May 16, 1997

In part one, we discussed how to grow tomatoes in our maritime climate. This week we'll cover some of the common tomato problems gardeners sometimes face.

Late Blight: Here in the maritime Pacific Northwest, this fungus is easily the biggest problem we tomato growers face. Your plants can go from healthy to dead in a matter of a few weeks. Understanding this disease is so important that we have a separate article devoted to it. If you want to know about Late Blight, please check out the FAQ regarding Late Blight.

Blossom End Rot: Many people think this is a disease, but actually it is a cultural problem. BER occurs as a result of the plant suffering from a calcium deficiency. This may be caused by a lack of soil calcium, but most often it results from the gardener overwatering the plants (Overwatering is another chronic disease in gardens everywhere! But I digress…). Tomatoes don't really need lots of water, but they do want a regular, even supply. Calcium is very soluble in water. If you supply more water than your soil can hold, it will sink down into your subsoil, taking the available calcium (and other nutrients) with it! The solution to BER is two fold: Lime the beds well, preferably with calcitic lime instead of dolomite; and provide consistent amounts of water at regular intervals. Drip irrigation is very effective when used in the tomato bed. Try the following: Water the tomatoes until the top 6-8 inches or soil are evenly moist; probably this will require the addition of about an inch of water to the surface. Wait two or three days (DON"T WATER EVERY DAY!); then dig down 6 inches into the bed (away from the plants). If the soil at that depth is dry, it is time to water again. If not, wait another two days, then check again. This will help you get a feel for how much water your tomatoes (your whole garden, actually) really need. It might be worth noting that peppers, which are also Solanaceous plants, can have this exact same problem with BER.

Verticillium Wilt, Fusarium Wilt, and other diseases: Keith Mueller's Tomato Page is a good guide to help you identify tomato problems, including diseases. The easiest solution to disease problems is to buy or grow varieties which are resistant to the disease in question. Modern tomato varieties often have a virtual pedigree of letters accompanying them, identifying which diseases they resist. For example, Celebrity has VFNTMV after its name, meaning it is resistant to Verticillium, Fusarium, Nematodes, and Tobacco Mosaic Virus.

Some diseases, such as Verticillium, can persist in the soil many years. Chemical solutions to these problems tend to kill everything in the soil, good and bad, and leave residues that I personally do not want around my edibles! A good organic solution is called solarization; unfortunately, it ties up the garden bed for most of the summer. To solarize a plot, first saturate it with water. Next take enough clear plastic to cover the bed, and lay it over the ground, making sure to weight the plastic down around all the edges. Finally, leave the whole thing to cook in the summer sun for 8 weeks or so. Maritime gardeners will get better results with two sheets of plastic - insert wooden blocks or bricks between the sheets to provide an insulating airspace for maximum heating.

Many of these diseases can be controlled, or even prevented, by rotating your planting locations from season to season, and by cleaning up plant litter consistently. We are fortunate that Verticillium is not normally seen in our region, but most of the others are as common here as they are elsewhere.

Tobacco Hornworms and Corn Earworms: Most insect pests are specific in their choice of targets. Tobacco is a relative of tomatoes, so it is easy to understand why hornworms also bother tomatoes. But corn earworms? I have no idea.

Both these pests are the larvae of moths. Bacillus thuringiensis (Bt; most often sold under the trade name of Dipel) is a bacterium that is harmless to humans, yet paralyzes the gut of all juvenile lepidoptera (that is, caterpillars: the larvae of butterflies and moths). If you only see a few of these creatures, hand-picking is the preferred control. Caterpillars can be squished, or dropped into a container of soapy water.

The large hornworm is rarely seen in our area - I've only seen one, ever. These incredible caterpillars can get as large as your finger! Fortunately their horn is only for show. If you haven't seen one before, take a look.

All contents © Travis Saling
This page was last updated November 18, 2013