44 articles tagged "Crop Culture".

Figure 1. Tomatoes are grown under a retractable tunnel system.

Tomato foliar diseases such as early blight, Septoria leaf blight, bacterial spot and speck that are commonly seen in the field are often less common on tomatoes grown in greenhouses and high tunnels. It is also true that high tunnel tomatoes have smoother skins than tomatoes grown in the fields. An important factor that determines this difference is rainfall. Pathogens that cause foliar diseases require leaves to be wet in order for infection to occur and rely on rain for spread. In addition, heavy rains cause tomato physiological disorders such as rain check. It is great that greenhouse and high tunnel structures prevent tomato canopies from direct exposure to rainfall, however, a significant initial investment is required for building the structures, and it is hard to relocate them after they are built. This summer, we used a retractable tunnel to grow tomatoes and peppers in the field (Figure 1). The tunnels[Read More…]


Figure 3. Broccoli ready to harvest.

A fall broccoli trial was conducted in a high tunnel at Southwest Purdue Ag Center in 2016 to test the potential of growing broccoli in high tunnels after tomatoes. This article describes what we found from the trial. Broccoli is a cool-season, frost-tolerant crop. The harvest portion of broccoli is the compact, slightly dome-shaped head that is comprised by numerous immature flower buds. Broccoli that forms a single large head and thick stalks requires 50-70 days to harvest. Vegetative growth occurs over a wide range of temperatures, but high-quality head development requires temperatures in the range of 54-68 ºF. If temperatures are below 41ºF, plant growth is significantly reduced. In Indiana, fall production of broccoli in an open-field can be challenging because of the relatively long growing season. But with increased heat accumulation in high tunnels, it is possible to have a second crop of broccoli following tomatoes. Broccoli can[Read More…]


Figure 1. A 30% black shade cloth was added to one of the high tunnels

Tomatoes growing in high tunnels are in the middle of or close to harvest. Developing and maturing fruit are under leaf canopies. On the top of the plants, many flowers are still blooming. These flowers will contribute to the second big harvest. Although tomatoes in June are most valuable, we certainly appreciate big, red and delicious tomatoes in July and August.  To ensure a sustained yield, it is important for these flowers to set fruit. The process of fruit set is very sensitive to excessively high temperatures. When temperatures rise above 100°F, even just for a few hours for a handful of days, tomato flowers may be aborted and fruit set fail. Night temperatures above 75°F may also cause tomato fruit set failure. In addition to fruit set, high temperatures affect fruit ripening process. Ethylene associated ripening decreases markedly at a temperature above 93°F. As a result, there might be an increasing number of[Read More…]


Figure 1. Grafted Fascination plants were grown on the right bed, ungrafted plants were grown on the left bed. The field were naturally infested with Fusarium wilt.

Watermelon production is threatened by Fusarium wilt, a widely distributed soilborne disease that can cause yield losses up to 100%. Currently, there are no watermelon varieties that are completely resistant to all races of Fusarium wilt. One way to control the disease is through grafting. The grafted plant combines a watermelon cultivar with a squash rootstock that has resistance to Fusarium wilt. In a study conducted at Southwest Purdue Ag Center (SWPAC), we found grafted watermelons significantly reduced disease incidence, and more than doubled watermelon yield in a Fusarium wilt infected field (Figure 1). In addition to controlling Fusarium wilt, grafted watermelons often show substantial advantages in early watermelon production due to cold tolerance from rootstocks. In a study conducted in Arizona, grafted watermelons that were transplanted in the field two months before soil temperatures reached 70 °F had twice as much yield as ungrafted watermelons grown in the same[Read More…]


Figure 1. A tomato plant showing nutrient deficiency symptoms.

Recent rain and cold conditions have brought detrimental effects to some of the early planted vegetables. In southwest Indiana, air temperatures have dropped into the 40s °F and soil temperatures have dropped into the 50s °F in early May. The low temperatures would have greatly inhibited absorption of water and mineral nutrients for many warm season vegetables. In one of our fields where watermelon and cantaloupe were transplanted on April 26, almost all the plants showed wilt symptoms on May 3. The wilt was caused by decreased water absorption from roots. The plants were dead due to the extended cold weather. Peppers and tomatoes that were planted about the same time maintained turgid and survived the cold period (Figure 1). But they showed symptoms similar to nutrient deficiency due to the reduced function of roots in the cold soil. The plants should start new growth when the temperature rises. Growers using low tunnels are more likely[Read More…]


Figure 2. A seedless cucumber

A plant is considered to be seedless if it is able to produce a fruit without or contain a much-reduced number of seeds, or in some cases, only present traces of aborted seeds. Seedlessness is a desirable fruit character because seeds are often hard, have a bad taste and produce hormones that lead to fruit deterioration. As a result, seedless fruit often has better quality and longer shelf lives. Seedless watermelons that were introduced in the 1990s have become the main type of watermelons grown in the U.S.  Besides seedless watermelons, breeders have developed seedless varieties for other fruiting vegetables. This article briefly introduces the different types of seedless fruit and discusses potential opportunities for growing theses varieties. Seedlessness exists in two forms. In the case of seedless watermelons, the fruit contains partially formed seeds that are aborted after fertilization (Figure 1.). Seedless watermelon plants are self-infertile. They must be[Read More…]


Effectively managing foliar diseases including late blight (LB), early blight (EB), and Septoria leaf spot (SLS), is one of the biggest challenges facing organic tomato growers. New, resistant hybrid varieties are available, but organic growers often plant heirloom varieties instead because they are perceived to have superior flavor and growers can save seed. Copper fungicides can provide fair control of these diseases, but these products are contact, not systemic, and must be applied often, which can negatively impact soil and water quality. The tomato organic management and improvement project (TOMI), led by Lori Hoagland in the Horticulture Department at Purdue, brings together a multidisciplinary team of researchers from across the U.S. to develop short, medium and long-term solutions to this challenge. In the short-term, the team aims to identify biofungicide and biostimulant combinations that can effectively control LB, EB and SLS. Greenhouse and field trials are underway testing various combinations[Read More…]


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There are several potential benefits of growing grafted tomatoes, particularly for early season tomato production in greenhouses or high tunnels. If you are interested in trying this technique but wondering whether it is possible to graft tomato plants by yourself, a Purdue extension publication, Techniques for Tomato Grafting, (https://extension.purdue.edu/extmedia/HO/HO-260-W.pdf ) provides a step-by-step guideline for small growers to explore this technique. A question I am often asked is: when should I start to plant the seeds to produce grafted plants? The chart below shows a general timeline and materials needed for producing grafted tomatoes on a small scale on your farm. As a general rule, the grafting process delays seedling growth for 6-7 days. The delay normally does not make a noticeable difference on the size of seedlings after the grafted plants are grown in a greenhouse for more than 2 weeks prior to transplant. As a matter of fact, grafted[Read More…]


Figure 2. Older leaves were pruned on cucumber plants.

Tomato is considered one of the most profitable crops grown in high tunnels, but continually growing one single crop leads to build-up of diseases. In addition, growers are facing more competition in selling tomatoes in the market. To enhance resilience of high tunnel system and increase access to consumers, crop diversification is important. In this article, instead of discussing tomatoes, we will focus on another high-value crop, seedless cucumber. Fresh consumed seedless cucumber is a popular crop in local food markets. It sells at a premium price in early seasons as does tomato. Seedless cucumbers grown under protected cultures are parthenocarpic, which do not require pollination. In addition, the climbing habit allows trellising, which maximizes the use of vertical spaces, making seedless cucumber an ideal crop for high tunnel production. Parthenocarpic cucumbers are available in different types. The long ones are often referred to as European, Japanese or English cucumbers. They have thin skins with longitudinal[Read More…]


As Indiana growers finish up the 2017 season, it is important to remember to clean and sanitize equipment and tools. In this article, I would like to discuss the importance of and how to sanitize. Bacteria and fungi that cause plant disease may survive on some types of equipment. Examples include: stakes, transplant trays, shovels, greenhouse benches etc. Equipment can be contaminated by diseased plants in close contact with the surfaces. For example, a tomato with bacterial canker may rub up against a wooden stake, transferring some of the bacteria to the stake. Such bacteria may cause disease problems next year. A transplant tray of cantaloupe with a damping-off problem may have the same disease next year if the tray is not properly cleaned and sanitized. It is important to clean the equipment of crop debris or soil prior to the use of one of the sanitizers described below. Equipment free of crop[Read More…]


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