58 articles tagged "Greenhouses & High Tunnels".

Figure 1. Powdery mildew on cucumbers grown in a high tunnel.

Powdery mildew is particularly severe in high tunnel and greenhouse growing conditions (Figure 1). It affects a wide range of crops including tomatoes and cucumbers. In addition to using synthetic fungicides to control this disease in high tunnels, we found powdery mildew on cucumbers can also be effectively controlled through variety selection and intensive plant pruning. Cucumber cultivars grown in high tunnels are parthenocarpic. Most of these cultivars are marketed as powdery mildew resistance. However, there are actually a wide range of different levels of resistance existed among parthenocarpic cultivars. In our trials, we found Japanese type cucumbers, especially cultivar Tasty Jade, was very susceptible to powdery mildew; Taurus was less susceptible than Tasty Jade, but much more susceptible compared to most Beit alpha (or mini) type, long English (or Dutch greenhouse) type and American slicer cucumbers. Comparing three long English cultivars in our evaluation, Kalunga was more susceptible compared[Read More…]


Figure 3. Cucumber cultivar Taurus were grown in the front, cultivar Corinto was grown in the back.

Supported by NC SARE (LNC17-390), we are continuing research for improving high tunnel cucumber production. One of the biggest challenges for growing cucumbers in high tunnels in the summer is two-spotted spider mites. Dry and hot environments featured in high tunnels allow two-spotted spider mite populations to increase rapidly. The mites cause leaf yellowing, necrosis, and defoliation that interfere with plant photosynthesis. Yield can be significantly reduced. The pest also causes direct damage on cucumber fruit, resulting in a sandpaper-like texture to the rind (Figure 1). Early detection is the key for controlling two-spotted spider mites. As soon as two-spotted spider mites are detected, control efforts need to be taken. In the early stage, yellowish specks on the upper side of the leaves may be noticed (Figure 2). Turn the leaf over, on the other side of where the yellow specks are, you may find the presence of two-spotted spider[Read More…]


Basic Aspects of High Tunnel Soil Fertility Management – (Petrus Langenhoven, plangenh@purdue.edu, 765-496-7955) – Spring has arrived! Every high tunnel grower is now thinking of planting summer vegetable crops in high tunnels or has already planted. Whichever scenario applies to you, I hope that you have submitted soil samples or are in the process of submitting samples to your closest laboratory. Have you analyzed your irrigation water? It will be a good idea to send a water sample along too. There is a lot of important information locked up in your water and soil test results. The results will help you to plan and manage your high tunnel fertility program. Remember, growing in a high tunnel is like growing crops in an irrigated desert. Natural rainfall is unavailable inside your high tunnel and therefore all your plants water needs are satisfied through an irrigation system. Fertilizer needs could be addressed[Read More…]


Bolting of crops overwintered in high tunnels is common in the spring. ‘Bolting’ refers to lengthening and blooming of the flowering stalk. Bolting is often a problem because the quality of the marketable part of the plant declines. Also, plants subject to bolting are programmed to die once they complete flowering and seed production so yield will decline in quantity as well as quality. Sometimes bolting is not a problem because the stalk, buds, and flowers can be sold as a new product while they last; this is often the case with kale,  mustards and related crops. Crops susceptible to bolting include those in the mustard family such as kale, mustards, tatsoi, bok choy (pac choi), mizuna, turnip, radish, etc.; carrots; beets and in some cases Swiss chard; onions; lettuce; and spinach. (Figure 1)   Bolting is triggered by environmental conditions. Some plant types are triggered to develop flowers by[Read More…]


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High tunnels, though relatively new, have gained popularity over the past decade among specialty crop growers who want to extend their growing season. However, these environments can make crops vulnerable to the development of soil-borne diseases that reduce yield. This is particularly true for tomatoes, which are the most commonly grown high tunnel crop and can be highly susceptible to soil pathogens. For most field crops, rotation systems are already in place to combat a build-up of pests and pathogens. In field-grown tomatoes, for example, growers are advised to wait a period of 3 years before replanting tomato in a particular field to break the disease cycle. In high tunnels, rotation systems are more challenging to implement due to space limitations, which results in many growers employing a tomato-on-tomato system from one year to the next. This could be especially problematic for heirloom tomatoes, which are popular high tunnel tomato[Read More…]


Figure 1. Cucumbers were grown in a greenhouse in April 2018

Cucumbers are extremely sensitive to cold. Locally grown cucumbers are almost only available in the summer. While in Asia, without the use of fancy heated greenhouses, cucumbers can grow all winter. Growing grafted cucumbers with cold tolerant squash rootstock is one of the key factors making this possible. Since 2016, we started to evaluate opportunities of using grafted plants to extend early season cucumber production under protected cultural systems in the Midwest. We observed promising results in our research trials. However, knowing research trials can only tell part of the story, we initiated multiple on-farm trials across Indiana to better understand if and under what circumstances growers would benefit from this technique. This article discusses the lessons we have learned so far and raises questions that need to be answered. Heated greenhouses A pronounced advantage of using grafted cucumbers was observed in the situations that cucumbers were grown in soils[Read More…]


charcoal rot

This disease was identified on a long Asian cucumber growing in a high tunnel in Mid-June in Knox County. The first symptom noted was wilting of the cucumber plant. Upon closer examination, a light, gray necrosis was observed on the lower portion of the plant. In Figure 1, you may notice dark spots in the necrotic area. These symptoms, plus the resin-like drops on the stem might look like gummy stem blight. However, a look under the microscope revealed fungal structures and spores that were not from the gummy stem blight fungus. Plus, gummy stem blight is rare in a greenhouse situation where there is little moisture. When we isolated for a fungus, we found numerous micro-sclerotia. The sample was sent up to campus to confirm that the fungus was Macrophomina phaseolina, causal agent of charcoal rot. The charcoal rot fungus has many hosts and the fungus is not new[Read More…]


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…]


Figure 1. Top left: old plastic viewed from inside High Tunnel 1. Top right: old plastic as it is being removed. Bottom left: old plastic on left and new plastic on right over a piece of lined paper. Bottom right: High Tunnel 1 with new plastic covering.

Have you ever wondered how much difference new plastic would make in terms of light getting to crops in a high tunnel? We replaced 6-year-old plastic on High Tunnel 1 at Pinney Purdue Ag Center last week. Figure 1 below shows the high tunnel before and after recovering, and pieces of the old and new plastic. We had a sensor measuring PAR (photosynthetically active radiation, light available for plant use in photosynthesis) in the structure, and a similar sensor in High Tunnel 2, which had new plastic in Dec., 2017. The Ag Center also has an automated weather station that measures solar radiation. Here is what these sensors showed us (Figure 1). Figure 2 shows the PAR readings throughout the day in the two high tunnels and solar radiation outside. High Tunnel 1 had the 6-year-old plastic. The plastic was removed on July 9. On July 7 and 8, before[Read More…]


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