Tomatoes

Normally at this time of year, I’d be writing about how bad yellow shoulders and other fruit ripening problems are in Maryland tomatoes. But this has been a strange season with May weather in March and March weather in May, which caused a great deal of catfacing problems this year. However, except for a few fields in a few places there have been far fewer troubles with tomato yellow shoulders or fruit ripening problems than we normally see this time of year—at least for now. Why is this?

Over the last few months in our area there have appeared problems with tomato ripening. The ripening problems are called various names such as blotchy ripening, yellow shoulder, grey wall, internal whitening, etc. (fig 1).

Several growers have complained that their second set of tomatoes is catfaced or are deformed and ripening poorly. Their first set of tomatoes looked good, but the second set is having problems in scattered areas throughout the field.

Tomato plants were transplanted on 7 May 2012 into black (grower standard), white or reflective plastic mulch.

Tomato Ripening Problems and the Role of Potassium

Tomato Ripening Problems and Cucumber Beetles

Every year about this time I write something about tomato ripening problems I start to see in the field such as blotchy ripening, yellow shoulders, grey wall, internal whitening, etc. (Figs. 1, 2 and 3). By now everyone or most everyone should know that they all have the same root cause; a lower level of potassium (K+) than what is needed by the fruit to ripen properly.

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.

Tomato plants were transplanted on 7 May 2012 into black (grower standard), white or reflective plastic mulch. Five different varieties of tomato were used: Mt Spring+, Celebrity, Mt Fresh+, Crista and Scarlet Red. When tomato plants began to develop fruit, a 30% shade cloth was randomly placed over 6-10 plants per row.

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.