Tomatoes

Vegetable and Fruit News, Volume 13, Issue 4 (July 2022). Topics in this issue are: Disease of Garlic Scapes, Blossom End Rot, Preventing Bruising in Apples and Peaches, Corn Disease Identification, Tomato Spotted Wilt Virus, Tomato Pith Necrosis, July IPM Tips, Mowing: IWM Tool, and Upcoming Events

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While visiting a tomato field this week I saw the tell-tale signs on the flowers that this field was being visited by bumble bees that were pollinating the tomato flowers. In the field wind movement is usually enough to cause pollination in a tomato flower, but at times there are very calm days and nights with very ‘heavy’ air and little wind movement. However, even with wind action it is always beneficial to have bumble bees perform buzz pollination, which can greatly in-crease fruit set..

Over the last few weeks in almost all of the tomato fields I’ve been in have rain check on the tomato fruit (fig. 1). Rain check is the many, tiny concentric cracks that form on the shoulder of the fruit and these small cracks can expand over time into unsightly scabs.

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.

Southern blight is a fungal disease that is most common in the tropics and subtropics, but also is found in the SE United States in the summer. In Maryland we usually find it in the southern part of the state in counties like St. Mary’s, Charles and Wicomico. It has been found this year in more northern counties such as Frederick, Montgomery and Baltimore.

Tissue tests taken in tomato fields over the last 6 weeks show that fields with good levels of potassium (K) (>3.2%) have overall lower levels of fruit ripening problems than fields with below recommended levels of K (< 2.5%). Figure 1 shows an example of a tomato with good levels of K, while figures 2 and 3 show what often happens when K levels are too low.

Tomatoes are grafted by joining the top of one plant (the scion) to the root system of another (the rootstock). The subsequent plant is more vigorous and productive. Several studies have been done over the last 10 years that show the benefits of using grafting for soil disease control in tomato production, but there is not much research that examines the influence of rootstocks when there is no disease in a tomato high tunnel production system.

Last week Gordon Johnson had an article about exhaust problems for greenhouse transplants. In Maryland we have seen a few problems with ethylene interactions with tomatoes in high tunnels. Ethylene (C2H4) occurs in trace amounts in gasoline and natural gas and is produced when these substances are burned. It also is present in wood and tobacco smoke.

Tomato Pollination and How to Increase it in High Tunnels