Finding new methods and developing innovative systems for growers is a top priority for many agricultural researchers. We want to find ways to help growers produce the best quality produce and stress less about crop protection. That is why the EVADE lab at Cornell AgriTech was excited to test out the mesotunnel system in 2020 and understand the benefits for organic cucurbit growers in NY. If you have been following the last few articles, then you are familiar with some of the benefits this system can provide growers. In this article we would like to share the preliminary results from the season, so you can see first-hand the impacts this could have on your cucurbit crop. Due to COVID-19 restrictions our trials had to be adjusted but we were still able to gain some valuable insight on the potential for this system.

The trial was located on certified organic land at Cornell AgriTech, Geneva. The information collected was focused on determining the impact of the mesotunnel on the insect pests and diseases of cucurbits. This included Cucumber Beetles and Squash Bugs along with the diseases they vector: Bacterial Wilt and Cucurbit Yellow Vine Disease (CYVD), respectively.  We also monitored the incidence and severity of two commonly encountered fungal diseases, powdery mildew and downy mildew. Along with this we observed the behavior of pollinators within and outside the mesotunnel. At the end of the season, we collected yield data which compared the numbers of marketable fruit to unmarketable fruit and noted the factors that contributed to the unmarketable category. Two crops were included in the study: muskmelon (var. Athena) and acorn squash (var. Honey Bear). Each crop was grown in a single three-row plot either within the mesotunnel or uncovered. 

So, what happened? Findings indicated that the mesotunnel system prevented insect pests from getting into the tunnel and causing damage. There was also a noticeable decrease in the incidence of plants affected by bacterial wilt and CYVD.

Squash. In the squash plots, cucumber beetles and squash bugs were present in the uncovered plot, but only a few cucumber beetles sneaked into the tunnel. This was late enough in the season, so no damage resulted. The squash bug infestation led to 41% of the plants in the uncovered plot to be affected by CYVD. None of the plants in the mesotunnel had symptoms of CYVD. Although the netting was highly effective at preventing most of the insect pests from entering, towards the end of the season there was a large spike of aphids that formed within the tunnel. Fortunately, most of the fruit on the vines were at or near maturity so it did not impact the yield. Over the next few seasons, we are planning on observing if this is a trend and determining the best methods to control aphid populations. The uncovered squash plot had a slightly higher marketable yield than the covered. This variety produced a large amount of vegetative growth which could explain the slight reduction in yield due to the restricted space for fruit development to occur. This upcoming season we are testing a different variety to see how well it compares in this system.

Both pictures are from within the mesotunnel showing misshapen and not mature fruit due to the growth under the main stem. Photos by Kellie Damann.

Muskmelon. In the muskmelon plots, cucumber beetle populations increased significantly from the middle of July through to the end of August. The influx in cucumber beetles lead to 65% of the muskmelon plants in the uncovered plot showing symptoms of bacterial wilt leading to plant death. On the other hand, only 29% of the plants in the tunnel showed symptoms of bacterial wilt. Symptoms of bacterial wilt were not observed until mid-August within the tunnel, so these plants already had produced fruit which were close to maturity. 

At harvest, some significant differences appeared between the mesotunnel and uncovered plots. Eighty-eight fruit were harvested from the mesotunnel while only 65 from the uncovered plot. Of the total number harvested, 70 fruit were deemed marketable in the mesotunnel plot, while only 24 were marketable in the uncovered plot. In the uncovered plot most of the damage was due to insect damage, cracking, soft spots, and poor netting. In the tunnels unmarketable fruit was mainly due to overripe fruits that had soft spots. Fruit within the mesotunnel also ripened about a week earlier than in the uncovered plot.

Looking forward to 2021. Trials in 2020 therefore showed significant promise at excluding pest insects and were especially effective in muskmelon. This year we will be conducting larger replicated trials to gain an even better understanding on how this system works in organic cucurbit production. We will also be including a trial to investigate weed suppression options for their compatibility in a mesotunnel system.

This article was published in the March 2021 NYS VegEdge Newsletter if interested in viewing this publication please follow the link: https://cvp.cce.cornell.edu/newsletter.php