The early bird doesn’t always get just worms. Sometimes it also gets a late frost; sometimes it also gets flea beetles; sometimes it gets both. Which is a roundabout way of saying that when you plant members of the mustard family early, you may not only not get an early harvest; you may not get a harvest at all, unless, of course, you replant. For, if the weather and the beetles aren’t on your side, time is. You get a second chance.
The Opinionated Gardener, sometimes known as the Impatient Gardener; sometimes known as the Curious Gardener, knows. She is usually in the garden by mid-April, planting and ready to try her hand at outwitting frost and fleas and whatever else comes her way. Frosts are easy: she prays for a cloud cover at night, deducts 10 degrees from the 9 p.m. temperature and if it appears there will be a frost, covers the young plants with a bunch of sheets or a batch of cap-less, bottomed-out gallon milk jugs.
Flea beetles – those skittish, shiny black, high-jumping pests that pepper young leaves of the mustard family with their signature “buck shot” holes – aren’t as easy. But, if, like the OG you are persevering you might try out-maneuvering them with delayed planting, hardy transplants, soapy water, garlic sprays, collars of rhubarb leaves, floating row covers and trap crops, as those consulted by the OG have suggested. Or else you can pray that the weather and soil conditions are right enough so that your germinating seedlings and transplants grow faster than the flea beetles can eat.
But if all of the above fails, you can replant. And replant the Opinionated Gardener did this spring. She replanted the mustard greens and some of the red cabbage but not the arugula, tomatoes and Spanish radishes, even though they had sustained considerable damage. There were moments when she considered doing so but then just in the nick of time, it turned cloudy, cooler and began to rain and the flea beetles? Well, they just sort of “disappeared,” at least from sight, for the moment. Of course by then all danger of frost, as they say, “had passed.”
And the garden and gardener both breathed a sigh of relief. For the moment.
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Early spring in the garden
After a winter spent at the weedy edges of the garden, the crucifer flea beetle* aka Phyllotreta cruciferae, the most notorious of flea beetles, emerges from “hibernation” hungry. Attracted by sulphur-containing chemicals called glucosinolates** that are characteristic of the tangy-tasting members of the members of the Brassiceacea (mustard) family, it readily finds a source of food in the germinating seedling of arugula, mustard greens, radishes, cabbages and the like. Not only does it find a food source, it also finds a mate in what could be called by the damage done – a feeding frenzy.
The glucosinolates give rise to what we know as mustard oil and it is the volatile oil that guides the crucifer flea beetle to the young and vulnerable plants. As the first wave of flea beetles arrive and start feasting on the cotyledons, leaves and stems, more and more of the volatile chemical*** is released attracting more and more flea beetles to the young plants.
But that’s only the first stage in the cycle. Eventually death comes to the adults but not before eggs are laid in the soil around the roots of the plant and the larvae that hatch feed on the secondary roots of the plant, adding insult to injury. There will be a third attack on the surviving plants in late summer by the new crop of adults. It usually goes unnoticed as the grown plants that survived the first two onslaughts are by then able to “ignore” the nibbling pests. Harvest will interrupt the cycle; the adults will head back to the weedy edges of the garden for the winter. Waiting ’till spring when the cycle will resume.
Patience and other suggested “remedies”
The OG first noticed that the flea beetles had arrived during an unsettling period of windy, hot and dry weather this spring. The young leaves of the mustard greens, arugula and radish were peppered with its signature holes and their growth appeared to be stunted. They were obviously stressed by the beetles and the weather. So the OG began to water daily. But with apparent little impact or so it seemed. And despite their waxy leaves, the transplanted red cabbages were also showing signs of damage.
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Reluctant to turn to the traditional dusting with “Rotenone,” the OG turned to her neighbors for advice. Some reminded her that she should have waited till after the “season of the flea beetles” had subsided before direct-seeding. But then she wouldn’t have spicy arugula to pepper her salad with. Others swore by row covers made of the synthetic material known as “Reemay” to keep them away from the seedlings. But she couldn’t find any stocked in local stores and sending away for them would take too long. Others talked of garlic sprays. Some even talked of just brushing them off every hour on the hour to take advantage of their skittish behavior or better yet brushing them off into solutions of soapy water so they couldn’t take flight.
Unsatisfied with all of the above, the OG turned to the Internet. At www.frenchgardening.com/tech.html she read that the leaves of rhubarb and artemesia appear to provide protection from flea beetles. A possible explanation was that the oxalic acid in the rhubarb leaves was acting as a repellant and that the strong smell of the artemesia was masking the mustardy scent that attracted the flea beetles to the plant. While the OG had no “Reemay,” she did have lots of rhubarb and artemesia. She quickly set about encircling the embattled plants with the leaves of the two plants. While it’s not clear that those remedies worked, they did provide a mulch to keep in the moisture in the soil around the plants during those hot, dry and windy days.
At http://ofrf.org she read that Richard Smith of the University of California Cooperative Extension had done experiments over a period of years to see if “trap crops” of mustard greens, which contain inordinately high concentration of glucosinolates, planted at the perimeter of the garden could be used to lure flea beetles away from “cash crops” such as broccoli and cabbage and reduce the damage to them. The results appeared to be inconclusive.
It’s not surprising that there are no sure-fire remedies to the damage done by the flea beetle. After all, it is a newcomer to the North America, having recently arrived in the 1950s from either Europe or Asia.
It’s late June now and the battle of the flea beetles appears to be subsiding. They haven’t disappeared but there appear to be fewer beetles about. And yes, the arugula and mustard greens and radishes and cabbages have increased greatly in size. Cosmetically they are a disaster but as for taste, they can’t be beat. As for next year? The OG has a year to think about it. Right now she is busy picking the mating cucumber beetles off the squash and pumpkin seedlings.
* There are some 4,000 species of flea beetles, 20 of which are considered agricultural pests including the eggplant flea beetle aka Epitrix fuscula and the potato flea beetle aka Epitrix cucumeris. The OG has also found the striped flea beetle aka Phyllotreta striolata feeding on her arugula and radishes.
** Check the Daily Bulldog archives: “Chemical Warfare in the Cabbage Patch.”
*** Mustard oil is a poisonous chemical that should be protecting the plant from the flea beetle, not attracting it to the plant. But evolution appears to have taken a turn in support of the flea beetle! According to the folks at the Max Planck Institute for Chemical Ecology some species of leaf eating insects have developed a way to neutralize the harmful chemical. The cabbage white butterfly has; perhaps the crucifer flea beetle has also. In fact it must have! And it is using it to its advantage, providing it with not only food but sex.
