We grow one bed (90 ft or so) of yellow squash in our hoophouse, to extend the season earlier. This year it is a dismal failure. We have had splendid success some years, with good harvests for several weeks before our outdoor squash are ready. What has changed?

One aspect is climate change including more variable temperatures in spring. This makes it harder to get frost-tender crops started in our greenhouse, and causes us to delay transplanting into our hoophouse, to avoid a wipe-out. We do have good thick rowcover to put over the hoophouse crops, but rowcover can only do so much. Also, it’s not simply a matter of life or death. Extended cold can permanently stunt tender plants.

Striped Cucumber Beetles

Our second biggest problem is striped cucumber beetles. We reckon if we can deal with the cucumber beetles in the hoophouse, we’ll be dealing with the mothers of that year’s population, and things won’t get so bad outdoors. Or, rather, if we don’t deal with them in the hoophouse, they’ll get really bad outdoors (we’ve seen that happen on nearby watermelons and squash).

Our approach is to nip the beetles in the squash flowers first thing each morning, with tweezers. It’s important to tackle them early in the morning, because as the day warms, so do they, and they take off flying around, making them hard to catch. We ignore the more numerous, smaller, cucumber flowers, because the beetles prefer squash flowers, and we’re only prepared to spend a limited amount of time on this task.

The hunting season for cucumber beetles here is on average about a month long. In 2017 it was early and only 8 days 4/25 to 5/3. This year we didn’t start till 5/4 and we’re still finding some 6/5.

One year we tried trapping the beetles using pheromone lures from Johnny’s. We hung the pheromone with a yellow sticky card from the wire hoops that previously held up the rowcover. I thought they were successful, but others on the crew didn’t want to use that method again.

One year we sprayed with Spinosad, which is organic and was very effective, but we try to avoid any spraying if we can. Recently we revisited the decision, and re-committed to hand picking.

To attempt to deal with our third problem while addressing the second, I just tried wrapping yarn round the tweezer arms, thinking they might do some pollinating for no extra effort, while I hunted beetles. It wasn’t very successful. The tweezers we’re using are very pointed and the yarn slides off. Too much yarn prevents the tweezers closing aggressively enough.

Unpollinated squash

Our third problem is unpollinated squash. The baby squash are hollow, and sometimes rot at the ends. We spend too much time removing the unpollinated ones to encourage the plants to try harder producing new squash, and to prevent the spread of molds which sometimes grow on the hopeless squash.

We look for bush varieties, as we don’t want sprawling vines in the hoophouse. In order to get harvests as early as possible we choose varieties that are fast-maturing. Since 2008 we have usually grown Gentry, a hybrid yellow crookneck squash with a bush habit, that mature in just 43 days from sowing in normal temperatures.

Early in the season some varieties of squash produce a lot of female flowers, which can’t get pollinated until some male flowers appear. Low temperatures and high light intensity promote this female sex expression, ie female flowers rather than male flowers. But our problems went on beyond the arrival of male flowers.

In 2006 we grew Zephyr, a beautiful bi-color hybrid yellow squash with green ends, which is our favorite for outdoor crops. It takes 54 days to maturity. In 2007 we grew Zephyr and a few Supersett, a 50-day hybrid crookneck yellow squash. We didn’t choose Supersett again, so I suppose we didn’t prefer it. What did we grow in the first few years 2004-2005? We didn’t keep good records.

In 2015 we tried Slick Pik YS 26, a 49 day hybrid, attracted by the claim to spinelessness. It didn’t do well for us, and we came to call it Slim Pickins. Some of the plants were weird. About 4 out of about 45 plants had darker green leaves and no female flowers. The male flowers were abnormal, halfway to being leaves. The petals were thick and greenish, and the flowers were small. Then the flowers dropped off, producing no fruit, so we didn’t grow that variety again.

Another option we once tried is a parthenocarpic variety. Parthenocarpic crops can set fruit without pollination. Some squash varieties, like Sure Thing (48d), Partenon (48d), Cavili (48d), and Easypick Gold (50d), are sold on the strength of being very good at setting fruit without any pollinators. See this article for all the details.

It’s not an all-or-nothing attribute – a number of squash varieties have some level of parthenocarpic capability.

In one study of zucchini (see the article link above), fruit set without pollination varied from zero to 42%, depending on the variety. In the 1992 study, 33 varieties of yellow summer squash were compared. Follow-up studies in the next few years. Chefini (51d  Breeder: Petoseed Co (SQ 28) Seems not to be commercially available any more), Gold Strike (a yellow straight-neck squash, likewise seems unavailable), Black Beauty (50d) and Black Magic (50d)  all did well. In a study including yellow squash and zucchini, most of the high-parthenocarpic producers were zucchini rather than yellow squash. Of yellow squash, Gold Strike seems unavailable, but Gold Rush (52d), Golden Glory (50d) look promising

See also Steve Reiners’ paper Producing summer squash without pollination – Ranking varieties

In that study Golden Glory (50d) is the big winner. Runners up are mostly zucchini: Dunja (47d), Noche (48d), Partenon (48d), Costata Romanesco (52d semi- bush variety), Safari (50d), Multipik (50d yellow squash). After that there are several that scored 29% down to 6% in the trial, and then a bunch of zeroes. Our much-beloved Zephyr scores zero in that trial!  I read that the retail demand for yellow squash is less than for zucchini, so most of the research goes into zucchini.

Next year, I’ll propose we try Golden Glory and Noche (a zucchini that does well for us in hot weather). Or perhaps Dunja, which scores higher.

Encourage pollinators

This is something else we could pay more attention to next year. We have now got honeybees again, after several years without. We could also plant a succession of flowers that attract pollinators, timed to flower the same time as the squashes. If we plant them in big pots we can cycle them in and out of the hoophouse for their “work shifts” and retire them when they stop flowering. See this blog post from Southern Exposure Seed Exchange: 10 tips for Attracting Bees and other Pollinators and Harvesting Great Cucumbers, Squash and Melons. Carolina Farm Stewardship Association also has some useful info about native squash bees. I’ll need to study up before next spring!

Import pollinators

We could buy boxes of bumblebees from Koppert. But that gets pricey. I prefer attracting existing pollinators.

Minor Problems; Squash bugs

We also have squash bugs, but they aren’t such a big problem for us.