I have been growing heirloom tomatoes for more than 10 years and have been...

Asked August 5, 2014, 2:08 PM EDT

I have been growing heirloom tomatoes for more than 10 years and have been constantly challenged by anthracnose. In addition to having new soil s[rayed with oxidate, newspaper and straw covering bare soil, and spraying plants with oxidate ZI still have an anthracnose problem. Suggestion?????

Talbot County Maryland

1 Response

. Your use of the soil drench and the mulch layers are appropriate, but you may have to resort to crop rotation and avoid planting solanaceous plants in the affected area for a year or two.

The following is an excerpt from one of our diagnostic publications.

"There are more than a dozen species of Colletotrichum, the fungal disease known as anthracnose. Affected crops include, pepper (see above photo), bean, tomato, eggplant, cucumber, muskmelon, watermelon, pumpkin, spinach, and pea. Sunken black lesions develop that may be covered with salmon colored spores under wet, humid conditions. On tomatoes, the soft sunken lesions develop dark centers. The fungus overwinters in seeds, soil, and plant residue.

Management: Lay a mulch of shredded leaves, dried grass clippings, or newspaper covered with straw under plants. Pick fruits regularly and quickly remove infected fruits. Avoid contact between soil and fruit. Avoid overhead watering during humid, cloudy weather. Remove all plant residue at the end of the growing season. Infected plant residues can be composted at sustained high temperatures- greater than 120° F. Otherwise, residues should be bagged up and discarded as garbage."

We find no tomato varieties that are resistant to anthracnose, and heirloom varieties are probably more susceptible to it than are the hybrids.

You should also ensure that your tomato plants are spaced appropriately to allow maximum air circulation around the plants and that the plants are not touching one another.