PPDL Picture of the Week

October 29, 2018

Anthracnose of tomato​

Dan Egel, Clinical Engagement Associate Professor-SWPAC, Botany and Plant Pathology, Purdue University

It’s that time of year when frost has ended many a backyard garden.  Perhaps you harvested tomatoes one last time before a predicted freeze.  These tomatoes were lined up on your kitchen counter to be added to a fresh salad at a later date.  However, when you went to grab one of these tomatoes, you noticed a sunken area, perhaps accompanied with an orange or salmon colored cast.  What’s going on and how did this happen?

The tomato in Figure 1 has a disease known as anthracnose.  This disease is caused by a fungus that probably splashed on the tomato before you harvested it.  Although the tomato looked healthy when you harvested it, the fungus had probably already infected the tomato.  This infection expanded while the tomato sat quietly on your kitchen counter.  Before the fungus splashed on your tomato, it probably survived on crop residue from a tomato or pepper plant from a previous year.  If it is possible to cut the lesion out of the tomato, go ahead and add it to your salad.  

Gardeners who what to avoid anthracnose next year should do their best not to grow tomatoes or peppers in the same area year after year.  Staking tomatoes to keep the tomatoes off the ground should help to lessen anthracnose problems.  Tomatoes mulched with plastic or straw will have less splash of soil onto the fruit and, therefore, fewer anthracnose symptoms.  Homeowners can find out more about controlling tomato diseases with the extension bulletin BP-184-W, Five Steps for Healthy Garden Tomatoes found here.  Commercial growers can find more information in the Midwest Vegetable Production Guide for Commercial Growers found here.