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

101 articles by this author

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NCR-SARE’s Professional Development Program (PDP) provides funds for professional development projects that provide sustainable agriculture training to agricultural professionals and educators. Projects can be up to three years in duration, and funding level is capped at $75,000 for each project. The 2017 call for proposals is now available online at http://www.northcentralsare.org/Grants/Our-Grant-Programs/Professional-Development-Grant-Program Proposals are due at 4:00 pm CDT on April 5, 2017.


OCCSP provides cost share assistance to producers and handlers of agricultural products who are obtaining or renewing their certification under the National Organic Program (NOP). Certified operations may receive up to 75 percent of their certification costs paid during October 1, 2016, through September 30, 2017, not to exceed $750 per certification scope. Certified organic producers and handlers who have paid certification fees may apply for reimbursement of the incurred cost. Producers and handlers may submit OCCSP applications to Farm Service Agency county offices beginning on March 20, 2017. More information about the program can be found at https://www.fsa.usda.gov/programs-and-services/occsp/ or https://www.fsa.usda.gov/Assets/USDA-FSA-Public/usdafiles/FactSheets/2016/organics_fact_sheet_2016.pdf


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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…]


Welcome to a New Year of the Vegetable Crops Hotline (VCH), Purdue Extension’s newsletter for people in the business of growing vegetables. Our goal is to provide timely information that will be useful for Indiana vegetable growers. If there is something you’d like to see included, please let us know. Frequently we include links to websites or publications available on-line. If you aren’t able to access these resources, please contact us or a local Extension office to request a hard copy of the information. Since last year, Vegetable Crops Hotline website has a new look. Articles that need your immediate attention are posted under Hot Topics and then will be included in the next issue. If you subscribe to VCH via email, you will receive an email when there is a Hot Topic article posted. All the previous articles published in VCH are available on the website. In addition, the[Read More…]


Figure 1. Seedless watermelon varieties in 2016 variety trial that have unique rind patterns

— Notes from Watermelon Research and Development Group Annual Meeting and 2016 Indiana Watermelon Variety Trial We are proud to be in Vincennes, the heart of watermelon producing counties in Indiana. In case you are unfamiliar with watermelon production here, Indiana is just behind Florida, Texas, Georgia, California and South Carolina in watermelon production nationwide. Indiana has more than 7,000 acres of watermelons valued at over $30 million value. In the recent Watermelon Research and Development Group (WRDG) annual meeting, the group that comprise members from academia, government and industry discussed watermelon varieties. In this article, I will summarize my notes from this year’s meeting and discuss the varieties we tested in Indiana watermelon variety trials in 2016. Mini-watermelons One of the interesting things I learned in the meeting is from a talk by Mr. Greg Hitt from Walmart. He shared data that shows Walmart increased the sale of mini watermelons[Read More…]


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Daikon radish is a member of Brassica family. It forms a large white tap root like a giant carrot. The tap root (12 to 20 inches long and 2 to 4 inches in diameter) penetrates into the soil leaving 2 to 6 inches protruding above ground.  Radishes are cool-season crops. They are best grown with air temperatures in the range of 50 to 65°F. They grow fast, forming a dense canopy in the fall.  They are winter killed when temperatures drop to low 20s °F for a few consecutive nights. Daikon radish is a common and popular vegetable consumed in the southeast and Eastern Asia (Figure 1). The large and white roots have a favorable mild flavor, very low calorie content and rich in vitamin C. Fresh or picked diced daikon roots are important ingredients in a variety of dishes and soups in Asia cooking. Leaves are also consumed as[Read More…]


Last fall, my lab received a carrot sample with disease-like lesions (Figures 1 and 2). There are at least 3 carrot diseases that may appear similar. These diseases are: Alternaria leaf blight (late blight), Cercospora leaf spot (early blight) and bacterial leaf blight. Often an examination in the laboratory is necessary. My examination revealed the characteristic spores (conidia) of Alternaria dauci, causal agent of Alternaria leaf blight. Figure 1  shows a stand of carrots with several leaves that appear chlorotic (yellow) and necrotic. A closer examination reveals small lesions on the leaves (Figure 2). Loss of leaves may lead to fewer or smaller carrots. Sometimes severe infections can lead to the premature separating of the leaves and root. Alternaria leaf blight can be rapidly spread between plants by the conidia that are produced on the plant surface. I could easily find these spores on the surface of the carrot leaves brought to my lab. The conidia may[Read More…]


The Midwest Cover Crops Council (MCCC) strives to facilitate widespread adoption of cover crops throughout the Midwest, to improve ecological, economic, and social sustainability. The Cover Crop Decision Tool is an initiative by the MCCC to consolidate cover crop information by state to help farmers make cover crop selections at the county level. The tool makes seeding date recommendations based on county specific weather information, and sorts cover crop species by desirable attributes of the farmer’s choosing. Indiana was the first state in the Midwest to implement a decision tool for field crops and Michigan is currently the only state with a decision tool for vegetable crops. Indiana SARE (Sustainable Agriculture Research and Education) is funding the creation of a decision tool for vegetable crops in Indiana this fall. Both the IN field crops tool and MI vegetable tool can be found on the MCCC website (mccc.msu.edu). We are seeking[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…]


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We have two new extension faculties join the Department of Horticulture and Landscape Architecture at the Purdue University. Please join me welcome Dr. Ariana Torres and Dr. Krishna Nemali. Dr. Torres’ background combines field experience in agriculture with theoretical and applied research on agricultural economics. After earning her B.Sc. in Agricultural Engineering at Zamorano University, she came to Purdue to pursue her graduate studies. She completed her M.Sc. in Horticulture and her Ph.D. in Agricultural Economics, both at Purdue University. She has worked on projects such as the impact of market channel choices on the certification and decertification process of organic farmers; the economic implications of social capital on entrepreneurship; and the resilience of small businesses after disasters. Her research focuses on the intersection between the horticulture industry and marketing decisions. Her goal is to conduct innovative outreach and applied research in Specialty Crops Marketing, with the end of promoting[Read More…]