Evaluation of the insect resistance of interspecific squash hybrids

Final Report for FNE11-709

Project Type: Farmer
Funds awarded in 2011: $4,022.00
Projected End Date: 12/31/2013
Region: Northeast
State: Connecticut
Project Leader:
Bryan Connolly
Green Dragon Farm
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Project Information


The purpose of this study was to trial interspecific hybrid squash (C. maxima-hubbard/kabocha x C. moschata-butternut) varieties in the northeastern U.S. to test their yield and tolerance to regional insects and diseases. Cultivars of C. maxima, C. moschata and C. maxima x C. moschata were grown in a randomized block design study that was conducted in 2011 and 2012. Varieties were assessed for yield, tolerance to striped cucumber beetle, and tolerance to squash vine borer. The C. maxima x C. moschata squash had comparable resistance levels to striped cucumber beetle as C. moschata, and twice the tolerance to squash vine borer as C. maxima. The hybrid cultivars had high yields with ‘Greenstone’ appearing particularly promising. In addition to traits formally assessed, C. maxima x C. moschata seems to be more tolerant of frost and powdery mildew than C. moschata, and more Plectosporium resistant then C. maxima, though replicated trials should be conducted to confirm these observations. Not only did the hybrids perform well in the field, the harvested squash have good keeping qualities and are of high culinary value.


Farm profile

We are a small part time operation growing one acre of vegetables for farmers market and the local co-op. Additionally we raise free-range broiler chickens for direct sales from the farm. Squash of all sorts are a large portion of our vegetable sales; some years we have grown more then 50 varieties. Previously we supplied FEDCO, Southern Exposure, and Baker Creek seeds with various squash seeds including the heirloom varieties: ‘Winter Luxury Pie’, ‘North Georgia Candy Roaster’, and ‘Galeux d'eysines’. We have grown up to 30lbs (extracted from about a thousand pumpkins) of ‘Winter Luxury Pie’ seeds per year.


Bryan Connolly, Farm Owner and primary researcher

Robert Durgy, Farm Manager Connecticut Agricultural Experiment Station Griswold Research Center 190 Sheldon Rd. Griswold, CT 06351 860-376-0365 [email protected]

Rob is the technical adviser for the project.

Project Objectives:


The project was conducted to evaluate the insect resistance of hybrid hubbard/kabocha (Cucurbita maxima) x butternut (C. moschata) squashes. Maxima squashes are known for their excellent table and ornamental qualities but they are extremely susceptible to both striped cucumber beetle and squash vine borer. Conversely, butternut squashes have good table quality and low ornamental value but excellent insect resistance. We wanted to evaluate the little known Japanese maxima x moschata hybrid squash ‘Tetsukabuto’ and compare it to the parental species. Additionally, we wanted to create new hybrids attempting to capture the table and ornamental qualities of maxima types and combine them with the insect resistance of the butternut squashes.


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  • Robert Durgy


Materials and methods:

Project design

Year one: C. moschata ‘Kikuza’, hybrid ‘Tetsukabuto’, and two maxima types ‘Blue Hubbard’ and ‘Burgess Buttercup’ were planted in a randomized block design with three replication of 5 hills of each variety, see diagram submitted with the proposal.

Project activities

‘Waltham’ butternut C. moschata was on back order from my seed supplier in 2011, I substituted a shorter wider selection of butternut I bred, named CCBN-1, for ‘Waltham’ so planting would not be delayed. Between hill spacing was 3ft, between row distance was 6 ft. Each hill had 3 individual squash plants, for a total of 45 plants of each variety and 225 squash plants for the entire experiment. Plants were not directly seeded in late May as originally proposed because of irrigations problems, but were sown instead in 4” pots. Striped cucumber beetle numbers and seedling survivorship instead of being monitored once a week through June, was just monitored once because beetle populations were low. Squash vine borer presence and adult plant survivorship also was not tracked weekly, it was record just once at the end of their active season, which was more time efficiently, but still effectively showing the tolerance to the pest. Deer began to damage the fruits; they were harvest on Sept 30, instead of in October. Squash fruit number per block, and variety were totaled and weighed. Data were analyzed using the statistical program SAS 9.1, mean separations were conducted with significance considered at p < .05. Squash were cooked and evaluated for culinary qualities in late fall to early spring. In 2011 yield may have been improved with additional nitrogen.

In addition to the survival and insect resistance experiment we had planned to conduct cross-pollinations to produce new hybrid plants. Three hills of ‘Gold Nugget’ (bush vine pink fruited C. maxima), “Bush Buttercup” (bush vine green fruited C. maxima), “Blue Ballet” (semi bush blue fruited C. maxima), and “Lakota” (striped green and orange C. maxima) were planted but they did not survive, due to woodchuck and insect activity, and cross pollination did not occur. We were able to pollinated ‘Burgess buttercup’ C. maxima with pollen from CCBN-1 C. moschata, four out of 10 pollinated flowers set. These four resulting fruits had several seeds each, plenty to use for the 2012 planting. Additionally, we discovered that there were other commercial C. maxima x C. moschata cultivars on the market and ordered seeds of Truinfo F1and Greenstone F1 to be trialed in 2012.
Year two: The seeds resulting from the above ‘Burgess buttercup’C. maxima x CCBN-1C. moschata pollinations were added to the block design. Three blocks of five repetitions of: ‘Burgess buttercup’C. maxima x CCBN-1 hybrid, ‘Triunfo’ F1 hybrid, ‘Greenstone’ F1 hybrid, ‘Tetsukabuto’ F1 hybrid,‘Waltham Butternut’ C. moschata, ‘CCBN-1’ C. moschata, ‘Kikuza’ C. moschata, ‘Burgess Buttercup’ C. maxima, and ‘Blue Hubbard’ C. maxima were planted with three plants per hill, totalling 45 plants per variety or hybrid equaling 405 plants for the complete experiment.

At our location we had almost no striped cucumber beetle activity in 2012, therefore damage assessment was not conducted. Otherwise planting, data collection, and analysis followed the methods of year one. Plants were side dressed with 10-10-10 NPK fertilizer in 2012 which may have boosted yields.

Research results and discussion:


In 2011 C. moschata, C. maxima, and hybrid squash were grown as planned. Striped cucumber beetle and squash vine borer evaluations were carried out. Squash were harvested, counted, and weighed. In 2011, the hybrid ‘Tetsukabuto’ had the least striped cucumber beetle damage of all cultivars, though only statically different from ‘Blue Hubbard’, which had the most damage. ‘Tetsukabuto’ had some squash vine borer damage but it was not significantly different than the C. moschata types that are considered highly resistant. Its tolerance to squash vine borer was statically higher than that of C. maxima types ‘Burgess Buttercup’ and ‘Blue Hubbard’.

In the 2011 growing season ‘Tetsukabuto’ yielded well in comparison to the other cultivars in the trial, it was second only to the butternut type CCBN-1. One surprising result of this year was how poorly the C. moschata type ‘Kikuza’ yielded; this cultivar had a high degree of insect resistance but flowered and fruited much later than the other varieties. It appears ‘Kikuza’ needs a longer growing season than that of northeastern Connecticut.

The intended hybridization did not occur in 2011, but we were able to cross ‘Burgess buttercup’ C. maxima with CCBN-1 C. moschata ten times, with 4 setting fruit, providing enough seed for planting in 2012.

In 2012 C. moschata, C. maxima, and hybrid squash again were grown as planned. Hybrid cultivars buttercup x CCBN-1, ‘Greenstone’, and ‘Triunfo’ were added to the trial. ‘Waltham’ butternut was also added, since seeds were not available in time for 2011 research. Squash vine borer evaluations were carried out. Squash were harvested, counted, and weighed.

Squash vine borer resistance in this year was significantly higher in all C. moschata types than all hybrids. The hybrids though were significantly more resistant than C. maxima cultivars. Though more susceptible to squash vine borer the hybrid had good production. By weight and number for yield, four out of the top five cultivars were hybrids. CCBN-1 was in both cases the only C. moschata that out yielded any hybrid. ‘Waltham’ and ‘Kikuza’ though highly resistant to the borer yielded poorly. As noted for 2011 ‘Kikuza’ does not seem adapted to the Connecticut climate. ‘Waltham’ was developed for New England and its poor yield is likely due to its powdery mildew susceptibility. The foliage of all C. moschata types at harvest was dead from powdery mildew. Hybrid foliage was infected by powdery mildew in the fall, but remained alive until frost. Any surviving C. maxima also had foliage that could tolerate powdery mildew. It appears that the hybrids combine some of the insect resistance of C. moschata with the powdery resistance of C. maxima resulting in higher yields.

The hybrid we created, buttercup x CCBN-1 did not yield as heavily as the other hybrids, but they had similar insect resistance. Our cross also had more compact vine, reaching only 10 feet long, were as the other hybrid types could grow to 20-30ft long. Buttercup x CCBN-1 also had smaller fruits that may be more acceptable to American consumers, being 2-3lbs, as compared to ‘Greenstone’ with fruits in the 5lb range. This cross we made is proof in concept that new hybrid cultivars can easily be created.

In 2012 we unexpectedly found out that the hybrid fruits were more frost tolerant than C. moschata. After harvest fruits were left out on a night that dipped down to 26°F, though the weather forecast only called for 33°F. Many of the C. moschata type fruits were highly damaged and many rotted, the hybrids tolerated these temperatures without injury. Additionally, the few C. maxima vines that survived the squash vine borer had a high degree of the fungus Plectosproium, the hybrids did show some signs of infections but it did not appear to be at a level that would reduce yields.

The culinary qualities of the hybrid squashes were also good. All C. maxima x C. moschata cultivars in the trial had sweet deep orange flesh, better in flavor than ‘Waltham’ butternut C. moschata, but not as sweet as ‘Burgess Buttercup’ C. maxima. The flesh was also moist unlike the dry ‘Burgess Buttercup’. The hybrid squash were successfully used in breads, pies, soups, and as a plain side vegetable. The fruits are also good keepers, many from the 2012 harvest were still holding well as of March 1, 2013.


This SARE project did not have an economic focus per se. But the high yield and decent insect tolerance of C. maxima x C. moschata cultivars could increase the production per acre and decrease costs through lower chemical use.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:


See article below intended for NOFA-CT and NOFA-MA newsletters March 2013.

Abóbora híbrida/Abóbora Japonesa (Hybrid Pumpkin) (Cucurbita maxima × C. moschata), A Japanese/Brazilian Squash Finds Fertile Ground in New England.

Winter squash are traditional in New England for their ornamental and culinary uses. They are also a staple crop for vegetable growers in our region. Butternut squash (Cucurbita moschata) and buttercup, hubbards, and kabocha squash (Cucurbita maxima) are familiar to northeastern consumers and farmer. Butternuts are known for a high degree of insect resistance, especially to squash vine borer and striped cucumber beetles, and are resistant to Plectorsporium blight. Though the tradition butternut cultivars are susceptibly to powdery mildew, newer varieties have had resistance to this fungus bred into them from wild gourd species. While the buttercup/hubbard/kabocha groups are prized for their culinary uses but are very prone to squash vine borer and striped cucumber beetles. Little known in North America is a cross between these two squash groups (Cucurbita maxima × C. moschata) known as Abóbora híbrida or Abóbora Japonesa in Brazil, and will be referred to as hybrid pumpkin for the remainder of this article. These hybrids were developed in Japan then around 1960 they migrated to Brazil where they have become quite popular. Several cultivars have been developed e.g. ‘Tetsukabuto’, ‘Suprema’, ‘Greenstone’ and ‘Triunfo’. In addition to being grown for the squash themselves, this cross is also used as a rootstock in many parts of the world for melons and watermelons. The University of Massachusetts lists this as an ethnic crop for this region but I had not heard of anyone growing this crop in New England. So, I had to try it out. To get first hand knowledge I applied for a USDA Northeast Sustainable Agriculture Resource Education (NE-SARE) producer grant to trial this hybrid. Luckily, I was successful in getting funding, see grant number FNE11-709.

Hybrid pumpkin seeds were purchased from the seed sources below. Cucurbita maxima × C. moschata produces fruit, but no seeds, and must be planted near a regular butternut type or buttercup/hubbard/kabocha type for pollination. Seeds of butternut, buttercup/hubbard/kabocha, and hybrid pumpkins were planted in Mansfield Center, CT in mid June in both 2011 and 2012 in a randomized block design to compare the squash types. Striped cucumber beetle damage, squash vine borer infestation, and yield were systematically assessed. Additionally, notes on powdery mildew tolerance, Plectosproium tolerance, freeze tolerance, keeping quality and table quality were taken. Harvest was conducted last week of September for both years.

Results, in short hybrid pumpkins did just fine in New England.

In our climate the plants matured fruit without a problem. The hybrids for the most part did combine the best traits of the parents. The crosses though not immune, were more insect and Plectosporium blight tolerant than the buttercup/hubbard/kabocha types, and also more powdery tolerant than traditional butternut types. During the second year of the study almost no buttercup/hubbard/kabocha types survived to produce because of insect damage, the hybrids did have mortality but a sizable crop was harvested. In 2012 harvested fruits were accidentally left out on a night in early October when temperatures sunk to 26°F. Butternut types suffered injury that some did not recover from, and many soon began to rot. The hybrid types recovered from this frost and most have kept well into February. In 2011 the crosses kept into March without a problem. In the kitchen the squash had deep orange flesh, with good texture and flavor, comparable to buttercup, though moister and not quite as sweet. I think this Japanese/Brazilian squash did find fertile ground in Connecticut, and I believe this crop has the potential to be widely grown throughout the Northeast. A technical peer reviewed paper of this squash trial is being prepared.

For additional information see:


Uretsky, Jacob. 2012. Development and evaluation of interspecific Cucurbita maxima x Cucurbita moschata hybrids for processing squash. Masters thesis. University of New Hampshire.

Seed Sources for Abóbora híbrida/Abóbora Japonesa (Hybrid Pumpkin):


Project Outcomes

Assessment of Project Approach and Areas of Further Study:

Future Recommendations


We plan on continuing to grow C. maxima x C. moschata hybrids. This is because in the field they yielded well in our region, tolerating both squash vine borer and powdery mildew. Additionally, not only do these squash grow well, they have good storage quality and have high culinary value.


Some additional ideas were generated while conducting this research. We hope to trial the few other commercial cultivars available that we could not include in this study. We would also like to continue hybridizing different C. maxima and C. moschata types to generate cultivars with differing traits than those currently on the market.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.