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

Article List

U.S. EPA approved a supplemental label to use Kerb SC® herbicide in leaf lettuce. Kerb® is a selective herbicide for control of certain annual grasses and broadleaf weeds. It can be used in direct seeded or transplanted leaf lettuce. Application can be made before or after planting but must be made prior to weed emergence. It may be applied at the rate of 1.25 to 5.0 pints of product (0.5 to 2 lb active ingredient) per acre broadcast application. Depending on application rates, 25 to 55 days of preharvest intervals are required. Refer to the label for more application information http://www.cdms.net/ldat/ld9R3003.pdf.


Food Safety Program A series of workshops will help produce marketers better understand food safety practices to lower the risk of contamination by a foodborne illness. Workshop “On-Farm Food Safety for Produce Direct Marketers” will be held on the following dates and locations (all times local): * March 23: Allen County Extension Office, 4001 Crescent Ave., Fort Wayne; 9 a.m.; James Wolff at 260-481-6826. * March 24: Kosciusko County Extension Office, 202 W. Main St., Warsaw; 6:30 p.m.; Kelly Heckaman, 574-372-2340. * April 5: Harrison County Extension Office, 247 Atwood St., Corydon; 6 p.m.; Miranda Ulery, 812-738-4236. * April 26: Morgan County Administration Building, 180 S. Main St., Martinsville; 7 p.m.; Amanda Dickson, 765-342-1010. * April 28: Posey County Fairgrounds, 111 Harmony Township Road, New Harmony; time to be announced. Jon Neufelder, 812-838-1331. There is no cost, registration is available at http://bit.ly/1nhXZyt. For any additional questions, contact Scott Monroe at jsmonroe@purdue.edu or 812-886-0198.   Workshop: Solar Energy[Read More…]


Tomatoes grown in controlled environment are exposed to conditions that are different from their original habitats. As a result, varieties that are not specifically bred for greenhouse production may respond to the controlled environment with abnormal symptoms. One group of the symptoms is called edema. Bumps, galls or blisters develop on tomato leaves, petioles or stems (Figure 1). In severe conditions, it causes leaf curling, distortion and abscission (Figure 2). A couple of factors including high humidity, excessive water in the soil, air pollution, and low light condition could cause the symptom. Tomato varieties respond differently in susceptibility to the physiological disorder, and the primary contributing factors can also be different among tomato varieties. The most severe case of edema that we have observed so far is on tomato rootstocks including ‘Maxifort’. This is not surprising as most of the commercial tomato rootstocks are hybrid of wild tomatoes Lycopersicon esculentum[Read More…]


If you are an Indiana beekeeper and if you are under 22, please note the 2016 Young Beekeeper of the Year Award  This is a statewide contest with great prizes. Application procedure and additional information can be found at YBA Information-Application Form. Application deadline is September 1, 2016.


If you received a hard copy of the Midwest Cantaloupe Variety Trial in Southwest Indiana-2015 at the Southwest Indiana Melon and Vegetable Growers Technical meeting in December, 2015, please note there was a mistake in Table 3, the firmness and fruit size columns. The corrected version of this report is available at https://ag.purdue.edu/hla/fruitveg/MidWest%20Trial%20Reports/2015/02-01_Guan_Cantaloupe.pdf. We are sorry for the confusion.


If you are an organic grower and use manure and compost, you might be interested in spending a few minutes to participate this survey conducted by University of California-Davis, The Organic Center and Organic Trade Association. The purpose of the survey is to characterize the use of manure and compost based soil amendments. Results from the survey will be used to study the use of untreated manure and compost in organic agriculture and the impacts of those practices on food safety. The survey can be found at https://www.surveymonkey.com/r/manurefoodsafety


2016 Indiana Small Farm Conference Location: Danville, Indiana Date: March 3 to 5, 2016 Keynote speaker of this year’s conference is Mary Dee Berry the executive director of The Berry Center, and Ben Hartman the author of The Lean Farm. More information regarding registration, conference schedule, as well as directions and lodging is available at https://ag.purdue.edu/extension/smallfarms/Pages/default.aspx. Southwest Indiana Melon & Vegetable Growers Meeting Location: French Lick Resort and Casino, 8670 W. State Rd. 56, French Lick, IN 47432 Date: March 4, 2016 Registration and viewing of commercial exhibits will begin at 8:30 a.m. Eastern Standard Time. The educational program begins at 9:00 a.m. Detail of the program is available at https://www.facebook.com/SWPurdueAgCenter/. Lunch, which will be available with the $15 registration, will be from 11:45 until 1:15 p.m.  The afternoon educational program has been approved for Private Applicator Recertification Program (PARP) credit and commercial pesticide credits have been applied for. Please[Read More…]


Welcome to a new year of the Vegetable Crops Hotline! Starting with this issue, I will be the new editor of VCH newsletter. If you do not know me yet, I am the horticulture specialist located at Vincennes, IN. I am excited to work more closely with VCH. I also feel responsible to continually provide you a great newsletter. As always, our goal is to provide timely information that is useful for Indiana vegetable growers. If you have any suggestions, comments, or just want to share with us your experience about VCH, please do not hesitate to contact me at 812-886-0198, or email at guan40@purdue.edu. Taking the opportunity, I would like to thank you for your unconditional support of VCH. Without your support, it is impossible for us to put everything together. I would also like to thank Liz Maynard for her years of dedicated service to VCH as an editor. What you[Read More…]


A grafted tomato plant growing in a high tunnel. (Photo by Wenjing Guan)

​You might have heard about tomato grafting, or you might even already have tried the new technique. Yes, it has multiple benefits: control of soilborne diseases, enhanced tolerance to abiotic stresses, and increased productivity. It works for some growers, but not all. Why? There are several reasons. First, effects of grafting on controlling soilborne diseases depend on the presence of the disease that the rootstock is designed to control. For example, grafting might not be very helpful for white mold, because current commercial rootstocks do not have resistance to white mold. However, grafting might work if the primary problem is Fusarium crown and root rot, as most commercial tomato rootstocks have resistance to this disease. With that said, it is very important to look at the disease resistance profile before deciding on the rootstocks. Second, grafting effects on improving yield depend on factors such as scion and rootstock cultivars, cultural[Read More…]


​Crop production, decomposition of organic matter, using ammonium-producing nitrogen fertilizers, and rainfall all lower soil pH. To maintain soil pH in the optimal range (6.5 to 6.8) for vegetable production, periodic application of lime is needed. The primary form of agricultural lime is calcium carbonate (CaCO3). It is the carbonate (CO3^2-) part that brings up soil pH. Whenever lime is applied, a large amount of calcium is also added to the soil. The good news is that calcium is an essential plant nutrient. Several vegetable problems that we are familiar with are caused by calcium deficiency for example, blossom end rot of tomatoes and peppers, and tip burn of cabbages. However, it should be noted that excess calcium might interfere with plant available magnesium and potassium. Therefore, it is always better to keep a balance of those nutrients. Some lime products are specified as dolomitic lime. Dolomitic lime is common[Read More…]