Liz Maynard

Clinical Engagement Assistant Professor of Horticulture
Department of Horticulture and Landscape Architecture
Liz Maynard's website

82 articles by this author

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Figure 2. Multi-leaf lettuces grown in a high tunnel (photo credit: Liz Maynard)

Winter farmers markets are becoming more and more popular. Lettuce is a primary type of vegetables grown for the market. As we are finishing up summer crops, it is a good time to learn and refresh knowledge about lettuce. This article discusses some of the basics of growing lettuce in high tunnels, as well as the lessons we learned from a trial conducted at Southwest Purdue Ag Center in fall 2016. Lettuce Types Lettuce has multiple morphological forms major types include crisphead (iceberg), butterhead (bibb), romaine (cos), Batavian (summer crisp), and multi-leaf lettuce (salanova). The first decision about growing lettuce is whether to harvest full-size heads of lettuce, or to harvest ‘baby-leaf’ lettuce (Figure 1). These harvest methods require very different production practices. Full-size heads are harvested one time as a single head of leaves. Baby-leaf lettuce is first harvested when single leaves reach about 4 to 5 inches, and[Read More…]


Figure 1. Yellowstriped armyworm on tomato leaf.

We are seeing small caterpillars feeding on tomato leaves in high tunnels at Pinney Purdue. The first sign may be feeding partially through the leaf, or ‘windowpane’ feeding, or small holes on the leaf. By turning the leaf over we find a yellowstriped armyworm or hornworm (Figures 1 and 2). In the morning, we find moths clustered along the hipboard at the top of the sidewall (Figure 3). See Rick Foster’s articles in this issue for information on control.  


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Dr. Steve Weller, professor and extension weed scientist in the Dept. of Horticulture and Landscape Architecture is retiring from Purdue. I’m sure many readers share the Purdue Vegetable Extension team’s appreciation for all the work he has done to help vegetable growers with weed management and wish him the best in life’s next adventures. Thanks from all of us, Steve! You will be missed.


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We are looking for sweet corn growers to participate in our 2017 Vegetable Field Day and Sweet Corn Tasting. Our field day on Aug. 15 at Pinney Purdue Ag Center in Wanatah, will feature tours of tomato production in moveable high tunnels, using both conventional and organic management systems. The event also will include walking tours of sweet corn and pumpkin variety trials, an overview of research findings about the opportunities available through high tunnels, and information about the NRCS program. Attendees will learn about managing pollinators; low-cost high tunnel structures for the home gardener; irrigation solutions; site and structure considerations for new high tunnel users; and finding, preserving, and preparing fresh produce. Private applicator recertification credits (PARP) are anticipated. This event includes a dinner and sweet corn variety tasting. If you would be willing to donate 2 ½ dozen ears of corn, please contact Lyndsay to arrange pick-up/drop-off arrangements. Lyndsay Ploehn, Purdue[Read More…]


Figure 1. Lettuce in high tunnel showing symptoms of lettuce drop caused by the fungus Sclerotinia sclerotiurum. Photo by Erin Bluhm.

Some of the red and green multi-leaf lettuce plants in Figure 1 are wilted and closer inspection reveals death and soft decay at the crown and well as freeze damage (Figure 2). Getting even closer as in Figure 3 we see white fuzzy mold and find hard black sclerotia 1/8 to ¼ inch across and up to ½ inch long at the base of the plants and in the soil. These sclerotia confirm that the plants have succumbed to white mold or lettuce drop caused by the fungus Sclerotinia sclerotiorum. The lettuce was transplanted in September or October 2016 and the photos taken in mid to late January. We continue to see more plants succumbing to the disease. Infection by this fungus begins when sclerotia buried in the soil produce small mushroom-like apothecia and spores from the apothecia land on susceptible plant tissue, germinate, and invade the plant. Sclerotia can[Read More…]




Figure 3. The fungus on this senescent female pumpkin flower (Choanephora sp.) is growing on a flower which did not develop properly.

There has been some concern about poor fruit set in pumpkin fields that otherwise have healthy vigorous vines. This summer we have experienced above normal temperatures for much of the pumpkin fruit set season and I suspect that has played a role. This article will consider temperature as well as other factors that influence pumpkin fruit set. In order for fruit set to take place, male and female flowers must be open on the same day, pollinating insects must be active, the plant must not be too stressed and it must have an adequate level of carbohydrates. Growers can influence some of these conditions. High temperatures promote death of female pumpkin flowers while still in the bud stage. Varieties differ in the their sensitivity to high temperatures. To determine whether flowers have died early in development requires close inspection of the pumpkin vine. An aborted bud often dries up and[Read More…]


The cool weather this spring means that many early-planted warm season crops have probably been stressed by cool temperatures more than usual. A number of herbicides labeled for vegetable crops include warnings not to use when the crop is or will be under stress. A stressed crop may not be able to detoxify the herbicide or outgrow its effects quickly enough. In the case of a soil applied herbicide, the crop roots may not grow into untreated soil fast enough to avoid injury. High rainfall amounts can also lead to crop injury from soil-applied herbicides. Many herbicides move with soil water, and when there is too much water they can move where they are not wanted. Preemergence herbicides may move deep enough to injure crops with a low margin of tolerance. For instance rain may move Curbit® deep enough to injure seeded pumpkins. If you are seeing some of the[Read More…]

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Purdue Extension publication PPP-110 ‘Options for Dealing with a Pesticide Drift Incident’ describes causes and effects of pesticide drift. It discusses actions a vegetable farmer (or anyone) might take if they suspect that herbicide drift may have injured their crop. The first step suggested is to find out what caused the symptoms. The publication explains that Purdue Extension educators can help in determining the cause of symptoms, but are not pesticide drift investigators. The Office of the Indiana State Chemist (OISC) investigates pesticide drift complaints. What happens once a complaint is filed is outlined step-by-step. There is also a list of the kind of information it is helpful to collect as soon as a problem is noticed. To order a free, single copy of the publication, call the Education Store at 765-494-6795. It may also be downloaded as a pdf at https://ag.purdue.edu/extension/ppp/Documents/PPP-110.pdf.

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