Tomatoes

In figure 1 you can see tomato plants that look a bit squirrely. I thought it was possibly herbicide or virus or nutrient problems. After eliminating the first and third we had the plants tested for a battery of viruses. There were 3 viruses found in the plants. The most unusual one was the Pepino mosaic virus, which belongs to the Potexviruses. This virus is very easily transmitted mechanically and has a low seed transmission rate. Seed transmission occurs at rates of less than one in a thousand when seed is not properly cleaned. The virus is external, contaminating the seed coat and not the embryo or endosperm.

Insect Pests of Tomato

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).

Normally at this time of year when I talk about any insect problems in crucifers I talk about harlequin bugs that feed by sucking out plant juices and inject toxins into the plant. But I have seen several fields and even some high tunnels with blister beetles feeding and defoliating several different vegetables such as tomato (including the fruit), leafy greens, crucifers, spinach and especially swiss chard (fig. 1). Blister beetles begin feeding on the edges of leaves eventually leaving only stems (fig. 1). The presence of blister beetles now is not unusual as they are often found in large clusters in late summer-early fall. They can arrive in large groups, seemingly overnight and can do a great deal of damage in a short period of time.

It is unusual that I see or hear about broad mites (Polyphagotarsonemus latus) being a problem in our tomato high tunnels. A grower was having symptoms of twisted growth and browning/bronzing of their tomato leaves this spring and guessed they might have broad mites. They did, with some plants severely damaged while others were fine. The grower had a late fall crop of cherry tomatoes that they kept into December but did not clean up their high tunnel until 2 weeks before they planted their spring crop of tomatoes. Unfortunately, the grower had a small infestation of broad mites in the fall crop of tomatoes that was able to overwinter.

This has been a bad year for stink bug damage in tomatoes. Just about every field I walk into has at least some damage while others have moderate to heavy damage (>20% tomatoes not marketable). Cloudy spot of tomato fruit is caused by the feeding of various species of stink bug (SB). On green fruit the damage appears as whitish areas with indistinct borders (Fig. 1).

I have seen and have gotten reports of stinkbug damage in tomatoes over the past few days. Stinkbug feeding damage is called cloudy spot in tomato fruit (fig. 1). It occurs when the adult or immature stinkbug puts its needle- like mouth part into the fruit and removes material from a large number of cells.

In the past, field trials I have conducted on gold flecking were inconclusive as to its causes as they showed more problems caused by environmental concerns than by thrips or mites. However, upon several visits to growers’ fields over the last 4 years that were having mite or thrips outbreaks there were almost always greater rates of gold flecking in the most heavily infested areas of the tomato field.

IPM Threshold Guide for Vegetable Crops

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.