Mesotunnels at Cornell University

Oct 29, 2024
Research indicates medium mesotunnels can exclude insects in cucurbits

Mesotunnels, intermediate in scale between low and high tunnels, can impact the incidences of pests, diseases and quality of fruit produced through such systems.

Two studies, one on integrated pest management and the other on pollination, focused on muskmelon Athenas and acorn squash cultivars under mesotunnels, which are 36 to 42 inches high.

In the pollination trial, mesotunnels increased marketable fruit by 730%.

Mesotunnels at Cornell University
Two Cornell studies are examining how growing in mesotunnels affect integrated pest management and pollination. Photos courtesy of Cornell University.

The three-year multistate research project’s overarching goal was to exclude insects that spread disease and foster pollination.

Researchers at Cornell University, the University of Kentucky and Iowa State, and growers in those institutions’ respective states, examined how pests could be kept away from plants with the medium tunnels. The IPM trial was to quantify the effects of mesotunnels and cover crops on pest and weed management, while the other trial was designed to evaluate pollination techniques.

Sean Murphy, a technician in the Pethybridge Lab at Cornell’s AgriTech School of Integrative Plant Science Plant Pathology and Plant Microbe Biology Section, presented on the feasibility of mesotunnels for cucurbit production during a session at the Mid-Atlantic Fruit and Vegetable Convention in Hershey, Pennsylvania.

Keeping pests at bay

Similar to other barrier systems, mesotunnels are designed to guard against insects and the pathogens they carry, and can also prevent hail damage. Striped and spotted cucumber beetles and squash bugs are the major pests that feed on the cucumbers, squash, pumpkins and melons. The beetles spread bacterial wilt, which produces dry and crispy leaves leading to crop loss.

Compared to uncovered plots, temperature and humidity in the nylon-mesh fabric can be 10% higher. Growers using tunnels can expect 90% of sunlight to reach plants. Too much heat can produce intense rotting, which can increase powdery and downy mildew more rapidly, but Murphy said he didn’t see a lot of plant death from it.

The IPM study tested mesotunnels with fabric, tunnels with a rye and clover cover crop mix, tunnels with rye only, and an uncovered plot for control purposes.

The pollination trial tested three ways. Mesotunnels covered crops throughout the season. In open- ended tunnel trials, they were closed except for two short ends left open for three weeks to allow natural pollinators to enter from both sides. In an on-off-on process, netting was applied throughout the season except for a three-week pollination period.

The studies generated a wealth of data, Murphy said. In the IPM study, uncovered production experienced the most insect pressure, while uncovered acorn squash saw the highest amount of cucurbit yellow vine disease (CYVD), at 75%.

Effective bug prevention

“Our most efficacious treatment for the cucumber beetles and squash bugs was exclusion,” Murphy said. “Tunnels with weed fabric had the least insect pressure. Anything that had a tunnel didn’t show that much disease. We were able to exclude enough of those insect pests that we didn’t get the disease pressure that we were seeing in the uncovered plots.”

The tunnel with the rye and clover cover crop mix and rye by itself experienced some weed pressure that accompanies cover cropping. The fabric helped keep weeds from the muskmelon, but not 100%. Landscape fabric provided equivalent suppression to cover crops. In acorn squash, landscape fabric was more effective for weed suppression, due to less cover crop biomass.

The most marketable fruit came from the tunnel and the fabric treatments, at 70%, with cover crops and uncovered producing less marketable fruit, likely due to light competition with the cover crops.

The uncovered plots produced more soft fruit that was more prone to rotting or fungal imperfections, Murphy said. In both studies, netting produced no significant change on fruit yield, Murphy said.

In the pollination results, the full season mesotunnels excluded cucumber beetles by a significant amount. The open-ended tunnels received some insects on the tunnel ends. Because of ease of access, the on-off-on encountered the most pest pressure, Murphy said. Bacterial wilt decreased by 86%.

Acorn squash doesn’t like growing in mesotunnels. Because researchers planted a variety that grows large, leaves pushed up on the netting, allowing insects to feed on them through the netting. Shorter varieties, less than 3.5 inches in height, would work better in tunnels, Murphy said.

“It all depends on the increasing importance of CYVD,” he said. “We now have a population in New York, thanks to our squash bugs. It could be coming to Pennsylvania.”

Entomologists at the University of Kentucky found that bumblebees are unsatisfactory cucurbit pollinators. Squash bees and syrphid flies are more effective cucurbit pollinators, Murphy said.

Netting effectively excluded most insect pests the researchers wanted to bar, Murphy said. Muskmelons saw zero CYVD or bacterial wilt. Cover crops were effective for weed suppression. While weed fabric was obviously the best, that method is more labor intensive, he said.

Overall, Murphy said the mesotunnel system could be cost- effective for short cucurbit cultivars as well as higher-value crops. Material costs, which have increased recently for netting and weed cloth, are factors to consider.

While the study’s three-year grant ended, on-farm trial data collection is ongoing. An economic analysis is also being conducted and will be posted at cucurbit.plantpath.iastate. edu.

Written by Doug Ohlemeier, Assistant Editor




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