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

Article List
Veg Crops Hotline - COVID-19 Image

New 6-3-2020: Application for Coronavirus Food Assistance Program (CFAP) open; Jim Mintert and Indiana FSA Director Steve Brown discuss CFAP application;Indiana State Dept. of Health – Food Safety Guidance (English and Spanish); Guidance for Migrant Farm Workers, Labor Camps Operators and their Employers (Spanish); FDA and USDA release recommendations for those short of PPE. What is new? (6-3-2020) Coronavirus Food Assistance Program Application Details with Purdue’s Jim Mintert and Indiana FSA Director Steve Brown – video and podcast  (5/27) https://ag.purdue.edu/commercialag/home/resource/2020/05/coronavirus-food-assistance-program/ Application for Coronavirus Food Assistance Program open on May 26 (5/27) https://www.farmers.gov/cfap Indiana State Dept. of Health – Food Safety Guidance – 5/29 update (6/3) English https://www.coronavirus.in.gov/files/IN_COVID-19_FoodGuidance_5.29.20.pdf Spanish https://www.coronavirus.in.gov/files/IN_COVID-19_FoodGuidance_03.31.20_version%20nueva.pdf Indiana State Dept. of Health – Interim Coronavirus Disease 2019 (COVID-19) Guidance for Migrant Farm Workers, Labor Camps Operators and their Employers – Spanish version (5/19) https://www.coronavirus.in.gov/files/COVID-19%20migrant%20worker%20Spanish%205.19.20.pdf FDA and USDA release recommendations for those short of PPE (5/22) https://www.fda.gov/food/cfsan-constituent-updates/fda-and-usda-release-recommendations-those-food-and-agriculture-sector-experiencing-shortages-ppe  Here are[Read More…]


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What is wrong with these strawberries?  Answer: The deformed fruit is likely caused by frost damage or poor pollination. More information about deformed strawberry fruit can be found in this issue’s article Factors may cause deformed strawberry fruit.      


Watermelon is best grown at temperatures around 80-90°F. Temperatures above 90°F reduce the growth rate; above 105°F may cause plant injury. Temperatures below 42°F result in watermelon chilling injury; below 32°F will kill watermelon plants. Extended cool days that lead to soil temperatures dropping into lower 50°F can also kill watermelon seedlings. Using low tunnels is one strategy to avoid chilling injury and encourage early plant growth. How does the plastic covered low tunnels modify temperatures in early watermelon season? Figure 1 shows the air temperature comparison between low tunnel (1 mil plastic film, perforated) and without low tunnels. The data was taken from April 24 to May 25, 2020 in a watermelon field at Southwest Purdue Agricultural Center. During the time period, the recorded minimal temperatures were below 40°F for 5 nights. Low tunnels increased the minimal temperature from 0-4.5 degrees (Table 1). Table 1. Minimal air temperatures with and[Read More…]


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This article discusses the abiotic factors that may cause deformed strawberry fruit. unevenly developed strawberry fruit (Figure 1): Frost damage is probably the most common abiotic factor causing misshapen strawberry fruit. Temperatures lower than 30°F kill the pistil (female part) of strawberry flowers. Depending on the extent of the injury and the stage of fruit development. The entire pistillate portion of the flower may be killed, which will result in the loss of fruit; Or a few pistils may be killed, fruit expansion stops at where pistils were killed. The damaged fruit then develops unevenly, resulting in misshapen fruit. Lack of wind for pollination is less likely a problem for field strawberry production but can be a concern for high tunnel production. Because high tunnels are typically closed at the peak strawberry blooming stage in order to attract heat. Air movement is very limited inside of the high tunnel that results in poor[Read More…]



Veg Crops Hotline - COVID-19 Image

New 5-21-2020: Application for Coronavirus Food Assistance Program will begin on May 26; Indiana Registered Disinfectants for Use Against COVID-19 (updated) What is new? (5-21-2020) Application for Coronavirus Food Assistance Program will begin on May 26 (5/20) https://www.farmers.gov/cfap  Indiana Registered Disinfectants for Use Against COVID-19 (updated) https://www.oisc.purdue.edu/pesticide/pdf/covid-19_disinfectants_051520.pdf Here are the categorized information resources Financial Application for Coronavirus Food Assistance Program will begin on May 26 (5/20) https://www.farmers.gov/cfap SBA COVID-19 DISASTER LOANS FOR INDIANA SMALL BUSINESSES (link update 5/7) https://isbdc.org/indianacovid19smallbusiness/ https://www.sba.gov/funding-programs/loans/coronavirus-relief-options SBA Help for Small (and Family) Businesses, Purdue Institute for Family Farms (update) (4/28) https://ag.purdue.edu/agecon/fambiz/Documents/SBA_Help_for_Small_Businesses.pdf COVID-19 Affected Business and Employee Resource Guide from Sen. Braun (3/27) https://www.braun.senate.gov/sites/default/files/2020-03/Senator%20Mike%20Braun%20COVID-19%20Affected%20Business%20and%20Employee%20Resource%20Guide_0.pdf Information about the Coronavirus Aid, Relief, and Economic Security (CARES Act); the Families First Coronavirus Response Act; and Small Business Economic Injury Disaster Loans (EIDL). Production COVID-19 response plan template and FAQ for fruit and vegetable farms from UMN. (5/7) https://blog-fruit-vegetable-ipm.extension.umn.edu/2020/04/covid-19-response-plan-template-and-faq.html This template can[Read More…]


USDA will soon begin taking applications for the Coronavirus Food Assistance Program. As part of applying for the program, you’ll need to contact the Farm Service Agency county office at your local USDA Service Center to schedule an appointment. Find your office at farmers.gov/cfap. Your local FSA staff will work with you to apply for the program, and through forms asking for this type of information: Contact Personal, including your Tax Identification Number Farming operating structure Adjusted Gross Income to ensure eligibility Direct deposit to enable payment processing Please do not send any personal information to USDA without first initiating contact through a phone call. FSA has streamlined the signup process to not require an acreage report at the time of application and a USDA farm number may not be immediately needed. If you are an existing customer, this information is likely on file at your local Service Center. What[Read More…]


Have you thought about produce your own value-added products that increase the value of your fresh produce? What are the challenges for you to start or expand your value-added business? How does COVID-19 affect your business? We would like to invite you to participate in the online survey to share your perspective and experiences on value-added production and we also want to learn about how COVID-19 pandemic affect your business. Your feedback will be very valuable for us to develop better learning materials for you and other growers. You can participate in this study if you are a Produce Grower. You do not need to have a value-added business! Please help us by completing this survey: https://purdue.ca1.qualtrics.com/jfe/form/SV_6RmMdQjLEFAr445 You will have the chance to receive a $35 Amazon e-gift card (odds: 1 in 10) if you enter your email address in the last survey question. The winner will be notified via[Read More…]


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Botrytis gray mold can cause disease on many different host plants, enabling the fungus to easily survive and disperse between crops. Host crops include flowers such as geraniums, vegetables such as green beans and fruit such as strawberries. The disease is favored by relatively cool temperatures and high humidity. We recently observed botrytis gray mold on tomatoes grown in a greenhouse and strawberry grown on a plasticulture system in the open field. Tomato: Gray mold of tomato is one of the more common diseases of greenhouse-produced tomatoes. Although it is often a minor problem, if left unchecked, gray mold can cause yield loss. Gray mold, or as it is sometimes called, Botrytis gray mold, may cause a light gray or brown necrotic lesion on leaves (Figure 1). The lesions on leaves are sometimes wedge shaped on the margin of the leaf. Stem lesions are a similar color and may encircle[Read More…]


Figure 2. Covering a strawberry field with a row cover.

Strawberries growing in the matted-row system are in the blooming stage. Open flowers cannot tolerate temperatures lower than 30°F (Figure 1). Strawberry growers should be prepared for the coming low temperatures this week. Row covers (Figure 2) can be effective in protecting strawberry flowers. In our earlier trial, 1.5 oz/sq row covers provided 4-6 degrees protection and successfully protected strawberry blooms in the earlier frost happened in middle April (the recorded lowest temperature was 24.5°F at Southwest Purdue Agricultural Center). Lighter row covers (0.05-1.0 oz/sq) provided fewer degrees of protection and double layers can be more effective. When using row covers for frost protection, be sure to have good soil moisture, sometimes running water through the drip line may add heat in the system. Apply row covers in the early afternoon to attract more heat before temperature drops. Although row covers can be effective in protecting strawberry blossom from frost[Read More…]