Spring’s Earliest Pests: Aphids

Jean R. Natter, OSU Extension Service Master Gardener

After all we’ve been through this past year, what with the COVID pandemic and quarantine, gardeners are getting itchy about planting. I was, too, until the middle of March when night time temperatures dropped into the 20s in mid-March. I imagine it was even colder for many of you.

Even though my dreams of planting soon were dashed – tomatoes, peppers and eggplants need consistent night temps of 50 to 55F – my thoughts soon drifted to insect pests, then to their natural enemies.

The leaders of the potential pest parade will be various species of aphids, also several kinds of caterpillars, the latter specializing on crucifers (cabbage and kale crops), among them cabbage whites (Pieris rapae) and several species of cabbage worms. Unfortunately, various species of both kinds may be present throughout the growing season.

Oh, and let’s remember that slugs and snails are ever-present through the season.

So, let’s review a few things, including safe management.

We should begin with the preferred pest remedy: An alert gardener, ready to spring into action, who knows which natural enemies (NEs) are allies, and who acts promptly. Prompt action, aided by the numerous beneficial insects already present, means pesticides are often unnecessary.

Aphids are small, soft-bodied, pear-shaped pests that tend to cluster on new growth which they sometimes distort as they remove plant sap from plant parts. (If you have roses, you’ll likely see them there first.) Aphids may be almost any color, perhaps even spotted, banded, or striped. Most infest buds, flowers and new leaves, often distorting them which sometimes mimics disease.

Caterpillars, also called chewing worms, are the plant-munching larvae of various moths and butterflies. (More about caterpillars next month.)

Recall that pest control is a lot like mowing the grass; it requires repetition. You get to do it over, and over, and over, again. (sigh)
Always start with the safest methods, namely search-and-destroy missions throughout the garden or ornamental planting. Reserve pesticides for those instances when the pests get out of hand. Always identify the pests and apply the appropriate product only to the hot spots of pest insurrections. Then, too, use pesticides strictly according to label directions.

As you likely know, aphids of one kind or another are present year-round locally. They’re perhaps the most common plant pest you’ll encounter. Aphids pierce plants with their hollow mouthparts to withdraw sugary fluids. Often, they’re undetected until leaves curl or the plant is coated with sticky honeydew (aphid excretions). Repeated sharp water sprays are often sufficient against aphids. Or increase your fire-power with a commercial insecticidal soap such as Safer’s, mixed according to label directions. For soap sprays to be effective, they must contact the pests. No home remedies, please; they may damage plant tissue.

Fortunately, you have lots of free help readily available among insects. Your skilled assistants (the NEs) are typically most active during the morning and late afternoon but hide during the heat of the day.

Ladybugs (aka lady beetles) are the most colorful aphid killers. Most of these ¼-inch, glossy, hemispherical adults are red, often dotted with black. The ladybug’s elongated ¼-inch youngsters are quite different, resembling the tiniest of alligators. Their soft bodies are slate-gray or black with tufts of dull orange hairs. Both adult and child chomp on aphids. In time, even the aphids’ toes will be gone.

In spite of advertising hype promoting sales of ladybugs, realize that they typically leave for other bug-filled garden. But, if you are determined to purchase natural enemies, know that lacewings are more valuable

because their diet is more diverse. After lacewings decimate the aphids, they’ll switch to other small, soft-bodied pests including young caterpillars, various insect eggs, or even mites.

Hereabouts, lacewings are naturally present year-round. You’re most likely to see the fragile, 5/8-inch, filmy-green adults fluttering from shrubs at dusk. The larvae are the aphid eaters, though. Look for 3/16-inch tan or gray, soft-bodied creatures similar to ladybug larvae but with Jaws that resemble old-fashioned ice-tongs. Eggs are easy to recognize, they’re small, greenish-white, and mounted on hairlike stalks.

Worm-like larvae of certain flies also kill aphids. The largest larvae (Syrphid flies, aka flower flies) are about 1/4 inch long but are difficult to spot because of their greenish or grayish color whereas the tiny, almost dot-sized, orange fellows (Midges) are easy to spot because of their color. All such larvae search for lunch by blindly groping. Just as do lacewing larvae, fly larvae pierce aphids, drain them, then abandon the empty carcasses.

Tiny, non-stinging wasps kill aphids, too. After they insert an egg into an aphid, their larva dines inside the aphid as it gradually transforms into a bloated, papery shell. Some weeks later, an adult wasp exits through a circular hole created in the aphid’s empty exoskeleton.

Impatient folks who would rather fight than wait for NEs to break into action need to understand that water,plain, or doctored with insecticidal soap, kills aphids but is safe for most helpful insects. Commercial pesticides are useful for uncontrolled hotspots but most kill more NEs than pests. When a pesticide is needed, consult with a garden center, then always follow label directions precisely. Because sprays rely on contacting the aphids, act before the pests are protected within crinkled and distorted leaves.

Power-assisted blasts can help you gain control quickly.Forceful water sprays are appropriate for sturdy plants whereas gentler handling is better for plants with rather soft tissue, among them such as violas and leafy lettuces. Aphids are so soft and squishy that harsh water sprays will injure them such that they’re unlikely to return to the plant. But, because healthy, intact aphids can give live birth to an aphid every 20-30 minutes, you’ll need to repeat the spray anyway. With more potent products, the goal is to only spray enough to coat the pests.

Realize that plant damage is possible with all pesticides, including soaps.That’s especially true if the spray is applied on a sunny day or was inadvertently – or not — mixed at too strong a rate. It’s always wise to test the spray on a few plants, then check for damage several days later. Browned or burned plant tissue is obviously serious whereas soap smudges are merely unsightly.

Resources:

• Sustainable Gardening: The Oregon Master Gardener Handbook

• Aphids: http://ipm.ucanr.edu/QT/aphidscard.html

• Lady Beetles: http://ipm.ucanr.edu/QT/ladybeetlescard.html

• Book: Pests of the Garden and Small Farm (ANR #3332; University of California)- Available at booksellers.

• Book: Natural Enemies Handbook {ANR #3386; University of California)- Available at booksellers.

• A Pocket Guide to Common Natural Enemies [revised 2021] https://catalog.extension.oregonstate.edu/ec16 13

Coming next month: Cabbage Worms and Other Chewers

Natter’s Notes

Jean R. Natter, OSU Extension Service Master Gardener

Once again, the annual Gardeners’ Itch is surging. That’s in spite of the mid-February snow storm that likely afforded one last browse through catalogs, or possibly created a faint cloud of apprehension as you wondered why you bought so many seeds.

Start your project with new containers or thoroughly wash used ones. Just about anything will do as long as it’s at least two inches deep and has drainholes. Plastic containers are a good choice as they slow moisture loss. Consider multi-celled propagation trays; 6-packs you’ve saved from previous years; individual small pots; or use 4- or 5-inch pots as community pans, each one with a different kind of seed.

If you’ll use individual peat pellets, pre-soak well prior to seeding. Then set them side-by-side, one pellet touching the next, thereby increasing moisture retention a bit. After the seeds sprout and begin to develop roots, the pellets will dry rapidly. You might consider a multi-cell tray with individual units the perfect size to hold just one pellet.

The method using individual peat pots is similar. Pre-soak the pots, fill with seeding mix, plant the seeds, then water to settle the mix. But when you transplant to the garden, strip off the peat pot to allow the roots unhindered access to the garden soil.

Fill your containers with a sterile, fine textured growing medium. Do it the easy way with a commercially-packaged seed-starting mix because they’re formulated to drain well in shallow pots. A bonus: The mix is sterile, that is, as long as you don’t set the filled pots on the ground.

Instead of scooping potting mix to fill the pots, use a professional trick to ensure the media remains light and airy, two qualities which guarantee good-sized air spaces that, in turn, allow excellent drainage.

To do so:

a. Set your containers in a group, the sides touching each other.

b. Slightly moisten the media: Add hot water and toss gently to combine, until the media is barely moist throughout.

c. Pour the barely moist media into the containers.

d. Level off excess media with the side of your hand. 

e. Pick up each container and gently tap it onto a hard surface 3 times from a height of 4 inches.

f. Lightly tamp the surface of the media in each container, just enough to level the surface.  (An excellent “tamping tool” is the bottom of another container that matches the available surface area.)

Sow your seeds on the surface of the mix.  Drop one or two seeds onto the surface of each of the smallest units.  If you’re using 4-inch pots, sparsely sprinkle about 20 seeds over the surface. With still larger containers such as a nursery flat, first create shallow rows, then seed. 

Cover the seeds with moist media, the depth to match the diameter of the seed.  Large seeds – such as beans, corn, radish, and squash – are best sown directly into the garden but, for these, wait until the soil is warm enough for rapid germination. Corn and basil planted early will fail.

Water each container thoroughly by setting it in water. Remove when the surface glistens with moisture, allow to drain, and set in a bright, moderately warm place. Alternately, group the pots in a nursery flat and use a gentle spray, moving it back and forth, to thoroughly moisten the media.

Create a mini-greenhouse, of sorts, for your seeds by slipping its pot into a clear container of some sort.  Match the “greenhouse” to the size of your project.  Use what you have at hand, perhaps a clear plastic bag which rests on bamboo sticks to allow head room; or clear plastic storage boxes such as those for shoes and sweaters.

Set the ‘greenhouse’ in a warm but not sunny place. If needed, lift the cover briefly to vent excess moisture that accumulates on the insider.

Seedlings require bright light! As soon as the seeds sprout, the main challenge is to provide enough light to develop sturdy seedlings.  Sunny windowsills rarely provide adequate bright light for seedlings.

Some folks use a commercial light stand but you can substitute a 2-tube fluorescent fixture suspended 2 inches above a workbench holding the plants. Suspend the fixture on chain so that you can adjust the height as the plants grow. My old-school strategy of one cool white and one warm white tube works well. The plantlets will thrive with 16 hours of light a day.

Seedlings will also benefit from a slightly lower temperature at this stage. On average, daytime temps of 65 to 70°F and nighttime temps of 55 to 60°F are adequate. Then, too, if seedling roots dry out, they die! Watering from the bottom is a gentle method, but dump the excess within 20 minutes.

Seedlings also require fertilizer! Begin fertilizing when the cotyledons ( seedling leaves) are flat out. Use fertilizer-enriched water at half-strength for every other irrigation. And always transplant seedlings, either to a larger pot or to the garden, when the first set of true leaves expand.

Always transplant seedlings when the first set of true leaves expand. But recall that you’ll need to harden off the seedlings prior to planting outdoors. Hardening off means to prepare tender, indoor-grown plants for a harsher life outdoors. (See “Sustainable Gardening.”)

And finally, be aware of the potentially unhappy side of gardening: Herbicide carryover in manure compost. And that’s true whatever the source, free or commercial. I recently responded to an Ask Extension inquiry from a gardener whose vegetables were affected during 2020. (See resource list for online links.)

Resources

• “Sustainable Gardening” – Your trusty, research-based MG Handbook.
• “Growing Your Own” – A free tabloid with an extensive planting chart for vegetables (Page 7 and various helpful gardening information. The metro counties are in Region 2. (https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9027.pdf)
• “Herbicide Carryover in Manures,” an overview – https://puyallup.wsu.edu/soils/clopyralid/
• “A Simple Bioassay for Herbicide Carryover” is an easy test to ensure safety for your plants. – https://s3.wp.wsu.edu/uploads/sites/411/2014/12/PDF_Clopyralid_Bioassay.pdf
• “What to do about Herbicide Carryover in the Garden” clearly outlines remediation. –https://pesticides.montana.edu/reference/contamination.html

Natter’s Notes

Jean R. Natter, OSU Master Gardener

In case you haven’t been outdoors recently, you need to know weeds are growing in spite of the soggy soil from all the recent abundant, rainfall. So, let’s review a few strategic management strategies for successful weed control in gardens and landscapes. As you may know, the PNW Weed Management Handbook (see resource list) has a thorough overview of the subject.

Annual weeds are classified as warm-season or cool-season plants, with each kind genetically destined to germinate (sprout) in the appropriate season, then survive for a year or somewhat less. The same categories are assigned to perennial weeds but these are considerably more long-lived, persisting for 3 or more years.

As a result, gardeners must be vigilant year-round.  

Several key principles limit weed populations in gardens and landscapes, among them these:

– Kill weeds when they’re young; ten fingers are always at hand.

– Don’t allow weeds to set seed.

– Annual weeds will die when cut just below the crown.  Use a knife, or any one of various hoes – standard garden hoe, diamond hoe, or a scuffle hoe.

– Perennials will re-grow when cut off, even if covered with mulch  Vigorous kinds will make it through a lasagna garden; and may lift landscape fabric and/or polyethylene sheeting. 

– To kill perennial weeds, you must starve the roots; to do so, remove all green growth every week for as long as it takes, very likely several years.

– Herbicides are rarely a “once-and-done” remedy.

Gardeners can make good use of creating a “stale seedbed” before planting a flower or vegetable bed, or even a lawn. The reason?  Hundreds of dormant seeds — termed the “Soil seed bank” – have been deposited in the soil during years and years of poorly managed, or unmanaged, weeds. Whenever soil is disturbed, some of those seeds are brought near the surface where they germinate because they are exposed to light, also appropriate temperatures and moisture.  

Start a stale seedbed a month or so prior to the desired planting date, thereby allowing for a cycle or two removing weed seedlings.  Do everything needed to prepare the planting bed: dig; remove obstructions and weeds; amend the bed; level the soil; then moisten the soil to settle it and allow for germination.  As soon as a good stand of young weeds about inch tall is present, destroy them using your preferred method: hand, hoe, flamer or, if you must, herbicide. 

The earlier a stale seedbed is started, the more germination cycles possible, the fewer weeds will be present to steal water and light from the desired crop.  Next, seed or transplant your veggies or flowers with minimal disruption of the soil, and deal with any seedling weeds promptly.

With perennial weeds, choose among these destructive techniques:

1. Dig it out; repeat as needed.

2. Cut it off; repeat as needed.

3. Herbicides are effective if the right kind is used according to label directions; repeat as needed for re-growth and/or use #1 and #2, above.

Tools to help limit weeds:

– Hands

– Hoes

– Herbicides, organic or synthetic: Contact products kill only top growth (fine for annual and seedling weeds); systemic products translocate (move) into other plant parts, sometimes into roots.

– Mulch, with the understanding that new weeds, in the form of seeds, will continue to arrive via clothing; muddy boots; new plants; birds; hitchhikers on mowers; or may be blown in.

– Flamer

Some trees are known to put up root suckers after they are cut down, among them are such broadleaf trees as ash, aspen, cottonwood, flowering cherry and poplar.  Conifers won’t re-sprout, even if the roots remain in the ground.

To limit root sprouting after a broadleaf tree is removed:

– Cut down the tree as soon as the new leaves have fully expanded in spring. 

(Principle: The tree used most of its reserves for new foliage, thus the stump/roots will put up fewer sprouts than if the tree is removed later in the season.)

– Immediately after the tree is cut off, paint a 2-inch-wide band of the other edge of the cut surface with an herbicide such as triclopyr or 2,4-D, following label directions.

– Remove new shoots as soon as they’re seen:

       – The more often new greenery is removed, the better the chances of decreasing the roots’ reserves; once a week is a good plan.

       – The longer new growth remains, the more reserves it sends to the roots, thereby extending the battle. 

– Be persistent and you will win; pause for a season and you lose.

Resources

– Sustainable Gardening (your MG Handbook)

– Weeds and Your Garden: https://ecommons.cornell.edu/bitstream/handle/1813/43859/weeds-in-garden-bro-NYSIPM.pdf;sequence=1

– PNW Weed Management Handbook: Online at  http://pnwhandbooks.org/weed/horticultural/home-garden-landscape-management  

– PNW Weed image gallery (from the 2010 Weed Handbook): Organized by common name, each weed with 1 to 3 images: seedling, flower and/or mature.  http://uspest.org/pnw/weedimages?weeds/id/index.html

– Weeds and other unwanted plants (text and images)  http://ipm.ucdavis.edu/PMG/menu.weeds.html