In our region, it seems like abnormal weather has been the norm in recent years. This is so frustrating for gardeners like me and you. My tomatoes are just sitting in the garden and hardly growing. At the beginning of the month, it seemed like the weather was turning hot, so I removed the protective water-wall cylinders that were providing extra heat to the plants. A week later, the weather has turned cooler and unsettled.
Tomatoes, peppers, cucumbers, melons and squash all grow best in warm weather. These warm-season crops have been stalled by the cool weather. Because of the cooler temperatures and rain in some areas, watering every day or every-other-day may be keeping plant roots too wet. This can lead to root damage and impair plant growth. It also encourages various plant diseases and leaches away valuable nutrients needed for growth. Before you irrigate, check the soil moisture in by digging down a few inches. If the soil feels moist, do not water.
Also related to our spring weather is the appearance of a bacterial disease called fire blight. This disease attacks certain members of the rose family. It is favored by mild (65 degrees or warmer) and moist spring weather. The bacteria enters the plant through wounds or natural plant openings like the ones that occur in flowers. A common means of transmission is via bees or other insects that pick up the bacterium from an infected plant and carry it unsuspectingly to uninfected plants.
Typically, members of the rose family that become infected are the ones that are in bloom at the time the conditions are right for infection. Apples, pears, crabapples and flowering pear are also prone to infection in our region. Other members of the rose family that are candidates for severe fire blight infections are photinia, pyracantha, cotoneaster, mountain ash, flowering quince and hawthorn.
How will you know if your plant is infected? Leaves, twigs and branches will become blackened as if scorched by fire. A closer look may reveal twig tips bent over to form the shape of a shepherd’s crook. These symptoms start where the bacterium enters the plant and move downward. If allowed to progress unchecked, fire blight can kill the plant.
To avoid spreading the disease, your pruning tools must be disinfected between each cut you make on the infected plant.
If you detect fire blight on any of your plants, act quickly. Because the infection is within the plant, your main means of stopping fire blight is to remove the infected portions of your plant with pruning. Prune at least a foot or more below the visible symptoms. Dispose of the infected materials in the garbage.
To avoid spreading the disease, your pruning tools must be disinfected between each cut you make on the infected plant. You can do this by dipping the blades in registered household disinfectants, such as Lysol or Pine Sol, and then it them off. While a bleach solution can be used, it tends to be corrosive on the blades and clothing.
Copper fungicide sprays applied when a plant is in full bloom next spring can help prevent reinfection of the plant and infection of susceptible plants in the area. Remember to read the label before using any pesticide. Another line of defense against fire blight is the selection of fire blight resistant cultivars when available. It is also advisable to avoid wetting the leaves and branches of the plant by using drip irrigation.
Next week, more about weather-related plant problems.
Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.