Dealing With Tent Caterpillars And Moths

Safe & Sensible Caterpillar Controls

Over the past few years, those revolting little tent caterpillars have been making a comeback. Gardeners all over the region have been seeing tent caterpillars’ ragged white tents, which can be found in some surprising places, but are most apt to feed on alders, cascara, willows, Indian plum, fruit trees, and rose family trees and shrubs. Native to these parts, the Western Tent caterpillar population explodes on a roughly 3-7 year cycle. If the caterpillars aren’t ravaging your home and garden, WSU tree scientists recommend leaving them alone. Huh? Well, as tent caterpillars thin the leafy forest canopy, young conifers capture more sunlight and put on extra growth. When you hear the pattering of caterpillar droppings hitting the ground, perhaps it may relieve your feelings to know that they help fertilize the understory of the woodlands. Or not.

When saggy bags full of ravenous tent caterpillars rip into the garden, it’s pretty hard to watch. Fortunately, there are a number of safe and effective ways to cope with these wild rascals. For starters, when pruning trees and shrubs in winter, check for egg cases and strip them off before they hatch. They look like little strips of dirty plastic foam, and peel off quite easily. You may also release tiny trichogramma wasps. These minuscule parasites could hold a party on a pinhead (4-6 of them could cluster there). They lay their own eggs in the egg cases of tent caterpillars, destroying the incipient tent caterpillars to nourish their own tiny offspring.

Buy Some Beneficial Wasps

Trichogramma wasps are among the most commonly used beneficial insects world-wide. When you buy trichogramma wasps, the container you purchase is not full of wasps. In it, you’ll find a postcard that you fill out and mail. In about a week to 10 days, the wasps arrive. You probably won’t be able to see them,  because they are so small, but they’re in there, raring’ to go. One cup is enough to control pests in most greenhouses or in the average city lot. For larger properties, place beneficial wasp cups about 50 feet apart, starting about 25 feet inside your property line. If the problem lies outside your yard, you may want to donate wasps to the neighbors or go in with them on a larger shared purchase. Each packet contains about 12,000 live trichogramma wasps, enough for an area of approximately 2,500 square feet.

The usual packaging holds a little paper card inside a plastic cup which can be hung from a tree branch or tucked between the trunk and a branch. Remove the cap from the cup, and your wasps will start hunting right away. For the best results, release your trichogramma wasps in the evening after a warm day. Their preferred temperature range is between 70 and 80 degrees F, but they cope quite well with the vagaries of maritime weather. To make any beneficial insect release more successful, lightly spray the release area with water before letting the insects go. All beneficials need a drink after coming out of dormancy and/or captivity. If there is plenty of moisture available, they’ll stick around to do the job you have in mind, rather than heading out to find water.

But First Identify Your Target

When caterpillars arrive, take time to identify your caterpillars before taking action. Tent caterpillars are about 2 inches long, dark brown and very fuzzy, with a white stripe down their back and linear or blobby red or blue side markings. If your caterpillars look like this and are emerging from baggy tents, you can move on to the next step, which is examining the caterpillars for signs of yet another kind of parasitic wasp. Typically, these head-of-a-pin tiny wasps lay a single egg on each caterpillar’s head, though an egg may appear anywhere on the body. The white eggs are about the size of a pimple and they mean certain death for the involuntary host when the baby wasps eat their way free.

Thus, if you find plenty of white-dotted tent caterpillars, let them be. Each parasitized caterpillar contributes to the population of the beneficial wasps, which are an excellent natural control. If the caterpillars are feeding on precious plants, you may want to do some hand picking. However, instead of squishing the pimpled ones, consider tossing them into an area of weeds or long grass, so they remain available to their natural parasites.

When Spray Is the Answer

If the caterpillars are everywhere and no dotted heads are in sight, it may be spray time. It’s important to know that toxic caterpillar pesticides only work on the caterpillars, not the webs, which are waterproof and impermeable to toxins. If your yard holds unreachable webs you can’t live with, spray surrounding foliage with Bt (Bacillus thuringiensis). This naturally occurring bacteria comes in several forms; the kind used on caterpillars interrupts their normal digestion and maturation processes. When they eat leaves sprayed with Bt, they stop eating and die within a few days.

Like most botanical pesticides, Bt doesn’t last very long, so you may need to spray several times if you have a bad infestation. Carefully targeted and timed Bt use minimizes or eliminates accidental non-target caterpillar kill. Because Bt dissipates so quickly, it won’t persist to be a problem for the later-appearing caterpillars of Painted Ladies and other handsome butterflies. Keep your eyes open if fluctuating spring temperatures cause caterpillars to hatch out in flushes, since timing is critical to success. Until caterpillars emerge from the webs, nothing is going to kill them, however deadly. Once babies emerge and begin to feed, you can start your spray program.

Play That Trombone

Always use a clean sprayer that has never been used for toxic herbicides. (Right?) Hand or backpack sprayers work well for treating shrubs and smaller trees. For tall trees, you may successfully apply Bt with a trombone sprayer, which can reach up to 20 feet or more. You’ll get more height if you don’t overfill the sprayer, as each gallon of water weighs about 8 pounds. Make sure the Bt is fresh (the package should have an expiration date), and mix it as directed, since brands can vary. Usually, the shelf life is a year or two for unopened bottles and about 3 months for opened bottles. Wettable powders may be good for two years if unopened. Bt that has frozen and thawed is probably no good.

As always, spray any pesticide on a calm, windless day when bees and other pollinators are not present (early morning or late afternoon). With Bt, you only want to cover the foliage surrounding the webs of feeding caterpillars. For light infestations, a single dose might be enough. trees and shrubs that are hosting emerged and feeding caterpillars. For a severe caterpillar attack, you may need to spraying Bt every 2 or 3 days for a week.

If You Just Give Up

If you do nothing, the caterpillars will pupate, then emerge as moths. A month or so after the last crawlers are gone (right about now), watch for large (2-inch) cinnamon brown or tawny, rust colored moths. You’ll probably spot them fluttering around light fixtures at night. In the morning, you may find dead moths under each outdoor light, looking like heaps of tattered leaves on the ground. Each moth lives for about three days, existing only to lay eggs that will hatch out next spring as tent caterpillars.

The number of tawny moths you see will be a good guide to the state of your yard next year. There are several good strategies for moth control, starting with  placing yellow light bulbs in your outside light fixtures. Next, set tubs of water beneath them, with a drop or two of vegetable oil added to help trap the moths. Soapy water works too, but tends to get stinky quickly in warm weather. If you see a lot of moths, set large tubs or kiddie wading pools out in open areas and float candles in them each evening to draw the moths to their doom.

Bats To The Rescue

The best predators for moths are bats and swallows, both of which are evening feeders. Swallow houses and bat boxes help bring these excellent critters into your yard where they can help reduce the moth population. Swallows like their houses placed in protected spots such as under the eaves of a house or garage. They also like their privacy, so position each nesting box so that the entrance can’t be seen from any neighboring boxes.

Bat houses need to be placed where they get a lot of sunlight for most of the day. Lack of warmth is the most common reason that bat houses remain unused. In his excellent book, Landscaping For Wildlife In The Pacific Northwest (U of W Press, 2000, 320 pp., $29.99), Russell Link offers lots of good tips on placement for successful bat house use. He also suggests painting bat houses brown or black to increase the warmth inside.

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Spring Bounty & Bliss

And Snap Peas & Sorrow

This weekend, I helped with a memorial event for Dave Ullin, a man who has been called the island saint, Bainbridge’s Thoreau, and the caretaker of Eagle Harbor, among other things. The Senior Center was packed with long time islanders and people from Dave’s past, and story telling was the main event. Amazing images from Dave’s life covered the walls and flowed above our heads on a big screen. In a smaller room, video interviews with Dave ran in a continuous loop.

Among my favorite Dave quotes is this, read by his niece, “I believe that working together in gardens bridges gaps in human relations by humbling the human ego out of the way through direct contact with, and subconscious absorption of, the sacred workings of nature. A garden can grow humans of care and respect which then influences that perception toward the whole. A little gentle guidance to inspire being with nature mindfully, quickens the perception.”

But Wait, There’s More

If you want to see some, here’s a short teaser that will give you the flavor of this one-of-a-kind (and very kind) person:

One With The Work

If that piques your interest, you may want to watch this longer documentary about Dave:

Against The Tide

or this one:

Saving the Yeomalt Cabin

And read some Dave stories…

Making Community Connections

Looking over the crowd, I was struck by how many different community groups Dave overlapped with, especially since he was not an outgoing person and preferred to do whatever work came to hand rather than anything that might seem frivolous. He did enjoy both practical and philosophical conversations about many things, from gardening and mending socks to defending personal freedoms and making sure no one was ever left out in anything he was involved with.

As we listened to Dave stories and music performed by loving friends, we also ate. Among the most popular nosh was a big burlap sack of local snap peas, plump and sweet. I saw peas on nearly every plate that passed among the tables filling the hall. I think all of us who ate them thought about Dave and his love for growing things and especially for fresh vegetables.

Kitchen Bliss And Peas

The first local peas do indeed deserve our full attention. Tender and crisp, their slight earthiness balances the sweetness that allows raw peas to mingle as readily with fruity as with spicy dressings. As spring slides into summer, one of my favorite dishes involves both the first ripe strawberries and those succulent snap peas. My Marshall strawberries are ripening daily, their juicy sweetness enhanced by their floral perfume. Both main ingredients get to shine in this simple salad that I’m making every day while both are simply perfect.

Sweet Pea & Strawberry Salad

1 cup sugar snap peas in pods
1 teaspoon avocado or safflower oil
1 teaspoon fresh lime juice
1 teaspoon maple syrup
2 green onions, thinly sliced on the diagonal
1 cup halved ripe strawberries with any juice
pinch of sea salt
2 cups ribbon-chopped Romaine lettuce (chiffonade)

Top and tail intact pea pods, pull off the strings and slice thickly, set aside. In a serving bowl, whisk together the oil, lime juice, and maple syrup. Add green onions, sliced snap peas, and strawberries, sprinkle with salt and toss gently to coat. Divide lettuce between two plates, top with pea mixture and serve immediately. Serves 2.

Or Try Peas With Sweet Cherries

As spring meets summer, incoming ripe cherries meet the green wave of garden peas. The combo may sound unlikely but it’s totally delicious; crisp, crunchy and alive with complex flavor notes. Raw cabbage adds to the crunch factor, though a few minutes rest in the dressing pre- “cooks” it a bit. I usually serve this salad with thick slices of whole grain sourdough toast or oatmeal bread slathered with soft goat cheese.

Snap Pea & Sweet Cherry Salad

2 cups (about 16) snap peas in the pod
1/2 cup chopped pitted Rainier or any cherries
1 cup very thinly sliced green cabbage
1/4 cup finely chopped Walla Walla Sweet onion
1/4 teaspoon sea salt
1 tablespoon minced mint
1 teaspoon avocado oil or hazelnut oil
1/2 organic lemon, juiced, rind grated

Top and tail intact pea pods, pull off the strings and slice thinly on the diagonal. In a serving bowl, combine peas, cherries, cabbage, chopped onion, and 1/4 teaspoon salt with the mint and oil. Stir in 1/2 teaspoon lemon zest and 1 teaspoon lemon juice. Let stand 10 minutes then adjust salt and lemon juice to taste. Let stand another few minutes, then serve when it’s just right. Serves 2.

Tart Cherries Too

Tart pie cherries are fun to cook with, crossing sweet/savory barriers with panache. Here, they partner with fresh snap peas in a robust entree salad with a mouth-tingling raw ginger dressing. If you don’t eat chicken, use slim strips of extra firm tofu and let them marinate for up to half an hour to absorb the zippy dressing.

Chicken Salad With Snap Peas & Tart Cherries

1 cup chopped cooked chicken OR thinly sliced tofu
1 cup chopped snap peas in the pod
1/2 cup chopped, pitted tart cherries
1/4 cup thinly sliced red onion strips
4 French Breakfast radishes (or any), thinly sliced
1/4 cup chopped cilantro OR parsley
2 tablespoons minced basil
1/4 teaspoon sea salt
Ginger & Garlic Dressing (see below)

Combine all ingredients, tossing gently with a few tablespoons dressing, let stand 10 minutes. Adjust dressing to taste and serve. Serves 2-3.

Ginger & Garlic Dressing

1 tablespoon cider vinegar
1 tablespoon chopped fresh ginger root
1 clove garlic, chopped
1 organic lemon, juiced, rind grated
1/4 cup avocado oil or safflower oil
1 teaspoon maple syrup
1/4 teaspoon sea salt

In a food processor, combine vinegar, ginger and garlic and 1 teaspoon lemon zest and grind to a fine paste. Add oil slowly, then season to taste with lemon juice (start with 2 teaspoons), maple syrup, and salt. Makes about 1/3 cup.

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Summer Transplanting

Making Smooth Summer Moves

I’ve recently been asked to advise on the moving of a long established garden. My first response was to wait until autumn, but sadly, that isn’t possible. Generally speaking, summer transplanting of mature woody plants is not a great idea, especially in years like this one, when weather swings wildly from chilly and damp to hot and dry. You can certainly plant anything you like from a nursery container, from trees to ground covers, as long as you can keep it adequately watered. However, digging up a large established plant and moving it to a new home is a job best left for cool, rainy autumn.

What’s the difference? Even when we are careful, digging a plant for removal inevitably breaks some of the plant’s roots. When the plant is moved, the rootball will be exposed to drying sun and wind. Even if placed in the shade, a rootball will start dying the moment it’s wrenched from the ground. This is true whether the plant was watered before you began digging or was in totally dry soil. As long as the root system was intact, the plant was probably coping adequately with the heat and drought. The minute their roots are damaged, plants go into shock.

Leave The Leaves

Conventional wisdom suggests that removing some or all of a shrub or perennial’s foliage helps transplanting survival rates. That can indeed work when moving a deciduous plant in October or November (which are good times to move plants). In autumn, deciduous plants are entering dormancy and losing their leaves naturally. Removing foliage doesn’t hurt anything at that season, though it’s often best to leave semi-evergreen foliage in place to protect against frosts that could damage a perennial’s crown.

In summer, a new transplant’s damaged roots can’t take up water or nutrients efficiently. The best way for a damaged plant to nourish itself is through the foliage (photosynthesis). With the foliage removed, the plant does not have much ability to restore itself. The good news is that many plants, especially hardy perennials, are pretty tough. If the rootball contains enough stored nutritional reserves, the lucky gardener may see new shoots within 4-6 weeks of the initial trauma. Unfortunately, the damaged plant will be more susceptible to drought, disease and pests than usual for at least a year after the transplanting experience.

Garden Etiquette & Advance Shovel Pruning

The folks who need to transplant their garden are moving to a new homesite. In their case, the new owners of their former home are well aware that the plants are not staying. The beds will be refreshed with new soil but the new owners prefer to make their own plant choices. This is rather unusual, since in general, people are buying the garden setting as much as the house itself. As a point of garden etiquette, it is customary when selling your house to mark any plants you plan to remove so the buyers know your intention. If at all possible, it’s preferable to arrange to make a return visit in fall, after the rains return, so you can move your plants then.

When that won’t work, you can prepare trees and shrubs for a move by shovel-pruning a few months in advance to make the plant more receptive to the later move. Use a sharp-bladed shovel (made extra sharp with a bastard file) to sever the plant’s outermost roots, demarking the rootball you plan to excavate. Don’t rock the plant or disturb the rootball, but do water it well and mulch the rootball area with 2-3 inches of moist compost. This technique encourages new roots to form within the newly formed rootball, closer to the main trunk. A few month’s notice can mean the survival of a plant that otherwise could not take the stress or removal.

Making The Moves

If you must move a plant in high summer, assess whether the plant is worth moving even if it dies. For instance, the most common summer transplanting questions I get concern Japanese maples. These are easily stressed in high summer, when a very hot day can cause the foliage to scorch or curl badly. Expert tree movers with equipment can usually move a maturing tree successfully, but the average amateur is almost certain to kill the tree. As a rule of thumb, if you can dig the tree yourself and move it easily in a wheelbarrow, you can probably move it successfully. If not…probably not. If you feel you must, pre-cut the rootball, then water the plant well every day for at least a week. On a cool day, or early in the morning, transplant it into a large pot (like a whisky barrel), using plenty of compost, and water it well, foliage and all. Use a hand truck to move the tree into the shade and keep it there for at least another week.

Before loading the tree on a truck for relocation, spray the foliage with an anti-dessicant product like Wiltpruf to keep the leaves from losing moisture during the move. Let that dry, then gently bundle up the branches with soft twine. Wrap the foliage loosely but thoroughly with woven row cover cloth (like Reemay) to prevent wind burn. Now load the plant, supporting it well (I use bags of compost or topsoil) to prevent rolling about in the truck bed.

After Care For Transplants

After the move, keep the plant in light shade for at least another week if at all possible. This transitional area should not be in deep, dank, dark shade, where mildews and molds prevail. Try to find a sheltered spot with good air circulation, where the plant receives gentle morning light but no direct afternoon sun. Ideally, you would leave your tree there until the autumn rains return. In October or November, transplant the tree, making sure the new site offers the proper amount of light and plenty of room for the tree to grow to its full mature size.

Again, use plenty of compost when replanting and carefully place the rootball at the same level it was at before. Planted too deeply, even trees can smother. Planted too shallowly, delicate roots can dry out and die. For anything but rhododendrons, azaleas, or blueberries, add a mixed-species mycorrhizal inoculant, placing it so it touches living roots. This beneficial substance will help the plant produce a healthy new root system quickly, often speeding up its recovery time dramatically.

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Planning A Low Pollen Garden

When The Garden Makes You Weep (Or Sneeze)

After seemingly endless rain, warmer, brighter days feel especially welcome. Our flowers seem to feel the same way, for blossoms on practically everything are bigger and more abundant than ever this year. However, lots of flowers also means lots of pollen, which spells acute discomfort for many people and even some pets. As pollen fills the air and dusts our cars and garden furniture and even us, we may be tempted to rip out the borders and turn them all to lawn. Well, except perhaps those of us who are allergic to grasses. (!) Fortunately there are more rewarding alternatives, since living without gardens hardly bears consideration.

Lowering the local pollen count begins with research. First of all, it helps to know your triggers. Pollen count websites usually list the major offenders at any given time, and sometimes we can simple look around and see which plants are wafting masses of pollen our way. Sadly, some of the worst offenders are mature trees, including willows, alders, cedars, firs, and so forth. Few of us can or would even think about removing all pollen shedding trees, but it’s worth taking time to explore low pollen alternatives to popular garden plants. So far, the best all-purpose resource I’ve found is Thomas Leo Ogren’s Allergy-Free Gardening, which offers both plant lists and strategies for pollen avoidance. Like most things, it comes with a caveat; allergic responses are idiosyncratic, making these and all such lists suggestions rather than fool-proof rules.

It’s A Guy Thing

Since heavy pollen shedders are usually male, we can eliminate probably problematic plants by replacing male clones of garden shrubs. If we’re creating or renovating a garden, it’s also wise to look for female versions of small trees (see more below). We can also select for low pollen production by choosing shrubs and perennials with large, showy, scentless or lightly scented blossoms. Such flowers are usually female and/or pollinated by insects and other critters rather than wind.

Wind-pollinated flowers are prime candidates for allergy triggers, since their light-weight pollen travels companionably to find us wherever we are. Flowers with wind borne pollen tend to be small and less vivid, so showboat flowers are better bets for pollen avoiders. So are bird-friendly plants, which are generally pollinated by nectar-seeking birds. Sterile hybrids of any kind don’t produce pollen at all, making them top picks for especially sensitive sufferers.

Low Pollen Perennials

If you aren’t sure what’s giving you grief, this list may help you figure out which plants are least likely to be the offenders. As always, some of us have specific responses to plants that don’t bother others, but these make better replacement choices for bad boy pollen producers.

Acanthus (bear’s breeches), Achillea (yarrow), Agastache (anise hyssop), Alchemilla (lady’s mantle), Anemone (windflower), Aquilegia (columbine), Astrantia (masterwort), Cynara (cardoon), Erysimum (wallflower), Eupatorium (jo pie weed), Gaura (wandflower), Geranium, Heuchera (coral bells), Hosta, Kniphophia (poker plant), Lavatera (tree mallow), Lythrum (loosestrife), Nepeta (catmint), Oenothera (evening primrose), Penstemon (beardtongue), Perovskia (Russian sage), Phlomis (Jerusalem sage), Phormium (New Zealand flax), Phygelius (cape fuchsia), Potentilla (cinquefoil), Rheum (rhubarb), Salvia (sage), Sedum (stonecrop), Sisyrinchium (blue-eyed grass), Verbena (vervain), Veronica (speedwell), Yucca (Spanish bayonet).

Low Pollen Annuals

Annuals are often bred for dazzle and many produce little or no pollen. Among the most reliable are: Calendula (pot marigold), Clarkia (winecup), Cosmos, Eschscholzia (California poppy), Godetia (satin flower), Nigella (love-in-a-mist), Lunaria (silver dollar plant), Meconopsis (Welsh poppy), Petunia, Tagetes (marigold), Verbena (vervain), Viola (pansy), Zinnia.
Low Pollen Edibles

Most root vegetables are harvested before they flower, and crucifers (broccoli, cabbage, kale, etc.) and alliums (chives, garlic, leeks, onions, shallots) are seldom troublesome.  Some herbs shed lots of pollen (chamomile, artemisias), others do not. Many pollen-sensitive folks can enjoy growing basil, chives, dill, mint, thyme, lavender, fennel, parsley and rosemary without pollen issues. (Many people are sensitive to lavender, but sensitivity to fragrant plants is not usually pollen related.)

Better Bet Grasses

As for grasses, some (like turf grasses) are major offenders in the pollen-shedding category while others produce modest amounts of pollen. Turf grass sensitivities can usually be reduced by regular mowing, but weed and ornamental grasses are another story. Here again, some are major pollen producers (Johnson grass, orchard grass, Timothy grass), while others are generally far less problematic. Here’s a list of beautiful garden grasses that are less likely to trigger allergies:

Anemanthele lessoniana (pheasant tail grass), Arrhenatherum elatius (oatgrass), Bamboo, Briza (rattlesnake grass), Carex (sedge grass), Elymus (lime grass), Nassella tenuissima (Mexican feather grass), Panicum (panic grass).

Low Pollen Shrubs

Shrubs are of course a key element in garden design and as such, can scarcely be left out of the picture. Clipping shrubs and shearing hedges before they bloom are good ways to eliminate allergic reactions to pollen. However, it’s far simpler to replace heavy pollen producers with less stressful plants. For instance, if you love willows (a notoriously heavy pollen producing clan), plant a corkscrew willow, or the weeping form called Weeping Sally, both of which are females. If you hope to avoid excessive pollen exposure from all your shrubs, consider planting some or all of these handsome shrubs:

Aronia (chokeberry), Berberis (barberry), Callicarpa (beautyberry),
Ceanothus (California lilac), Chaenomeles (quince), Cornus (twiggy dogwood), Escallonia, Fuchsia, Holodiscus (ocean spray), Kolkwitzia (beautybush), Lonicera (shrubby honeysuckle), Nandina  (false bamboo), Oemleria (Indian plum), Philadelphus (mock orange), Physocarpus (ninebark), Potentilla (cinquefoil), Rosa (rose), Rosemarinus (rosemary), Santolina (cotton lavender), Spirea, Symphoricarpos (snowberry), Vaccinium (blueberry, huckleberry), Viburnum (guelder rose).

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