaves and plant debris to reduce infection sources.

   • Sterilize pruning tools between cuts to prevent pathogen spread.

Resistant Varieties:

1. Choose Disease Resistant Plants:

   • Choose plant varieties that are resistant to common diseases in your area. Resistant varieties are bred to be resistant to specific pathogens and can reduce disease pressure significantly.

Chemical Controls:

1. Use Fungicides and Treatments Sparingly:

   • Use fungicides and other chemical treatments as a last resort, follow label instructions carefully.

   • Integrate chemical controls with other management practices for a holistic approach to disease prevention and treatment.

Clubroot is a tough opponent for brassica growers but with prevention and management strategies in place its impact can be reduced. By improving drainage, managing pH, good hygiene and choosing resistant varieties you can protect your brassicas from clubroot and have a healthy garden. Regular monitoring and being proactive with disease management is key to keeping your plants healthy.

Conclusion

As we look at the diseases in July in the UK it’s clear that proactive management is the key to a thriving garden. From the sneaky spread of powdery mildew to the devastation of clubroot on brassicas each disease requires attention to detail and prompt action.

By taking preventive measures like improving air circulation, proper watering and choosing resistant varieties gardeners can reduce the risk of infection. Regular monitoring and quick response to early symptoms can make a big difference in controlling outbreaks before they affect plant health.

Remember a healthy garden isn’t just about green leaves and flowers – it’s a reflection of the care and attention you put into your plants. By incorporating these into your gardening practices you not only protect your plants but also have a garden that’s vibrant and thriving and brings you joy all season long.