Posts Tagged: garden pests
Aphids in the Garden
Aphids can be a scourge in the garden. There are over 4,000 species of aphids in the world, but fortunately only(!) about 250 species are attracted to the plants we grow in our gardens and landscapes.
Aphids are small, slow-moving insects that come in a variety of colors—green, yellow, brown, red, or black. They sometimes match the color of the plant they feed on, but not always. They have long legs and antennae, and usually have a pair of cornicles (tube-like structures) sticking out of their hind end. No other insects have cornicles. Some adult aphids have wings—this can occur when populations are high or during spring and fall—that can allow them to disperse to other plants.
Aphid reproduction is interesting. Adult females can give birth to up to 12 live offspring each day without mating. During warm weather, many aphid species can grow from newborn nymph to reproductive adult in a week. No wonder it seems like they appear overnight.
Aphids are attracted to plants on which they can feed. Plants that are actively growing are prime targets. Right now, these include plants in our winter gardens such as kale and broccoli and landscape plants such as roses, but also the many winter weeds growing abundantly in many neighborhoods.
Aphids have sucking mouth parts, somewhat like little straws. They use them to suck sap (which is a plant's sugar source). What they excrete is commonly referred to as ‘honeydew' which contains sugar and is therefore sticky. Ants are attracted to this honeydew and will actively “farm” the aphids and protect them against natural predators.
Many plants, especially trees and shrubs, can survive just fine with low to moderate numbers of leaf-feeding aphids. Damage can occur with larger populations. Yellowing leaves and stunted growth are common.
Aphids can also transmit viruses from plant to plant on many vegetable crops and ornamental plants. Symptoms can include mottled, yellow, or curled leaves, along with stunted growth.
Controlling aphids
Understanding their life cycle is key to their management. By checking plants twice a week while they are growing rapidly, you can catch infestations early. With small populations of wingless aphids, hosing them off with a strong stream of water works well. Once off the plants, aphids are unlikely to be able to return. You can also prune out the most infested parts. Make sure you also remove nearby weeds that can serve as a reservoir of new infestations.
Natural enemies are important for aphid control. Parasitic wasps lay eggs inside live aphids, causing them to turn into mummies. You can recognize these by light-colored aphid bodies with circular holes on top where the wasp has emerged. Lady beetles (especially the larvae), syrphid fly larvae, and green lacewings are voracious eaters of aphids. See this website: https://ipm.ucanr.edu/natural-enemies/
If spraying with water is not effective enough, insecticidal soaps and oils are the best choices for most situations. Oils include petroleum-based horticultural oils or plant-derived oils such as neem or canola oil. These products kill primarily by smothering the aphid, so thorough coverage of infested foliage is required. Soaps and oils kill only those aphids present on the day they are sprayed, so applications may need to be repeated. Although these products can kill some natural enemies that are present on the plant and hit by the spray, they don't leave a toxic residue.
It is easier to manage aphids earlier in an infestation than later when populations are high. Some aphids cause leaves to curl around them, protecting them from sprays and beneficial insects.
Prevention
- When you purchase new plants, inspect them carefully.
- Don't over-fertilize. Excess fertilizers, especially too much nitrogen, can stimulate plants to put out lush new growth that will entice aphids to set up home.
- Excessive pruning can also stimulate plants to put out attractive new growth.
- Use a row cover, especially on seedlings and new plants. This will keep out aphids but also protect from other pests.
- Control ants that can protect aphids.
For more information, check these websites:
https://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html#TABLE1
https://ipm.ucanr.edu/QT/aphidscard.html
Wingless adults and nymphs
Aphids killed by parasitic wasps become mummies
Three-lined Potato Beetle
Tomatillos (Physalis ixocarpa) are so easy to grow, they are almost weeds. Since I first grew...
Spring Vegetable Gardening Class a Success!
On Thursday, February 7, the University of California Cooperative Extension (UCCE) Stanislaus...
audience
Can You Outsmart the Crow In Your Garden?
Garden Advice from the Help Desk of the
UC Master Gardeners of Contra Costa County
Description of the client's problem:
Advice from the Help Desk:
Crows have become more prevalent in Contra Costa County in the past 15 years, mainly moving in from the decreasing agricultural areas of east County. They are large (17 to 21 inches long) and intelligent birds. Crows are omnivorous, opportunistic feeders that eat a wide assortment of foods, such as grain crops in agricultural fields, seeds and fruits, insects including pest species like lawn grub larvae, bird eggs, earthworms, fish, amphibians, reptiles, carrion and road kill, and a variety of human-associated food, ranging from pet food to garbage.
If they are digging in your lawn, here is a link to information from the University of California on how to control lawn insects: http://www.ucdavis.edu/PMG/PESTNOTES/pn7476.html. Some treatments may not completely take care of the problem and there are other pests, such as raccoons and skunks, that may be causing the damage.
Scare tactics can be effective in dispersing crows. Frightening devices include loud sounds and motion-sensing water sprinklers. In a residential neighborhood you probably want to avoid noise rockets, so the motion-sensing sprinklers are your best bet. These are attached to a hose (one model has its own reservoir) and when it senses motion, it fires off high-pressure water. Some also emit ultrasonic sound but birds don't hear at that frequency so it is probably not helpful. You can do an Internet search for “motion sensing sprinklers” or you may also find them at a local nursery, hardware store or home improvement store.
Farmers have been trying to protect their fields from crows and other birds for centuries. One method is to stretch a cord or a fine wire at intervals across a field at heights about six to eight feet above the ground. Aluminum or cloth strips can also be tied to the wire. The reason why this works is not entirely clear, but the wire appears to represent an obstacle that is difficult for a flying bird to see, especially when rapid escape may be necessary. You might try temporarily stringing lines above your lawn to see if this will deter them. Another website that may be of interest is: http://icwdm.org/handbook/birds/AmericanCrows.asp.
Crows are very intelligent birds and many have become habituated to people and our attempts to discourage them. They have often lost their wariness and, unfortunately, may not respond to any of these suggestions. If you find a new and effective technique, please let us know.
********************************
Editor's Addendum: In reviewing and preparing this blog, I also reviewed a recent web interview at http://awaytogarden.com/the-gifts-of-the-crow-with-john-marzluff/ specifically about crows by the noted ornithologist Dr. John Marzluff, professor of wildlife sciences at the University of Washington. My take-away message from the interview is that you have a formidable and intelligent garden opponent and friend in the crow. I highly recommend the web interview.
********************************
Help Desk of the UC Master Gardeners of Contra Costa County (SEH)
Note: The UC Master Gardeners of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Blog (//ucanr.edu/blogs/blogcore/blogroll.cfm).
Stalking Big Game in Your Garden
The allure of stalking game wasn't something I understood until I spent a perfect day planting...