By Brent McGhie, Butte County Master Gardener, November 13, 2015
Peach leaf curl is a fungal disease affecting only peaches and nectarines. Its distinctive symptoms include the curling, reddening, and thickening of leaves as they open in the spring. Diseased leaves will die and fall off, but are usually replaced by new, healthy leaves once the weather becomes warmer and drier. Still, if this disease is left untreated, defoliation can lead to sunburned limbs followed by borer attacks. Over several years, affected trees may decline and fruit production can be reduced.
To prevent peach leaf curl, trees must be sprayed with a fungicide after their leaves have dropped and they are dormant. This is usually in late November, or December. If it is a particularly wet winter, a second application of fungicide can be made in early spring, just as buds begin to swell. An easy way to remember is to target spraying for “curly leaf” at Thanksgiving and again at Dr. Martin Luther King's Birthday. Once peach leaf curl symptoms appear (when trees leaf out in the spring) it's too late for anything to be done to stop the disease. Spraying after symptoms show up is ineffective and removing diseased leaves or shoots will not remedy the problem.
For the home gardener, there are two treatment options. The most effective is the fungicide chlorothalonil (commercially sold as Daconil, Fung-onil, and Ortho Garden Disease Control, among other brands). However, it must be handled with care because it is listed as a likely carcinogen and can cause skin and eye irritation if handled improperly or if protective clothing and equipment (gloves and goggles) aren't worn. A somewhat less effective treatment is copper ammonium complex sold as Liqui-Cop (a Monterey Lawn and Garden product), or Kop R Spray Concentrate (a Lilly Miller brand). It can be made more effective by applying it with 1% horticultural spray oil in the spray solution. As is the case with all garden chemicals, be certain to read and follow all cautions and instructions on the label.
If you prefer not to spray, you can avoid leaf curl by planting resistant varieties of peaches and nectarines. Resistant peach varieties include Frost, Indian Free, Muir and Q-1-8. Although the Frost peach variety is very resistant to leaf curl, it must receive fungicide applications in its first two to three years of growth. Kreibich is a nectarine variety that is resistant to leaf curl.
Citrus blast and brown rot are diseases that attack citrus trees. Although citrus blast is caused by a bacterium that attacks leaves and shoots and brown rot is a fungal disease that causes fruit to rot and turn brown, both of these diseases can be controlled by spraying with the same copper ammonium complex used to treat peach leaf curl.
When heavy rain, high winds and low temperatures occur together, conditions are optimal for citrus blast, especially on the windward side of the tree. Leaves affected by this disease have a withered, bleached appearance, as if “blasted” by a blow torch. Diseased leaves and twigs will die and occasionally a larger branch can die back. In most cases, fruit production is reduced and the appearance of the tree is adversely affected.
As with peach leaf curl, once the symptoms of brown rot or citrus blast appear, it's too late to treat them. Both of these diseases are associated with cool, wet conditions, so the best time to spray is before the winter rains begin if you wish to protect navel oranges from brown rot, usually mid-October. A second spraying in mid-December and a third in mid-January has been shown to be effective in reducing the severity of citrus blast. For maximum protection, all parts of the tree should be thoroughly coated. The rough texture of mandarin skins can make it difficult to wash spray residue off of fruit. If this residue is not acceptable, an option is to delay spraying until immediately after fruit has been harvested.
- Author: Brent McGhie
By Brent McGhie, Butte County Master Gardener, November 27, 2015.
Freezing temperatures damage plants by causing ice crystals to form in their cells. Frost-damaged vegetation withers and turns a dark brown or black. Ice crystals can also form in citrus fruit, causing juice vesicles inside the fruit to rupture and the fruit to dry out. Although frost-damaged fruit is edible after a freeze, it is susceptible to decay and often becomes unusable soon after the damage occurs.
Leaves, green wood and fruit are more frost sensitive than hard wood. Ripe fruit is more cold tolerant than green fruit because sugars in the juice act like antifreeze and lower the temperature at which it will freeze. Fruit is slightly less cold tolerant than leaves, and trees with fruit are less tolerant than trees without fruit, so in addition to preventing damaged fruit, picking fruit before a predicted freeze will not only save the fruit, but will help protect the entire tree as well.
Where a tree is planted can affect whether or not it is damaged by frost. Trees that are growing in open areas are more likely to suffer frost damage. Cold air tends to collect in low areas, so avoid these sites as well when planting citrus. On the other hand, trees can benefit from reflected and reradiated heat if they are planted near walls or other structures.
Certain cultural practices can also mitigate frost damage. Healthy, well-irrigated trees are better able to endure freezing temperatures. The full, leafy canopy of a healthy tree also helps shelter the fruit. In addition, moist soil retains heat better than dry soil and can actually warm the air near the soil surface. It is also a good idea to keep the ground around trees bare during the winter months. Bare, moist soil is better able to absorb and reradiate heat than soil insulated with mulch, weeds, or other ground covers. Fertilizing and pruning both encourage new growth, and delicate new growth is far more frost-sensitive than mature foliage. Thus, pruning and fertilizing of citrus trees should occur in the spring and early summer in order to give the new vegetation time to mature and harden off before cold weather sets in.
Frost-sensitive young trees can be protected by wrapping them with insulating material from the ground up to the main branches. In frost-prone areas, you might also consider covering trees that are one to three years old entirely, using a light material to trap heat being radiated by the ground. A frame or stakes should be used to minimize contact between the cover and leaves because ice may form where the cover touches any leaves. Sheets, burlap, or tarps are a better choice of cover material than plastic because plastic transfers more heat and if leaves come in contact with it they are more likely to freeze. The cover should extend as close to the ground as possible and be removed the next morning after the temperature rises.
If trees do show signs of frost damage, resist the urge to prune out “dead” wood in the early spring. Allow a few months for the trees to recover with the return of warm weather. Once new growth appears, the actual extent of the frost damage will be apparent and frost-killed branches can be removed without accidentally pruning out living material.
This article was based on information from the following sources:
http://homeorchard.ucdavis.edu/8100.pdf
http://ucanr.edu/sites/placernevadasmallfarms/files/135464.pdf
By Eve Werner, Butte County Master Gardener, December 11, 2015.
Fall and winter are the perfect seasons to plant a native pollinator garden. Pollinators are the buzzing, flying creatures responsible for the formation of many of the fruits and vegetables that we humans love to eat. Planting for pollinators is a colorful way to attract interesting and beautiful birds, butterflies, bees, and insects to your garden while increasing the productivity of many edible plants.
Pollen is found in the flowers of plants. Different pollinators prefer variously shaped flowers to accommodate their personal anatomy. Selecting an assortment of California native plants with diverse flower shapes and staggered bloom times ensures that a wide variety of native pollinators will thrive in your garden.
Hummingbirds, for example, reach into tubular flowers with their long, thin beaks. Zauschneria californica (California Fuchsia; also known as Epilobium canum) is a perennial native to Butte County that is covered with brilliant orange-red tubular flowers from mid-summer through fall. This plant is a hummingbird magnet! Zauschneria ‘John Bixby' and Zauschneria ‘Calistoga' are especially attractive and well-behaved varieties of California Fuchsia. Plant Zauschneria in part- to full-sun areas of your garden. Water once or twice a month during the dry season. To keep it looking tidy, cut this perennial to within a couple inches of the ground annually in late fall/early winter.
To attract a miniature zoo over a long period, pair early-summer-blooming Salvia ‘Winnifred Gilman,' (Winnifred Gilman Sage), with late summer-blooming Eriogonum nudum, (Naked Buckwheat) or Erigonum fasciculatum (California Buckwheat). Plant these beauties in full sun. Water the sage once or twice a month. The buckwheats need no added summer water after the first year but can tolerant semi-weekly watering. Sit quietly and watch numerous species of tiny (non-stinging) native bees and wasps harvest nectar from the ball-like flower clusters of these plants. See if you can spot one-quarter-inch-long metallic green sweat bees among the crowd.
Mimulus (Diplacus) aurianticus (Sticky Monkey Flower) offers deep, wide tubular flowers that provide a helpful ‘landing pad' for several species of butterflies and bees. Hummingbirds love them, too. The soft orangey-yellow blossoms light up part shade gardens in the spring. Water Sticky Monkey Flower once or twice a month during the summer. It is stress deciduous, so it will lose its leaves or look wilted during the heat of summer.
Planting for pollinators is an easy and fun way to add a new dimension of interest to your native garden!
By Michael-Anne Foley, Butte County Master Gardener, December 25, 2015.
Winter is the time many gardeners reflect upon what worked in the garden over the past year, plan changes to implement in the coming months, and consider new plants to introduce. This January, why not begin planning a more wildlife-friendly garden? You can encourage birds, butterflies, lizards, frogs and a host of other beneficial native animals and insects to visit or reside in your garden by adding desirable habitat and plants to your home landscape.
By choosing to develop and maintain a garden that follows a few basic wildlife-friendly steps you can help contribute to a better local environment while reducing your water usage and maintenance costs, conserving local flora and fauna, and making our urban and rural areas more ecologically sustainable.
Why Attract Wildlife to the Garden?
It is enjoyable and satisfying to witness the activities of natural visitors in our gardens. Beneficial insects and animals also help to naturally control garden pests.
Creating a Wildlife-Friendly Garden
Provide food, shelter, and water, and avoid the use of toxic chemicals. Food required by beneficial wildlife includes pollen, nectar, and pest bugs. Shelter can be as simple as native bunch grasses that lady beetles use for winter shelter, while the bare ground next to the grasses can provide nesting sites for predatory ground-nesting wasps. A simple wide-rimmed shallow dish with a layer of sand on the bottom creates safe water access for many insects.
Hummingbird feeders filled with a solution of one part sugar to four parts water (brought to a boil and cooled) will give hummingbirds the energy to catch and eat the flying insects that constitute their main source of protein.
Selecting Wildlife-Friendly Plants
Our own native plants require less water, have fewer pests and attract beneficial insects that prey on the undesirable insects that feed on vegetables and fruiting plants.
- As a general rule, flowering plants that have a landing zone (the petals) for insects to settle on allows them to move by foot to the pollen and nectar. Cosmos, sunflowers, daisies, zinnias, salvias and echinacea are good examples.
- Planting in groups increases pollinator efficiency. If a pollinator can visit the same type of flower over and over, it doesn't have to relearn how to enter the flower and can transfer pollen to the same species, instead of squandering the pollen on unreceptive flowers.
- Plant with bloom season in mind, providing food from early spring to late fall. The goal is to provide pollen and nectar throughout the entire year.
- Herbs used in the kitchen support many species of pollinators. Chives, mint, marjoram, parsley, lavender, rosemary, dill, basil and fennel are all attractive to insects.
Providing Shelter
- While bird, bat, and owl boxes are familiar to most gardeners, shelters can also be constructed for native bees. There are many species of native bees that live all around us, but their nesting and rearing requirements can generally be broken into two categories: 1) those that nest above the ground in dead wood, hollow twigs, or crevices; and 2) those that nest in tunnels deep in the soil. About 30% of native bee species nest in wood or twigs and 70% nest in the soil. Soil nesters are more difficult to shelter: sometimes the best we can do is notice their small entrances and try to avoid compacting the soil above their tunnels.
Today, native insects face many challenges for survival through loss of habitat; use of pesticides and herbicides; diseases; predators; and disappearance of native flower populations. As gardeners in the Central Valley of California we can shape our environment in an ecologically sustainable way that celebrates our native wildlife.
By Barbara Ott, Butte County Master Gardener, January 8, 2016.
During the long days of summer sunlight, trees cast shade created by leaves that use sunlight to convert water and carbon dioxide into sugar. This is the process of photosynthesis, which feeds the tree and its leaves. Chlorophyll, responsible for the green color we see in leaves, is an important pigment that absorbs the light energy used in photosynthesis. As days grow shorter and temperatures begin to cool, trees respond by producing less chlorophyll, and photosynthesis slows and eventually comes to a stop. When that happens, pigments of yellow, orange and brown in the leaves (called carotenoids) begin to show through. Some trees produce pigments called anthocyanins in their leaves during the fall, creating red leaves.
A severe drought can delay the arrival of fall color by a few weeks. A dry fall with plenty of warm sunny days and cool nights contributes to vibrant late fall foliage.
Deciduous trees begin to release their leaves when cool temperatures trigger a hormone that sends a chemical message to the leaves to “let go.” Located where the leaf stem meets the branch is a thin bumpy line of microscopic cells called Abscission cells. These cells “cut” the leaf away from the stem when they receive that message. When the air moves them, these dangling leaves fall away. If the abscission cells do not develop, wind will not blow the leaves off. This is why some trees keep their brightly-colored fall foliage long after most other trees have dropped their leaves.
The yellow, orange and brown carotenoid colors in leaves remain fairly constant from year to year. Carotenoid is always present under the chlorophyll and does not change in response to weather. But when a series of warm autumn days and cool non-freezing nights occurs, it's a good year for red fall foliage. The warmth allows the leaves to produce sugar through photosynthesis, but the cool nights prevent the sap from flowing through the leaf into the branches and trunk.
Scientists offer several reasons for why some trees produce the anthocyanin that leads to bright reds. Primarily, it seems that anthocyanins protect leaves from excess sunlight and enable trees to recover remaining nutrients. This helps trees prepare for the next growing season. Anthocyanins give leaves their bright shades of red and purple. So, thanks to the warm days and cool nights we had this past fall, we enjoyed spectacular, vibrant leaf color all autumn long.
