You may have had your own tears, and understandably so. Late Blight of potatoes and tomatoes was the disease responsible for the Irish potato famine in the mid-nineteenth century. Spores are spread by rain/watering splash, insects, and wind, and through our hands and tools and through these mediums they can travel distances. Spore spread is most rapid during conditions of high moisture, marine layer days, and moderate temperatures, 60°-80°F. Once established, the fungi can over-winter in your garden soil, on debris and weeds.
Fusarium Wilt is commonly found throughout the United States, is a soil-borne pathogen. Plants susceptible to Fusarium Wilt are cucumber, potato, tomato, eggplant, pepper and beans. Fusarium wilt causes foliage to yellow, brown spots on leaves, leaves to curve the length of the leaf, wilt, then turn brown and die. Your plants become stunted because they can no longer function properly.
The list of plants susceptible to Verticillium Wilt is impressive. You might have thought it was just tomatoes, but look: Peanut, Horseradish, Rutabaga, Cabbage, Brussels sprouts, Pepper, Safflower, Hemp, Watermelon, citron Cantaloupe, honey dew, Pumpkin, Cotton, Okra, Mint, Radish, Rhubarb, Castor bean, Eggplant, Potato, Spinach, New Zealand spinach, SaIsify, Yard-long bean, Cowpea! Cucumber, tomatoes and strawberries are particularly susceptible.
Verticillium wilt is most active in humid climates. Cool nights and moist conditions, the kind that favors peas, tend to encourage it. It lives in the soil, entering plants through the roots and is drawn up to stems, leaves and fruit through water uptake. At the same time, it is robbing the plant of moisture. The first symptoms of verticillium are usually seen in wilting, yellowing and curling leaves. Discolored streaks are often seen in strawberry stems and runners, and in berry canes.
To determine if a plant is infected with bacterial wilt, press together two freshly cut sections of a stem and slowly pull them apart. If a “stringy” sap (bacterial growth and associated resins) extends between the cut ends, the plant has bacterial wilt.
Especially Tomatoes! And of those, Heirlooms are particularly susceptible to the wilts. Instead, get varieties that have VFN or VF on the tag at the nursery. The V is for Verticillium, the F Fusarium wilt, N nematodes. Ace, Early Girl, Champion, Celebrity, are some that are wilt resistant/tolerant. In these drought conditions, consider getting only indeterminates. In the Mother Earth News tomato survey, they found gardeners chose heirlooms over hybrids if their soil is wilt/blight free. Otherwise, the longer the gardener has gardened, they more they chose wilt resistant toms if their soil has the fungi.
Western striped cucumber beetles are deadly to cucumbers. They are referred to as ‘plant-wounding insects’ and also transmit bacterial wilt. Feeding on blossoms and leaves, they carry the wilts and also spread it among squash, melons, and pumpkins. Cucumber beetles also vector viruses such as cucumber mosaic but do so much less efficiently than aphids. Spiders are one of the predators that eat the beetles. Let those spiders live! A tachinid fly and a braconid parasitoid wasp parasitize them. Grow plenty of flowers for these beneficial insects!
Radish have become my new religion! Radish repel the beetles! You do have to plant your radish ahead of installing your transplants or have it up before the seedlings start growing from seed. Grow your radish companion along where you will let the vine travel. The part of the vine growing up over an arch won’t be helped, so if you have space and infected soil, you may opt to keep your vines on the ground. Plant enough radish so you can eat some, but let some grow out so the whole plant is big and protecting your cukes and other vines. Broccoli also repel cucumber beetles. Grow cucumbers under over summering Broccoli. Put in plenty of straw mulch to keep the brocs cool and the cukes off the ground. Whenever you see these beetles don’t fall for how cute they are. Squish.
Transplant rather than direct seed! Tiny seedlings are most susceptible to cucumber beetle feeding damage and to bacterial wilts.
Washington State Extension says:
Apply straw mulch! Straw mulch can help reduce cucumber beetle problems in at least 3 different ways. First, mulch might directly slow beetle movement from one plant to another. Second, the mulch provides refuge for wolf spiders and other predators from hot and dry conditions, helping predator conservation. Third, the straw mulch is food for springtails and other insects that eat decaying plant material; these decomposers are important non-pest prey for spiders, helping to further build spider numbers. It is important that straw mulch does not contain weed seeds and to make certain that it does not contain herbicide residues which can take years to fully break down.
Cucumber Beetles have their preferences! Bitter is their favorite. Not interested in watermelon at all, but watermelon does get the wilts, just from other sources! Anyway, see more details and rankings of varieties of different kinds of veggies. Varieties make a huge difference.
Special Planting and growing tips!
- Regarding soil fungi like Fusarium and Verticillium wilts/fungi, how you care for cukes and toms is super important! Cucumbers are even more susceptible than tomatoes to the wilts fungi, die pretty instantly, in about 3 days, if they get infected. So when you plant them, treat them similarly to your tomatoes if you have wilts fungi in your garden.
- Plant cukes and toms on a raised mound/basin with the bottom of the basin above the regular soil level. This allows good drainage. Top that with a 1/2″ of compost, cover that with only 1″ of straw to let in air and sun to dry the soil. Keep the LEAVES OFF THE GROUND from the get go. Leaves touching the soil is the main way toms get the wilts. Remove lower leaves that might touch soil when weighted with dew or water from watering. Keep a regular watch for new foliage at ground level and remove it. AVOID WATER SPLASH when watering at ground level. The fuzzy damp leaves of toms and eggplant are perfect fungi habitat.
- When they are about a foot tall, water neighboring plants, but not your toms. That keeps the soil drier near your plant, so the fungi can’t thrive there. Since toms have a deep taproot, they will get plenty of water from what you give neighboring plants. Water near them but not at them or on them. In fact there are farmers who dry farm tomatoes! Read more!
- If you are comingling beans with cukes lower along a trellis, plant the beans between the raised cucumber mounds. Beans don’t get the wilts, but love the water, so lower is good. They are a big plant with continuous high production and short roots that need to be kept moist. Mulch ASAP with straw under cukes to keep leaves and fruit off the ground, and out of the insect zone. Put a stake in the middle of the basin so you know where to water when the leaves get dense. Water gently below the leaves at ground level, no splash. Keep those leaves dry. When your plant gets bigger you can remove lower leaves.
- Since the fungi are airborne as well as soil borne, plant in different places as far apart as possible. Plant so leaves of one plant are not touching another plant. Remove sickened foliage ASAP to reduce fungi population and slow spreading. Prune on hot, dry, unwindy days, mid morning to midday, after dew has dried, so cuts can dry and heal with less chance of airborne fungi getting into them. Try not to touch the cuts after they have been made. Use clippers for a clean cut. Wash your tools and hands often.Trimming away infected leaves is a sad and tedious process. It’s practically impossible not to spread the fungi as your touch leaves that have it and try to remove them without touching any other stems or leaves. The very cuts you make are open to fungi. Then, naked stems are susceptible to sunscald – see image below. You come back a few days later and more leaves are wilting. The disease is internal, has spread out to the leaves. At some point soon after that, a lot of gardeners pull the suffering plant. It’s done. Not good to leave it and let windborne fungi infect neighboring plants.
Do not compost infected plants or trimmings. The fungi has amazing survival ability and being soil borne, it is right at home in your compost. Put it in the trash, carefully bagged so as not to spread or leave any trace. Wash your hands. If you can, burn the infected plants.
- The wilts can’t be stopped. Sooner or later the plant leaves curl lengthwise, get the dark spots, turn brown then blacken and hang sadly. Plants can produce but the fruit doesn’t ripen properly if it does produce. It’s agonizing to watch. Sometimes they somewhat recover later in the season after looking totally dead. You had stopped watering them, summer heat dries the soil and kills enough of the fungi for the plant to be able to try again. But production is so little and fruits don’t ripen properly. It’s better to pull it, reduce the fungi population that can blow to other plants. The safest bet is to remove the entire plant. Get all of the root as best you can. The root is where the wilt’s mycelium first congregate and infected roots left in the ground will start the whole process again. Replant in a different place if possible.
Preventive Foliar Mix that can help!
Apply to newly installed transplants, and during the season every 2 to 3 weeks, so new growth will be covered. Wet both the undersides and tops of leaves. Per gallon add:
- One dissolved regular strength aspirin
- 1/4 Cup nonfat powdered milk
- Heaping tablespoon baking soda
- 1/2 Teaspoon mild liquid dish soap
After the tomatoes set, add some nitrogen. Boost your plant’s immune system with some worm castings at the same time. You don’t want to add too much nitrogen to your tomatoes before they set fruit. Too much nitrogen before fruiting leads to more leaves and less fruit. Add N only once. Stressed plants are the most susceptible to the fungus. Water regularly and deeply. Use well-balanced, slow-release organic fertilizers that aren’t overly heavy with nitrogen. A healthy plant tends to fight off the spores.
Blight can also be transmitted through seed, so NO seed saving from infected plants. Fresh seeds and resistant varieties are in order.
Remove volunteer tomatoes and potatoes. If they are a not a resistant or tolerant variety, when they get sick, they increase the chances of your resistant varieties having to fight harder to live, and your good dear plants may not win the battle.
Air circulation, plant staking and no touching. Air circulation allows the wind to blow through your plants. This allows the timely drying of leaves and it helps break up micro climates. If your plants are packed too tightly together, they themselves become barriers to drying. Staking your plants to poles and using cages helps them grow upright and it creates gaps between the tomato plants. You want wind and sun to reach through and around your plants. Moisture is needed for fungi to spread. Dry is good. Tomatoes should be planted with enough distance that only minor pruning is needed to keep them from touching each other.
Spray proactively. Wettable sulfur works. It is acceptable as an organic pesticide/fungicide, is a broad spectrum poison, follow the precautions. It creates an environment on the leaves the spores don’t like. The key to spraying with wettable sulfur is to do it weekly BEFORE signs of the disease shows. Other products also help stop the spread. Whatever you select, the key is to spray early and regularly.
At the end of the season remove all infected debris, don’t compost. Don’t leave dead tomato, eggplant or peppers in the garden to spend the winter. Pull weeds because spores can over-winter on weed hosts. Many weeds, including dandelions and lambsquarters, are known to host verticillium wilt. During our winter season, turn your soil about 10 inches deep. Let the soil dry and the fungi die. Burying the spores helps remove them, it disturbs cucumber beetle eggs and exposes snail eggs to die!
If you have space, crop rotation is an important tool in fighting wilt. If you’ve had trouble with wilt, don’t plant potatoes, eggplant, or other solanaceous vegetables where any of them have grown for at least four years.
Practice prevention, be vigilant. If you don’t have wilts in your soil you are so blessed!
The Green Bean Connection started as correspondence for the Santa Barbara CA USA Pilgrim Terrace Community Garden. All three of Santa Barbara city’s community gardens are very coastal. During late spring/summer we are often in a fog belt/marine layer most years, locally referred to as the May grays, June glooms and August fogusts. Keep that in mind compared to the microclimate niche where your veggie garden is. Bless you for being such a wonderful Earth Steward!
Love your Mother! Plant bird & bee food! Think grey water! Grow organic!