For three years we have been working with five NY organic vegetable growers to gain their insight on how the mesotunnel system worked on real life, commercial farms. The purpose of this project is to see if mesotunnels are feasible and effective for organic cucurbit growers, so why not turn directly to them and gain their input!

The growers were located across the state and each grower provided critical information to understand the value of the mesotunnel. Along with gaining feedback it provided us a chance to test different variables and cucurbit crops to have a better idea where this system could be most beneficial for organic growers.

Growers evaluated how mesotunnels performed compared to their traditional cucurbit production methods. For example, the growers tested the mesotunnel against low tunnels, and used different types of weed suppression, pollination methods, and harvest methods.

Results

As we expected and have seen in our trials, the mesotunnel did an exceptional job at keeping out insect pests like cucumber beetles and squash bugs. For instance, at one organic farm, we saw a 90% reduction in cucumber beetle populations within the mesotunnel compared to the low tunnel. Low tunnels are great for early season protection, however, once the weather starts warming and the crop begins to bloom the cover has to be removed. Cucurbits are prone to overheating in low tunnels and generally need pollinators to set fruit. Moreover, by removing the low tunnel, the plants are then susceptible to insect pests, disease, and weather-related injury.

These similar trends in significantly reducing insect pest populations were observed over the three years with both cucumber beetles and squash bugs in nearly all trials. Reducing insect pest’s populations also led to a decreased incidence of the insect-vectored diseases, Bacterial Wilt (BW) and Cucurbit Yellow Vine Disease (CYVD).

However, one thing to consider with this system are aphids. The growers observed aphid populations building within the mesotunnel as the season progressed. Our trials and the on-farm trials used a 60-gram nylon mesh netting from Tekknit. Recently, the manufacturer switched production to using an 85-gram nylon mesh, which should exclude most aphid species. So, this could be beneficial for the aphid problem. However, it may be worthwhile investigating ways to introduce predatory insects to help keep the aphid populations in check.

But the true testament to how the mesotunnel faired with the common ways of growing organic cucurbits was yield. What produced greater yields? The mesotunnel or the standard practice.

Overall, we had mixed results. Some crops did exceptionally well in the mesotunnel, and others had no significant difference from the standard practice.

Here’s what we found:

Acorn squash:

2020

Two locations: One compared the mesotunnel to an uncovered control; the other looked at mesotunnel production without an uncovered comparison.

• Low to no insect damage or vectored disease within the mesotunnels.
• The farm which only had a mesotunnel found that 64% of the squash grown in the tunnel were marketable.
• The other farm who compared the mesotunnel to an uncovered plot saw higher yields in the uncovered plot with 2.55 fruits per plant versus the tunnel which averaged 1.67 fruits per plant.
• Unmarketable fruit was mainly due to being misshapen, and a large amount of vegetative growth resulted in little room for fruit to form within the tunnel.

 

2021

One location: Compared the mesotunnel to an uncovered control.

• 32% more squash were harvested in the uncovered plot.
• However, 77.8% more unmarketable squash were found within the uncovered plot compared to the mesotunnel.

 

2022

One location: Compared the mesotunnel, an uncovered plot with landscape fabric, and an uncovered plot with bare ground (Images shown below).

• Cucumber beetles were observed in all plots in low numbers. Only 10% of the uncovered with bare ground plants showed BW symptoms.
• Squash bugs were only observed in the uncovered plots with significantly higher populations in the uncovered fabric treatment.
• Marketable weight was 26.7% higher in the mesotunnel than the uncovered fabric plot and 72.7% higher than the uncovered bare ground plot.

 

Slicing and Pickling Cucumbers:

2021

Two locations: One compared the mesotunnel to an uncovered control; the other to a low tunnel.

• 90% of cucumber beetles at one farm were excluded by the mesotunnel.
• Cucumber yields were not significantly different between plots at either location.

 

2022

One location: Compared the mesotunnel to an uncovered control.

• 79% of the cucumber beetles observed were in the uncovered plot. No BW was found in the slicing cucumbers. There was a 20% incidence of BW in both the covered and uncovered pickling cucumbers.
• Downy mildew incidence was 40% and 60% higher within the mesotunnel for pickling and slicing cucumbers, respectively.
• Fruit weight was 52.5% higher in the mesotunnel than in the uncovered plot.

Zucchini:

For three years we trialed zucchini in this system. Mixed results were found. In each of the three years, one location compared the mesotunnel to an uncovered control.

2020

• Cucumber beetles were present and accounted for about 50% of the plants having BW symptoms in the uncovered plot with several dying, but not in the mesotunnel.
• The mesotunnel almost doubled the fruit yield (14.7 kg control; 26.98 kg mesotunnel).
• Yields were 12% higher within the mesotunnel than the uncovered plot.

 

2021

• Powdery mildew incidence was 60% higher in the uncovered plot.
• Squash vine borer and squash bugs were only observed in the uncovered plot. Some cucumber beetles were within the tunnel, but no BW was detected.
• 103.7% more zucchinis were harvested within the mesotunnel compared to the uncovered plot.

 

2022

• Cucumber beetles and squash bugs were found within the mesotunnel.
• No BW was detected, but 40% of the zucchini plants showed CYVD symptoms both within and outside of the mesotunnel.
• Only a 2 lb. difference was observed between plots with the uncovered plot producing slightly more fruit.

 

Delicata Squash:

In 2022, a grower tested Delicata squash within the mesotunnel, a low tunnel, and an uncovered control.

• Cucumber beetle populations were observed in the low tunnel and uncovered plot.
• 20% of the plants within the low tunnel and uncovered plots showed BW symptoms.
• Squash bugs were also only observed in the low tunnel and uncovered plot.
• Average fruit weight and number of fruit per plant was 100% and 138.1% higher in the mesotunnel than the uncovered plot

 

Butternut Squash:

In 2022, a grower tested butternut squash within the mesotunnel, a low tunnel, and an uncovered control.

• Cucumber beetle populations were observed in the low tunnel and uncovered plots.
• 20% of the uncovered squash showed BW symptoms.
• Squash bugs were also only observed in the low tunnel and uncovered plots.
• Average fruit weight and number of fruit per plant was 29.8% and 30.8% higher in the mesotunnel than the uncovered area.

Ornamental Pumpkins

• • In 2022, a grower used the mesotunnel to protect their plants from high cucumber beetle pressure on their farm. Here is what the grower said, “One thing I did notice is that we had more flowers this year that were undamaged by the elements (heavy rain/wind) but less pollination with the nets. Those that were not netted however, had significant loss due to rabbits and groundhogs. The netting seemed to help keep them at bay, so less marks in our pumpkins and better quality. I am going to use the nets again next year because they helped… I would say 75% less beetle damage and viruses caused by the beetles, and very little powdery mildew and wilt. I will however learn how to hand pollinate the pumpkins, that seems to be the best option to maximize the use of the netting…”

 

Big take-a-ways

What most growers suggested is that the mesotunnel has its place with the right crop. Many of the growers agreed that crops which have a single harvest or a handful like winter squash or melon will be easier to produce in this system. Also, growing cucurbit crops which are high value, like specialty melons could be worthwhile, since the mesotunnel can be laborious.

An area in which many growers were also curious is fit with other crops, such as brassicas (broccoli, cabbage, kale) for the control of Swede midge, Diamondback moth, and potentially flea beetles; and Allium species for the control of Allium leaf minor and thrips (if the netting size is sufficiently small). These crops have an additional advantage in a mesotunnel system in that pollination is not required, so the plants can be excluded by the netting until harvest. We also had one grower mention using this system for seed production on farm.

This year we will be piecing together the economic analysis and all the data we have gathered over the last three years to see which direction the mesotunnel research should be taken. So, stay tuned!