Friday, July 15, 2011

Too Much Water! by Carol King

The afternoon rains that have persisted over the last couple of weeks are a mixed blessing for gardeners. While we revel in the much need moisture, too much water can cause as many maladies as not enough water.

Here are some problems to be on the look out for:


Early Blight on tomato
 Early blight in tomatoes is caused by the fungus Alternaria solani. Symptoms become prevalent during the hotter months. This disease produces brown to black, target-like spots on older leaves. If severe, the fungus also attacks stems and fruit. Affected leaves may turn yellow, then drop, leaving the fruit exposed to sunburn. Sanitation is the best control. Remove all diseased plant tissue on the ground. Avoid overhead irrigation. If the infestation is heavy, sulfur dust may help protect new leaves from infection. Follow label directions carefully, as sulfur can burn leaves when temperatures are high.

Septoria leaf spot
 Septoria leaf spot is another fungal disease found in tomatoes. Characteristic symptoms are white or gray spots on leaves, surrounded by a black or brown margin. Control is similar to early blight.

Root rot fungus is directly related to overwatering. Management of root rot requires soil improvement, and proper watering. Avoid overwatering. Always allow the soil around plants to dry out a few inches below the surface before watering again. Improve moisture conditions around the crown of the plant by exposing it to drying conditions. Remove some of the mulch or pull it back from the base a few inches. However, do not expose roots.

Powdery mildews are characterized by spots or patches of white to grayish, talcum-powder-like growth found on leaves, flower buds and stems. Once the disease becomes a problem:
Powdery Mildew
Avoid late-summer applications of nitrogen fertilizer to limit the production of succulent tissue, which is more susceptible to infection.
  • Avoid overhead watering to help reduce the relative humidity in the canopy of the plant.
  • Remove and destroy all infected plant parts (leaves, etc.). For infected vegetables and other annuals, remove as much of the plant and its debris in the fall as possible. This decreases the ability of the fungus to survive the winter. Do not compost infected plant debris. Temperatures often are not hot enough to kill the fungus.
  • Selectively prune overcrowded plant material to help increase air circulation. This helps reduce relative humidity and infection.
If cultural controls fail to prevent disease buildup or if the disease pressure is too great, an application of a fungicide may be necessary. Follow the instructions on the fungicide label for use on specific plant species, varieties, rates to be used, timing of applications, and waiting periods before harvest.

Lawn and Flower Beds:

Sprinkler Systems should be adjusted. Do not continue to water on a scheduled basis until water is actually needed. Let Mother Nature be your sprinkler!

Powdery mildews can be found on shrubs, grass, and flowers and are characterized by spots or patches of white to grayish, talcum-powder-like growth. Control is the same as for vegetables.

Fairy Ring
 Mushrooms. Heavy rains or prolonged rainy periods often encourage the growth of mushrooms (toadstools) in home lawns and other turf areas. Most often, the mushrooms will appear randomly across the lawn. Mushrooms may also emerge in more organized circular or part-circle patterns, "fairy ring". Mushrooms found growing in lawns should NEVER be eaten, unless you are well acquainted with the different species. Many mushrooms are poisonous to some degree and ONLY an expert can distinguish between edible and poisonous species. Since young children and pets may be tempted to eat mushrooms, remove the obvious fungal structures by raking, mowing, or hand-picking can avoid the possibility of poisoning or illness.

All Around the House:

 Mosquitoes. Encephalitis, dog heartworm, and West Nile Virus are the primary mosquito-borne diseases in Colorado. Beyond viral and parasitic diseases, other health problems caused by mosquitoes include allergy and infection. Mosquitoes can be a SERIOUS health issue.

Fight the Bite Colorado recommends the following:

  • Check for items that might hold water including wheelbarrows, tires, hubcaps, toys, garden equipment, pool covers, tarps, plastic sheeting, pipes, drains, boats, canoes, recycling bins and trash.
  • Remove standing water in ponds, ditches, clogged rain gutters, flower pots, plant saucers, puddles, buckets, jars and cans. Completely change water in birdbaths and wading pools weekly. Drill drainage holes in tire swings.
    Stock ornamental ponds and fountains with fish that eat mosquito larvae.  
  • Avoid mosquitoes by staying indoors at dawn and dusk when they are most active. 
  • Wear long-sleeved shirts and long pants while outdoors.
  • Apply insect repellent that contains DEET. Follow directions carefully.
    Install or repair window and door screens to keep mosquitoes out.
A complete check list can be found at their website. (
For help with these or other garden problems, call the Garden Hotline at Jefferson County CSU Extension at 303-271-6620.