Veraison refers to the time when grapes begin ripening.
If you grow grapes, you know that they start out as clusters of tiny spheres that don’t look anything like a grape. As they grow, they become more grape-like in appearance, but you wouldn’t want to eat one. An unripe grape is tough and very sour.
Grapes first grow to full size and then veraison begins. This is when acidity drops and sugar levels rise. This is also when grapes start to change color. Scientists do not know what triggers veraison, but now you know a garden word that most other people do not!
Pheromone traps use chemicals to trick insect pests.
We all know that smell is a powerful trigger for many species. Smell is why we are drawn to freshly baked bread, why we are soothed by lavender and vanilla, and why we wear cologne and perfume. The chemicals that stimulate these and many other responses are called pheromones.
Pheromones are chemicals that stimulate a response within a species. Since most insects only live for a single season, reproduction is critical to species survival. Insects frequently use pheromones to find each other. Pheromones are categorized according to the response they stimulate:
Most over-the-counter pheromone traps are of the sexual variety. They use synthetic female pheromones to attract males. Chemical signals loft into the wind and are picked up by sensory receptors on a male insect’s antenna. He follows the trail in search of love. What he ends up finding, in most cases, is a paperboard tent lined with a deadly stickum, right next to a little tab of luscious pheromones. In other cases, he may find a tray filled with powdered female pheromones. He joyfully rolls in it, finds nothing, and flies away - smelling like a female. Alas for him, in either case.
What pheromone traps can and cannot do
Pheromone traps interrupt mating. They do this by confusing the males with all the extra aromas and by trapping them on the sticky goo. Contrary to packaging claims and popular opinion, pheromone traps are not effective at eliminating a specific type of pest. In fact, they can do just the opposite! Your lone apple tree may have skirted a codling moth disaster until you hung a pheromone trap in it. Suddenly, every codling moth on the block wants to party at your house!
Proper use of pheromone traps
To be effective, pheromone traps are used to monitor specific areas for invasive or particularly destructive pests. Pheromone traps to help you to determine the best time for particular treatments.
How to use pheromone traps
Since pheromone traps are species specific, you must first identify the pest you are trying to monitor. Next, you need to learn the best time of year to employ pheromone traps. These tips can help you make the most of pheromone traps:
As the number of trapped insects changes, you can see become more aware of the rise and fall of breeding populations. This provides you with the information you need when deciding on which insecticide or other treatment plan is best suited to your garden or orchard. [If you feel like getting really technical, you can also calculate degree days for more effective information.]
Insects monitored using pheromone traps
Since reproduction is so important to short-lived species, pheromone traps continue to be an effective monitoring device for a large number of insects. Some of the most troublesome Bay Area insect pests that are monitored using pheromone traps (during specific time frames) include:
Crops best suited to pheromone trapping
Pheromone traps do not provide benefits to all crops. The most common applications of pheromone traps include:
Don’t be put off by this shift from quick-fix solution to data collection and informed decision making. The extra knowledge and effort can spell the difference between hosting a party of undesirables or producing an abundant crop of delicious food.
Blistered leaves and warty twigs are signs of eriophyid mites.
Eriophyid mites are a family of microscopic plant parasites that include blister mites, gall mites, bud mites, and rust mites. While you will probably never see them without a 20x hand lens, at 1/100” in length, they can be a translucent yellow, pink, white, or purple, with two pairs of legs up near the head.
Symptoms of eriophyid mite feeding include:
Blister mites commonly attack beech, boxelder, cottonwood, elm, maple, live oak, walnut, willow, poplar, roses, privet, and alder. Unfortunately, they also feed on tomatoes, peach, apples, pear, and grapes. I have also heard of them on plum trees in the Bay Area. Eriophyid mites spread on the wind, so there isn’t much you can do to stop them from showing up in your landscape. Luckily, the damage they cause is mostly aesthetic and poses no real threat to otherwise healthy plants. That being said, who wants warty leaves or scabby twigs? Also, eriophyid mites may also carry viruses that can cause real damage.
Insecticidal soaps and horticultural oils can be used on heavy infestations, but simply removing affected leaves, buds, flowers and twigs is really all that’s needed. Sulphur and neem oil have also been shown to be effective. Before you work too hard at getting rid of these minor pests, you may want to keep in mind that the eriophyid mite serves as a replacement food for predatory spider mites and other beneficials, when their foods of choice are absent.
Isn’t it nice to know that some problems in the garden are not big enough to worry about?
You reach in to deadhead a rose and a tiny white insect flies out from under a leaf. On the underside of that leaf is a strange white spiral. You have discovered whiteflies.
Whiteflies are not related to flies at all. Instead, they are close cousins to aphids, mealy bugs, soft scale and armored scale.
Whiteflies got their name because most whitefly species look like tiny white flies. Adult bodies are actually yellow, but it’s hard to see. They have 4 white wings and are often no bigger than 1 mm. Some whitefly species are black or yellow. You can see a chart of the most common whiteflies found in California at the UC IPM Pest Note on whiteflies.
Whiteflies are quick and very difficult to see. It is much easier to tell if a garden is infested with whiteflies by noticing white spirals on the underside of leaves. These spirals are whitefly eggs. The adult walks a spiral path, laying eggs in a waxy trail that holds the eggs to the leaf. In warmer parts of California, whiteflies can breed year-round. Whiteflies go through four instars. Eggs hatch out nymphs (crawlers). The next three stages are nearly immobile, much like scale insects. The final instar is a pupal stage. At each stage, these pests are sucking plant juices, spreading disease, and leaving a behind drops of honeydew. Whitefly larval feeding can distort leaves and cause significant losses in some vegetable crops.
Whiteflies can reproduce at mind-boggling rates. They use piercing mouthparts to suck the sap from the phloem of a wide variety of garden edibles and ornamentals. Heavy infestations can cause leaf drop. The honeydew (sugary poop) left behind is host to sooty mold. Honeydew also attracts ants, which then protect whiteflies from their natural enemies. Some whitefly larva may transmit viral diseases and adults can also carry pathogens. Low whitefly populations are not a significant problem, but they can make citrus, pomegranate and avocado trees look shabby.
How to control whiteflies
Natural predators are the best defense against whitefly. Very often, population explosions are caused when gardeners apply broad-spectrum pesticides that kill off predators, or when ants are allowed free access to host trees. Ants can be prevented from protecting whiteflies by applying sticky barriers around the trunks of trees and shrubs. Dusty conditions can also put the odds in favor of whiteflies. Hosing off dusty plants can help reduce whitefly populations.
Heavy whitefly populations are very difficult to control. Any leaves with whitefly eggs should be removed and discarded. If the leaf looks particularly healthy, you can simply rub your thumb over the eggs to destroy them. Reflective mulches repel adult whiteflies, aphids, and leaf hoppers. Also, yellow sticky traps can be used to trap and monitor whitefly populations.
According to companion planting lore, whiteflies can be discouraged from an area by planting basil, mint, thyme, and nasturtium. Whitefly predators, such as parasitic wasps and flies, and hummingbirds, can be attracted to an area by planting zinnias, bee balm, hummingbird bush, and pineapple sage.
California is famous for its wine grapes, but did you know it is easy to grow your own table grapes at home?
Not only will you get sweet, luscious grapes, but the vines can be trained over a patio or pergola, providing a nice shady spot in summer!
How to grow grapes
Pruning grape vines
The variety of grapes being grown determines which of two pruning methods to use.
Grapes are either spur-pruned or cane-pruned. This is because different grape varieties produce fruit on different bud spurs.
‘Thompson Seedless’ and ‘Concord’ are cane-pruned grapes. Cane-pruned grapes should be pruned so that 2-4 horizontal arms (‘bilateral cordons’) can be trained along each of the horizontal trellis wires. One cane-pruning method is called the Four Arm Kniffen method and the University of Maine offers an excellent how-to video here.
Spur-pruned grapes are more productive so it is necessary to limit their crop to only two canes per wire. ‘Flame Seedless’, ‘Tokay’, and ‘Ribier’ are spur-pruned grapes.
In either case, you will want to trim each cane to have no more than 14 spurs. Otherwise, all the plant’s energy will go into vegetative growth, rather than producing grapes.
While most of a grape vine’s roots are in the top 3’ of soil, some of those roots can go down as much as 15’ deep! Grapes perform best when they are watered deeply and allowed to dry out between waterings. The amount of water needed depends on the type of soil, the depth of the roots, and the weather. At the peak of summer, grape wines may need 8-10 gallons of water per day, if a drip system is being used. On average, a deep watering every 2-3 weeks, during summer, is adequate. During cooler or wet weather, little or no water is needed. Once your vines have bloomed, it is important to water regularly, rather than allowing the soil to dry out. As fruit develops, erratic watering can lead to water-stress and cracked fruit.
Feeding grape vines
If grapes are being grown in rich soil, nothing needs to be added. Too many nutrients can reduce or eliminate fruit production. Remember, in the plant world, it’s all about reproduction. Grapes are the reproductive part of the vine. If the plant doesn’t feel the need to reproduce, it won’t.
Assuming your soil isn’t perfectly rich, nitrogen and potassium can be added before berry set. (‘Berry set’ is when the grapes are 1/4” in diameter.) Zinc should only be added before the vines bloom. The only way to know if these additives are needed is to have your soil tested by a reputable lab.
To reduce the chance of pest problems, harvest grapes as soon as they taste ripe. Unripe grapes will not ripen off the vine. Grape clusters should be cut, not pulled, from the vine, and then cooled after being harvested. Do not rinse grapes off before storing them. Do that just before eating.
Pests & diseases of grapes
Spider mites, aphids, mealybugs, cutworms, thrips, click beetles, leafhoppers, branch and twig borers, and ants can infest grape vines. Diseases such as Eutypa Dieback and Pierce’s Disease can infect grape vines and powdery mildew is a common problem. Birds and rodents can also wreck havoc on your harvest. Monitor grape vines regularly for these pests and diseases to ensure timely control. Contact your local County Extension office for information specific to your region.
While grape vines take some time to become productive, an established grape vine can produce fruit for 50-100 years! Only one or two vines are needed to provide a family with an abundance of grapes.
Get yours started today!
I hope this information inspires you to grow more of your own food. You can ask your garden questions on my Home page.