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Multiple Stages of Aphids

Rx FOR HEALTHY ROSES - SUCKING PESTS
by Nanette Londeree, Master Rosarian

It’s the prime time of year for the first wave of pests to come visiting. Spring brings longer days, warmer temperatures and explosive growth on your favorite plants. Those same conditions are perfect for many insects to go from their overwintering, dormant state to their active stages. If you’ve got bad bugs on or around your roses, it’s a good bet that they’re “suckers,” pests that feed by poking a hole in tissue and drawing out the plant fluid, or rasping (scraping away plant tissue) and sucking. These are the bad actors in the garden - not only do they cause direct damage to tender foliage and delicate blossoms, but as they suck out plant sap, many pump out a sweet, sticky substance called “honeydew” that collects on leaves and stems. That sugary substance attracts ants, and supports the growth of sooty mold, a black fungus, rendering it rather ugly and reducing photosynthesis. And to add insult to injury, the sucking insects sometimes transmit disease to roses in the process of feeding.

The most prevalent sucking pests in the rose garden this time of year are aphids, leafhoppers, scale and thrips. These pests go through an incomplete metamorphosis – the young resemble adults upon hatching except they are smaller and without wings. As they grow, they molt leaving cast skins behind (a good diagnostic sign). Symptoms of direct damage from sucking pests include spotting, stippling or bronzing of leaves, curled, puckered or malformed leaves and petals or leaf and stem distortion.

Aphids, spittlebugs and leafhoppers may look grotesque but are usually not too harmful to the plant unless in huge numbers. They’re also the easiest to get rid of. There are loads of chemical products available to spray these little beasts into oblivion, but generally, they’re not necessary to either get rid of them, or reduce their population to a tolerable level. Some suggestions for managing the “suckers” in your garden include:

  • Cultural methods – provide plants with good growing conditions and proper cultural care, especially appropriate irrigation so they are more resistant to attack; vigorous plants usually outgrow damage. Remove and dispose of old, spent flowers and other garden debris. A major attractant to sucking pests is lush new growth so go light on chemical fertilizers high in nitrogen; use less soluble forms of nitrogen and apply it in small portions throughout the season rather than all at once.

  • Mechanical and physical methods – many sucking pests are soft-bodied and a blast of water can knock them to the ground. If pest populations are localized on a few curled leaves or new shoots, prune the areas out and dispose of them. If you see ants (they protect the honeydew-producing pests from natural enemies), put a band of sticky material (Tanglefoot, etc.) around the base of the plant to prevent the ants from getting up. Teflon products, which are too slippery for ants to climb up, have also been used. Dusty conditions often lead to spider mite outbreaks; rinsing off foliage and areas around roses to remove dust can help reduce infestations.

  • Biological methods – many predators love to dine on soft-bodied sucking pests; provide habitats that encourage natural enemies like lady beetles, lacewings, minute pirate bugs and syrphid flies.

  • Chemical methods – there are lots of products to choose from to control sucking insects, though most infestations don’t warrant getting the “big guns” off the pesticide shelf. Start your management approach with the least toxic chemicals; reach for a broad spectrum product (they kill anything they contact) only as a last resort.

    Spittlebug Nymph

  • A dormant spray with horticultural oil may help reduce pests from overwintering. Sun Spray’s Ultra-Fine Horticultural Oil Spray is a parafinic-oil product that can be used year-round to smother a wide range of pests. Safer’s Pest Out is a composite of botanical oils from cotton seeds, cloves and garlic, and is an Organic Materials Review Institute (OMRI) listed material. OMRI is a national nonprofit organization that lists (or approves) products allowed for use in organic production and processing. (Both labeled Caution)

  • Garden Safe Brand Rose & Flower Insect Killer is purportedly effective at managing aphids, leafhoppers, thrips, whiteflies (another sucking pest that doesn’t usually bother roses) and mites. It contains potassium salts of fatty acids as the active ingredient along with a small amount of ethanol. (Labeled Caution)

  • Botanigard ES represents a newer type of pest control; it is labeled as an “emulsifiable suspension mycoinsecticide” which roughly translates to a liquid containing a fungus (it contains live spores of the naturally occurring fungus, Beauveria bassiana Strain GHA) that can be mixed with other liquids. It is targeted for control of aphids and thrips, along with mealybugs and whiteflies. (Labeled Caution)

  • Probably the most challenging of the sucking insects to manage is scale, though not often a problem on rose plants that are pruned heavily each year. Enstar II is a biopesticide insect growth regulator labeled for use against both soft-bodied and armored scale. While available to consumers over the internet, it is not intended for home use. (Labeled Warning)

  • Pyrethrins are naturally occurring, potent pesticides derived from chrysanthemums. Pyganic EC contains pyrethrum and, according to the label, provides rapid knockdown and kill of more than one hundred plant pests including many sucking types – aphids, leafhoppers and thrips. It is OMRI listed. (Labeled Cautio)

  • Pyrethroids are synthetic products that have a similar mode of action to naturally occurring pyrethrins. Bayer’s Advanced 3-in-1 Insect, Disease & Mite Control is a triad of chemicals aimed at insects, mites and disease. The insecticidal active ingredients are the pyrethroid fluvalimate along with a neonicitinoid imidacloprid; the combination controls a wide range of pests. (Labeled Caution)
  • Though many pesticides are labeled “Caution,” do read the label before using to determine their effect on beneficial insects, bees, and other wildlife. It’s not worth knocking out lots of good guys just to get rid of some of the sucking nuisances in the garden.

    Photo of aphids is by the author, Nanette Londeree. Photo of the spittlebug is courtesy of David Cappaert, Michigan State University, http://www.bugwood.org/.

    Author’s disclaimer: Inclusion of a product in this series of articles does not constitute endorsement either by the author or the Marin Rose Society. Products are included for informational and descriptive purposes only.


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    Last Modified: 08/06/2013