Q. My apple tree has some kind of bug that has infected the fruit and as a result it has worms in the apples. What can I use to get rid of these unwelcome visitors? August 2014
A.
The worms are probably the larvae of the codling moth.
Here is an article from Planet Natural (www.planetnatural.com) on non-toxic control of this pest. It’s not quick or easy, but with persistence should be effective.
The Monterey Bay chapter of the California Rare Fruit Growers recently organized a members-only tour of a local citrus nursery’s growing grounds, in Watsonville.
Aaron Dillon, our tour guide, shared the history of Four Winds Growers, which was started by his great grandparents. He described the current operations and the pests and diseases that are challenging the entire citrus business.
One threat to citrus trees is the citrus leafminer (Phyllocnistis citrella), a very small Asian moth that lays its eggs in the tissue of citrus leaves. The eggs hatch into larva that feeds on the leaf, leaving a clearly visible, serpentine trail just below the surface of the leaf. Leafminers disfigure the leaves but rarely cause serious damage.
A greater threat is the Huanglongbing disease (HLB), which is known by the common names “citrus greening disease” and “yellow shoot disease.” HLB kills citrus trees.
A tiny insect, the Asian citrus psyllid, transfers this disease from tree to tree as it feeds. Because there is no cure for HLB, the control strategy is to find and stop the insect from spreading the disease. This pest has greatly reduced southern California’s citrus nursery industry, and has very recently been spotted in the San Jose area.
The citrus industry has developed regulations and procedures for propagating citrus trees in greenhouses, while keeping Asian citrus psyllids outside. The tour group entered an enormous greenhouse through an antechamber, in which a large fan produced positive air pressure to exclude any psyllids. The outer door closed, the fan was turned off, and an inner door opened to allow the group to enter the working area of the greenhouse.
Inside, a greenhouse worker, Alicia, expertly demonstrated the process of grafting a citrus scion to a robust rootstock. A skilled worker can graft 1,000 plants in a single day.
Aaron Dillon engaged the interested visitors with a wide-ranging presentation of many aspects of growing citrus trees. He demonstrated the extensive facilities in a large greenhouse where roses had been grown previously, and proudly showed an even larger new greenhouse now being readied for an expansion of propagation activities.
Now Amazon has a new line of products made of citrus, specific for eye care, a example is amazon eye masks.
Four Winds Growers propagates popular varieties of orange, mandarin, lemon, lime, grapefruit, and kumquat. For details, visit the nursery’s website <wwwlfourwindsgrowers.com> and click on “Our Citrus Trees.” Dillon listed three interesting varieties that consumers will enjoy in the future:
For information on these and many other varieties, browse to the amazing Citrus Variety Collection website, maintained by the University of California, Riverside <http://www.citrusvariety.ucr.edu/>.
Many varieties of citrus trees grow well in the Monterey Bay area, and local nurseries have many choices in stock currently. Growing information is readily available on the websites of the California Rare Fruit Growers < www.crfg.org/> and Four Winds Growers. Pest control advice for home gardeners is offered by the Citrus Pest & Disease Prevention Program www.californiacitrusthreat.org/.
Codling moths are serious insect pests of apples. If your apples have “worms,” you probably have codling moths.
Life Cycle of the Codling Moth
The codling moth’s life cycle has an important stage in the soil or organic debris around the base of your apple tree. The full-grown larvae of the moth, in silken cocoons, overwinter in this environment, and develop into adult moths around mid-March to early April.
The moths fly into the tree to mate and deposit their eggs on the leaves, spurs or immature fruit. They are one-half to three quarters inch long, with a dark band at their wingtips. They can be difficult to spot because their colors blend with the tree’s bark, and they are active for only a few hours before and after sunset.
The eggs hatch in early to mid-May, and the young larvae tunnel into the core of the fruit and eat their fill, leaving behind reddish-brown frass (insect waste).
After they develop fully, the larvae drop from the fruit and tree to continue their life cycle in the soil or debris at the base of the tree.
A second generation often occurs in cooler coastal environments such as the Monterey Bay area, with the new group of young larvae attacking the fruit in mid-July.
Management of the Codling Moth
Organic pesticides for home gardeners are CYD–X Insecticidal Virus, which infects and kills the larvae of codling moths, and Spinosad, which is a nerve and stomach poison derived via fermentation from naturally occurring bacterium. These products might be found in a garden center; or can be ordered from GrowOrganic.com or other online sources.
Apply insecticide sprays as the eggs hatch and the larvae begin to attack the fruit and make the first “sting” (a tiny mound of frass on the fruit, marking a larva’s entry). Timing can be tricky, because temperature and other factors affect the moths’ schedule. For example, mating occurs only when sunset temperatures exceed 62 degrees Fahrenheit.
A Good Reference
The primary source of information for today’s column is the University of California publication, “Codling Moth: Integrated Pest Management for Home Gardeners and Landscape Professionals.” For additional approaches to management of these pests, download this free publication at www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7412.html.
Managing an established population of codling moths will require both insecticide sprays and additional methods. For example, sanitation, always a good practice, involves promptly removing infested and dropped fruit.
Eating a fresh apple from your own tree can be delightful, but you might have to compete with the wildlife.
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Here is one of several Spinosad products that have been formulated and packaged for home gardening. This products is available in gardens centers and online from Peaceful Valley ,
Monterey Garden Spray Concentrate – Spinosad (Pint)
$19.99 + $9.99 shipping
Spinosad for home gardeners Use on vegetable and fruit crops, ornamentals, and turf to control caterpillars as well as beetles, leafminers, thrips, Colorado potato beetles, fire ants and more! Use 4 Tbs/gal water. Spinosad insecticides are nerve and stomach poison derived via fermentation from naturally occurring bacterium Saccharopolyspora spinosa. New chemistry represents an alternative to Bt for worm control and offers excellent control of targeted pests and low toxicity to non-target organisms, including most beneficial insects. Low mammalian toxicity, helps conserve beneficials.
Each year, around now, I plan to spray my four small apple trees and indulge my optimistic vision of harvesting apples that are beautiful, tasty and—most of all—free of worms.
My apple trees include a small Fuji, a Gala espalier, a second espalier with eight familiar varieties of apple and my prize: a dwarf Cox’s Orange Pippin, originally from England. Here is Wikipedia’s description:
“Cox’s Orange Pippin is highly regarded due to its excellent flavour and attractive appearance. The apples are of medium size, orange-red in colour deepening to bright red and mottled with carmine over a deep yellow background. The flesh is very aromatic, yellow-white, fine-grained, crisp and very juicy. Cox’s flavour is sprightly sub-acid, with hints of cherry and anise, becoming softer and milder with age…One of the best in quality of the English dessert apples; Cox’s Orange Pippin may be eaten out of hand or sliced.”
The worms that ruin these great apples annually are the larvae of the codling moth (Cydia pomonella).
My usual plan of attack has been to spray the tree three times with horticultural oil, before it sets buds, to smother insects as they hatch. I have never accomplished this task in a timely and thorough manner, and never had satisfactory results.
This year, I learned that horticultural oil treatment can eliminate aphids, but has no impact on codling moths or other pests that attack the fruit. A fruitless strategy!
I mentioned my concern this week to a member of the California Rare Fruit Growers, who said he has a detailed regimen for treating the soil around his trees, has never sprayed and has no pest problems. At the moment, I couldn’t write down his method and it seemed like a long-term process anyway, so I researched the issue.
Valuable advice is available from Michael Phillips’ highly regarded book, The Apple Grower: A Guide for the Organic Orchardist (2nd edition, 2005). He advocates treating the soil to promote the development of fungi that help trees to deal with pests and diseases. This might be the method practiced by my CNGF contact.
Apple farmers use two effective new organic products: Surround, a spray that coats apples with insect-repelling kaolin clay, and Entrust, based on Spinosad, a poison that is derived from naturally occurring bacterium. These products are sold in commercial quantities for licensed users.
Spinosad is also available in smaller quantities for usage by unlicensed home gardeners, in Captain Jack’s Dead Bug Brew, Green Light Lawn & Garden Spray with Spinosad 2, Monterey Garden Insect Spray and other products.
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Entrust, a Spinosad product, is available only in larger quantities for commercial fruit growers. Here is an example of one such product, Entrust.
Entrust 80 WP – Spinosad (1 LB) – PBI400
$599.00 This product qualifies for $9.99 flat rate shipping in the Continental US.
This is a special order item. Please call 888-784-1722 to place an order.
This product is not registered for sale in the following states: PR
Pesticide ID # is required for all CA commercial growers AND all Nevada County, CA residents
Spinosad insecticides are nerve and stomach poison derived via fermentation from naturally occurring bacterium Saccharopolyspora spinosa. New chemistry represents an alternative to Bt for worm control and offers excellent control of targeted pests and low toxicity to non-target organisms, including most beneficial insects. Low mammalian toxicity, helps conserve beneficial insects.
Dry formulation of spinosad labeled for cole crops, corn, cucurbits, fruiting and leafy vegetables, pome fruits, potatoes, stone fruits, strawberries, bushberries and cranberries. Controls caterpillars, certain beetles, thrips and leafminers, including many pests prone to resistance problems such as diamondback moth, cabbage looper, fall armyworm and Colorado potato beetle. For Colorado potato beetle, use only every other year to help prevent resistance.
Apply .5 – 2 oz per acre.
Note: At the recommended application rate, one pound of Entrust would be enough for on treatment for between eight and thirty-two acres of crops. Other information sources indicate that multiple treatments may be required, because the coating can be rubbed or washed off easily.
Happily, Spinosad products are available in both commercial quantities and smaller quantities for home gardens. See the following essay: “Apples Without Worms, Part 2”
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Surround, a spray based on kaolin clay, seems interesting for commercial fruit growers, but appears not to be available (yet) in quantities that are appropriate for small orchards in a residential garden. Here is an example of a commercial product:
Surround WP (Kaolin Clay)
$37.50/25 lb. bag at Planet Natural.
Made from modified kaolin clay, Surround WP Crop Protectant is sprayed on as a liquid, which evaporates leaving a protective powdery film on the surfaces of leaves, stems and fruit. Controls a long list of insect pests on vegetables, fruit trees, ornamental plants s and more. OMRI Listed for use in organic production.
Surround works to protect plants and deter insects in three specific ways:
DIRECTIONS FOR USE: Application rates are dependent on the amount of foliage
that needs to be covered. Mix 1/4 to 1/2 lb. per gallon of water (25 to 50 lb. per 100 gallons of water per acre). May be applied up to the day of harvest.
Active Ingredient: Kaolin ….. 95.0%
Inert Ingredients: 5.0%
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Surround WP Kaolin Clay – Insect Repellent
Description Surround W. P. is made from 95% kaolin clay, a naturally occurring mineral. When applied to fruit trees, crops, and other plants, it forms a white film. Surround suppresses a wide range of pests, especially those that damage fruit crops including pears, apples, grapes, berries, and some vegetables. It can be applied up to day of harvest and is easily rubbed off when the fruit or produce is ready to eat.
Surround can help control pests such as: pear psylla, cutworms, pear midge, pear slug, apple sucker, climbing cutworm, eastern tent caterpillar, gypsy moth, Japanese beetle, June beetle, grasshoppers, green fruit worm, leafrollers, lygus bug, Mormon cricket, cicada, stink bug, tarnished plant bug, thrips, fabria leafspot, apple maggot, codling moth, plum curculio, rose chafer, aphids, naval orangeworm, husk fly, blueberry maggot, blackberry psyllid, flea beetles, orchards, grape leaf skeletonizer, bean leaf beetle, Mexican bean beetle, powdery mildew, cucumber beetle, boll weevil, armyworm, black vine weevil, and fruit flies.
How it works Insects are repelled by Surround. It sticks to their body parts and encourages them to move on elsewhere. At harvest time, the white film can be removed simply by rubbing off.
General usage: Use in orchards, fields, vegetable gardens.
Advisories Do not apply directly to water, or to areas where surface water is present or to intertidal areas below mean high water mark.
Application rates General rate varies between 25 – 50 pounds per 100 gallons of water. Amount of water used will depend on amount of foliage to be treated.
Apple half-treated with kaolin clay
Synthetic chemicals have a variety of garden uses: adding nutrients to the soil (or directly to plants), discouraging/killing harmful insects and other small pests, and protecting plants from viruses, fungi and other scourges.
These benefits, however, come with downsides, including destroying microorganisms in the soil and beneficial insects, accumulating salts in the soil, and harming (or worse) pets and gardeners themselves. And there’s more, too much to review in this column.
Our present focus is on the harm that synthetic chemicals bring to insect pollinators: honeybees, native bees (which are different) and butterflies. Concerned scientists and citizen scientists have recorded significant population declines among these pollinators, and have pointed to pesticides as the likely cause of these declines.
Our gardens need these pollinators. They are essential in sexual reproduction of plants, including the development of fruits, vegetables and berries, all of which bear seeds, and both natural and human-directed hybridization of plants.
There are also asexual forms of plant reproduction, to be sure, but we’re concerned here with the pollinators.
The first priority in attracting pollinators to your garden is to adopt organic gardening methods, i.e., no synthetic chemicals. Safe organic products are available to address any gardening need, and integrated pest management (IPM) strategies work better and cheaper in the long run than the quick fixes of synthetic chemicals.
The next important priority is to plant more flowers as food resources for bees and butterflies. An excellent resource this subject is The Xerces Society for Invertebrate Conservation, a non-profit organization. The Society offers reliable information on all aspects of attracting pollinators.
The Society’s guidelines for California gardeners get to the point:
Another helpful resource is The Melissa Garden: A Honeybee Sanctuary, which is located in Sonoma County. The owners offer an extensive list of plants that attract bees, and offer tours and classes in beekeeping, attracting pollinators, and related topics. “Melissa” is from the Greek word for honeybee.
Visit ongardening.com for links to The Xerces Society, the Melissa Garden and other resources for attracting pollinators to your garden, as well as for information on organic gardening and integrated pest management.
As you add flowering plants to your garden, choose some for the bees and butterflies.
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Attracting Pollinators to Your Garden Using Native Plants
Organic Gardening: There are many books and magazines on this subject. A classic in the field is Maria Rodale’s Organic Gardening: Your Seasonal Companion to Creating a Beautiful and Delicious Organic Garden (Rodale Press, 1998)
Integrated Pest Management The University of California’s Integrated Pest Management program is a valuable resource for California gardeners. Another useful resource is the U.S. Environmental Protection Agency’s webpage on IPM Principles.
Happily, several years have passed since I’ve noticed thrips in my garden, but they are back!
Thrips are flying insects that are less than 1/20 of an inch long and eager to suck juices from plants. There are over 500 genera and 5,000 species of thrips, some of which are beneficial predators of mites, scales and even other thrips. Others feed on fungal spores or pollen, and some feed only on favored plants, such as avocados, citrus, blueberries, or various others.
My garden’s visitors almost certainly are Western Garden Thrips (Franklinia occidentalis), which attack a wide range of herbaceous ornamentals, vegetables, fruits and some shrubs and trees, including roses and stone fruits.
Thrips are poor flyers but can find juicy plants and infest all of a large shrub or a good-sized bed of a plant that they find tasty.
In my garden, they found a 200 sq. ft. bed of Bergenias (an unidentified cultivar of the popular species, Bergenia crassifolia). This plant from central Asia has numerous common names: Elephant Ears, Pig Squeak, Large Rockfoil, etc. It is an attractive groundcover plant, growing one-to-two feet high, with clusters of small, bell-shaped pink flowers on stems that rise above the foliage in early spring.
Bergenias are generally free of pests, at least until thrips discover them.
Thrips might make only limited damage to ornamental plants and could be ignored. When conditions are favorable, however, they can cause great cosmetic damage.
When thrips attacked my Bergenia bed, nearly all the leaves, each about four by six inches, became discolored and distorted, and their upper surfaces turned silvery gray, the result of losing their waxy surface. The leaves also were stippled with black specks of the thrips’ fecal matter.
The normal growth of Bergenias has new leaves emerging above older leaves that turn brown without dropping off. New leaves cover the old leaves, but removing the dead leaves improves the plant’s appearance. In this instance, the action of the thrips revealed the dead leaves, and the entire bed was devastated.
The damage was limited to the leaves. The stems and roots of the plants were alive and well, and able to produce new leaves. Our treatment was to remove all living and dead leaves, using garden clippers, and then spray the plants with Spinosad, an organic pesticide that kills insects both by direct contact and by ingestion.
I used a Spinosad-based product, Captain Jack’s Deadbug Brew, in a container designed conveniently as a hose-end sprayer. Despite its promising name, the spray doesn’t guarantee success: a follow-up spray might be needed to control the newest of up to eight generations of thrips for the year.
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Thrips are members of the order Thysanoptera. The earliest fossils of thrips date to the Permian Period, 250 to 299 million years ago. This period was the last part of the Paleozoic Era, which ended with the largest mass extinction in Earth’s history, when nearly 90% of marine species and 70% of terrestrial species died out.
That thrips were among the survivors of that period suggests the difficulty of eliminating them from our gardens.
When the gardener suspects that thrips are present, they can be detected either by close examination of the underside of affected leaves, or by beating or shaking a branch or flower onto a sheet of paper. Yellow sticky traps also can be used to monitor their presence.
The most important way to encourage biological control of pest thrips is to conserve naturally occurring populations of beneficial insects, e.g., predatory thrips, minute pirate bugs, predaceous mites, and green lacewings . This can be done by controlling dust and avoiding the use of persistent pesticides in the garden.
For other control, see the University of California’s Integrated Pest Management information page on How to Manage Pests—Thrips.
