Wenjing Guan

Vegetable Crops Hotline Editor & Clinical Engagement Assistant Professor
Department of Horticulture and Landscape Architecture
Area(s) of Interest: Commercial Vegetable and Melon Production
Wenjing Guan's website

215 articles by this author

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Welcome to a new year of the Vegetable Crops Hotline (VCH), Purdue Extension’s newsletter for people in the business of growing vegetables. As usual, we will have fifteen issues throughout the 2020 growing season. The first issue of the year is sent to all who subscribed to VCH via US-mail in 2019 as well as new subscribers for 2020. To continue receiving future copies through US-mail, renew your Hotline subscription using the form attached  to this issue. The year that your subscription is paid through is on the bottom right hand side of your envelope. Note that we provide an up-to three years’ subscription of VCH at a reduced price. If you receive the issue through email, you will continue to receive the newsletters on the issue dates. In addition, you will receive emails if there are articles or announcements that need your immediate attention. These articles will be posted under Hot[Read More…]


A grafted tomato plant grown in a high tunnel

Tomato and Cucumber growers who are interested in grafting tomato and cucumber plants by themselves may find this information helpful. Step-By-Step instruction of how to graft tomato plants is available from Purdue Extension publication Vegetable Grafting: Techniques for Tomato Grafting https://mdc.itap.purdue.edu/item.asp?Item_Number=HO-260-W as well as a Purdue Extension video https://www.youtube.com/watch?v=7Ufx66Isf88 A cucumber grafting instruction was also released. It provides step-by-step guidance of cucumber splice grafting technique. The publication is available at https://www.extension.purdue.edu/extmedia/HO/HO-328-W.PDF The cucumber grafting video is available at https://www.youtube.com/watch?v=z-tXoobiMnY&t=1s


Table 1. Growing media evaluated and major ingredients as listed by manufacturer.

Growing media for organic transplant production vary a lot in their chemical composition: pH, electrical conductivity, nutrient levels, and C:N ratio. This of course influences how seedlings grow. Knowing the characteristics of growing media can help growers decide whether adding nutrients or materials to adjust pH are likely to improve seedling growth. As part of our research into media for organic transplant production we would like to test growing media used by Indiana growers using organic practices. The media could be a commercially available product, or a product made on the farm. If you would like your media to be tested, please fill out the form at https://purdue.ca1.qualtrics.com/jfe/form/SV_eezVW7ubRhgh3Ip . Wait for notice that your submission will be accepted and then send 4 pints of media to Liz Maynard, Purdue University, 1101 Glendale Blvd, Suite 101-A, Valparaiso, IN 46383. To request a hard copy of the form, contact Liz Maynard, emaynard@purdue.edu, [Read More…]


It is time to renew your Indiana Vegetable Growers Association (IVGA) membership for 2020. Please use the form attached to this newsletter or download from ivga.org/renewal.pdf and send in with your membership dues. About IVGA IVGA was established in the early 1900’s to be the Voice for Vegetable Growers in Indiana and is dedicated to the improvement of vegetable production and marketing in Indiana. The IVGA supports education and research about vegetables and melons in Indiana, and as your advocate, the IVGA is your resource to help find solutions for your everyday problems. Join today and be a part of a great team in Indiana!


Figure 1. Take soil samples at 6 inches deep

This article introduces a new soil test for high tunnel growers. Why is there a need for a new soil test for high tunnel production? Soil tests are valuable tools helping growers decide how much fertilizers and/or other soil amendments to apply for growing a specific vegetable crop. It also helps growers to detect soil fertility-related problems early. The routine soil test and its recommendations for vegetable crops were developed based on research conducted in the open field. When it comes to high tunnel production, the routine soil test and recommendations become less valuable for at least three reasons: Crops growing in high tunnels typically have a much higher yield potential; they require more nutrients than the same crop grown in the open-field with lower yield potential. Therefore the soil test index (low, medium, high) and recommendation for specific nutrients may not apply for high tunnel crops. Since there is[Read More…]


Warm-season vegetables like tomato, cucumber, pepper etc. often receive premium prices if they were sold at farmers’ markets earlier in the season. The same happens on summer squash, with the different fruit shape and color, summer squash provides a great diversity to the market. High tunnels that  are planted with warm-season vegetables are often closed to maintain heat inside the structure in the spring. Growers often hesitate to bring beehives to high tunnels because of the increased production cost and potential worker safety concerns. Under such circumstances, crops that can set fruit without pollination (parthenocarpic) have an advantage for early-season high tunnel production. Previous studies indicated parthenocarpic character exists in some summer squash cultivars. But such information is not always clearly indicated in seed catalogs. Without knowing the information, farmers may miss the opportunity of growing summer squash and targeting for an early harvest in high tunnels. In the spring[Read More…]


Recent studies have suggested that on-farm food safety practices can have unexpected economic and ecological impacts. Despite the potential for negative consequences, limited data is available on the costs and benefits of implementing specific practices. Co-managing farms for food safety and sustainability is further complicated because farms are linked to adjacent environments so that management decisions can have unexpected ecological, economic and food safety consequences. A comprehensive understanding of the links between agricultural and adjacent environments is key to ensuring environmental health, sustainability, and food safety. A new survey, funded by the Atkinson Center at Cornell University, promises to give a clearer picture of these linkages and what this means for growers. Specifically, to meet this need, a new collaborative research project between researchers at Cornell University, the University of California, and the University of Rochester is reaching out to growers in the Eastern United States to fill out a[Read More…]


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Southwest Indiana Melon and Vegetable Growers annual meeting will be held in French Lick, IN on March 13, 8:30 am to 4:00 pm. Participants will learn from Purdue extension specialists about the newly searchable Midwest Vegetable Production Guide; new updates on food safety; watermelon grafting; impacts of pesticide use on pollinator health; weed management; lessons from truck and equipment collision. In addition, Jamie Campbell Petty from the Midwest Hemp Council will give the presentation Hemp as a New Crop. A detailed agenda is attached. The meeting is sponsored by Southwest Indiana Melon and Vegetable Growers Association. Everyone is welcome to participate in the meeting. $15.00 per person will be collected at the time of registration to join or renew your Southwest Indiana Melon and Vegetable Growers Association membership, which includes lunch on March 13, as well as dinner at a winter technical meeting, which will be held in Nov. at[Read More…]


Thanks to the support from NC-SARE, we are going to continue the study of evaluating grafted cucumbers for early season production in greenhouses and high tunnels by collaborating with farmers in 2020. You can find our 2019 on-farm trials’ summary here:  https://ag.purdue.edu/arge/swpap/Documents/Summary%20of%202019%20On-farm%20Grafted%20Cucumber%20Trials.pdf. The same as in previous years, we are going to supply grafted and normal cucumber transplants for free. These plants were grown in a conventional greenhouse using untreated rootstock seeds. What we want from growers is to grow the same number and variety of grafted and normal cucumber plants, and keep track of the performance of the plants and the yields. We will provide a stipend for your efforts in tracking the data. In addition, we encourage farmers to learn grafting technique and produce grafted plants on your own. We will provide you with technical support and help with the process on-site if it is needed. For more[Read More…]


Agricultural producers face a plethora of wildlife issues on the farm, from biosecurity in animal agriculture to food safety requirements for fresh produce farmers. Many wildlife species have social or economic value and may be regulated or protected, constraining timely mitigation strategies. Additionally, research and science-based management recommendations to help farmers address wildlife on the farm are limited, available for some crops and pest species but not others. The last national United States Department of Agriculture (USDA) survey of U.S. wildlife damage to agriculture took place in 2001 and estimated $944 million in losses. At the national level, primary wildlife species resulting in losses to field crops included deer, turkeys, raccoons and waterfowl (collectively 75% of the reported losses), with 22% attributed to other species. For vegetables, fruits and nuts, deer, ground squirrels and other small rodents, crows, raccoons and rabbits were most frequently reported (64%), with other species accounting for 36%[Read More…]