Use of alternative row covers and pollinators to manage insect pests and improve cucurbit production and profitability

Use of alternative row covers and pollinators to manage insect pests and improve cucurbit production and profitability

Summary

The cucurbit crop industry is valued at nearly $1.5 billion in the United States and growers throughout the Northeast region recognize the value of these crops to their vegetable crop rotations and their farm’s bottom line. However management of cucurbit pests (squash bug, cucumber beetle and squash vine borer) in these crops is a challenge, especially for those growers utilizing organic or other natural production methods.

Growers continue to experiment with various control methods, with some simply over planting these crops accepting quality and yield losses due to cucurbit pests. Various published and independent surveys of growers throughout the U.S. have indicated that controlling cucurbit pests as high priority. The need is great to identify cost-effective, environmentally neutral control methods for cucumber beetle, squash bug and vine borer.

Previous research has shown that row cover can have a positive impact on cucurbit crop yields by providing a barrier to insect pests. This project is intended to build upon preliminary studies conducted at two farms during 2007 by the host farmers and by staff from the Penn State/PASA on-farm research 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. 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.

Objectives/Performance Targets

• Identify a cost-effective, environmentally neutral control method for cucumber beetle, squash bug and vine borer.

  These studies will focus on using row covers and introduced pollinators to control cucurbit pests, optimize cucurbit flower pollination and increase cucurbit crop yields.

  Outreach to other farmers, educators, researchers, etc. about cucurbit pest lifecycles, various control methods and other key factors – participating farmers will become important teachers to other regional growers on this topic.

Accomplishments/Milestones

Each participating farm has a slightly different crop mix and production method. However each participating farm did use the same alternative row cover, called Agralan Enviromesh. This nylon, netted material is said to have a lifespan of 5 years, while allowing plenty of light penetration and airflow.

Each farm trial site used the row cover material in a different way. Details for each farm are below:

Farm #1 – Beech Grove Farm
Producers Anne and Eric Nordell elected to utilize a tunnel design that is included in the SARE-sponsored High Tunnels manual and accompanying DVD by Ted Blomgren and Tracy Frish.

Their caterpillar tunnel measured approximately 102 ft x 10.5 ft wide. Using materials on hand at the farm, the tunnel was erected and the Enviromesh was placed over the hoops, which was secured to the soil with plastic row cover pegs. Greenhouse plastic (6-mil) was then layered over the Enviromesh and hoops for protection until risk of frost had passed. The poly cover was held in place with clothesline over the tunnel and tied to 36 inch rebar stakes set halfway between each hoop. The ropes created the segmented “caterpillar” look and allowed for side ventilation by propping up the plastic with boards or forked branches.

In the tunnel the outer beds were planted with three rows of early lettuce (Apr. 23 – May 2) to maximize space in the tunnel. Lettuce sales were approximately $1200, which equaled the total estimated cost of the caterpillar tunnel materials (rebar, poly, clothesline, anti-insect barrier) at 2008 prices.

On May 8 cucumbers (variety Olympian) were transplanted 12 in. apart on bare soil in the middle bed of the tunnel. For comparison, a field planting of cucumbers (same variety) was planted 12-15 in. apart on bare soil on May 7. These rows were covered with Agribon-19 until removed for pollination on June 15.

Cucumber yields were determined by marking three, 10 ft. sections in each row (in the hoophouse and the field trial) and collecting the total number of cucumbers harvested. Harvest from the standard (bare soil, Agribon row cover removed for pollination) 72 ft. of cucumbers, July 8-August 2 yielded 463 marketable fruit and 97 culls (21%).

Harvest yields from the new practice in the caterpillar tunnel yielded, from 102 ft. of cucumbers June 30-August 4, 1246 marketable fruit and 166 culls (16%). The growers consistently harvested 40 or more cucumbers per day beginning July 3.

Bumblebee colonies purchased from Koppert Biology Systems were used to pollinate the cucumbers in the caterpillar tunnel was placed on June 19. All farm trial sites used bumblebee colonies as their pollination source.

Advantages to this system included low labor and inputs, as well as frost protection plus increased soil warming and air temperature. This method resulted in 100% cucumber beetle control during crop establishment and minimal bacterial wilt (two plants).

Caterpillar construction was low cost and labor. Compared to floating row cover, the caterpillar increased air and soil temperature before and after pollination resulting in significantly earlier and larger harvest. The insect mesh is the key to providing side ventilation without bumblebees escaping or cucumber beetles invading.

Disadvantages included the caterpillar tunnel requiring more labor and materials for construction and management than floating row cover. Headroom is somewhat limited (6.5 ft at peak), access is awkward under the sides, and soil preparation is not possible with field equipment.

Although cucumber beetle damage to leaves and fruit was minimal, a fair number of these determined insects managed to get in the tunnel, by the third week of July, possibly under the sides where the anti-insect screen was not secured tightly to the ground and definitely at the ends of the caterpillar where the mesh did not reach the soil (due to miscalculation when ordering the material). Regardless, the earlier, higher quality harvest of cucumbers added diversity and income to their stand at their farmers’ market.

They intend to use the caterpillar tunnel for cucumbers again in 2009, with modifications to improve the seal of the Enviromesh.

Farm #2 – White Frost Farm
Producers Kit and Cathy Kelley elected to use the EnviroMesh material to cover two hoophouse structures approximately 60 ft x 12 ft. Plantings included one hoophouse where direct seeded winter squash (variety Waltham) was planted under black plastic, and the second with transplanted winter squash under black plastic (same variety). T-tape was used for irrigation. This year they did not use a bed former to lay the black plastic and t-tape, instead it was covered with old hay to hold it in place. The plastic should then come up easily and the hay will be put into the ground as mulch.

For comparison field plantings of winter squash (same variety) in two beds, under black plastic measuring 130 ft x 3 ft were created. One bed was direct seeded and the other transplanted. Yields were determined by collecting weights and counts of all marketable squash.

The first hoophouse was transplanted with butternut squash on June 27. The hoophouse with the direct seeded butternut squash was planted with zucchini squash on the north side and cucumbers on the south side. They thought there would be several week delay between the direct seeded hoophouse and the transplanted hoophouse, as well as providing an earlier crop of zucchini so the introduced bumblebee pollinators would have a natural pollen source and they would have an early crop for market. Same varieties of zucchini and cucumbers were planted uncovered outside the hoophouse, as well as direct seed butternut squash.

In August the producers realized the foliage had grown so large on the zucchini that they decided to harvest the zucchini as a one-time picking and pulled the plants to provide more space for the butternut squash. In retrospect, the extensive growth habit of the butternuts the 12 ft. of width in the high tunnel is not enough for the vines to fully extend.

On August 9, 65 pounds of zucchini was harvested from the direct seeded hoophouse and 86 pounds were harvested from the direct seeded, uncovered plot in two pickings. Butternut squash harvests resulted in the following; for direct seeded uncovered, 107 marketable fruit and for direct seeded hoophouse, 112 saleable fruit. For transplants the results were for uncovered, 137 saleable fruit and hoophouse transplants yielded 164 saleable fruit.

The material performed as these growers had hoped. The Enviromesh held up to high winds, was maintenance free and maintained a captive bumblebee population for pollination.

Bumblebee colonies purchased from Koppert Biology Systems were used to pollinate the winter squash in both hoophouse structures.

Farm #3 – Tewksbury Grace Farm
Producers Leah & John Tewksbury elected to use the row cover on two raised beds measuring 75 ft x 4 ft wide. On May 27 twelve varieties of winter squash using 24 inch spacing, with two plants offset down the rows were planted. Heavy straw mulch was applied after planting. Using 9-gauge wire hoops and flexible 10 ft. pieces of ½ in. PVC piping inserted over rebar, we covered a 75 ft x 20 ft wide section with Enviromesh to accommodate the vining growth pattern of the winter squash. A bumblebee colony was placed in the mini-tunnel on June 27.

Winter squash was transplanted into those two beds varieties; Long Island Cheese, Sweet Meat, Candy Roaster, Flat White Boer, Sweet Dumpling, Stella Blue, Uncle David’s Dessert, Kabocha Black Forest, Sunburst Patty Pan, Warted Green Hubbard, Sugar Hubbard, Guatemalan Blue, Jarrahdale and Tahitian.

Squash bugs were visible on the exterior of the material in June. As the squash plants grew, leaves pressed against the material, and squash bugs were observed feeding and laying eggs on the leaves through the material (squash bugs are unable to do this through Agribon). The Enviromesh material is not knit and if snagged in any way it tends to open and unravel.

Upon inspection on July 29 a widespread infestation of squash bugs (eggs and nymphs) were found throughout the patch. Plants were hand groomed, but on a subsequent inspection on August 3 they found a continued infestation and also noticed a few striped cucumber beetles under the material. Again hand grooming of plants was done to remove egg masses, etc.

On August 3 a few squash plants were pulled and with moderate damage to plants the fruit that has formed seemed to be maturing. We were unable to determine how such a severe infestation occurred. The few scattered holes did not seem sufficiently large and accessible enough to allow such a severe infestation. There were no cucurbits on these beds prior to 2008.

The Tewksburys noted advantages of this material were no problem with wind pickup, as wind moves through screen and creates no resistance, there were no problems with heat trapping, and it is a strong material despite some drawbacks and it should be able to be reused.

Disadvantages of Enviromesh on their farm included the cost of the material and it not being available in the United State, tendrils of plants can create holes, and if leaves of plants touch the material squash bugs can feed and lay eggs on leaves.

In 2009 the producers may go back to using Agribon floating row cover for winter squash production and scale back to about half of a 75 ft. raised bed.

The Tewksburys also used the material on one 75 ft x 4 ft bed with cucumbers, varieties Mini White, Fountain, Suhyo Long, Marketmore, Babylon, Straight 8, Diva, Tasty Jade, Telegraph, Shantung Suhyo, planted in three successive plantings. The first transplants were planted on May 31, the second round on June 5 and the final round on June 11. The growers planted 1/3 of the bed each time with 24 in. spacing and two transplants offset down the row. After the transplants were in a heavy layer of straw mulch was applied to the bed. Then the bed was hoped with 9-gauge wire, covered with Enviromesh and bricked down on all edges. A bumblebee colony was placed under the cover for pollination purposes on June 13.

This worked well, although the plant tendrils would latch on to the mesh and create small openings. No striped or spotted cucumber beetles were seen inside or outside the material. The producers plan to use these control methods for cucumbers in the future.

Cucumbers yields were excellent yielding 880 pounds overall from June 27-August 18 and bore unblemished fruit. This is compared to 475 pounds for the 2007 growing season.

All project partners met in early November to discuss outcomes of the 2008 projects and begin planning for 2009. After reading a report from the Organic Farming Research Foundation entitled “Evaluation of screen high tunnels for production of organic vegetables in Colorado” project partners are now investigating potentially using another material called LS Econet for some trials in year two of this project.

Impacts and Contributions/Outcomes

So far in 2008 we have held one twilight growers meeting at Farm #2 – White Frost Farm. This meeting attracted 21 area growers to visit the farm to learn more about the research being conducted, hear directly from all three producers involved in the research, as well as specific project designs and results on their farms. In addition, Penn State entomologist Shelby Fleischer discussed details of cucurbit pest lifecycles, other research and other pertinent topics.

We have also produced one newsletter article about this work that has so far appeared in the July/August 2008 edition of the PASA newsletter.

Collaborators: