72 articles tagged "Tomato".

​ Last year at the Southwest Purdue Agricultural Center (SWPAC) we conducted a tomato high tunnel trial described here. In this article, I would like to talk about the trial we will conduct in 2015, a repeat of the 2014 trial. In particular, I would like to talk about what we have done for fertility. Before deciding on a fertility scheme, it is critical to conduct a soil test each year. Our soil test from November 2014 showed that our high tunnels were low in sulfur, boron and moderately low in zinc. In fact, plant tissue tests conducted during the 2014 season were low for both sulfur and boron. As a result of these tissue tests, we added a 10% liquid boron product and ammonium thiosulfate (7%) to the fertigation during the 2014 season. However, the next set of tissue tests carried out during the 2014 season also came back[Read More…]


The tomato seedlings above exhibit downward curled leaves (red arrows) which maybe a symptom of ethylene damage and yellow seed leaves with lesions (red circles)

​This is the time of year when growers often call to complain about tomato transplants that do not look right.  One possibility is that the seedlings suffer from heater problems.  In particular, tomato plants are very susceptible to damage from the gas ethylene.  In Figure 1, some of the seedlings have leaves that are curled down and stems that are twisted (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. A second clue is to take a closer look at the yellow seed leaves (Figure 1). Ethylene damage does not include yellowing. Furthermore, there is a spotting on the lower leaves that is not typical ethylene damage. I believe that the symptoms on seed leaves were as a result of a different compound,[Read More…]



Photo by E. Maynard

​Sometimes newly transplanted crops don’t take off like we’d expect. Consider the newly transplanted tomato seedlings in these images. In Figure 1, lower leaves are chlorotic (yellow) and leaflet edges and leaves curl downward. In Figure 2, lower leaves are chlorotic or bleached and some had necrotic (dead) spots. In Figure 3, some leaves have died and others have ‘scorched’ margins or tips. Figures 1 and 2 are from a high tunnel; Figure 3 is from the field. What they have in common is that the tomato plants are not thriving after transplanting. It may be hard to say exactly what is going on with each of these, but it would not be surprising if they were cases of over application of a fertilizer or soil amendment, leading to toxicities for the plant. Ammonium toxicity is common when soil is cool and wet, soil pH is low, and there is[Read More…]


White mold

In early March, I observed white mold of recently transplanted tomato plants in a greenhouse situation. I have described the symptoms, biology and management of white mold at https://ag.purdue.edu/arp/swpap/VeggieDiseasesBlog/Lists/Posts/Post.aspx?ID=18 . I have never observed white mold (a.k.a, timber rot) in February before. I have observed white mold of tomato transplants in April. However, the very small mushroom (smaller than a dime) that is part of the life cycle usually emerges in the spring after a cold period. The appearance of white mold in February may be as a result of the presence of the mushroom in the greenhouse that produced the transplants. To reduce severity of white mold of tomato, I recommend that tomato growers: Inspect transplants for stem lesions which may be a symptom of white mold. Bring questionable symptoms to my attention or send them to the Purdue Plant and Pest Diagnostic Laboratory (http://www.ppdl.purdue.edu/ppdl/index.html). Clean and sanitize greenhouses[Read More…]


One way insects communicate with individuals of the same species is with pheromones. Pheromones are volatile chemicals released by an insect that usually can be detected only by individuals of the same species. There are a number of different types of pheromones, but the most common type is the sex pheromone. Usually the females will emit a tiny amount of a chemical that attracts the male to her and increases the likelihood of mating. Because the chemical is volatile, air currents carry it. The male detects the pheromone in the air with receptors on his antennae. He then flies upwind to find the source of the pheromone, a prospective mate. The chemical compositions of pheromones for a number of pest species have been identified and synthetic copies can be produced in the laboratory. Synthetic pheromones can be used in conjunction with traps to catch male insects. Listed below are some, but[Read More…]


Bacterial spot of tomato is one of the most serious diseases facing tomato growers in Indiana. As described at Vegetable Diseases in Greenhouses (PDF), bacterial spot is more of a problem for field tomatoes than for greenhouse tomatoes. Symptoms and management of bacterial spot are described briefly at Bacterial Spot of Tomato and Pepper (PDF). A more detailed version of this article is found at An Update on the Use of Copper Products for Managing Bacterial Spot of Tomato (Blog Post). This article will discuss why copper products have become less useful in the control of this important disease and options for managing bacterial spot of tomato. Copper products have been used for many years to help control bacterial spot of tomato. However, some strains of the bacteria that cause this important disease are resistant to copper—that is, the bacteria have mutated to a form that is no longer sensitive to copper. Some of[Read More…]


Over the last several years, the number of questions I have had about tomato production in high tunnels has increased dramatically. Since I am a plant pathologist, most of the questions I have been asked are about diseases of tomatoes in high tunnels. However, I also have been asked production questions. One particular question about tomato product that may impact disease severity is this: how many staked tomatoes can be grown in a high tunnel effectively? To be honest, the above question is one that I often ask myself when I observe high tunnels in Indiana. It isn’t necessarily one that is asked by growers. But maybe it should be. It has been my observation that growers often try to place too many staked tomatoes in a high tunnel. The result may include diseased tomato plants due to insufficient air circulation, poor quality fruit and even reduced yields. I was[Read More…]


While visiting my son in Lincoln, Nebraska this past summer, I had the chance to browse in a second hand store.I felt myself drawn to the book section where I found a green hard cover book titled, “Yearbook of Agriculture, 1928”. From 1894 until 1992, the Department of Agriculture published a Yearbook of Agriculture annually. These books provided updates, features and statistics for the year. The reports actually go all the way back to 1862, when the head of the agriculture department, Isaac Newton, submitted a report to the Commissioner of Patents. (It turns out most of these books have been scanned and are on-line-I could have saved myself $1.50 had I known!) It is my plan to report on parts of the 1928 book that I think might interest vegetable growers in Indiana. The first subject which caught my eye were the statistics for processing tomato production. Below I[Read More…]


​For 100 years bacterial spot has been causing huge losses for tomato ​growers worldwide. For 100 years products containing copper have held the key to controlling this devastating tomato disease. As tomato growers enter their second century of dealing with bacterial spot, the question has become whether copper applications lessen the severity of bacterial spot-or perhaps even make the disease worse. This article will discuss bacterial spot of tomato, why copper products have become less useful in the control of this important disease and finish with options for managing bacterial spot of tomato with and without copper. The first symptoms of bacterial spot one is likely to observe are small, less than 1/8 inch dark lesions on tomato leaves. The lesions may appear watersoaked, especially in the morning and are often surrounded by yellow (chlorotic) tissue. These lesions, whether found on leaves or stems, may coalesce to cause the loss[Read More…]


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