Tomatoes

Botrytis in High Tunnel Tomatoes

Black dot root rot found in high tunnel tomatoes

Corky root is caused by the fungus Pyrenochaeta lycopersici. Tomato plants affected with corky root may appear stunted and generally lack vigor.

I visited a few tomato fields this week and found 2-4-week-old tomato plants with some early blight (Alternaria solani) and in some cases bad early blight lesions. This is very early in the season to be seeing this level of early blight. Many of the plants had a few flea beetle adults on the plant (fig 1) and in the areas where the early blight was found also had moderate to high flea beetle feeding (fig 2).

Another disease we might be seeing now and in the next week or so is late blight. The weather conditions of the past week have been favorable for its development: cool (for summer temperatures) daytime and nighttime temperatures along with ample moisture.

Tomatoes are grafted by joining the top part of one plant (the scion) to the root system of another plant (the rootstock) (fig. 1). The resulting plant is usually more vigorous and productive.

In the last week tomatoes from different counties in Maryland were found with the same unusual disease symptoms, called tomato pith necrosis. All the problem tomatoes were from early planted fields. Tomato pith necrosis is caused by the soilborne bacterium Pseudomonas corrugata. It has occurred infrequently in Maryland over the past few decades. The disease usually is found in early planted tomatoes when night temperatures are cool, but the humidity is high, and plants are growing too rapidly because of excessive nitrogen application.

To no one’s surprise this week has seen a great number of problems pop-up in tomato fields throughout our area. The first of course has been disease with bacterial and fungal diseases spreading. The fungal pathogens usually can be contained with timely (as difficult as that is) fungicide applications. Bacterial spot or speck on the other hand can be much more difficult to control once it gets started and the weather remains wet and warm. In figure 1 on the right hand side is a row of tomatoes that had been sprayed with fungicides and copper for the last several weeks. Bacterial spot has ravaged this row.

A very unusual and seldom seen tomato foliar blight was found by an intrepid county educator in Southern Maryland last week.

I recently received an inquiry from a high tunnel grower about unusual symptoms on tomato leaves.