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

The 2019 production season started with above-normal rains. The wet conditions affected agriculture production, including watermelon and cantaloupe. In this article, we will review some of the watermelon and cantaloupe problems that are often associated with wet conditions. Manganese toxicity– This nutrient disorder occurs more often on cantaloupe that is grown in soils with pH lower than 5.5. Although liming before planting is a common practice, it is not unusual that we see soil pH that has dropped below 5.5 in sandy soil, especially during wet years. Manganese exists in soil solution as either reduced (Mn2+) or oxidized (Mn3+) form. Plants take up manganese in the reduced form (Mn2+). The proportion of exchangeable Mn2+ increases dramatically as soil pH decreases, and this reaction is promoted in waterlogged soils with low oxygen condition. As raindrops fall through the air, they dissolve CO2 and form enough carbonic acid to lower the pH of[Read More…]


thumbnail image

Meigs High Tunnel Field Day Date: July 18, 2019 Location: Purdue Meigs Farm, 9101 S 100E, Lafayette, IN 47909 Topics of the field day include Production of specialty melons in high tunnels; Early detection of bacterial wilt; Impact of crop rotation and rootstock on the resilience of high tunnel tomatoes. Lunch and refreshments are provided. Registration is free, but required. Register here https://purdue.ca1.qualtrics.com/jfe/form/SV_0HXQwDluRiOnwAB For questions please contact Lori Jolly-Brown at ljollybr@purdue.edu or (765) 494-1296   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 basic planning tools for a sustainable small farm operation, testing and[Read More…]


Figure 2. Yellow striped army worm feed on strawberry fruit.

At the Southwest Purdue Ag Center, we are studying annual strawberry production on plastic mulch. Our hope is to gather information for best production practices in our area. As we learn about insect and disease problems, we will pass this information on to producers. This article is about the insect pests we have observed in our strawberries that were planted in March 2019. Armyworm– Toward the end of the spring harvest, we observed significant damage on strawberry fruit caused by armyworms. Beet armyworm and yellowstriped armyworm larvae were found in the field (Figure 1 and 2).  They feed on both green and ripe strawberries. More than 30% fruit became unmarketable because of the insect feeding. Damage was also observed on flowers. Armyworms also cause significant damage when they chew on strawberry crowns and leaves of summer-planted young strawberry plants. Midwest Fruit Pest Management Guide provides several options for controlling the[Read More…]


thumbnail image

Indiana Horticultural Society Summer Meeting  Date: June 25, 2019. 9:30 am Location: Huber Orchard and Winery, 19816 Huber Road, Starlight, IN 47106 The summer meeting is co-sponsored by Indiana Horticultural Society and Indiana Vegetable Growers’ Association. The meeting will focus on commercial production of fruits and vegetables and farm marketing. All those interested are welcome to attend. A registration fee of $5.00 per family or farm is payable at registration. A catered lunch will be served onsite. This will most likely be fried chicken with vegetables and drinks. There is a $10/person charge for lunch, collected onsite. Please go to the following website to RSVP  https://purdue.ca1.qualtrics.com/jfe/form/SV_6oqUlioijOUNb0x 9:30 am – Convene and registration at Huber Orchard and Winery. 10:00 am – Introductions, a brief walking tour of facilities – winery, market, icecream store, banquet hall 10:30 am – Field tour – apples 11:45 pm – Lunch – $10 – RSVP requested[Read More…]


thumbnail image

Indiana Horticultural Society Summer Meeting  Date: June 25, 2019. 9:30 am. Location: Huber Orchard and Winery, 19816 Huber Road, Starlight, IN 47106 The summer meeting is co-sponsored by Indiana Horticultural Society and Indiana Vegetable Growers’ Association. The meeting will focus on commercial production of fruits and vegetables and farm marketing. All those interested are welcome to attend. A registration fee of $5.00 per family or farm is payable at registration. A catered lunch will be served onsite. This will most likely be fried chicken with vegetables and drinks. There is a $10/person charge for lunch, collected onsite. Please go to the following website to RSVP  https://purdue.ca1.qualtrics.com/jfe/form/SV_6oqUlioijOUNb0x 9:30 am    Convene and registration at Huber Orchard and Winery. 10:00 am  Introductions, a brief walking tour of facilities – winery, market, icecream store, banquet hall 10:30 am  Field tour – apples 11:45 pm Lunch – $10 – RSVP requested (see below) 1:00 pm   [Read More…]


Figure 3. Cucumber cultivar Taurus were grown in the front, cultivar Corinto was grown in the back.

Supported by NC SARE (LNC17-390), we are continuing research for improving high tunnel cucumber production. One of the biggest challenges for growing cucumbers in high tunnels in the summer is two-spotted spider mites. Dry and hot environments featured in high tunnels allow two-spotted spider mite populations to increase rapidly. The mites cause leaf yellowing, necrosis, and defoliation that interfere with plant photosynthesis. Yield can be significantly reduced. The pest also causes direct damage on cucumber fruit, resulting in a sandpaper-like texture to the rind (Figure 1). Early detection is the key for controlling two-spotted spider mites. As soon as two-spotted spider mites are detected, control efforts need to be taken. In the early stage, yellowish specks on the upper side of the leaves may be noticed (Figure 2). Turn the leaf over, on the other side of where the yellow specks are, you may find the presence of two-spotted spider[Read More…]


thumbnail image

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 2: Eight day-neutral stawberry cultivars grown under retractable low tunnel systems (picture was taken on May 20)

With the support of the Purdue Extension AgSeed Program, we are currently evaluating different production systems for growing strawberries in an open-field with plastic cultural systems for our area at Southwest Purdue Agricultural Center in Vincennes, IN. A day-neutral strawberry cultivar evaluation trial was established in the Spring of 2019. The evaluated cultivars include Portola, Evie-2, Mara Des Bois, Albion, Seascape, San Andreas, Monterey, and Tribute. Bare-root plants purchased from Nourse Farm and Indiana Berry were planted on black plastic mulch on Mar. 22. Cultivar Portola was planted on Apr. 10 due to back-order. Each of the eight cultivars were grown either with a retractable low tunnel system or without it (Figure 1). Although strawberries were planted this spring, most cultivars started to bloom toward the end of April. Removing runners started in early May. During the week of May 13, harvest started on the early cultivars: Tribute, Mara Des[Read More…]


Figure 1. Watermelon seedlings planted in a week

In the past week, we have observed a few cases where newly planted watermelon seedlings were severely damaged or dead (Figure 1). In some fields, we observed rotted roots and lower stems caused by fungal pathogens. However, such diseases were in response to the cold soils and would not normally cause problems in warm soils. Most of the dead plants had intact stems, although growers did report seedcorn maggot and wireworm in the stems of a few dead plants. The same thing happened in May 2016. Coincidentally, rain, cloudy days, and lower than normal temperatures were observed in the same period in both years. Since early May, We have had consecutive days with the lowest temperatures in the 40s°F. There was no risk of frost damage, however, this temperature was low enough to cause chilling injury on young cucurbit plants.  This article ‘Protect Early Planted Warm-Season Vegetables from Low Temperature’[Read More…]


thumbnail image

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…]