- Author: Alison Collin
Each fall my Gravenstein apple gets a small patch of fluffy exudate on the bark at the base of the tree. These are caused by woolly apple aphids, Eriosoma lanigerum. I hose them off with a jet of water which is usually the end of the problem. However, this year the tree is much more severely affected which has encouraged me to look into this pest more deeply.
This aphid infects apple trees not only above ground but also underground where they can cause distortion of the roots which become small fibrous masses with the formation of galls and knots. The underground damage which is caused by overwintering nymphs is often more severe than the damage caused to twigs and branches. On the exposed parts of the tree it is often suckers, watersprouts, pruning cuts or wounds that get attacked first. This year, on my tree most of the individual leaf nodes are affected.
Alternate hosts for this aphid are elm trees, and unfortunately these are ubiquitous in many parts of the Owens Valley. Eggs are laid in cracks in the bark in the fall, and these hatch in spring. After a couple of generations living on these trees, in the summer a generation develops wings and migrate to apple trees (or other members of that family – hawthorn, pear or mountain ash) where several more generations are produced. In areas where elms no longer grow the aphid will live on apple trees year round.
Although natural enemies such as syrphid flies and parasitic wasps feed on the above-ground woolly apple aphid these appear to be scarce to nonexistent in November in the Owens Valley, and the aphids are proliferating at an alarming rate. While one does not want to use pesticides which will potentially harm beneficial insects I am considering trying neem oil to achieve some sort of control. There appear to be no methods of controlling the underground nymphs.
Several rootstocks used in the grafting of apple trees are resistant to woolly apple aphid. One of these is M.111 and the Merton series of Malling rootstocks. Interestingly, in my own garden, while the Gravenstein apple is severely affected the Golden Delicious tree right next to it has no evidence of this pest. Although rootstock varieties have been lost in the mists of time I can only assume that this is what has caused the difference. There are differences in susceptibility of different cultivars, so perhaps Golden Delicious is more resistant.
With our climate becoming hotter, our trees, already under considerable stress, will be facing greater challenges so perhaps it is time to pay more attention to such factors as the rootstock used when buying fruit trees for the home garden.
For more detailed information on woolly apple aphids, see one of the links below.
- Author: Alison Collin
I had long ago become resigned to the fact that I cannot grow perfect, blemish-free apples on the two trees that we inherited when we moved to Bishop. There is the challenge of keeping codling moths and aphids under control, thinning prodigious numbers of tiny apples in the spring, and chasing house finches away from the maturing fruit. I have learned to accept peck marks and am happy to remove a codling tunnel or two when canning large volumes, but nothing prepared me for the miseries of an enormous crop of rotted fruit.
Both trees are mature, one being a Gravenstein, the other a Golden Delicious. They ripen about one month apart with the Gravenstein leading the way. This year in spite of the young fruit being thinned and sprayed with Surround, the fruits on both trees were severely affected by codling moths, yet for some reason surface damage on the Gravenstein generally did not go very far into the apple and with a quick flick of the knife it was gone. So when the Golden Delicious started swelling and various small marks and blips appeared on the skin I really did not think too much about them. However, very soon the branches were laden, not with crisp, juicy apples ready to pick, but with brown patches on almost every fruit. Even tiny specks allowed this fungus to enter, and the codling moth damage enabled the fungus to take hold with a vengeance. I thought that I would be able to salvage something to eat from those fruits with minimal damage, but this infection moves fast, frequently entering the fruit through either the calyx or stem and rapidly affecting the core and surrounding tissue and producing the typical fungal odor.
It's likely that a codling moth strike created an opening for some pathogen to enter.
Botryosphaeria species cause "white rot" — a fungus that is extremely common and can affect many woody plants ranging from birch to blackberry and pears to Rhododendron, where it can infect woody tissue and cause cankers. In apples it may infect fruit early in the season without showing, but the rot begins to spread in the warm weather as the fruit matures and shows as circular brown areas.
Brown Rot is caused by a fungus called Monilinia, and it usually affects stone fruits beginning as brown spots which rapidly coalesce to form patches, and then affect the whole fruit. Being primarily a disease of stone fruits, when it does occur on apples (rare), it is usually because the fruit are near infected plums, peaches or nectarines and conditions are optimal for its growth. The sunken brown tissue develops fruiting spores that begin as tiny black spots which then develop whitish heads. Fungicides don't work once the disease has appeared since it enters the fruit through a wound. At the end of the season affected fruits may stay attached to the trees where they shrivel and eventually become mummies, or may drop to the ground, but either way they spread infection through spores being distributed by wind, rain or sprinkler irrigation. Due to our dry climate, brown rot is not a common occurrence in Owens Valley on stone fruits, but it is not unheard of, either.
Photos of fruit infected with a recently recognized fungus, Paecilomyces niveus , look identical to many of the samples from my trees, but the color patterning of the damage looks completely different on other fruits. I hope that it is not this fungus since it produces a toxic substance, patulin which can sicken people, and can survive the high temperatures used in the pasteurizing processing.
A physiological disorder called bitter bit can also cause discoloration, but the lesions are much smaller. It is caused by a calcium deficiency in the developing fruit. (Link to more information.)
Another possibility is a combination of spoilage organisms taking advantage of an opening caused by a codling moth strike. Sometimes it's impossible to tell!
Control of fungal infections is achieved by removing all affected fruit and mummies and disposing of them in some way to prevent the spores from being blown onto other plants. I have buried these in a deep pit, raking up and removing all fallen leaves and pruning out and disposing any twigs that appear to be blighted. Dormant spraying to reduce damage by pests in the following season and thinning fruits early to give plenty of space around each one, monitoring for codling moth and taking appropriate action to control them, should help to control the damage which gives a port of entry for the rot spores. Information on fungicides on backyard apples in California can be found at this page.
I intend to be much more aggressive in taking control measures in future, but since my apple trees are alternate-year bearers, I will have to wait a very long time to know if I have been successful!
For more information about fungal infections of fruit, follow one of these links:
- 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.
- Author: Alison Collin
If you have fruit trees you are probably now getting a little tired of raking up fallen fruits which are the result of a natural occurrence known as the “June Drop”. This year the phenomenon is extending well into July, to the point that one wonders if there will be a crop left to harvest. So what is normal, and when do our trees need help?
Apples and pears produce several flowers on each cluster in spring, and depending on pollinator activity, and the local availability of another apple to cross pollinate, many, many flowers may set fruit. However, there will also be numerous little fruitlets that did not get pollinated properly, are damaged by insects, or require more carbohydrates than the tree can produce, and these fruits wither and fall off, frequently in large numbers.
As the remaining fruits begin to swell many more get attacked by codling moth, are affected by lack of sufficient water, or otherwise get damaged, and since the tree can only support a certain sized crop it goes through another round of shedding, usually beginning in June and continuing until early July, often resulting in carpets of larger fruit on the ground - frustratingly too immature to use for any practical purpose.
It is thought that warm nights may cause the fruit drop to be excessive since the respiration rate of the tree causes more carbohydrates to be consumed during the hours of darkness, leaving less available for fruit production.
Another factor could be lack of nitrogen, so a careful fertilization regime should be followed, being aware that too much nitrogen can also cause fruit drop and excessive growth. For information on fertilization see: http://homeorchard.ucanr.edu/The_Big_Picture/Fertilization/
In areas such as ours lack of water will also be a factor, so make sure that you check your irrigation system and remember to seasonally adjust the amount. A mature semi-dwarf tree can produce over 400 pounds of apples which, after all, are made up mainly of water!
On a large, heavy cropping tree, thinning young fruits early in the season reduces the natural shedding, and picking off any obviously damaged fruit as the season progresses will also help, but not eliminate the problem entirely. If a fruit is scarred or misshapen this will only grow with the fruit, so one might as well remove it and save the tree from wasting resources trying to get it to maturity. Infected fruits should be properly disposed of so that they do not create a source of infection. For information on thinning: http://homeorchard.ucanr.edu/The_Big_Picture/Fruit_Thinning/
Generally speaking, if the tree looks healthy and has a heavy crop of fruit falling in mid-summer should not be cause for concern.
- Author: Dustin Blakey
If you open up a pest management guide for apple or pears—those books really exist, by the way—the first insect listed is always the dreaded codling moth. These are the creatures responsible for turning an apparent bountiful harvest of fruit into a brown, wormy mess in late summer. Codling moth is the main insect pest that attacks apples and pears in our region.
After overwintering as larvae, the moths emerge in spring, mate and then proceed to lay eggs on the fruit. These eggs hatch into tiny larvae that eat their way into your fruit, ruining it in the process. Fully grown larvae fall out of the fruit, pupate into adult moths (usually on the ground), and the process repeats. In the Owens Valley, there are usually two generations that we worry about controlling. Their development is mostly driven by temperature.
The first generation of adults usually emerges in April, and egg laying follows in a few weeks. The exact timing varies each year and by location, north or south, in the valley. The second generation lays its eggs over an longer period, but it is usually in July. Most of the complaints of ruined fruit by gardeners are from this second generation.
Because there are at least two generations to be concerned with, it is essential to get control during the first generation so that you have fewer moths to fight later on.
While it's possible to achieve control by just using continual sprays through the season with insecticides, this isn't usually how we deal with this pest since that's wasteful and carries risks. Codling moth is usually controlled through a combination of means.
Commercial codling moth control is a complex topic. There is a great body of peer-reviewed literature on the subject. In the home landscape it really isn't possible to implement a full, successful control program. UC has a simpler set of guidelines for landscapes and gardens here.
The approach I would recommend to is to watch your fruit closely. Ideally you should learn what a codling moth egg looks like and learn to identify it. If you want to control with sprays, egg laying is the only feasible time to apply an insecticide, Organic or otherwise.
Codling moth eggs are tiny and hard to see. They look like tiny translucent pancakes about as big around as a pencil's lead. These are usually laid near the blossom end of the fruit. I find them easier to see in the morning or late afternoon when the sun is low in the sky. They are slightly reflective and having sunlight reflecting on them is a big help. Check those fruits you can reach easily from the ground for the eggs by turning the fruit and looking around the blossom end. The third week in April is a good time to start looking in our area. Continue this through mid-May. Remember that Bishop is about 1 week behind Lone Pine in timing. Check for eggs again in late June through July. Egg laying is your best shot for applying controls.
If your eyes aren't good, you'll have a hard time knowing when to time sprays by finding eggs, but there are other options. A favorite home control technique of mine is to remove all fruit of the first generation that has a worm. This alone can go a long way in getting control, especially if you're not surrounded by neighbors with wormy fruit.
If you really want to have clean fruit, in June you can bag fruit to protect them from insect attack. Garden supply companies sell bags for this purpose, but you can improvise as well. Have bags on fruit before egg laying commences. Since we have wind issues, you'll need a way to secure the bags onto the fruit. Bagging is a lot of work! Anytime you see fallen or damaged fruit on the tree, you should remove it immediately whether you bag or not.
Unless you are committed to bagging fruit, most homeowners who demand high levels of control will need to spray some product. These vary from biological organisms that kill the target pest as well as naturally or synthetically derived insecticides. Because these products and recommendations change so often, I'll direct you here for current recommendations. (See bottom of that page.)
Codling moth control is definitely a challenge, but you can expect reasonable control with a little effort on your part. Even if you lose some crop each year, you should still have enough to make growing apples and pears worth your while.
