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

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Figure 1. Initial symptom of blossom end rot on pepper.

In the past few weeks, we have received several reports about blossom end rot on tomatoes and peppers as the crops start to set fruit. Blossom end rot is a physiological disorder (not an infectious disease) that commonly occurs on tomatoes and peppers. Initial symptoms of the physiological disorder include dark green or brown water-soaked leisure occurring on the bottom of the fruit (Figure 1). The lesion then expands into sunken, leathery brown or black spots (Figure 2 and 3). In severe cases, the lesion can expand to half size of the fruit. The symptoms on tomatoes can be observed on fruit from fruit set to fruit the size of golf balls. Fruit on the same cluster tend to show symptoms simultaneously. On peppers, the symptoms are more likely appear during fruit expansion. The affected fruit often change color prematurely. Under moist conditions, opportunistic molds might develop on the affected tissues[Read More…]


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Purdue Extension and Indiana University are collaborating to offer a series of field days featuring high tunnels. The events will be hosted July 18 at the Meigs Horticulture Research Farm in Lafayette; Aug. 10 at the Southwest Purdue Agricultural Center in Vincennes; Aug. 15 at the Pinney Purdue Agricultural Center in Wanatah; and Sept. 27 at the Hamilton County Extension Office and Full Hand Farm in Noblesville. Meigs Horticulture Research Farm High Tunnel Field Day Date: Tuesday, July 18, 10 a.m.-1 p.m. (EDT) Location: Meigs Horticulture Research Farm, 9101 S. 100 E, Lafayette, IN, 47909 Registration: Visit http://tinyurl.com/yc5lqvez or call (765) 494-1296 For more information, contact: Lori Jolly-Brown at (765) 494-1296 or ljollybr@purdue.edu The field day at Meigs Horticulture Farm will focus on high tunnel production of cucurbit crops. It will feature tours of conventional and hydroponic high tunnel cucumber and melon production. The use of insect-exclusion screens to control cucumber[Read More…]


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Indiana Fruit & Vegetable Field Tour The tour will be held at Tuttle Orchards, 5717 North 300 West Greenfield IN 46140, June 28, 9:00 am -4:00 pm. On-site registration 9 am at Tuttle Orchard. Registration fee is $5 per person. For further questions contact Lori Jolly-Brown at ljollybr@purdue.edu or (765) 494-1296. Southwest Purdue Ag Center Field Day  Southwest Purdue Ag Center Field Day will be held on June 29, 2017 at Southwest Purdue Agricultural Center, Vincennes, IN. The field day provides two choices of tours: Horticultural Crop Production and Agronomic Crop Production. The Horticultural Crop Production tour will feature Organic Tomato Production, High Tunnel Vegetable Production, Grape Research, Protecting Pollinators while Managing Insect Pests in Watermelon Production, and Produce Food Safety. A meal will accompany the tour with PARP classes available after lunch. Please contact Barb Joyner (joynerb@purdue.edu, (812) 886-0198) for registration, or register online at https://purdue.qualtrics.com/jfe/form/SV_0rICQrMVJmiMnqZ. Organic Vegetable Seed Production & Varietal Selection Workshop  The workshop[Read More…]


Recent dry weather raises concern about effectiveness of preemergent herbicides.  Preemergent herbicides applied on the soil surface need to be moved into the soil where the target weed seeds are germinating (normally 1-2 inches deep) in order to be effective. The process normally requires 0.5 to 0.75 inch of water within a few days of herbicide application. For example, product labels state that Curbit 3EC® needs 0.5 inch of water within 5 days of application, and Dual Magnum® needs at least 0.5 inch water within 10 days of application. In nonirrigated areas where rain is not anticipated, a shallow cultivation is needed to move the herbicide into the zone of weed seed germination. Most areas of Indiana were dry the last week of May and first week of June. If preemergent herbicides were not incorporated in a timely manner by water or machine, unsatisfactory weed control might be observed. In that case,[Read More…]


Figure 1. A 30% black shade cloth was added to one of the high tunnels

Tomatoes growing in high tunnels are in the middle of or close to harvest. Developing and maturing fruit are under leaf canopies. On the top of the plants, many flowers are still blooming. These flowers will contribute to the second big harvest. Although tomatoes in June are most valuable, we certainly appreciate big, red and delicious tomatoes in July and August.  To ensure a sustained yield, it is important for these flowers to set fruit. The process of fruit set is very sensitive to excessively high temperatures. When temperatures rise above 100°F, even just for a few hours for a handful of days, tomato flowers may be aborted and fruit set fail. Night temperatures above 75°F may also cause tomato fruit set failure. In addition to fruit set, high temperatures affect fruit ripening process. Ethylene associated ripening decreases markedly at a temperature above 93°F. As a result, there might be an increasing number of[Read More…]


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Horticultural Business Webinar  The webinar featuring Advanced Influence and Sales Strategies will be held on June 20, 2017, 11:00 am-12:00 pm EDT. For more information: https://ag.purdue.edu/hla/Extension/nle/Pages/Horticultural-Business-and-Marketing-Symposium.aspx. To register: https://purdue.qualtrics.com/jfe/form/SV_bae0QfPySyoUt0x Indiana Fruit & Vegetable Field Tour The tour will be held at Tuttle Orchards, 5717 North 300 West Greenfield IN 46140, June 28, 9:00 am -4:00 pm. On-site registration 9 am at Tuttle Orchard. Registration fee is $5 per person. For further questions contact Lori Jolly-Brown at ljollybr@purdue.edu or (765) 494-1296. Southwest Purdue Ag Center Field Day  Southwest Purdue Ag Center Field Day will be held on June 29, 2017 at Southwest Purdue Agricultural Center, Vincennes, IN. The field day provides two choices of tours: Horticultural Crop Production and Agronomic Crop Production. The Horticultural Crop Production tour will feature Organic Tomato Production, High Tunnel Vegetable Production, Grape Research, Protecting Pollinators while Managing Insect Pests in Watermelon Production, and Produce Food Safety. A meal will accompany[Read More…]


Southwest Purdue Ag Center Field Day  Southwest Purdue Ag Center Field Day will be held on June 29, 2017 at Southwest Purdue Agricultural Center, Vincennes, IN. The field day provides two choices of tours: Horticultural Crop Production and Agronomic Crop Production. The Horticultural Crop Production tour will feature Organic Tomato Production, High Tunnel Vegetable Production, Grape Research, Protecting Pollinators while Managing Insect Pests in Watermelon Production, and Produce Food Safety. A meal will accompany the tour with PARP classes available after lunch. Please contact Barb Joyner (joynerb@purdue.edu, 812-886-0198) for registration, or register online at https://purdue.qualtrics.com/jfe/form/SV_0rICQrMVJmiMnqZ. More information about the tour can be found here.   Beginning Farmer Tours and Workshops  Join Purdue’s beginning farmer team for farm tours in 2017. June 15. Clay Bottom Farm near Goshen, IN uses intensive growing methods to support a CSA program on less than an acre of land. Learn about their ‘lean farm” approach to support a CSA,[Read More…]


Figure 1. Grafted Fascination plants were grown on the right bed, ungrafted plants were grown on the left bed. The field were naturally infested with Fusarium wilt.

Watermelon production is threatened by Fusarium wilt, a widely distributed soilborne disease that can cause yield losses up to 100%. Currently, there are no watermelon varieties that are completely resistant to all races of Fusarium wilt. One way to control the disease is through grafting. The grafted plant combines a watermelon cultivar with a squash rootstock that has resistance to Fusarium wilt. In a study conducted at Southwest Purdue Ag Center (SWPAC), we found grafted watermelons significantly reduced disease incidence, and more than doubled watermelon yield in a Fusarium wilt infected field (Figure 1). In addition to controlling Fusarium wilt, grafted watermelons often show substantial advantages in early watermelon production due to cold tolerance from rootstocks. In a study conducted in Arizona, grafted watermelons that were transplanted in the field two months before soil temperatures reached 70 °F had twice as much yield as ungrafted watermelons grown in the same[Read More…]


Southwest Purdue Ag Center Field Day  Southwest Purdue Ag Center Field Day will be held on June 29, 2017 at Southwest Purdue Agricultural Center, Vincennes, IN. The field day provides two choices of tours: Horticultural Crop Production and Agronomic Crop Production. The Horticultural Crop Production tour will feature Organic Tomato Production, High Tunnel Vegetable Production, Grape Research, Protecting Pollinators while Managing Insect Pests in Watermelon Production, and Produce Food Safety. A meal will accompany the tour with PARP classes available after lunch. Please contact Barb Joyner (joynerb@purdue.edu, 812-886-0198) for registration, or register online at https://purdue.qualtrics.com/jfe/form/SV_0rICQrMVJmiMnqZ. More information about the tour can be found here. Beginning Farmer Tours and Workshops  Join Purdue’s beginning farmer team for farm tours in 2017. June 15. Clay Bottom Farm near Goshen, IN uses intensive growing methods to support a CSA program on less than an acre of land. Learn about their ‘lean farm” approach to support a CSA, supply[Read More…]


Figure 1. A tomato plant showing nutrient deficiency symptoms.

Recent rain and cold conditions have brought detrimental effects to some of the early planted vegetables. In southwest Indiana, air temperatures have dropped into the 40s °F and soil temperatures have dropped into the 50s °F in early May. The low temperatures would have greatly inhibited absorption of water and mineral nutrients for many warm season vegetables. In one of our fields where watermelon and cantaloupe were transplanted on April 26, almost all the plants showed wilt symptoms on May 3. The wilt was caused by decreased water absorption from roots. The plants were dead due to the extended cold weather. Peppers and tomatoes that were planted about the same time maintained turgid and survived the cold period (Figure 1). But they showed symptoms similar to nutrient deficiency due to the reduced function of roots in the cold soil. The plants should start new growth when the temperature rises. Growers using low tunnels are more likely[Read More…]