Article on clovers, sowing of clovers, arrival of pickleworm

GFM_September2014_cover_300pxThe September issue of Growing for Market magazine is out, including my article about growing clovers for cover crops, which I mentioned on my blog last week. I wrote how we had ideal “transplanting weather” (rain) when we needed to top up the transplanted cabbage and broccoli, and then “ideal hoeing weather” (not a cloud in sight) when we started removing the rowcovers and hoeing the rows. We tilled between the last rows in the end, as the grassy weeds got ahead of us (all that rain the week before) and we couldn’t get done with the wheelhoes in time, while the weeds were small. We got  “perfect clover broadcasting weather” yesterday (drizzle), and I managed to get the clover mix sowed after lunch. I was in my raincoat, with a bucket of seed under my arm, striding forth. I ended up happy, with lots of mud and clover seed between my toes! It feels good to have that job done. We’re having more drizzle this morning – seems perfect to get the clover seed to germinate there on the surface, without drying out. It’s saving a lot of fussing with overhead irrigation.

Crimson clover is a beautiful and useful cover crop. Credit Kathryn Simmons
Crimson clover is a beautiful and useful cover crop.
Credit Kathryn Simmons

And you can read more about undersowing clovers for all year cover crops (Green Fallow), and other uses of clovers for winter cover crops in Growing for Market magazine. For next month I’m writing about another of our favorite leguminous winter cover crops, Austrian winter peas.

The September issue also has an article generated by a competition among readers to send in ideas for easy DIY hoophouse ventilation. Ideas include high end wall windows (Tennessee), sidewalls rolled up onto pipe hangers (Louisiana), internal end-wall sliding doors (Alaska) and roll-up ridge vents (North Carolina).

Chris Blanchard writes about increasing production efficiencies and scaling up for increased production. He wisely recommends first taking a cool calm review of how your current plans have been working, and which bits haven’t been working. Don’t expand unless you have a successful grasp of what you are already doing. If you are unsure, focus first on improvements, then revisit the idea of expansion. Get better before getting bigger. Chris has a lot of wise advice and this is a good time of year to review and plan for next season. he recommends keeping a file folder labeled “Painful Things to Remember in November”. You drop a note in the folder whenever you hit a problem during the year, so that in the winter you can be reminded (helpfully!) and you can devise solutions or changes before next year. I like this. I try to do some of this, but a dedicated folder, or maybe a box, like a Suggestions Box, in the shed, for any of the crew to drop in a note. . .

There is an article on the food safety risks introduced by irrigation water and by compost, written by Meredith Melendez and Wesley Kline from Rutgers NJAES Co-operative Extension Service. We all need to be reminded to take appropriate care to make sure our food really is as healthy and good for us as we want it to be.

Gretel Adams writes about preparing for Mothers’ Day flowers – yes, now is the time to plant for that event, one of the biggest in the flower farmers’ calendar.

Large pickleworm larva. Photo University of Florida
Large pickleworm larva. Photo University of Florida

And then – the pickleworm has arrived in our part of Virginia. This tropical insect, Diaphania nitidalis overwinters in south Florida (and maybe south Texas) and spreads up the east coast each year. It regularly reaches South and North Carolina in August or September. It reached here in the first week of September. This is the first time I’ve seen this pest on our farm. I’ve read that it can reach as far north as Michigan and Connecticut some years. We’re reassured that it can’t overwinter here, and that we could get at most 3 generations. Sort of reassured. The adult is a night-flying moth, which lays tiny eggs on buds and flowers. Despite the name, this pest likes yellow squash more than pickling cucumbers. (And winter squash, gherkin and cantaloupe can be colonized if necessary.)We first found ours on Zephyr yellow squash and initially the neighboring Noche zucchini was untouched. But yesterday some of the zucchini also had holes.

Yes, I’m getting to that. When the eggs hatch, the small multi-spotted white, brown-headed larvae/caterpillars burrow into a squash, where they eat and grow, and do what everyone does, poop. If you don’t act quickly, the inside of the squash gets tunneled out, until the fifth instar, up to an inch long, is ready to pupate. The fifth instars are the easiest to find, being biggest, although they have lost their spots and are now colored according to what they’ve been eating, somewhere in the pale yellow-green part of the spectrum. The dark copper-colored pupae (haven’t seen those yet) nest in a leaf fold or among dead plant mater, for 8-9 days, then a new adult moth emerges. What’s a busy organic (small o) farmer to do?

Soldier beetles and some carabid beetles eat them. Steinerama carpocapsae nematodes attack them. We’d have to buy those in. Bacillus thuringiensis (Bt) would kill them if we could reach them, but they are living a sheltered life inside our squash! We could cover the plants every night and uncover them  every morning to let polllinators in, but oh dear, the days are so full already! We decided for this week, we’ll just harvest the squash a bit smaller than usual and see how that goes. Maybe not many moths arrived, and frequent harvesting (and slicing up of holed squash) will stop any future generations. Slicing the squash at the level of the hole does usually decapitate the larva. I wonder how long the moths live for?

The eXtension website publication Biology and Management of Pickleworm and Melonworm in Organic Curcurbit Production Systems by Geoff Zehnder of Clemson U provides the useful information that “research by Brett et al. (1961) demonstrated marked resistance to pickleworm in the following varieties: Butternut 23, Summer Crookneck, Early Prolific Straightneck, and Early Yellow Summer Crookneck. The varieties more susceptible to pickleworm are Cozini Zucchini, Black Caserta Zucchini, and Benning’s Green Tint Scallop squash.” I might add Zephyr squash. Spinosad might be effective, but as with Bt, I think it would be difficult to get the spray on the beasties as they are inside the squash.

For pictures of the damage, see Sunninglow Farms blog. They are in Florida and posted this in April. I shouldn’t complain too loudly. It is September here.

Pickleworm damage to yellow squash. Credit Sunninglow Farms
Pickleworm damage to yellow squash.
Credit Sunninglow Farms

Now I must get on with finishing preparing my powerpoints for Heritage Harvest Festival and Mother Earth News Fair in Pennsylvania. Hope to see some of you there!


Sweet potato harvest – all in!

Our sweet potato harvest well underway.
Photo credit Wren Vile


Usually sweet potatoes are harvested the week the first frost typically occurs. In anticipation of frosts (that didn’t happen) on Sunday and Monday nights, we harvested this week. Contrary to myth, there is no toxin that moves from frozen leaves down into the roots. On the other hand, cold injury can ruin the crop, and roots without leaf cover are exposed to cold air temperatures, and have lost their method of pulling water up out of the soil. Cold wet soil can quickly rot sweet potatoes (I know, it’s happened here).

To harvest, we first remove the vines from the area to be harvested that day. There is usually 3 afternoons’ digging for ours, and we want to leave live vines to protect the rest of the crop overnight. We use pruners to snip the vines where they emerge from the soil, leaving stumps to show where to dig. We roll the vines into the spaces between the rows.           Using digging forks, we carefully dig up the roots, which grow in the ground in a bunch-of-bananas shape. We want to select good potatoes for seed, and we grow several different kinds (Georgia Jet, Beauregard, and a couple of heritage varieties whose names we don’t know), so we make sure not to mix potatoes from different rows. As we dig, we set the potatoes out beside the spot where they’ve grown, one clump per plant, so it’s easy to identify the most productive plants.

It’s important not to bruise the roots, or to leave them exposed to temperatures higher than 90°F (32°C) for more than half an hour, or they will get sun-scald. Below 55°F (13°C), they’ll get chilling injury. We also avoid any abrasion of the skin, which is very fragile at this stage. We leave the sweet potatoes to dry on the ground for 1-2 hours, unless the weather is unsuitable. This year we had ideal weather, not too hot, not too cold; breezy enough to dry the skins, sunny.

We want to grow our own slips (baby plants) next year, so we save at least 1 root per 5 slips wanted.  (1 good slip every 16″.) So to plant 800 row feet, (600 slips), we save 100 each of our two main varieties and 20 each of the two heirlooms. That should be plenty. Some will shrivel or rot, so we allow a margin. We don’t save for seed any roots that look diseased. We choose plants with a high yield and no string (rat-tail) roots. From these plants, we choose small-medium sized potatoes with typical shape and color.

When grading and crating the roots in the field, we first choose the seed potatoes, and then sort storable from “Use First” roots. Large open broken surfaces will cure and can be stored, but any roots with soft wet damaged areas or deep holes (whether from voles, bugs or fork tines) will not store, and should be graded out, for composting or immediate use. We sort into 4″ deep wood flats or 5″ plastic crates for curing, and buckets for the “Use First” category.

Immediately after harvest, we took the boxes of sweet potatoes into a warm damp basement below the dining hall, to cure. This allows the skin to thicken, cuts to heal over and some of the starches to convert to sugars. Uncured “green” sweet potatoes are not very sweet at all, and are better used in dishes where they combine with other foods. A baked uncured sweet potato is a sad disappointment.

We stack our boxes of roots on pallets, and put wooden spacer sticks between boxes in each stack, to ensure air flow. We get quite good temperatures, but keeping humidity up is difficult for us. We cover the flats with newspaper to hold in some moisture. The best result seems to come from splashing water on the concrete floor several times each day. We use box fans to improve the airflow, and the basement already has some natural ventilation.

Ideal conditions for curing are 85-90°F (29-32°C), and 80-95% humidity for 4-7 days, with some airflow and ventilation. Curing takes longer if conditions are less then perfect. The length of the curing period also varies with the dryness of the soil just prior to harvest. We usually reckon on 10-14 days. During that time, we’ll be taking turns to stoke the stove in the basement to keep the temperature up.

So – how did we do this year? Middle of the road, I’d say. Decent yields, but not a bumper crop – we still had empty boxes left over. The deer were regularly eating our vines until quite recently. Last year we had a dog to chase the deer off, but he met with a road accident. His replacement was old, and she just wanted to be a pet, so we had deer again. We used drip irrigation and biodegradable plastic mulch this year, and did a good job of weeding, so I put the lower yields down to deer damage.

Last year’s (weedier!) sweet potato field.
Photo credit Kathryn Simmons

Now the harvest is complete, we will disk the area and sow cover crops. It’s too late in the year for oats. We can sow wheat, winter rye and Austrian winter peas up till 10/31. We prefer winter wheat after the sweet potatoes,  because we’ll use that area next year for spring white potatoes in mid-March, and rye takes too long to break down early in the spring.