2021 was our second year evaluating the mesotunnel system at Cornell AgriTech in New York. Our team expanded the trials this year to examine different factors that could impact cucurbit crop health and ultimately yield. This year we focused on how pollinators (naturally occurring or purchased bumblebees) behave in this system and its effects on yield in muskmelon. We also evaluated how different weed suppression methods impacted insect populations and disease pressure in muskmelon and acorn squash. The main insect pests being evaluated were: (i) Cucumber beetles that transmit the bacterium that causes Bacterial Wilt (BW); and (ii) Squash bugs that transmit the bacterium that causes Cucurbit Yellow Vine Disease (CYVD).  We also evaluated the effect of the mesotunnel treatments on powdery and downy mildews. Each of these can play a significant role in diminishing cucurbit production. Our goal was to better understand the relationships and trade-offs between this form of exclusion and these pests.

So, let’s look at the trials!

 

Pollination trial. This trial was conducted on 150 ft beds, three rows wide with 7 ft centers, so the whole tunnel was 21 ft by 160 ft. For this experiment ‘Athena’ muskmelon was used and three different treatments were compared. Our objective was to better understand how netting treatments affected pollination and the effects on yield and marketability of the fruit. A secondary objective was to evaluate the effect of these techniques on pest populations and diseases.

The three treatments for this trial were (Fig. 1):

• Full season: the exclusion netting (ExcludeNet®) was placed on the crop at transplanting and remained in place until harvest; a purchased bumblebee hive from Koppert Inc. was used for pollination.
• Open ends: the exclusion netting was placed on the crop at transplanting, but during pollination the short edges were opened so natural pollinators (honeybees, squash bees, etc.) could enter the tunnel.
• On/off/on: the exclusion netting was placed on the crop at transplanting, but removed completely during pollination for natural pollinators and then replaced.

The pollination period lasted for three weeks within each treatment, after which the bees were taken out or the netting was reinstalled until harvest.

 

2021 Pollination Trial Results

All data was collected from the center row of each plot.

Disease and insects

• Cucumber beetle populations and bacterial wilt incidence were significantly higher in the on/off/on treatment compared to the open ends but were not significantly different between the open ends and full season treatments.

Harvest

Treatment had a significant effect on the number and weight of marketable muskmelons.

• The on/off/on treatment produced 20.7% more marketable fruit than the open ends treatment, and 64% more marketable fruit than the full season treatment.
  • The number of marketable fruit was 35.8% higher in the open ends treatment than the full season.
• Marketable fruit weight in the on/off/on treatment was 66.4% higher than tunnels with a bumblebee hive.

So, what’s the takeaway from this year’s pollination results?

We took into consideration the trade-offs of different treatments on insect populations, disease pressure, marketability of fruit and the economics of each treatment. Results indicated that the open ends treatment may be the most feasible and cost-effective for NY muskmelon growers. However, this trial will be repeated next year to see if similar trends are found.

IPM trial. This trial evaluated ‘Table Ace’ acorn squash and ‘Athena’ muskmelon in three different types of weed suppression methods and the differences between them using an exclusion net or leaving the plots exposed throughout the season. Each plot was 30 ft long with 3 beds and 7 ft centers, so the entire mesotunnel was 21 ft by 40 ft. Our objective was two-fold: (1) to quantify the effects of the mesotunnel on major diseases and pest populations and (2) understand how weed suppression methods impacted weed management.

Each crop had four treatments and they all had black plastic in row (Fig. 2):

• Full season mesotunnel with landscape fabric between rows (FsF).
• Full season mesotunnel with annual ryegrass between rows (FsR).
• Full season mesotunnel with annual ryegrass/white clover mix between rows (FsRC).
• Uncovered with landscape fabric between rows (UF).

Each treatment with the full season mesotunnel had one purchased bumblebee hive for pollination and the uncovered plots used natural pollinators.

 

2021 IPM Trial Results

All data was collected from the center row of each plot.

Disease and Insects

• The treatments with the full season tunnel did an exceptional job at excluding insect pests (cucumber beetles and squash bugs) and the pathogens they spread.
  • Bacterial wilt was only found in the muskmelons. The incidence was significantly higher in the uncovered plots (65%) compared to the covered treatments (25-35%).
  • CYVD was only observed in the acorn squash; and similarly, the uncovered plot had a significantly higher incidence (55%) compared to the covered treatments (0-10%).
• The incidence of powdery mildew was higher in all muskmelon plots than acorn squash plots.
  • Most treatments had between 95-100% incidence of powdery mildew, except for the uncovered squash which only had a 65% incidence.
• However, even with the higher powdery mildew incidence in muskmelon the disease severity was higher in acorn squash plots.

Harvest

Muskmelon

• The number of fruit harvested was higher in both landscape fabric plots compared to the cover crops (ryegrass and ryegrass/white clover).
• Average marketable fruit was higher in the covered landscape fabric plots compared to those established with the cover crops, but not significantly different from the uncovered plants with landscape fabric.
• Unmarketable fruit number was not significantly different between treatments.
• Marketable weight (lbs./acre) was significantly higher in both landscape fabric treatments (~25,166 lbs./A in FsF; ~20,560 lbs./A in UF) compared to both cover crop treatments (~9,046 lbs./A in FsRC; ~10,145 lbs./A in FsR). 
  • However, fabric treatments had a higher unmarketable weight than the cover crop treatments. Marketable weight was 15,020 lbs./A higher in the FsF plots compared to the FsR plots.

Acorn Squash

• There was no significant difference among the treatments in the total number of fruits harvested and the marketable fruit number.
  • However, the uncovered treatment had significantly more unmarketable squash (Average: 9.8 squash) when compared to the covered treatments (Average: 2 FsRC, 3 FsR, 4.3 FsF).
• Fruit weight was not significantly different between treatments.

As for the weed aspect of this trial, a larger weed population and biomass was observed in the cover crop treatments than the landscape fabric plots (as expected).  However, significantly more weeds were found in the full-season mesotunnel with the annual ryegrass + white clover mix acorn squash plots (85.8%) than the full-season mesotunnel with annual rye only squash plots (47.8%), but there was no significant difference among the muskmelon cover crop plots (Fig. 3). This result could be due to poor clover germination and the weeds having a slight advantage in those plots.

So, what’s the takeaway from this trial, you might ask!

The mesotunnel system does a great job at keeping out insects that vector harmful pathogens. Moreover, landscape fabric provided excellent control of weeds within the mesotunnels. Stand-by for results this year so we can evaluate the reproducibility of the 2021 results. We are also in the process of doing a partial cost-benefit analysis on the pros and cons we have tested in this system. More updates will be forthcoming soon!!!