72 articles tagged "Tomato".

A grafted tomato plant growing in a high tunnel. (Photo by Wenjing Guan)

​You might have heard about tomato grafting, or you might even already have tried the new technique. Yes, it has multiple benefits: control of soilborne diseases, enhanced tolerance to abiotic stresses, and increased productivity. It works for some growers, but not all. Why? There are several reasons. First, effects of grafting on controlling soilborne diseases depend on the presence of the disease that the rootstock is designed to control. For example, grafting might not be very helpful for white mold, because current commercial rootstocks do not have resistance to white mold. However, grafting might work if the primary problem is Fusarium crown and root rot, as most commercial tomato rootstocks have resistance to this disease. With that said, it is very important to look at the disease resistance profile before deciding on the rootstocks. Second, grafting effects on improving yield depend on factors such as scion and rootstock cultivars, cultural[Read More…]


Cercospora leaf mold symptoms on the upper leaf surface. Note distinct chlorotic lesions. Photo by Dan Egel.

​ This disease does not typically affect Indiana tomatoes, instead preferring tomatoes grown in tropical and sub-tropical areas. Since Cercospora leaf mold was observed in two different areas of Indiana in the 2015 season, it makes sense for growers to become aware of this disease in case it returns to Indiana in 2016. The two locations where Cercospora leaf mold was observed in Indiana in 2015 were 1) a homeowner garden in southern Indiana and 2) a high tunnel in central Indiana. The fungus that causes Cercospora leaf mold, Pseudocercospora fuligena, normally does not overwinter outside of tropical and subtropical areas. It may be that a wind blew the fungus in from the south in 2015. Symptoms of Cercospora leaf mold are similar to leaf mold caused by Passalora fulva. Both diseases cause chlorotic (yellow) lesions which are visible on the upper side of the leaf. The chlorotic area caused by Cercospora leaf mold is[Read More…]


​Late blight has been reported on processing tomatoes in Cass County Indiana. This is a late blight update from when this disease was reported on potatoes and tomatoes in LaGrange County Indiana. The latter outbreak and some disease management tips are reported in the Vegetable Crops Hotline Issue 603 at ag.purdue.edu/hla/Extension/VegCropsHotline/Pages/Latest-Articles.aspx?article=117 This article was originally published on the veggiediseaseblog.org on August 24, 2015.


(Photo by Shubin K. Saha)

​Tomato growers who utilize high tunnels to reach early markets often find that there are few economic alternatives to tomato. Therefore, many growers grow tomatoes after tomatoes instead of rotating to a different crop. The repeated cropping of tomato in the same area can lead to disease problems such as Fusarium crown rot and white mold (timber rot). Soil solarization takes advantage of solar radiation to heat the soil to temperatures that are lethal to many fungal pathogens, nematodes, and weed seeds. In Indiana, soil solarization is not always practical for field use since the period where soil solarization would be useful, summer, is also the period where most growers must produce crops. The use of soil solarization in high tunnels, however, may be more practical since these crops are produced earlier than field crops. Additionally there is chance for greater heating of the soil if the high tunnel vents[Read More…]


(Photo by Dan Egel)

​We have received a number of reports of outbreaks of spider mites, primarily in watermelons and in high tunnels. 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. With all the rain we have had, it’s a little surprising that we are seeing problems in watermelons, but the older I get, the less I’m surprised by how infrequently arthropods behave the way we expect them to. In both scenarios, we don’t really have treatment thresholds for mites. Generally speaking, if populations are increasing, they need to be controlled. Once the decision to treat has been made, that’s where things get very different. In watermelons, we have a variety of pesticide choices. See page 115 of the Midwest Vegetable Production Guide (ID56) for the[Read More…]


(Photo by John Obermeyer.)

​I have seen more green stink bugs this year than at any time in my career. I have no logical explanation for their abundance. It was thought that as the invasive brown marmorated stink bug became established, it might outcompete the native stink bugs such as the green stink bug, causing numbers to decrease. However, this year, brown marmorated stink bugs have been relatively uncommon, and green stink bugs seem to be everywhere. Stink bugs feed with their sucking mouthparts and are likely to feed on a wide variety of vegetable crops, including cabbage, sweet corn, cucumber, bean of all types, okra, mustard, peas, peppers, and tomato. Check the Midwest Vegetable Production Guide (ID-56) for your particular crop for insecticide recommendations.


Late blight can cause brown necrotic lesions on tomato leaves that may be surrounded by growth of the causal fungus under moist conditions (Photo: Tom Creswell).

​Late blight has been reported on potatoes and tomatoes in LaGrange County.Potato and tomato growers in northern Indiana should follow the management recommendations listed below and in the Midwest Vegetable Production Guide for Commercial Growers 2015 (ID-56). Late blight thrives under cool, wet conditions. The disease can easily spread from plant to plant. Under ideal conditions, the disease can spread rapidly, causing symptoms on all above ground plant parts (Figure 1). The lesions may be green to brown and under moist conditions may be ringed with white fungal growth. Affected tomato fruit may have large brown lesions. The fungus-like organism that causes late blight does not usually overwinter in Indiana. Therefore, the disease must be blown or brought into Indiana. All strains of the fungus-like organism that affect tomato will cause disease on potato. However, not all potato strains will affect tomatoes. It is best for tomato and potato growers[Read More…]


Vegetables such as this watermelon may become sunburned if lack of foliage cover exposes the fruit to excess sun and heat. (Photo by Dan Egel)

​Loss of foliage due to poor growing conditions or disease can cause fruit to be exposed to the sun. Hot temperatures and direct sunlight can lead to areas of the fruit that appear bleached or sunburned. Sunburned fruit may not be marketable. To reduce the probability sunburned fruit, every effort should be made to maintain foliage throughout the season. Early wet weather encouraged foliar disease and recent hot, dry weather may have restricted foliar development. Orienting vegetable plantings to minimize damage from the prevailing winds and providing windbreaks such as strips of rye or wheat may help to reduce sunburn. Several products are available that are labeled for use as a preventive for sunburn. These products may be broken into two groups: kaolin (clay) based products and calcium carbonated based products. Kaolin based products include Surround®. Some Surround® products are labeled for use as sunburn protection, while others are not. For example,[Read More…]


Leaf lesions of Botrytis gray mold are often a light gray or brown color and the sporulation of the causal fungus can be seen on the leaf margin.

​Gray mold of tomato is one of the more common diseases of greenhouse-produced tomatoes. Although it is often a minor problem, if left unchecked, gray mold can cause yield loss. Gray mold, or more properly, Botrytis gray mold, often causes a light gray or brown necrotic lesion on leaves (Figure 1). The lesions on leaves are sometimes wedge shaped on the margin of the leaf. Stem lesions are a similar color and may encircle the stem, causing the death of the upper portion of the  stem. Occasionally, gray mold may cause the rot of tomato fruit. Whether on leafs, stems or fruit, the gray fungal sporulation is often easily seen, thus the name. It is a rare symptom, but when fungal spores land on tomato fruit that is wet, the spores may germinate, causing a symptom known as a ghost spot (Figure 2). Botrytis gray mold can cause disease on many different host plants, enabling[Read More…]


Powdery mildew of tomato is easily recognized from the sporulation of the white fungus on the leaves.

​This disease has been reported near West Lafayette and in Wanatah Indiana. Powdery mildew of tomato can be recognized by the white fungal colonies on both leaf surfaces (Figure 1). Occasionally, stems may also be infected. Severely affected tomato plants may have leaves that turn chlorotic and necrotic. Fruit will not be directly affected. The causal organism has been tentatively identified as Pseudoidium neolycopersici, formerly Oidium neolycopersici. This fungus may survive as resting structures on host material. The spores are easily wind dispersed to additional tomato plants. Development of this disease is favored by temperatures below 86°F. As with most powdery mildew diseases, high humidity allows the disease to develop; leaf wetness is not necessary. Since high humidity favors powdery mildew of tomato, greenhouse environments often favor the disease. Reports of powdery mildew on tomato are not common in Indiana. There is no data on yield loss from this disease on tomato. Nevertheless, if this disease is present, management options should be considered. Several systemic[Read More…]


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