By: Mary Ellen Ellis
Verticilliumwilt can be a devastating infection for a tomato crop. This fungalinfection comes from the soil and it cannot be treated with fungicides. Thebest way to avoid it is to use resistant tomato varieties. It is also importantto know the signs of the disease to avoid spreading it from one area of yourgarden to another.
Verticillium wilt is a fungal infection that can affectnumerous plants, including tomatoes.The fungus persists in the soil and on plant material. It forms threads thatinfect plants through the root hairs. The best conditions for verticillium tothrive are those of early spring: cool and wet. Moist soil at a temperaturearound 75 degrees Fahrenheit (24 Celsius) is ideal for the fungus to startinfecting roots.
Although the infection usually begins in spring, you may notsee signs of it until summer. One of the first signs of tomatoes withverticillium wilt is yellowing of older leaves. Yellow changes to brown andthen the leaves die.
The disease also causes discoloration of vascular tissue,which you may see as brown streaks up the stems of tomato plants. Thisdiscoloration may also be patchy. New shoot tips may wilt and leaves start tocurl upward and sometimes drop. The entire plant and individual fruits may bestunted.
There is no fungicide that can be used to treat verticilliumwilt on tomatoes or other plants, so prevention is necessary to avoid thedamage this disease causes. First, start with resistant plants. Resistantcultivars are available and have the letter “V” after the name to indicatethis.
Verticillium fungi will easily spread from one plant toanother if you aren’t careful. Practice good sanitation when you haveinfections. Keep your tools and equipment washed and disinfected between usingon affected and clean plants.
Also important is croprotation. If you keep planting susceptible crops in the same soilyear after year, the fungus will build up and cause repeated infections. Someof the more vulnerable plants in addition to tomatoes are potatoes,strawberries,eggplant,and melons.Plant cover crops, grains, or corn in off years to reduce the fungus in thesoil.
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Juglone is produced by several tree species, including black walnut, English walnut, Persian walnut, butternut, hickory, and pecan. Black walnut trees, in particular, are infamous for affecting nearby plants вЂ“ hence the disorderвЂ™s name.
Juglone is formed in the leaves, fruit hulls, inner bark, and roots of the walnut tree and other members of the walnut family. With rain, it leaches from nuts, leaves, and bark and readily released into the soil. Uptake in tomatoes occurs when tomato roots make contact with the tree roots.
JugloneвЂ™s toxicity to tomatoes directly depends on how close tomato plants are to walnut trees. Those within a treeвЂ™s root spread (two to three times the circumference of its branches) are more severely infected. They wilt and die quickly. Those further away wilt more slowly.
Remove affected solanaceous crops, such as potato, tomato, pepper and eggplant, from the garden immediately to limit the spread of fungus wilts. Additionally, strawberries and raspberries are susceptible to Verticillium wilt. Prune affected branches of trees and shrubs, such as fruit trees, maples and flowering or fruiting shrubs.
Destroy infected plant material by burning. Never add wilt-infected materials to compost piles.
Find wilt-resistant plants to replace garden plants.