38 articles tagged "Greenhouses & High Tunnels".

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Driving across IN now, it is not uncommon to see many recently built high tunnels standing along the roadsides. These structures have become an important tool for farmers to extend production seasons of vegetable and fruit crops. Compared with traditional greenhouses, high tunnel demand much less energy as they are heated by solar energy and ventilated through natural air circulation. Similar to high tunnels, Chinese-style solar greenhouse is an important tool for season extension in specialty crop production in China. The structures are facing south, featured by supporting north walls (Figure 1 and 2). The north walls are essential in maintaining temperatures inside the structure. They are made up with materials having good insulation properties and with a thickness more than 30 inches. The south sides are arch-shaped, supported by steels and covered with polyethylene or polyvinyl chloride films. From north to south, the structures span 26-46 feet. A short[Read More…]


Figure 1. Hornworm feeding on tomato leaves in a high tunnel.

Hornworms can be pests of tomato and pepper in field grown crops, but for some reason seem to be particularly severe in high tunnels. Hornworms are very large caterpillars, measuring up to 4 inches long (Figure 1), and they can consume large quantities of foliage and will also feed on green fruit (Figure 2). In fields, hornworm damage is usually localized and tolerable, although treatment is sometimes required. In high tunnels, hornworm damage, particularly to tomato, is often severe (Figure 3) and will require several applications of insecticides. In field situations, the treatment threshold is one hornworm per two plants. Since the infestations are often localized, it may not be necessary to treat the entire field. In high tunnels, there is no established threshold, so my recommendation would be to treat as soon as you seen caterpillars or their damage. The good news is that hornworms are fairly easy to control.[Read More…]


Figure 1. A ladybug feeding on aphids

Supplementing the natural enemy population to control insect pests, i.e. augmentation biological control, is of interest to many high tunnel producers. Augmentation biological control has proven very effective at managing a number of greenhouse pests and there are a variety of commercial suppliers. For high tunnels, the greatest challenge is keeping the released predators or parasitoids inside the tunnels and choosing agents that are effective under high temperatures, during the peak of the growing season. We have evaluated some of the more common control agents in high tunnel cucumber and tomato production. The convergent ladybug, Hippodamia convergens, is not grown in a growth facility but rather caught in the wild in the western U.S. (typically California) and shipped throughout the US for control of aphids in particular. They are a fairly inexpensive predator (1500 for about $15.00), the immature form (larvae) and adults feed on aphids (Figure 1). However, you[Read More…]


Last week, the highest temperature reached 110°F for a few successive days inside of our high tunnels. As a result, we observed some blossom drop on tomatoes. More information on high temperature effects on tomato fruit set can be found here. In addition to blossom drop, high temperature and high light intensity contribute to sunscald injury, uneven ripening, and cracking of tomato fruit. To protect tomatoes from damage caused by excessive heat, we placed 30% black shade cloth on top of the high tunnel. By installing the shadecloth, we expect there will be less cracking and more uniformly ripe tomatoes. Tomato marketability will increase. However, using shade cloth also has some negative effects. In this article, we review the effects of high temperatures on tomatoes, and discuss positive and negative aspects of using a shade cloth. Excessive high temperature (above 100°F) lasting for a few hours for successive days could cause tomato flower abortion and affect[Read More…]


Figure 1. Aphids on tomatoes in a high tunnel (Photo credit Wenjing Guan)

We have begun to receive the first reports of aphid outbreaks in high tunnels on tomato, pepper, and cucumber (Figure 1). Aphids are a very common problem in high tunnels because the covering excludes rainfall, which is a major mortality factor for small insects like aphids. Some growers are interested in using biological control in their high tunnels because the ability to contain natural enemies within the tunnels increases the likelihood of achieving control. Based on our experience, we believe that lacewing larvae hold the greatest promise for successful biological control of aphids in high tunnels. Because they don’t fly, they are less likely to leave the high tunnel than many other biological control agents. There are a number of biological control suppliers who can provide lacewing larvae for growers. For growers interested in chemical control, some of the insecticides that could be expected to provide good control and are[Read More…]


I have observed leaf mold of tomato in greenhouses and high tunnels recently. This article will discuss this disease and management options. In the last issue of the Hotline, I discussed Botrytis gray mold. I noted how gray mold is favored by the cool, cloudy weather we experienced earlier this spring. The warmer and sunnier weather we have experienced more recently should favor leaf mold over gray mold. Leaf mold is caused by the fungus Passalora fulva. Cercospora leaf mold of tomato is rare in Indiana and is discussed here (https://vegcropshotline.org/article/cercospora-leaf-mold-of-tomato/). The first symptom of leaf mold one is likely to notice is a pale yellow lesion on the top side of the leaf (Figure 1). When the leaves are turned over, the fungal mold that gives the disease its name becomes evident (Figure 2). Leaf mold often becomes a problem under humid conditions (85% humidity or greater) and temperatures between 71 and 75°F, although leaf[Read More…]


Planting density plays an important role in the optimization of labor efficiency and productivity of your high tunnel. For the purpose of this article I will focus on tomato which is commonly grown as a high value crop on small farming operations. Usually growers select varieties according to customer (market) preference and then try to combine that with other attributes such as ease of production, disease tolerance/resistance and productivity (yield). Consumer preference usually helps to determine the fruit color, size and shape, and the sweetness (soluble solids) of the tomato variety to be grown. The grower again is interested in earliness, growth habit (determinate and indeterminate), and ease of pruning, trellising and picking. Most growers in Indiana choose determinate varieties for high tunnel production, because it has limited growth and is easy to stake and allows for early production (short production cycle), with most fruit ripening before field grown tomatoes[Read More…]


Recent cool weather increases the occurrence of zippering on high tunnel tomatoes. We observed at least 20% of developing fruit (most on the first and second flower clusters) on the variety Mountain Spring showed the zippering symptoms in our high tunnel. A typical symptom of the disorder is a thin, brown, necrotic scar that starts from the stem end and extend fully or partially to the blossom end. The reason the symptom is called zippering is because transverse scars are along with the longitudinal scar that looks like a zipper (Figure 1). In more severe cases, the scar is open and reveal locule (Figure 2). In the initial stage, zippering is often observed with anthers adhering to the fruit (Figure 3), the attached anthers is believed to disturb fruit development and cause the symptom. Zippering symptom is more noticeable with cool weather. Optimum temperatures for tomato fruit set are 60-75°F (night) and 60-90°F[Read More…]


The recent cool and cloudy weather has influenced conditions in the field as well as in greenhouses and high tunnels. I have observed more Botrytis gray mold of tomatoes in greenhouses this spring than usual. This is due in part to the weather. This article will discuss this disease on tomatoes and some management options. Gray mold is caused by a fungus that attacks many types of vegetables and ornamentals. The fungus is not a strong pathogen and often starts on weakened or senescent tissue such as old flower petals. The gray mold fungus, Botrytis cinerea, may be a weak pathogen, but it is a good saprophyte, growing well on old crop debris and organic matter until a good plant host is available. Figure 1 shows a tomato leaf on which a flower petal has fallen. Since the gray mold fungus is sporulating on the flower petal, there is a[Read More…]


In a recent visit to a high tunnel, we observed a severe salinity problem on tomatoes. Approximately one month after planting , most tomato plants in the affected area had not sent out any new leaves. Roots did not grow at all (Figure 1).  After conducting a soil test, very high soluble salt level explains these symptoms. This article reviews the basics of soil salinity. Salinity describes salt content in the soil. Virtually all fertilizer materials are salts, but they vary in their effects to increase salt concentration in soil solutions. In a field situation, precipitation in the form of rain and snow tend to leach salts.  Since high tunnels exclude rain and snow, elevated salt levels are a common concern for high tunnel vegetable growers. Table 1 are the salt indexes of common fertilizers. If you are using a premixed fertilizer such as 12-12-12, check the fertilizer components on[Read More…]


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