- Author: Help Desk Team
If you have a history of “worms” in your apples, pears, or English walnuts, and have felt perplexed as to how to manage this problem, the very first step is to understand what is happening. When one understands that, the management becomes more understandable and approachable.
The “worms” are actually caterpillars, the immature stage of an adult moth. The life cycle is egg, larva (caterpillar), pupa, adult. The adult moth is mottled gray and small (½ to ¾ inch) and therefore hard to see and often goes unnoticed.
The adult female moth lays her eggs on or near developing fruit. The egg hatches and the caterpillar immediately will chew its way into the fruit where it lives and feeds. Entry holes are referred to as “stings” and typically exhibit a sawdust like residue called “frass”. If one sees a sting, the larva has already entered the fruit and is impervious to insecticidal sprays.
When it is ready to pupate, it will chew its way out and drop to the ground where it pupates in soil or leaf debris or under tree bark. After pupation an adult emerges and starts the cycle all over again.
The rate of development varies with temperature, proceeding more rapidly in warmer weather and climates. Depending upon the climate, codling moths can have two, three, and sometimes four generations per year. Our county has warmer climates inland and cooler climates by the coast. This means adult moths will start flying sooner and have more generations in the warmer areas and start flying later and have fewer generations in the cooler areas. Adult moths can start flying and laying eggs as early as March. The link below shows the approximate timing of the multiple generations.
https://ipm.ucanr.edu/PMG/PESTNOTES/pni7412-3.html
Codling moths can be difficult to manage, and a goal of 100% undamaged fruit may be unrealistic. A more reasonable goal would be to harvest enough undamaged fruit to meet your needs. In most backyard situations, the best course of action would be to combine a variety of the following non-chemical and low toxicity chemical methods early in the season.
Non-chemical:
- Pheromone traps (sticky traps laced with female pheromone to attract males) are not an effective management approach by themselves. They may be helpful if multiple traps are placed in a tree, but primarily they are used to monitor when adults are flying in order to time chemical applications. Traps can be purchased at most home and garden stores or online.
- Thinning your crop is important. The moths are most attracted to the place where two apples touch. Four to eight weeks after bloom, thin the fruit to only one per cluster, about every 6 inches.
- If you have thinned your fruit you may want to go one step further by “bagging” it. Although tedious and time consuming, placing bags over individual fruits early in the season, when the fruit is ½ to 1 inch in diameter, provides excellent control. The bag could be paper or cotton string. The link below provides a drawing of the bagging process. https://ipm.ucanr.edu/PMG/PESTNOTES/pni7412-2.html
- Beginning about six to eight weeks after bloom, and continuing every week or two throughout the season, check fruit on the tree for signs of damage (stings). Remove and destroy any infested fruit. Do not put the culled fruit in your backyard composting system, rather place it in green waste so it gets removed from your property.
- Since pupation takes place in litter on ground under the tree, keep the area continuously clean throughout the season, even though winter.
Low toxicity chemicals:
- CYD-X is a biological insecticide, a granulosis virus that affects only codling moth caterpillars. It kills by ingestion, therefore it must be ingested by the caterpillar prior to or as entering the fruit. To achieve this, it needs to be applied weekly beginning at the time of egg hatch. CYD-X is primarily available online.
- Spinosad is a biological insecticide, a bacterium that is toxic to insects in general. It kills by both contact and ingestion, therefore it needs to be applied at 10-day intervals beginning at the time of egg hatch. Spinosad is readily available at most home and garden stores.
- Adding 1% horticultural oil to either of the above improves effectiveness.
- Identifying the timing of egg hatch is key to the success of chemical applications. Egg hatch can be estimated by visually monitoring first stings or by using the UC Degree Day Calculator for codling moth https://ipm.ucanr.edu/calludt.cgi/DDMODEL?MODEL=CM&CROP=landscape
It is important to begin implementing control measures early in the season. The link below to the UC Integrated Pest Management website provides the detailed information you will need for implementation of your codling moth management program.
https://ipm.ucanr.edu/PMG/PESTNOTES/pn7412.html
Photo credits: Three photos above: Copyright UC Regents - photographer Jack Kelly Clark
Help Desk of the UC Master Gardeners of Contra Costa County (EDC)
- Author: Ed Perry
If you decide to fight them, now is a good time to plan your strategy since the most critical time to protect your fruit from the pest is spring. Warm spring weather causes most of the first generation moths to emerge within a few weeks. The moths may take 6 weeks or more to emerge during a cool spring. Once they have emerged, the codling moths are still affected by temperature. They do not lay eggs or mate when it's below 62°F at sunset or fly when it's 55°F.
The moths emerge from pupae in early spring about the time when fruit trees are in full bloom. Each moth lays 50 to 75 eggs on fruit, twigs, or leaves. Eggs hatch into larvae which tunnel into the young fruit. Inside the fruit, the larvae feed for several weeks, then tunnel to the fruit's surface and search for protected sites such as under tree bark, in branch wounds, weeds, grass or other litter. The larvae changes first to a pupa, then to an adult and repeats the cycle.
You can also trap many larvae under bands. Take a 6-inch wide strip or burlap or corrugated cardboard, wrap it around the trunk several times, then fasten it in place with a loop of wire or twine. If you use corrugated cardboard, the exposed flutes (ridges) must be at least 3/16 of an inch wide and face toward the tree; otherwise, the larvae won't form cocoons in them. Place a band on each tree no later than mind-May. During warm weather remove the band once a week, and during cool weather once every two weeks. Destroy all the larvae and pupae under the band, and then put the band back on the tree. Keep doing this until you've harvested all the fruit.
Insecticidal sprays are usually the most effective means of controlling codling moths. Sprays give best control when you apply them just after a large number of larvae hatch, but before they burrow into the fruit. These times are several days after a period of peak moth flight and vary according to the year and location.
When using any chemical, carefully follow dilution rates and other directions given on the container label. Do not spray within the number of days before harvest indicated on the label. You can read more details about the life cycle of this pest and management, including chemical controls in the UC IPM Pest Notes: Codling Moth.
Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County where he worked for over 30 years.
- Author: Jeannette E. Warnert
The Community Alliance with Family Farmers and UC Cooperative Extension are working with farmers to establish six demonstration sites in walnut orchards that will examine the effectiveness of mating disruption to control two major pests of the crop – codling moth and navel orangeworm.
The three-year research effort is funded with a $1 million award from the California Department of Agriculture Biologically Integrated Farming Systems program.
“The project sites will be in the Sacramento and northern San Joaquin Valleys, but we expect the demonstration to be of interest to walnut farmers across the state,” said Sara Tiffany, CAFF director of ecological farming and the project lead. “Farmers who grow related crops, like almonds and pistachios, will also be able to benefit from the findings.”
“Farmers need alternatives. In this project, we will be studying the effectiveness of alternatives that already exist,” said Jhalendra Rijal, UC Cooperative Extension integrated pest management advisor for San Joaquin, Stanislaus and Merced counties, the lead scientist on the project. The California Walnut Board is also part of the project team.
Six farmers will be recruited to enroll at least 80 acres each in the demonstrations – three farmers in the Sacramento Valley and three in the northern San Joaquin Valley. The entire acreage will be managed following UC IPM guidelines for walnut production, including cover crops, reduced risk pesticide options and biological control.
Forty acres will be treated with commercially available mating disruption products, while the other 40 acres will not. The treatment works by confusing the pests. Codling moth and navel orangeworm moths naturally release pheromones that help them find mates. The female lays eggs in the immature nuts, and when they hatch, the larvae feed on the nuts, rendering them unmarketable. In the treated area, the orchards will be flooded with a synthetic pheromone that makes it much more difficult for male and female pests to hone in on one another.
Besides codling moth and navel orangeworm, the project will systematically look at the effects of cover crops and predatory mite release on pest mite populations, and improvement in other natural enemy populations in walnut orchards.
The results of the IPM practices will be shared widely with growers, pest control advisors and certified crop consultants in articles, meetings and field days.
“Currently the use of mating disruption in walnuts is significantly lower than in almonds,” said Rijal, who is also the associate director for Agricultural IPM with the UC Statewide IPM Program. “We believe when farmers see the results of using mating disruption, along with other sustainable walnut production practices, we will improve the adoption rate.”
- Author: Jan Rhodes
I love apples…crisp and juicy, sweet and tart, green or red. I eat one daily, sometimes with peanut butter or almond butter… I even add a few raisins and some cinnamon now and then for a special treat. I have four lovely apple trees in my yard – Pink Lady, Honeycrisp, Arkansas Black and a Yellow Transparent Apple that someone was going to take to the dump because it wasn't what they wanted. I couldn't bear the thought of a perfectly good apple tree going to the dump, so I planted it and, I have to say, the apples are tasty and early.
With so many apple trees, you would think I could satisfy my apple appetite. And, though I have gotten a few over the years, mostly what I get is tasty chunks after I carve out the coddling moth damage. Ewwww. So, this season, I decided to take action, enough is enough. I water, prune, and dutifully spray these trees…I really should get something more in return.
My winter time research left me daunted – traps and pheromones, recording temperatures and sheesh – too much for someone who likes to keep it simple (you can translate that as “lazy”). So, I remembered my trip to Japan some years back where I paid $6 for an apple (I really wanted one) and realized why they were so expensive when I saw workers in the orchard lovingly placing bags on each apple to prevent insect damage. No wonder those apples looked so perfect and cost so much.
With that idea in mind, my Internet wanderings led me to apple bagging. I found a wealth of information, including video how tos. Seems I am not the only one who thought of this, in fact, lots of growers, backyard and commercial organic orchards are on board. There are even a number of sources for bagging materials of different kinds. There is even an added bonus for embracing this technique. Not only does bagging prevent coddling moth, it can help prevent other apple pests and problems … all without pesticides, fungicides, spraying and other rather bothersome tasks. This practice is most commonly used for apples and pears, and can help guard against such threats as codling moth, curculio, apple maggot, apple scab, and other impediments to a quality harvest. Bagging may even help deter birds and squirrels.
I decided to give it a try, however, since this was an experimental effort, I was determined to use what I had on hand and to try not to bag more than a dozen apples per tree. Why go all out if it might not work, right? The process begins with thinning your apple crop, that is, keeping one baby apple in each cluster. I always thin my apples (same for my grapes). The yield is less, but the apples are bigger and the tree is healthier. Per my research, I thinned my apples and when they reached about half an inch in diameter, I bagged them.
There are a good number of options for bagging – lots of bagging supplies to buy from Internet resources, including bonafide Japanese Apple Bags. And, there are lots of folks who use resealable plastic bags or nylon stockings (really!) I happened to have small (6”x8”) plastic bags (not zip lock) that I use for baked goods and backpacking. They seemed to be a good size for apples, so I used them and fastened them with a twist tie. It didn't take too long and kind of made me chuckle. A real conversation piece when company came by.
Over the summer, I kept my eye on them. With the heat, some moisture collected in the bag, and some articles suggested cutting the bottom corners to let the moisture drain. I decided I didn't want to risk insects getting in, so I opted not to do this. In the end, it did not seem to make a difference. The apples grew and matured as usual. Some articles suggested removing the bags some weeks prior to harvest, I opted not to do this, also – didn't seem to make a difference. I did have to wait a bit longer for the bagged apple to take on their color.
The proof of the pudding, so to speak, came a harvest time – though not all bagged apples escaped coddling moth – a few sneaked through the twist tie area (probably my bad) – I was excited to finally harvest and eat a good number of apples from my very own trees. In chatting with other Master Gardeners, I found that several had also tried this method, all with varying success. So, while it appears that this idea is not new in these parts, I found it to be worth the time and effort, and will definitely employ bagging next season. I do, however, intend to find biodegradable bags for the process.
I have included resources and photos here. Now, excuse me while I munch my home-grown apple!
FRUIT BAGGING OPTIONS
There is an array of options when it comes to bagging fruits. Plastic resealable bags and brown paper bags can be used to protect your fruit and are readily available. Additionally, there are specialized Japanese fruit bags that can be ordered online, or nylon mesh bags that may be better to use for softer fruits. In most cases, the bags can be reused the next year!
Some sources of commercial fruit bags I found:
- http://www.raintreenursery.com/Apple-Maggot-Control-Bags-144-Bags.html
- http://www.wilsonirr.com/ecommerce/red-apple-bag-6-large.php
- http://www.seattletreefruitsociety.com/maggot-barriersArticles about fruit bagging:
- http://www.homeorchardsociety.org/growfruit/apples/bagging-apples/
- http://magazine.uc.edu/issues/0408/japanese_apples.html
- http://www.seattletreefruitsociety.com/maggot-barriers
- http://homeguides.sfgate.com/bag-tree-fruit-56567.html
- Videos about apple bagging:
- http://www.youtube.com/watch?v=zRQxDnYJRAg
- http://www.youtube.com/watch?v=IUIETl-QxDw
Inclusion does imply endorsement by the University. Other sources are available. These are a good place to start.
/h3>Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request (via phone message) Last year my apple tree was seriously impacted by codling moths. I understand that there are routines timed to the hatching of the moth that a home gardener can follow to minimize, maybe even eliminate, damage to the apples. Can you advise me on those routines.
MG Help Desk Response: Thank you for your call to the UC Master Gardener Program Help Desk. Your message indicated you are looking for information on the hatching timing for codling moths in your area.
In cooler areas (e.g., west Contra Costa County), look for first stings in early to mid-May and stings from a second generation mid-July to mid-August. In warmer areas (inland Contra Costa County) start looking for first stings by mid-April. Inland, there may be as many as 3 generations hatching through the summer, all requiring treatment.
To use the calculator, you will need to know the date of when moths are found in your traps and sunset temperatures have reached 62 degrees. This date is known as the biofix date. When asked to select a UC CIMIS weather station, choose the one of five in Contra Costa County that is closest to you. That will produce a chart with expected degree days for the time period you specified and recommendations for degree-day accumulations for each spraying.
For more information on codling moths and their control, see this UC document: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7412.html. For a calendar of gardening operations for apples: http://homeorchard.ucanr.edu/Fruits_&_Nuts/Apple/.
Please let us know if you have further questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (SEH)
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