Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Help Desk Response (via email after phone conversation followup to original email request) Thank you for contacting the UC Master Gardener Help Desk. It was nice to speak with you about your unidentified plant with “black stuff” on the leaves. As we discussed, your plants have sooty mold covering the tops of the leaves. It's growing on the honeydew that was excreted by insects living under the leaves above. From your description, those insects are most likely scales of some kind.
The sooty mold is really no problem for the plant, except in extreme cases where it blocks the sun and stops photosynthesis. It won't spread to other plants that don't have honeydew on them. Here's a link to more information about it: http://ipm.ucanr.edu/PMG/PESTNOTES/pn74108.html.
Many species are well controlled by natural enemies, but ants can protect the scales against the predators, so take measures to control the ants. Spraying horticultural oil during the dormant season or early summer when crawlers are moving may be all the treatment you need.
Information about scales and their control: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7408.html and
Information about ants and their control: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7411.html
Please let us know if you have more questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (SEH)
Note: The UC Master Gardeners Program 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 (http://ucanr.edu/blogs/CCMGBlog/).
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- Author: Ben Faber
There are 4,000 species of earthworms grouped into five families and distributed all over the world. Some grow uo to 3 feet long, while others are only a few tenths of inches. We call them nightcrawlers, field worms, manure worms, red worms and some people call them little diggers.
In California, we have some native species of earthworms, but in many cases non-native introduced species have come to dominate. The predominant native species belong to the Argilophilus and Diplocardia while many of the non-native are of European in origin in the Lumbricidae family. Many of these non-natives were probably introduced by settlers bringing plants from home, which had soil containing the worms. A survey of California earthworms by the US Forest Service can be found at:
https://www.fs.fed.us/psw/publications/documents/psw_gtr142/psw_gtr142.pdf
This is a wonderful description of earthworm biology and their occurrence in the landscape.
When digging in citrus orchards, it is common to find earthworms in the wetted mulch under tree canopies. Many of our citrus orchards were initially established by “balled and burlap” nursery trees that brought worms along with the soil. In the case of many avocado orchards, on the other hand, it can be rare to find earthworms in orchards. Most avocado orchards have been established since the 1970s when potting mixes and plastic liners were the standard practice and worms were not part of the planting media. Even though there is a thick leaf mulch in avocado orchards, the worms have not been introduced, and it is rare to find them.
Numerous investigators have pointed out the beneficial effects of earthworms on soil properties. One of the first of these observers was Charles Darwin who published Earthworms and Vegetable Mould in 1881. He remarked on the great quantity of soil the worms can move in a year. He estimated that the earthworms in some of his pastures could form a new layer of soil 7 inches thick in thirty years, or that they brought up about 20 tons of soil per acre, enough to form a layer 0.2-inch-deep each year.
Earthworms, where they flourish, are important agents in mixing the dead surface litter with the main body of the soil. They drag the leaves and other litter down into their burrows where soil microorganisms also begin digesting the material. Some earthworms can burrow as deeply as 5 to 6 feet, but most concentrate in the top 6 to 8 inches of soil.
The worm subsists on organic matter such as leaves and dead roots near the soil surface. The earthworm ingests soil particles along with the organic matter and grinds up the organic matter in a gizzard just as a chicken does. This is excreted in what we call worm casts. The castings differ chemically from the rest of the soil, as they are richer in nitrogen, potassium and other mineral constituents.
Castings are a natural by-product of worms. When added to normal soils in gardens or lawns, they provide the same kinds of benefits as other bulky organic fertilizers. Castings today are not commonly used as fertilizer by commercial plant growers because of their cost relative to other fertilizers. However, castings are used by some organic growers and are sold commercially as a soil amendment or planting medium for ornamental plants grown in pots.
The physical soil churning process also has several important effects:
-Organic residues are more rapidly degraded with the release of elements such as nitrogen, sulfur and other nutrients.
-Some of the inorganic soil minerals tend to be solubilized by the digestive process.
-Extensive burrowing improves soil aeration.
-Burrowing can improve water penetration into soils
-The earthworm carries surface nutrients from the soil surface and imports them into the root zone of the plant.
Although earthworms are considered beneficial to soil productivity, few valid studies have been made to determine whether their presence will significantly improve plant growth. This may seem odd since many of us have learned from childhood that worms are good. It is something like the chicken and the egg analogy. The conditions that are conducive to earthworms are also ideal for plants. Both plants and worms need temperatures between 60 and 100 degrees F for good growth; both need water, but not too much or little; they both require oxygen for respiration; and they do not like soils that are too acid or basic or too salty. By correcting soil conditions that are unfavorable for one will also improve the outlook for the other. The earthworm is a natural component of the soil population. If the soil is properly managed this natural population will thrive. In this sense, the presence or absence or earthworms can be an indicator of the "fertility" of one's soil.
- Posted By: Stephen J. Vasquez
- Written by: Pete Christensen, Stephen Vasquez and Matthew Fidelibus
Rain is predicted for this Tuesday and Wednesday, October 4-5, 2011. Should rain occur, follow these practices to minimize damage and infestation to raisins:
Tray-dried raisins
• Slip trays to prevent their sticking to the soil. Move them just enough, 1 to 2 inches, to break the seal between the paper and the soil. This interrupts the wicking of moisture from the soil into the tray.
• Turn the trays as soon as possible to expose bottom fruit.
• Do not save fruit stuck to the bottom of trays or mix it with other fruit. Use new trays as needed, or reverse old trays at turning by putting the soil side next to the raisins (but only if soil is not sticking to the underside of the tray) and leaving stuck fruit on the outside.
• Pick moldy or rotten fruit off the tray before rolling. This is the best opportunity to reduce moldy fruit by hand.
• Get rolled fruit out of the field as soon as possible. Do not fill bins with raisins above 18 percent moisture. Use half-filled bins at 18 to 20 percent moisture. Sweat boxes are suitable for raisins up to 20 percent moisture; half-fill them with raisins between 20 and 22 percent moisture. Begin on-farm or commercial drying as dictated by moisture. Immediate drying is needed when raisin moisture exceeds 22 percent.
DOV raisins
• Raisins that are dry enough to be harvested should be removed from the vineyard. DOV raisins that do get rained on will pick up moisture. However, depending on the weather after the rain event, they will dry down to their previous moisture but may need 1 to 2 additional weeks to meet delivery standards. Late season rain events will greatly reduce the chances of naturally drying the fruit. Growers should make arrangements with a packer or dehydrator to finish drying the fruit. NOTE: DOV fruit is sensitive to excessive handling and should be delivered to a packer as soon as possible.
Boxing and Delivery
• Watch for spoilage in boxed raisins. Dump fruit over and spread into more containers at first signs of spoilage.
• Run fruit across a shaker, if possible, to reduce insect infestation and to provide another chance to pick out mold. Do not run fruit with too many uncured berries over a shaker.
• Cover tightly with polyethylene during rainy, foggy, or humid weather. Otherwise, raisins will absorb moisture directly from the air. Use paper covering, such as tar-impregnated paper, underneath the plastic to prevent water condensation.
• Deliver the raisins as soon as possible to the packer so that they can be fumigated.
Commercial washing and drying (wet reconditioning) may be necessary to further remove mold and embedded sand. The service is offered by many packers and most commercial dehydrators. The need can be determined by a USDA inspection.