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

238 articles by this author

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The Indiana Pesticide Clean Sweep Project is a great opportunity to legally dispose of unwanted chemicals. It is free of charge up to 250 pounds. To dispose of pesticides, complete the Pesticide Clean Sweep Planning form (the form is attached with the newsletter) and mail, fax or e-mail the completed form to Kevin Neal at Purdue University. 175 South University Street, West Lafayette, IN 47907-2063, 765-494-4331 (fax) or nealk@purdue.edu no latter than Monday, August 1, 2016. Then bring your labeled, leak free and safe to transport containers to the collection site. Do NOT mix materials. Pesticides will be accepted from 9:00 am to 3:00 pm local time at the following dates and locations: August 16 – Dubois County Fairgrounds/Huntingburg August 17 – Jackson County Fairgrounds/Brownstown August 18 – Jefferson County Fairgrounds/Madison August 23 – Newton County Fairgrounds/Kentland August 24 – Allen County Fairgrounds/Fort Wayne August 25 – Hendricks County Fairgrounds/Danville More information about[Read More…]


Figure 1. Strawberries grown inside a high tunnel at Southwest Purdue Agricultural Center. Photo was taken on April 16 2016.

We are familiar with strawberries grown as a perennial crop in Indiana. Bare root strawberry plants are set in the spring. Fruit is first harvested in the second year and the planting is renovated annually. Using this system, strawberry seasons last for three to four weeks from middle May through June. The traditional system has been replaced with an annual plasticulture system in the southern United States ever since the 1980s. In the annual plasticulture system, strawberry plugs (rooted runner tips) are transplanted in plastic covered beds in late summer or fall. Fruit are harvested in spring in the next year. After the fruiting season, the plants are removed. The annual plasticulture system is favored in the south because it has a longer harvest period and produces strawberries with better quality. In Indiana, trials established to test the annual plasticulture system had limited success because of short fall season and harsh[Read More…]


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Driving across IN now, it is not uncommon to see many recently built high tunnels standing along the roadsides. These structures have become an important tool for farmers to extend production seasons of vegetable and fruit crops. Compared with traditional greenhouses, high tunnel demand much less energy as they are heated by solar energy and ventilated through natural air circulation. Similar to high tunnels, Chinese-style solar greenhouse is an important tool for season extension in specialty crop production in China. The structures are facing south, featured by supporting north walls (Figure 1 and 2). The north walls are essential in maintaining temperatures inside the structure. They are made up with materials having good insulation properties and with a thickness more than 30 inches. The south sides are arch-shaped, supported by steels and covered with polyethylene or polyvinyl chloride films. From north to south, the structures span 26-46 feet. A short[Read More…]


Pickin’ and Packin’: 2016 Postharvest Produce Workshop Date: July 12, 2016, 9:00 AM – 12:30 PM (EDT) Location: Purdue University, Nelson Hall of Food Science, Rm 1195, 745 Agriculture Mall Dr. West Lafayette, IN 47906 Workshops will be offered for updating produce growers on the Food Safety Modernization Act Produce Rule and other food safety issues. It will also provide practical advice for postharvest handling of produce. The workshop is free. Participants are asked to pre-register at http://bit.ly/2016PostharvestWorkshop. For more information please contact Scott Monroe at (812) 886-0198 or jsmonroe@purdue.edu. Beginning Farmer Tours July 14, 2016: Melon Acres, Oaktown. Community-supported agriculture and agritourism. Sept. 29, 2016: River Ridge Farm, Roann. Four-season vegetable farming, operating an on-farm store, and farm-to-school programs. The tours are free, but registration is required. Registration at https://mdc.itap.purdue.edu/wk_group.asp?wk_group=BeginFarmer For more information about the Beginning Farmer and Rancher program, or the farm tour schedule, contact Kevin Gibson at (765) 496-2161 or kgibson@purdue.edu. Illinois Pumpkin Field[Read More…]


Last week, the highest temperature reached 110°F for a few successive days inside of our high tunnels. As a result, we observed some blossom drop on tomatoes. More information on high temperature effects on tomato fruit set can be found here. In addition to blossom drop, high temperature and high light intensity contribute to sunscald injury, uneven ripening, and cracking of tomato fruit. To protect tomatoes from damage caused by excessive heat, we placed 30% black shade cloth on top of the high tunnel. By installing the shadecloth, we expect there will be less cracking and more uniformly ripe tomatoes. Tomato marketability will increase. However, using shade cloth also has some negative effects. In this article, we review the effects of high temperatures on tomatoes, and discuss positive and negative aspects of using a shade cloth. Excessive high temperature (above 100°F) lasting for a few hours for successive days could cause tomato flower abortion and affect[Read More…]


Pickin’ and Packin’: 2016 Postharvest Produce Workshop Date: July 6, 2016, 9:00 AM – 12:30 PM (EDT) Location: Oaktown Produce Depot. 13990 N. Old Hwy 41, Oaktown, IN 47561 and Date: July 12, 2016, 9:00 AM – 12:30 PM (EDT) Location: Purdue University, Nelson Hall of Food Science, Rm 1195, 745 Agriculture Mall Dr. West Lafayette, IN 47906 Two workshops will be offered for updating produce growers on the Food Safety Modernization Act Produce Rule and other food safety issues. It will also provide practical advice for postharvest handling of produce. The workshop is free. Participants are asked to pre-register at http://bit.ly/2016PostharvestWorkshop. For more information please contact Scott Monroe at (812) 886-0198 or jsmonroe@purdue.edu. Beginning Farmer Tours June 25, 2016: Silverthorn Farm, Rossville. Organic fruits and vegetables, pastured pork and working with restaurants. July 14, 2016: Melon Acres, Oaktown. Community-supported agriculture and agritourism. Sept. 29, 2016: River Ridge Farm, Roann. Four-season vegetable farming, operating an on-farm store, and[Read More…]


Beginning Farmer Tours June 25, 2016: Silverthorn Farm, Rossville. Organic fruits and vegetables, pastured pork and working with restaurants. July 14, 2016: Melon Acres, Oaktown. Community-supported agriculture and agritourism. Sept. 29, 2016: River Ridge Farm, Roann. Four-season vegetable farming, operating an on-farm store, and farm-to-school programs. The tours are free, but registration is required. Registration at https://mdc.itap.purdue.edu/wk_group.asp?wk_group=BeginFarmer For more information about the Beginning Farmer and Rancher program, or the farm tour schedule, contact Kevin Gibson at (765) 496-2161 or kgibson@purdue.edu.   Illinois Pumpkin Field Day Dates: August 31, 2016 Location: Ewing Demonstration Center, 16132 N. Ewing Rd; Ewing, IL 62836 For more information, contact Nathan Johanning at (618) 687-1727 or njohann@illinois.edu


If you visit the Vegetable Crops Hotline on-line, be sure to visit our new addition: Veggie Extras.  The articles that you’ll find when you click on the Veggie Extra link include brief observations, photos, research updates or in-depth subjects  that we hope the vegetable professional might find interesting.  Articles that are in the Veggie Extras might not be of immediate importance; therefore, Veggie Extra articles will not be included as part of regularly scheduled newsletters. However, we will keep you informed of new Veggie Extra posts with announcements through email. Thank you for your continued support of the Vegetable Crops Hotline.


We sometimes hear that excessive nitrogen could delay fruit set, stimulate excessive vine growth, and depress overall yield of pumpkins, but it is often unclear how much nitrogen is too much. This article reviews research on nitrogen fertilizer rates for pumpkins, and discusses the potential factors that might affect the recommended nitrogen rate. In a study conducted in 1987 and 1988 in Kilbourne, IL, four nitrogen rates were compared: 50, 100, 150 and 175 lb N/acre. The first three rates (50, 100 and 150 lb N/acre) were applied through fertigation, while the highest rate (175 lb N/acre)  was applied preplant and about a month after seeding. The study found the highest early and total marketable yields were obtained with fertigation of 100 lb N/acre. The lowest total yield was associated with the lowest nitrogen rate (50 lb N/acre). Fertigation with 150 lb N/acre and dry-blend with 175 lb N/acre delayed[Read More…]


Figure 1. Colorado potato beetle larvae found on high tunnel tomatoes.

Last week we had a report of an infestation of Colorado potato beetle larvae on tomatoes in a high tunnel (Figure 1). Potato beetles are a pest of most of the solanaceous crops (potato, tomato, eggplant, pepper), but they rarely become a serious problem on tomato in Indiana. In addition, we have not seen them in high tunnels before, so this is a new problem for us. There are a number of insecticides that are labeled for use on Colorado potato beetles, but that list gets much shorter when the problem is in a high tunnel. Remember that in Indiana, a high tunnel is considered a greenhouse, so insecticides that are prohibited in greenhouse cannot be used in high tunnels. The effective products that could be used in this situation are Admire Pro®, Intrepid®, Entrust® and Exirel®.