Now is the time to take action against tomato fungal disease. Late Blight (Phytophthora infestans) has been confirmed  in Connecticut for the first time this 2010 growing season. Last year Late Blight devastated many home and commercial plantings not protected by fungicides. There are organic fungicides and chemical fungicides labeled for use against Late Blight and other fungal diseases of tomatoes.

Cultural controls also go a long way in keeping tomato plants healthy and strong. The best defense is a strong plant, able to fend off attacks by pathogens. Late Blight resistant varieties of tomatoes are Legend, Santa, Juliet, Mountain Magic, and Plum Regal. Each year rotate planting sites within the garden. Proper soil pH and nutrient levels give the best start to transplants in the garden. Soil tests should have been done prior to planting to determine health of the soil and adjust pH. Tomatoes prefer a pH of around 6.5 but are adaptable. A well balanced fertilizer applied at planting time and again later when blossoms begin to appear is a good rule of thumb. Stake or cage plants to keep foliage and fruit up off of the ground. If tied to a stake and growing tall, remove the lower leaves up to one foot to lessen the chance of leaves coming in contact with the soil where several different disease fungi live. Mulch plants to provide a physical barrier between the soil and the plant. Some diseases live in the soil and are splashed up onto the leaves when it rains or when watered. The mulch stops this action. Mulches can be grass clippings, chopped leaves, bark mulch or plastic strips. Fungal spores that land on a leaf need moisture to germinate. Water plants in morning only so leaves can dry before evening. When watering plants, use soaker hoses or drip irrigation,and avoid overhead watering. Try to not get the leaves wet. This is obviously unavoidable during rain. Space plants far enough apart to promote good airflow and leaf drying. Slow the spread of disease by hand picking off any leaves as soon as you see a spot it and dispose  in the garbage.

Other common fungal diseases in Connecticut that attack tomatoes are Early Blight (Alternaria solani) and Septoria Leaf Spot (Septoria lycopersici). All of these cultural controls help to prevent other diseases as well.

Fungicide is used as a preventive measure, stopping the germination of the fungal spores once they land on the plant. Conventional gardeners can use chemical fungicides. These include the active ingredients  chlorothalonil, mancozeb or manix.  Chlorothalonil can be used on the same day of harvest while mancozeb and manix restrict harvest to five days after application. Several different brands of those named active ingredient are available at better garden centers. Read and follow all label directions for use.

Organic fungicides include copper based fungicides, Bacillus subtilis and few others listed below.  Care should be taken when using  copper based fungicides  as they can cause damage to leaves and fruit. Follow all label directions.

Organic products with late blight on label
• Serenade ASO (Bacillus subtilis) 6 qts/A
• Serenade MAX (Bacillus subtilis) 1-3 lb/A
• Sonata (Bacillus pumilis) 2-6 qts/A
• Oxidate (hydrogen dioxide) 40-128 fl oz/100
• Sporan EC (rosemary, clove, thyme oils) 1-3
• Sporatec (rosemary, clove, thyme oils) 1-3
• Copper fungicides

(list from

Whichever fungicide is used, thorough coverage is essential and applied regularly to protect new growth.


Early Blight

Early Blight

Late Blight (Phytophthora infestans)

Late Blight (Phytophthora infestans)

septoria tomato leaf

Septoria Leaf Spot

I returned from a week of vacation to the find the gardens full of weeds! Everything grew like gangbusters in my absence. Those little weed seedlings grew to flowering stage in just a week! If we could only get the peppers and cucumbers to produce like that I would be happy. Mulch would have prevented many of the weeds from germinating in the first place. I also should have weeded well before I left instead of dealing with the larger weeds now. Hind site is always better.

I  gathered a large garbage bag full of seaweed from the beach. Once home I spread  it out on the lawn to rinse it thoroughly of salt and sand, let it dry in the sun and worked it into the soil of the beds of the finished peas, spinach and lettuce. I will replant different crops in these newly enriched beds. Leaf crops grow extremely well in seaweed amended soil. I love free fertilizers.

My tomato crop is slowly developing despite have spotted and yellowed leaves of septoria leaf spot fungal disease. Mulch would have helped here, too. Mulch provides a physical barrier between the soil and leaves above. The fungal spores of septoria live in the soil from year to year and can be splashed up onto the leaves of the tomatoes. Fungicides can be used before the infections happens to prevent the spores from growing on the leaves. Now it is too late. These spots start on the bottom leaves, progress to produce new fruiting spots that release more spores that land on higher leaves, moving the fungus from the lower leaves up the plant.

The non-stop rains and cool spring has brought the northeast the perfect conditions for another fungal disease, Late Blight, (Phytophthora infestans). This is the same fungus that caused the Irish potato famine in the 1850’s. We have identified the disease if both tomato and potato plants of commercial fields during the last two weeks. We will have to see how the remainder of the summer progresses relative to moisture to see how bad the outbreak becomes. Spores are spread by rain splash and carried by wind for up to several miles. The disease starts as a water soaked spot on the leaf,  stem or fruit, rapidly turning dark brown to black. The entire plant wilts and collapses.  Cornell has a great fact sheet here.

I would like to mention Magic Wings Butterfly Conservatory located in South Deerfield, Massachusetts this week. They are a butterfly conservatory open year round that folks can visit to see and walk among the beautiful creatures with their native plants. Another ‘beautiful creature’ is George who works there. A mother called me at the center last week looking for a source to purchase ladybugs to release at the funeral of her nine year old daughter’s friend. With only two days notice on Thursday afternoon, no commercial ladybug provider was willing to ship them to her in time. On a hunch, I called Magic Wings and relayed the information to George. They do not sell ladybugs but ladybugs do live in the conservatory with the butterflies. He came through magnificently! Mother and daughter drove to South Deerfield on Friday to pick up the box of ladybugs and thank George in person. They also visited the conservatory and several butterflies landed on the daughter. Quite a special experience for a grieving family. We at UConn add our thanks to George and Magic Wings.