67 articles tagged "Tomato".

: These lesions of bacterial speck of tomato were observed on a tomato transplant for sale to homeowners at a retail outlet. Tomato transplants should be inspected for disease symptoms during production or at delivery.

Many Indiana growers may have tomato transplants growing in a greenhouse for field or greenhouse/high tunnel production. The three most likely diseases are bacterial spot, bacterial speck and bacterial canker. This article describes symptoms for these diseases and some management options. While these bacterial diseases thrive in transplant production where plants are often overhead watered, these diseases are not common on tomatoes grown to maturity in greenhouses or high tunnels. This is because, for the most part, tomatoes grown to maturity in a greenhouse or high tunnel do not have the necessary leaf wetness required for these diseases. Bacterial canker is occasionally observed in greenhouse/high tunnel situations since this disease may become established in transplants and becomes systemic in plants. Once bacterial canker is systemic in the plant, it ‘spreads’ within each plant even if it does not spread from plant to plant. Bacterial speck and spot – The symptoms produced by these two diseases are[Read More…]

Effectively managing foliar diseases including late blight (LB), early blight (EB), and Septoria leaf spot (SLS), is one of the biggest challenges facing organic tomato growers. New, resistant hybrid varieties are available, but organic growers often plant heirloom varieties instead because they are perceived to have superior flavor and growers can save seed. Copper fungicides can provide fair control of these diseases, but these products are contact, not systemic, and must be applied often, which can negatively impact soil and water quality. The tomato organic management and improvement project (TOMI), led by Lori Hoagland in the Horticulture Department at Purdue, brings together a multidisciplinary team of researchers from across the U.S. to develop short, medium and long-term solutions to this challenge. In the short-term, the team aims to identify biofungicide and biostimulant combinations that can effectively control LB, EB and SLS. Greenhouse and field trials are underway testing various combinations[Read More…]

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There are several potential benefits of growing grafted tomatoes, particularly for early season tomato production in greenhouses or high tunnels. If you are interested in trying this technique but wondering whether it is possible to graft tomato plants by yourself, a Purdue extension publication, Techniques for Tomato Grafting, (https://extension.purdue.edu/extmedia/HO/HO-260-W.pdf ) provides a step-by-step guideline for small growers to explore this technique. A question I am often asked is: when should I start to plant the seeds to produce grafted plants? The chart below shows a general timeline and materials needed for producing grafted tomatoes on a small scale on your farm. As a general rule, the grafting process delays seedling growth for 6-7 days. The delay normally does not make a noticeable difference on the size of seedlings after the grafted plants are grown in a greenhouse for more than 2 weeks prior to transplant. As a matter of fact, grafted[Read More…]

These tomato plants are exhibiting epinasty or a downward growth of the leaves in response to ethylene produced from a malfunctioning heater in a greenhouse. The topmost leaves are growing normally because the plants were removed to a separate greenhouse after exposure to ethylene. (Photo by Dan Egel).

Almost every year, I have a greenhouse tomato grower or two call me about tomato plants that are distorted and don’t seem to be growing right. The problem often turns out to be ethylene damage. This year, I have decided to write an article about it before I get those calls. Tomato plants with ethylene damage often have leaves that are curled down and stems that are twisted (Figure 1). Stems or leaves that are curled downwards are said to have epinasty (in botanical terms). Epinasty is a common symptom of ethylene damage. Ethylene is a common by-product of incomplete combustion of several different types of fuel. Incomplete combustion is often the result of heaters that are not working efficiently. Tomatoes are very sensitive to ethylene damage; however, other crops may also show ethylene damage. The tomato plants in figure 1 also have yellow seed leaves. Ethylene damage does not include yellowing.[Read More…]

For many vegetable growers, the season is in full swing. All that hard work in season preparation, planting and maintenance is paying off with harvest. One of the on-going season maintenance issues is applying fungicides. In other articles, I have described how and when to spray. In this article, I want to address when to stop. To limit the scope of this article, I will concentrate on tomato, cantaloupe and watermelon crops. These are crops where the fruit is consumed, not the foliage. For most vegetable crops, there is no need to apply a fungicide shortly before the final harvest. Foliage needs to be protected to preserve fruit quality. A plant with reduced foliage will produce a smaller fruit and/or fruit that have fewer sugars and other desirable compounds. I don’t know how much foliage needs to be reduced to affect fruit size or quality. However, I do know that for many foliar diseases, symptoms will not be obvious[Read More…]

Southern blight of tomato thrives under hot, dry conditions. Usually, such conditions are more common in August than early July. However, 2016 has been relatively hot and dry in southwest Indiana. Perhaps for this reason, I have observed this disease in my own tomato plots. This article will discuss the symptoms, biology and management of southern blight of tomato. Southern blight has a wide host range affecting many vegetable, field and ornamental crops. Tomato is the most important host. The disease is caused by the fungus Sclerotium rolfsii. This fungus is related to the one that causes white mold. The first symptom one is likely to observe of southern blight is plant wilt. At the base of the plant, one is likely to notice a canker with sclerotia that may be as large as a sesame seed (Figure 1). These sclerotia are survival structures for the fungus and allow the disease to occur[Read More…]

Figure 1. Hornworm feeding on tomato leaves in a high tunnel.

Hornworms can be pests of tomato and pepper in field grown crops, but for some reason seem to be particularly severe in high tunnels. Hornworms are very large caterpillars, measuring up to 4 inches long (Figure 1), and they can consume large quantities of foliage and will also feed on green fruit (Figure 2). In fields, hornworm damage is usually localized and tolerable, although treatment is sometimes required. In high tunnels, hornworm damage, particularly to tomato, is often severe (Figure 3) and will require several applications of insecticides. In field situations, the treatment threshold is one hornworm per two plants. Since the infestations are often localized, it may not be necessary to treat the entire field. In high tunnels, there is no established threshold, so my recommendation would be to treat as soon as you seen caterpillars or their damage. The good news is that hornworms are fairly easy to control.[Read More…]

Below, I will briefly discuss four diseases that I have observed on tomatoes recently. White mold of tomato – Perhaps the most common symptom of white mold of tomato is the light brown area on the lower stem (Figure 1). This brown area is essentially dead and will result in the wilt and death of the tomato plant above that point. Either on the outside of this dead area or inside the stem, dark, irregularly shaped fungal bodies can usually be found. These fungal bodies (known as sclerotia) are diagnostic of white mold. The fungal spores responsible for white mold are released early in the spring from a very small mushroom (several mushrooms could fit on a dime). The spores will enter a plant where tissue is dead or senescent, such as old flower petals. Fortunately, white mold, once established, will not spread from tomato to tomato plant. However, growers may observe more symptoms as later[Read More…]

We have received a number of reports of outbreaks of spider mites, primarily in watermelons in the field and cucumbers in high tunnels. Spider mite damage can be recognized by the chlorosis often observed on older leaves (Figure 1).  Plus, the underside of leaves affected by spider mites often appears ‘dirty’ due to the debris caught by the webbing (Figure 2).  The problems in high tunnels are not unexpected because one of the primary causes of mortality in mite populations is rainfall washing them off the plants and, of course, that is lacking completely in high tunnels. In addition, the warmer temperatures present in high tunnels allow mites to complete generations faster so populations can build to high levels quickly. The hot weather recently is helping to drive population increases in fields as well. In both scenarios, we don’t really have treatment thresholds for mites. Generally speaking, if populations are increasing,[Read More…]

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