76 articles tagged "Tomato".

target spot

The following two articles describe two vegetable diseases new to Indiana that were recorded this past season. While neither of the disease reports are from severe outbreaks, it might be a good idea to become familiar with what may become a new disease situation. Target spot of tomato was identified from a tomato plant growing in a high tunnel in early July in Carroll County. At first glance, the disease appears to be early blight (Figure 1). Target spot may cause necrotic lesions in a concentric pattern. Although target spot may cause lesions on fruit, we did not observe such lesions. After incubation of the leaves, spores that appeared to be Corynespora cassiicola, causal agent of target spot were observed. This fungus was isolated in our lab and the identity of the fungus was confirmed by sequencing on campus. This is the first report of target spot of tomato in Indiana.[Read More…]


I visited a few high tunnels around the state recently and used a hand-held soil electrical conductivity (EC) meter to test soil salinity levels inside of the structures. Although the hand-held EC meter may not give ratings as accurate as a soil test lab could provide, I had comparative ratings from several farms. Interestingly, by talking to growers, I found tomatoes grown in the high tunnels that have relatively high EC ratings seem to suffer more problems in the past season. In most cases, the unhealthy plants have been taken out of the tunnels by the time I visited (in early August). In one situation, the farmer reported flower abortion and a lot of blossom end rot. In another situation, the farmer described a widespread leaf spot symptom that was not a disease. He followed the recommendation based on plant tissue analysis, but the problem was not solved. In the third situation, tomato[Read More…]


Cercospora leaf mold symptoms on the upper leaf surface. Note distinct chlorotic lesions.

In the fall of 2015, I wrote an article for the Hotline about Cercospora leaf mold of tomato since this disease had been observed twice in the 2015 season. I wrote that Cercospora leaf mold was normally a subtropical disease. There have been several observations of Cercospora leaf mold on tomato in Indiana this year. I’m still not certain of the importance of this disease, but this article will compare Cercospora leaf mold and leaf mold of tomato. Leaf mold of tomato is caused by Passalora fulva and is common in Indiana, especially in high tunnels where the high relative humidity favors this disease. Cercospora leaf mold is caused by Pseudocercospora fuligena and is more common in the warm, humid climate of the tropics or subtropics than in the Midwest. Both diseases cause chlorotic (yellow) lesions which are visible on the upper side of the leaf. The chlorotic area caused by[Read More…]


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Bacterial spot of tomato has been observed across Indiana this summer. Leaf spots are usually 1/16 inch, and dark. Where lesions are numerous upon a leaf, the tissue may be chlorotic (yellow) (Figure 1 & 2).  (In contrast, each lesion of bacterial speck is often accompanied by chlorosis whether lesions are numerous or not.) Lesions of bacterial spot on fruit are dark, raised and up to 1/3 inch in diameter (Figure 3). The disease prefers warm, wet weather. Overhead irrigation will also spread this disease. Although much of Indiana has been dry recently, rainy weather earlier in the year has increased the severity of bacterial spot. Bacterial spot is much more common in field tomatoes than in greenhouse or high tunnel tomatoes. This is because bacterial spot requires leaf wetness for infection to take place and rain to spread the bacteria from leaf to leaf and from plant to plant.[Read More…]


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Below, I will briefly discuss a few of the diseases that I have observed on tomatoes recently. Powdery mildew of tomato – Powdery mildew of tomato is not usually a common problem in Indiana. However, in recent years, there have been more reports of this disease than usual. Powdery mildew is more often observed in a greenhouse situation than in a field. The key symptoms of this disease are the talc-like lesions on the upper and lower leaf surfaces (Figure 1). It is important to note that the location of the upper and lower lesions do not correspond with each other. When the lesions are young, it may almost seem as if the lesions can be ‘wiped off’. Few varieties exist with good levels of host resistance, although growers may notice some difference in susceptibility between varieties. It may not be necessary to treat tomatoes affected with powdery mildew with fungicides. If[Read More…]


I have recently received a number of calls from growers about how to prune determinate tomatoes in a stake and weave system. Although this is relatively easy compared to how to prune indeterminate tomatoes with a trellis system, there are a few things I would like to call to your attention. What to prune  The common practice is to prune the suckers at the bottom of tomato plants. The benefit of this practice is to improve airflow which may help to control foliar diseases. Shoots of determinate tomatoes stop growing once they set a terminal bud. Most of us understand that if suckers are pruned too much, plants may have reduced yield.  However, there is confusion about exactly what to prune. Normally, the bottom 6-7 suckers should be pruned until the first flower cluster. But it is important to note that the sucker just below the first flower cluster develops a[Read More…]


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I recently encountered some lesions of Tomato Spotted Wilt Virus (TSWV) that appeared relatively large and had a ring-like structure.  I was able to confirm the presence of the virus, but at first glance, the lesions could be mistaken for a very common tomato disease: early blight. This article will describe how the foliar lesions of these two diseases might be distinguished. First, a bit about the symptoms of these diseases. Early blight is perhaps the most common foliar disease of tomato in Indiana. One might first notice that the older leaves turn necrotic. If left uncontrolled, the diseased lesions appear to ‘move’ up the plant. A closer look at early blight lesions may reveal the bull’s-eye lesions of this disease (Figure 1). These lesions may also be described as having concentric rings similar to a target. (Early blight is not the only disease to have concentric rings.) I usually[Read More…]


Figure 2: A tomato with tomato spotted wilt virus has necrotic ring spots.

While many virus diseases affect pepper and tomato plants, in the Midwest, the most common virus diseases of these two crops are tomato spotted wilt virus (TSWV) and Impatiens necrotic spot virus (INSV). These diseases are usually observed in greenhouse or high tunnel situations. The two viruses, TSWV and INSV are closely related. In fact, at one time, they were both considered TSWV. Therefore, the symptoms, biology and management of these two diseases are similar. This article discusses the symptoms, biology and management of these two diseases. Both TSWV and INSV affect many hosts, including vegetables and flowering ornamentals. Symptoms vary according to host, stage of plant affected and environmental conditions. Both diseases can cause stunting, yellowing, necrotic rings, leaf mottle and more. Figure 1 shows a tomato leaf with necrotic rings caused by TSWV. Figure 2 shows a pepper transplant with ring spots caused by INSV. Additional symptoms may[Read More…]


A grafted tomato plant grown in a high tunnel

Awareness of tomato grafting has increased tremendously in the past years. Some growers fall in love with this technology and apply it to every tomato they grow. While others find this technology is not cost effective. The growers who have successfully adapted this technology are often small-scale, high tunnel or greenhouse growers who have mastered the grafting technique. They graft tomatoes by themselves and often can achieve a high survival rate. In this case, the added cost for grafted plants is mainly the cost of rootstock seeds, which is roughly 30-50 centers per plant. A small amount of yield increase could easily compensate for the added cost. This is particularly true for tomatoes grown in high tunnels that often sell at a higher price. In situations that farmers buy grafted plants, the cost rangs from $1 to $3 per plant. Farmers would expect a high percentage of yield increase to compensate for[Read More…]


Figure 1. Galling of tomato roots infested by root-knot nematode.

In a recent grower visit in southwest Indiana, we saw a severe root-knot nematode infestation on high tunnel tomatoes. Soil fumigation is by far the most effective approach to control nematodes, but many soil fumigants are not labeled for greenhouse (high tunnel) use. In addition, the types of equipment that used for soil fumigation are often hard to fit into high tunnels. Considering the constraints, this article focuses on cultural practices to control root-knot nematodes that can be easily adopted by small-scale, high tunnel growers. Root-knot nematodes are small, colorless roundworms that dwell in the soil. They penetrate into plant root in the juvenile stage. Once they find a favorable location in plant tissues, they stop moving. Infested root cells start swelling and form galls that are the characteristic symptom of root-knot nematode infestation (Figure 1.). Infested roots fail to absorb water and nutrient resulting  in stunted growth, yellowing and[Read More…]


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