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

106 articles by this author

Article List

High Tunnel Tour at SWPAC Location: Southwest Purdue Agricultural Center, 4369 North Purdue Road, Vincennes, IN 47591 Date: May 9, 2016, 3:00 PM to 5:00 PM EST Please join us for a high tunnel tour at Southwest Purdue Agricultural Center. You will see state-of-the-art high tunnels, learn about season extension of strawberry production under high tunnels and early season frost protection by using row covers. We will also discuss the potential of grafted tomatoes and cucumbers grown in high tunnels. The tour is free, to register please call (812) 886-0198. For more information please contact Wenjing Guan at guan40@purdue.edu.     USDA-AMS webinar: Standards for the Growing, Harvesting, Packing and Holding of Produce for Human Consumption, i.e., the Produce Safety Regulation Date: April 21, 2:00-3:00 EST For more information, please visit https://amsfv.webex.com/amsfv/onstage/g.php?MTID=eeb487e80d56a3c58d4b6f4a242bd75ae   Beginning Farmer Tours Location: South Circle Farm in Indianapolis Date: May 26, 2016. 10:45 AM to 4:00 PM EST Learn about key[Read More…]


High Tunnel Tour at SWPAC Location: Southwest Purdue Agricultural Center, 4369 North Purdue Road, Vincennes, IN 47591 Date: May 9, 2016, 3:00 PM to 5:00 PM EST Please join us for a high tunnel tour at Southwest Purdue Agricultural Center. You will see state-of-the-art high tunnels, learn about season extension of strawberry production under high tunnels and early season frost protection by using row covers. We will also discuss the potential of grafted tomatoes and cucumbers grown in high tunnels. The tour is free, to register please call (812) 886-0198. For more information please contact Wenjing Guan at guan40@purdue.edu.   Hops Workshop Location: 8508 Trentman Road, Fort Wayne, IN 45816 Date: April 16, 2016, 1:00 PM to 3:00 PM EST Topics to be covered include: obtaining and establishing rhizomes and transplants; soil tests and nutrient management plants; weed management; downy mildew management plans; when and how to train bines. The[Read More…]


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We went through an unseasonably cold period in early April (Figure 1). In southern Indiana, a few high tunnel tomato growers have already planted their crops. These plants may need some extra help. In Vincennes, IN, we used row covers to cover the newly planted tomatoes in high tunnels the past few nights, our recorded lowest temperature was 37 °F under row covers. Plants all look good. However, the temperature is apparently too cold for cucumbers. The majority of the early planted cucumbers in our high tunnels were dead. We are waiting for the weather to warm up (soil temperature at least above 60 °F) to reset the cucumbers. Please let us know if you also ran into problems in the past a few days because of the low temperature. It might be issues in the greenhouse, the high tunnels, or even the field. We would appreciate you sharing your experiences with us.      


Soil pH plays an important role in plant nutrition. However, we might not be familiar with how nitrogen fertilizers influence soil pH over time. This article explains how nitrogen fertilizers influence soil pH over time and discusses some considerations in choosing N fertilizers. Plants can take up N in two forms: ammonium and nitrate. Ammonium (NH4+) is positively charged, while nitrate (NO3–) is negatively charged. When plant roots take up a charged ion, they typically release an ion with identical charges to maintain a balanced pH in plant cells. Following this rule, plants release a hydrogen ion (H+) when taking up an ammonium ion; and release a hydroxide ion (OH–) when taking up a nitrate ion. As a result, the net effect of taking up nitrate-N is to increase soil pH around root zones; taking up ammonium-N reduces rhizosphere soil pH. Nitrogen fertilizers contain N in the forms of ammonium,[Read More…]


The VAPG program helps agricultural producers enter into value added activities related to the processing and marketing of bio-based, value-added products. Independent producers, agricultural producer groups, farmer- or rancher-cooperatives and majority-controlled producer-based business ventures are eligible to apply for the program. Beginning farmer or rancher, a small or medium-sized farm or ranch structured as family farm receive priority. The total program funding is $44 million, 50% matching funds are required. Grant and matching funds can be used for planning activities or for working capital expenses related to producing and marketing a value-added agricultural produce. Application deadline is July 1, 2016 (paper application) and June 24, 2016 (electronic application). More information about the grants can be found at http://www.rd.usda.gov/programs-services/value-added-producer-grants.


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.