Cucurbit Crop Growth and Development

Indiana produces over 15,000 acres of cucurbits including watermelons, muskmelons, pumpkins, cucumbers, and squash. It ranks among the top ten states for production of watermelon, muskmelon, pickling cucumbers and pumpkins. An understanding of the growth and development of these crops aids in planning and troubleshooting during production. Cucurbits have an indeterminate growth habit. Healthy plants produce new leaves, flowers, and fruit until environmental conditions prevent further growth. Cultivars may be described as having a full vine, restricted vine, or bush growth form, depending on the length of main stem and branches. Flowers form in leaf axils after a period of vegetative growth. Most cultivars have separate male, and either female or perfect flowers; some cucumber cultivars produce female flowers only. Fruit set requires the activity of pollinators, such as honey bees or native squash bees. Temperature plays a critical role throughout crop development, influencing germination, vegetative growth, flowering, ratio of male to female flowers, fruit set, and fruit development. Optimum temperatures vary for the different species, but all are warm season crops and are susceptible to chilling injury below 50°F. Plastic mulches are widely used for muskmelon, watermelon and summer squash in part to promote early growth; low and high tunnels are also used to extend the growing season. Grafting can be used to increase cold tolerance. This is a relatively new practice in Indiana but has been used in other countries for many years. Adequate water is critical for even stand establishment, flowering and fruit set, and development of high quality fruit. An uneven water supply or drought stress can lead to misshapen fruit, blossom end rot, or lack of fruit set altogether. The various cucurbit crops differ in their tolerance to low soil moisture levels. Land Grant Universities continue to develop new information about cucurbits through a variety of research programs.

Weed Management in Cucurbits
Weed management in cucurbits is typically tailored for one of three production systems: 1) direct-seeded into bare ground; 2) transplanted into black (opaque) plastic mulch; 3) no-till direct-seeded into crop stubble or killed cover crop. For system (1), one or more pre-emergence herbicides are applied after seeding, followed by cultivation, hand weeding, and application of postemergence broadleaf and/or grass herbicide if needed. For system (2) a pre-emergence herbicide may be applied under the mulch or just between the rows of mulch (depending on product and weediness of field), followed by use of nonselective herbicides in a shielded sprayer, and if needed, cultivation, hand weeding, and application of postemergence broadleaf and/or grass herbicides. System (3) may begin with broadcast application of a nonselective herbicide prior to seeding, followed by a pre-emergence material after seeding, and then a nonselective herbicide in a shielded sprayer, and/or postemergence broadleaf or grass herbicides. Some cover crops can be killed mechanically and heavy cover crop residue may provide good weed suppression for several weeks. Producers using organic methods may rely on use of a stale seedbed, mulches, and mechanical and thermal control measures.

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Liz MaynardRegional Extension Specialist for Commercial Vegetable and Floriculture Crops
Purdue University
emaynard@purdue.edu
www.hort.purdue.edu/fruitveg/

Liz Maynard has served since 1992 as Regional Extension Specialist for Commercial Vegetable and Floriculture Crops in the Dept. of Horticulture and Landscape Architecture of Purdue's College of Agriculture. Prior to coming to Purdue, she completed graduate school at Cornell University. Liz is housed at Purdue's North Central Campus in LaPorte County. She is on the organizing committee for the Indiana Horticulture Congress and the Illiana Vegetable Growers' School, and regularly speaks about vegetable production at those and other Extension programs. She conducts vegetable variety evaluations and other trials at the Pinney-Purdue Ag Center in Northern Indiana, with the greatest emphasis on sweet corn, pumpkins, and tomatoes. Liz works closely with the Indiana Vegetable Growers' Association (www.ivga.org), acting as secretary/treasurer since the mid 1990s. Liz is also involved in education and research about organic production. For more information about commercial vegetable extension and research at Purdue, see the Purdue Fruit and Vegetable Connection at www.hort.purdue.edu/fruitveg/