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

206 articles by this author

Article List
Figure 2. Wilt of watermelon seedlings due to grown in a high EC medium.

Producing healthy transplants is a critical step for a successful growing season. Choosing the proper growing media is an important first step. Supported by a USDA Specialty Crops Block Grant through the Indiana State Department of Agriculture, researchers from Purdue have been evaluating different organic growing media with and without adding supplemental organic fertilizers for tomato and cucurbit transplant production. In this article, we have highlighted a few transplant symptoms that are associated with growing media with excessively high or low electrical conductivity (EC) or pH. It is always a good idea to test EC, pH, and other important nutrient content of a medium when you are making your own or using an unfamiliar media. Most soil laboratories provide a saturated media extract test that provides information on these important parameters. More information about this test and suggested range of EC and pH can be found in this article http://www.soiltest.uconn.edu/factsheets/InterpSMEGreenMedia.pdf[Read More…]


Southwest Purdue Agricultural Center Field Day Date: June 27, 2019. Registration begins at 8:30 am. Location: Southwest Purdue Agricultural Center, 4669 N. Purdue Road in Vincennes, IN 47591 Topics related to vegetable production include: Organic Tomato Production: Dan Egel will discuss the Tomato Organic Management and Improvement Project — including foliar disease management of tomatoes. High Tunnel Grafted Cucumber & Specialty Melon Production: Wenjing Guan and Petrus Langenhoven will discuss cucumber and melon production in high tunnels. Applying IPM Principles across Cropping Systems to Increase Insect Pollination and Profitability: Laura Ingwell will discuss best management practices for watermelon production by quantifying pest pressures, pollinator health, and crop yields. Annual Strawberry Production: Wenjing Guan will discuss annual plastic culture for strawberry production in southern Indiana. Other topics include: Termites to the Rescue: In this presentation, Rick Meilan will discuss the use of enzymes derived from termites to control invasive woody species. Removing[Read More…]


Figure 4. Connect four stakes in a rectangle shape (A), cross the hook (12’’) with the central-string (B) and hook it to the side-strings between the two tomato plants (C).

The Florida-weave or sometimes called stake and weave is a commonly used tomato trellis system (Figure 1). It has several benefits and is easy to implement. However, sometimes the plants grow too tall and can hardly be supported by the stakes, or they may be too vigorous and break the strings. In this article, we will introduce an alternative tomato trellis system, Spanish-weave, and discuss its usage in tomato production. How to trellis tomato plants with the Spanish-weave system? Materials: tomato stakes, tomato strings, and hooks. We made the hooks from steel wire. They were made at 4-inch, 8-inch and 12-inch length (Figure 2). Prune bottom leaves of the tomato plant and suckers until the first flower cluster (Figure 3). Install tomato stakes on each side of the rows at every two tomato plants (A); Tie strings across the two wooden stakes at the beginning and the end of each[Read More…]


Southwest Purdue Agricultural Center Field Day Date: June 27, 2019 Location: Southwest Purdue Agricultural Center, Vincennes, IN 47591 Tentative schedule of this event will include: Removing invasives and cultivating natives; Growing hemp in Indiana; Bee health; Organic tomato production; Drones to help scout for crop problems; High tunnel cucumber and specialty melon production; Low tunnels in strawberry production; How termites can benefit and control of invasive plants. The event is free. Registration details will be announced soon.   Small Farm Education Field Day at Purdue Student Farm  Date: August 1, 2019 Location: Purdue Student Farm, West Lafayette, IN 47907 The Purdue Student Farm is proud to announce its second annual Small Farm Education Field Day.  The event is packed with educational sessions during the morning, followed by a tour and hands-on experiences on the farm. Topics of discussion throughout the day include Cover Crop Choices, Scheduling of Crops in High[Read More…]


Great information on pest management of brassica crops can be found at the Brassica Pest Collaborative website (https://ag.umass.edu/vegetable/resources/brassica-pest-collaborative). This project recently conducted several online workshops on managing insect pests of brassicas, including imported cabbageworm, cross-striped cabbageworm, cabbage maggot, flee beetle. All the webinars should be posted on the above website after April 12.  


Two types of injury on young warm-season vegetable plants are caused by low temperatures: frost/freezing injury and chilling injury. Frost/freezing injury occurs when temperatures drop below 32°F. Ice formation in plant tissues cut cell membranes. When the tissue thaws, the damage results in fluids leaking from the cell, causing water soaked damage. Frost/freezing injury is detrimental to warm-season vegetables, such as melons, cucumbers, tomatoes, peppers, beans. To avoid damage, the best way is to plant warm-season vegetables later in the spring, after the last frost has passed. However, weather is difficult to predict, and there is a growing trend of planting early to achieve early harvests. For the early planted warm-season vegetables, here are a few suggestions that may protect plants from low temperature damages. Covering. The idea of covering the seedlings is to create a microclimate around plants. Because the heat accumulated in soil irradiate back at night, covering[Read More…]


Figure 1. Cucumbers start to wilt following a night average soil temperature was 58 °F

Chilling injury occurs when temperatures are above 32°F and below 55°F. The plant tissue becomes weakened that leads to cellular dysfunction. The most noticeable visual symptom of chilling injury is leaf and hypocotyl wilt (Figure 1). This is caused by the rapid decline in the ability of roots to absorb and transport water. It also caused by the plant’s reduced ability to close stomata. If temperatures do not improve, plants may be killed. Low temperatures also have an effect on mineral nutrient uptake of the plants. Absorption of ions by roots is difficult, as well as their movement in the above-ground parts of the plants. As a result, chilling injured plants often show symptoms similar to nutritional deficiency. Although warm-season vegetables are all susceptible to frost/freezing damage, their susceptibility to chilling injury varies among plant species. Pepper plants seem to have greater difficulty recovering after chilling injury compared to tomato[Read More…]


Bacterial wilt is a serious pest of cucumbers and melons. This disease is caused by the bacterium, Erwinia tracheiphila. However, it is spread by the striped or spotted cucumber beetle. Most management schemes have concentrated on controlling the cucumber beetle in order to lessen the severity of bacterial wilt. Currently, management of bacterial wilt often takes the form of a soil applied systemic insecticide such as Admire Pro® at transplanting and follow up pyrethroid products applied foliarly about 3 weeks post transplanting. The pyrethroid applications are made when the 1 beetle per plant threshold is met. Every year, there is a melon variety trial at the Southwest Purdue Agriculture Center in Vincennes, IN. In 2018, the trial included several specialty melon varieties. We noticed more bacterial wilt than usual (Figure 1). Therefore, we decided to rate the varieties to see if there were any differences in susceptibility. Figure 2 shows[Read More…]


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Cover Crop Workshop & Field Tour Date: Thursday, April 4, 2019 9:00 am – Noon Location: SEPAC – 4425 E. 350 N., Butlerville, IN 47223  


Figure 2. Personal size (mini) watermelon cultivars.

Watermelon variety trials are conducted every year at the Southwest Purdue Agricultural Center in Vincennes, IN. In the 2018 trials, it included 38 standard-size seedless watermelon cultivars and 10 personal-size watermelons. This article discussed the top yielding varieties in our trials in 2018. The full report of the variety trials, and  information about the previous trials  can be found at https://ag.purdue.edu/arge/swpap/Pages/SWPAPPDFPresentstions.aspx Standard size seedless watermelons Tailgate is a new cultivar from Seminis. First time entered into our evaluation in 2018. Tailgate had the top yield variety in the 2018 trial. It produced large-sized fruit, average fruit weight was 18.5 lb, 37% fruit in 36 counts and 20% in 30 counts category. Firm flesh, good quality. Tailgate was one of the five cultivars that did not have hollow heart fruit among the 12 fruit selected for the quality test. Bottle Rocket had a consistent high yield in both 2017 and 2018 trials.[Read More…]