50 articles tagged "Greenhouses & High Tunnels".

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…]


Figure 1. Blossom end rot of tomato.

We recently received several calls reporting blossom end rot of tomatoes (Figure 1). Although blossom end rot is caused by deficient supply of calcium to the developing fruit. The occurrence of this physiological disorder often relates to inconsistent supply of water. As a general rule, vegetables require 1-1.5 acre-inches of water per week. Since there is no rain in high tunnels, all the required water should be applied through irrigation. How does one determine if enough water has been applied to vegetables? This article provides some ideas. The first information needed is the irrigated area. For example, tomatoes are growing in a 30 × 96 high tunnel with 6 beds that are about 4 feet wide. Then the irrigated area is about 2,304 square feet (6 × 4 × 96 = 2,304). An acre has 43,560 square feet. So the irrigated area is roughly 2,304 / 43,560 = 0.05 acre.[Read More…]


Figure 1. A cucumber plant grown in a high tunnel died because of bacterial wilt.

Bacterial wilt is one of the most destructive diseases in high tunnel cucumber production. The reason bacterial wilt is so important is because, like other wilt diseases, it ties up with the entire vascular system of a plant, causing systemic effects (Figure 1). The relatively less important roles that other cucumber diseases play also make bacterial wilt the major limitation for high tunnel cucumber production in Indiana. For example, common cucumber diseases such as angular leaf spot, anthracnose and Alternaria leaf blight seldom occur in a high tunnel scenario; improved resistance to powdery mildew was observed in some of the newly developed cucumber varieties; downy mildew in general does not occur in Indiana until end of the high tunnel cucumber production season. The causal organism for bacterial wilt of cucumbers is Erwinia tracheiphila. After the bacteria enter the plant vascular system, it multiplies quickly. As a result, it interferes with[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…]


Figure 3. A cucumber beetle on the 0.7 x 1.0 mm screen (photo credit: John Obermeyer)

One of the most problematic insect pests that organic vegetable growers have to deal with is the striped cucumber beetle. The insect feeds on all the cucurbit crops, but can be particularly devastating to muskmelons and cucumbers because those two crops are susceptible to bacterial wilt of cucurbits, which is caused by a bacterium carried by the beetles. The only way to avoid this devastating disease is to prevent the beetles from feeding on the plants. There are no effective organic insecticides for managing striped cucumber so we have to look for alternative methods. Row Covers: Row covers can be used to physically prevent beetles from feeding on the plants. To be effective, these need to be placed over the plants immediately after transplanting or before direct seeded crops emerge. The edges of the row covers should be sealed with soil to prevent the beetles from crawling under the fabric[Read More…]


It’s that time of year, where we are prepping high tunnels and getting back into the full swing of production, slowly, here in the Midwest. Many of you have already begun to transplant and may have encountered your first pests on these new crops. Aphids are one that remain a problem in high tunnels, and may even have plagued your winter production (Figure 1,2,3). Some keys to preventing or controlling these pests rely first on sanitation and then careful scouting. Try to remove any green bridge material that may already be infested before transplanting into the space. This includes weeds, lingering winter crops or residues. Having a week without vegetative hosts should get rid of any overwintering residents. After transplanting scout diligently, at least weekly, or more often on susceptible young transplants. Aphid infestations tend to begin on the growing points or younger tissues of the plant. Be sure to[Read More…]


Figure 2. Plants died in the second day after average soil temperature was 54 °F

Growers start to plant tomatoes in unheated high tunnels around the end of March in southern Indiana. Around that time, there may still be a few light frosts, or even heavier ones, like the one we just experienced in the past week. With additional help from row covers inside of high tunnels, temperatures normally can be maintained above 32°F. Tomatoes typically do not have problems with the short-term low temperatures. However, this may not be the case for cucumbers. Although they are both warm season crops, Cucurbits (cucumbers, cantaloupes, and watermelons) are much more cold sensitive than Solanaceous crops (tomato, pepper). From a temperature perspective, this article discusses important considerations for deciding the time for planting cucumbers in a high tunnel. The best condition to grow cucumbers is when soil temperatures are above 70°F. This situation may not happen until the middle of May inside of the high tunnels, according to our[Read More…]


Figure 3. A Japanese type cucumber grown in a high tunnel.

Cucumbers are produced with very different production systems. The ideal cucumber variety for process pickling production is not the variety used for greenhouse production. Choosing the suitable variety for a specific production system then becomes important. Where do you find recommended cucumber varieties for high tunnel production in seed catalogs? Some of the seed catalogs have a category called Greenhouse or Protected culture. Varieties listed in this category are recommend for greenhouse or high tunnel production. Other seeds catalogs may call this group Parthenocarpic hybrid or European slicer. Cucumbers listed under these names are also suitable for greenhouse or high tunnel production. A few technical words (parthenocarpic, monoecious, gynoecious) occur frequently in the descriptions of high tunnel-grown cucumbers. Understanding their meaning is important in choosing the right varieties. Parthenocarpic means that the plant can set fruit without pollination. Since pollinators are not required in this case, parthenocarpic is a desirable characteristic for cucumbers grown in protected[Read More…]


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This article is my response to a grower’s question about lowering soil pH in a high tunnel. The soil test indicated pH of the soil in his high tunnel was 7.7. The high pH could be partially caused by alkaline water he used to use for irrigation. The grower has changed the water source, but high soil pH is still a concern. ‘I have soil sample from the high tunnels if I could have your input on them I would appreciate it. I am concerned with the pH, should I use sulfur to bring it down, if so, how much?’ Following is my response to the grower’s question. My response is mainly based on the publication ‘Lowering Soil pH for Horticulture Crops‘. Purdue Extension HO-241-W. We have a few choices to reduce soil pH. Adding elemental sulfur is one way to do it. If you want to reduce soil pH[Read More…]


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