Alternative Row Covers and Cucurbits

Use of Alternative Row Covers and Pollinators to Manage Insect Pests and Improve Cucurbit Production & Profitability

This project was funded with a Partnership Grant from the Northeast Sustainable Agriculture Research & Education (SARE) Program

Read the final 2010 grant report here

The cucurbit (cucumber, squash, melon, etc.) crop industry is valued at nearly $1.5 billion in the United States. While growers throughout the northeast U.S. recognize the value of including cucurbit species in their vegetable crop rotations and to their farm’s bottom line, insect pests can present a significant obstacle to realizing that value.

Management of cucurbit pests such as cucumber beetle, squash bug and squash vine borer poses a greater challenge for those growers utilizing organic or other natural production methods. Although numerous insecticides exist to control all three of these major cucurbit pests, many are not allowable by organic certification or naturally grown standards. Those that are allowed may not be as effective, cost-prohibitive or desirable, especially when many growers are concerned about impacts on native, beneficial and pollinating insect species.

Management of these pests can include hand harvest and destruction of individual insects, along with attempting various cultural controls and insecticide-alternative methods. Growers continue to experiment with techniques such as row covers, delayed planting of cucurbit crops, use of transplants instead of direct seeding, crop rotation, debris removal, resistant cultivars, companion planting and others, as means to control cucurbit pest pressure. Some growers simply over plant some of these crops to produce enough marketable fruit, as many simply accept the oftentimes-huge quality and yield losses caused by the pests. Other growers are unwilling to accept losses and have eliminated cucurbits from their cropping system.

Various published and independent surveys of growers throughout the U.S. have indicated that control of cucurbit pests is a high priority. As costs of production continue to climb, and as the demand for organic produce continues to increase, it is important that many small to mid-sized mixed vegetable growers are able to produce a successful cucurbit crop each year. The need is great to identify a cost-effective, environmentally neutral control method for cucumber beetle, squash bug and vine borer.

Previous research has shown that row covers can have a positive impact on cucurbit crop yields by providing a barrier to insect pests that include cucumber beetle, squash bug and squash vine borer. Although these results are promising, a disadvantage for using row covers is that they need to be removed to allow natural pollinators access to cucurbit crop flowers. This removal of the barrier also enables pest insects to access and damage the crop.

This project is intended to build upon preliminary studies conducted on two farms during 2007 by the host farmers and staff from the Penn State/PA Association for Sustainable Agriculture On-Farm Research (OFR) program. As with the 2007 studies, this project will focus on using row covers and introduced pollinators to control cucurbit pests, optimize cucurbit flower pollination, and increase cucurbit crop yields. We propose an expansion of the activities to include three farms during 2008 and 2009.  These cooperating farms have a strong interest in further developing their knowledge of cucurbit pest control and sharing those findings with other farmers.

Prior to the 2007 growing season, two cooperating farms had nearly total cucurbit crop losses (winter squash, cucumber, pumpkin and zucchini). Both growers were interested in maintaining cucurbits as part of their rotation, since they are valuable crops for direct to consumer and restaurant sales. Our previous research at both farms involved using the lightest weight, spun-bonded row cover material on the market, while covering winter squash crops for the entire growing season. The row cover was never removed to provide native pollinators access to crop flowers. Instead, reared pollinators were introduced and maintained for the remainder of the season under the row cover. One farm also compared yields from covered and non-covered plants that were established both by transplanting and direct-seeded planting.

Both cooperating growers were pleased with crop yields and offered modifications for trials outlined in this proposal. As these cooperators increase their knowledge of these insect pest lifecycles, various control methods and other key factors, they will become important teachers to other regional growers on this topic.

Along with project advisors, each cooperating producer will customize the project particulars to best suit their farm specifics and personal production goals. The cooperators in this project share a strong interest to experiment and implement new practices on their farms that will not only benefit their long-term sustainability as farmers, but also the natural environment and their communities. With the help of the OFR team, they have already hosted a meeting to detail research methods from the 2007 season and they will continue to serve as a positive example for other producers in the region. Through on-farm research, this project will address questions concerning improved cucurbit production and profitability when row covers are used in specific situations.

Each of the three farms that will participate has a slightly different crop mix. While squash is grown on all these farms, the specific varieties grown will vary between the three.  Cucumbers likely will be planted on at least two farms, with varieties again differing between farms. While it would be ideal from a biological and statistical standpoint for all farms to conduct comparisons of protected and unprotected plantings of the same varieties, we believe uniformity of this type is less important than measuring the performance of the species and varieties each farmer is comfortable growing for his/her market. Results from a preliminary study conducted during 2007 have shown that exclusion of insect pests on cucurbits with a row cover can be an effective means to improve both yields and quality of fruit. This study seeks to determine the efficacy and especially the cost effectiveness of exclusions that are more durable than the spun polyester material that was good for only one year’s use.

Most cucurbit plantings on these farms are started from direct seedings. Each farm often will start small plantings from transplants, but the percentage of the total crop being started from transplants will likely be less than 40 percent. The focus of this project will be to document the increase in production and income per unit land area that can be realized when cucurbit insect pests are controlled with some type of exclusion.  It is expected that 90 to 95 percent of the area planted to each type of cucurbit will be grown under the cover (treated) and the remainder grown without the protection of the exclusion (control).

With the knowledge that exclusions that keep out crop pests and keep in some necessary pollinators can result in a marketable crop, this project will focus on determining the cost effectiveness of these measures. Unlike the typical experiment where all plots or experimental units are of similar size, these trials will be arranged so that uncovered controls will consist of areas that are only 5 to 10 percent the size the treated areas. Treated and control areas will be paired where the crop species and varieties in each will be identical. On each farm, there will be two or three large areas of treated plants. Adjacent to each treated area will be a small area of six to ten control plants. The exclusion screen material will be placed over plants early during their development to minimize the possibility that pest insects will find the cucurbits.  When the crop begins to flower, pollinator bees purchased from a commercial insectary will be placed under the exclusion, and will remain with the plants during the remainder of the growing season. The boxes in which the bees are shipped are able to be closed to hold the pollinators while the exclosure is removed and fruit are harvested. Fruit will be counted and graded for quality during each harvest.

The uncovered control plants will provide more than a baseline of data to which production from treated crop will be compared. These control areas will provide some habitat for a group of pollinators known as solitary bees to work and feed. Bee researchers are learning that while honeybee colony collapse continues to negatively impact crop pollination on our farms, several species of native bee that are collectively referred to as solitary bees are becoming more important providers of this vital service. Maintaining some habitat in the form of uncovered cucurbits will be beneficial in maintaining or increasing the populations of these desired insects.

Production data will be subjected to statistical analyses with a simple paired t-test to determine if real differences occurred in the amounts and market values of harvested fruit. The final analyses will consist of economic assessments that will contrast the increased value of the harvested fruit with the increased costs of enclosure material, its supports, the pollinator bees, and the additional labor necessary to manage such a system.

In-season field days and meetings are planned for two sites; one event will be held during the first year at one farm and a second event held at one of the other two farms during the second growing season. Programs such as these in this area of Pennsylvania have historically attracted fifteen to 50 people.

Cooperating Farms:

Cathy and Kit Kelley organically manage their farm, White Frost Farm, near Washingtonville PA. While the Kelley’s farm is not currently certified organic, they use no chemical fertilizer, herbicides or pesticides. The farm consists of 39 acres. Approximately 2 acres are used in the production of organically grown vegetables marketed at two local farmers’ markets, three local restaurants and two specialty grocery stores in Montour, Union and Northumberland counties.

The Kelley’s also have a 150 hen; free-ranging laying flock that is fed certified organic feed exclusively. They raise approximately 200 broilers annually that are also fed exclusively certified organic feed and are raised on pasture via portable range pens.

They currently have two acres planted in soft red winter wheat and three and a half acres planted in spelt.  In the spring, they plan to plant hard red spring wheat and oats.  The small grain fields are under-seeded with medium red clovers. The remainder of the acreage is planted in rye, medium red clover, hairy vetch/field peas or in a fallow state of grasses/clover.

In 2006, their entire pumpkin/winter squash crop was rendered unmarketable by the infestation of squash bugs.  The resulting fruit was very small and marked /soiled by the overwhelming pest population. So in 2007, Cathy and Kit were partners in an On Farm Research Project that used row covers to isolate the winter squash plants, from seed/transplant to harvest, from the squash bugs using bumble bees as pollinators under the row covers.  Cathy and Kit have expressed their desire to continue, in a concerted manner with the On Farm Research Team, the project from the 2007 season.

Cathy and Kit are both from farm families and have been gardening on various scales for 30 years. They have been managing their 39 acres as farmers since 1999.

Leah and John Tewksbury produce sustainably-grown heirloom vegetables, herbs and Shiitake mushrooms on their farm located on 21 acres of mixed farmland, open meadows and hardwood forest in Muncy Hills area of Montour County. Their produce is hand-cultivated, completely organic, and uses no mechanized equipment such as tractors, rototillers or mowers, on 1.5 acres of raised garden beds. They practice conscientious stewardship of our earthly home through farming and community service. Their heirloom vegetable varieties, which feature old-fashioned or unusual seeds, provide exceptional flavor, nutrition and freshness that can only be found in diversified local farm systems. Their produce is marketed to customers and restaurants in Lycoming, Union and Columbia counties.
 
Anne and Eric Nordell have been growing organic produce and herbs for over 20 years at Beech Grove Farm in Trout Run, PA. They also write regularly for the Small Farmers Journal about their bio-extensive approach to vegetable production which relies on cover crops and horse-drawn tillage for weed control, soil quality and moisture conservation. Their produce is marketed to customers and restaurants in the Lycoming county area.

Progress Reports for 2008
Kit & Cathy Kelley - White Frost Farm (PDF file)
Anne & Eric Nordell - Beech Grove Farm (PDF file)
Leah & John Tewksbury - Tewksbury Grace Farm (PDF file)
PASA Newsletter Article - July/August 2008 (PDF file)

Progress Reports for 2009
Kit & Cathy Kelley - White Frost Farm
Anne & Eric Nordell - Beech Grove Farm (PDF file)
Leah & John Tewksbury - Tewksbury Grace Farm (PDF file)