Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your question about navel orange fruit splitting.
Splitting citrus fruit is a common problem, especially with navel oranges. The following link (http://anrcatalog.ucanr.edu/pdf/8038.pdf) is a short 1-1/2 page informative UC document which describes the condition, along with suggestions for resolution. Very briefly, fruit splitting is likely the result of stress to the tree, and is probably related to extreme fluctuations in temperature, humidity, soil moisture, and possibly fertilizer levels. The disorder is often caused by a combination of these factors rather than by a single cause.
Avoiding fluctuations in soil moisture (suggest adding mulch under the tree and consistent and ample water, especially during heat spells) as well as fertilizer levels throughout the growing season may help to minimize fruit split.
I hope this is helpful, please contact us again with any further questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (MCW)
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, although we will be moving this spring. We will notify you if/when that occurs. 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/)
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client's Request: Good Morning Gardeners! I drive by your beautiful community garden (MGCC's “Our Garden” in Walnut Creek) every morning on the way to my daughter's preschool in the Shadelands area. I've noticed that you've already covered your citrus trees for frost protection. I have a small backyard orchard with 5 citrus trees...4 of them with fruit on now, and I have not covered them yet.
I have these dark colored tree covers that I bought and use (basically a large cloth bag, kind of like an outdoor patio chair cover with a drawstring at the base of the tree), but the directions that came with them advise removing them by day so the tree can receive light. It's a hassle putting them on by night and taking them off each morning. What do you use? Do they allow light in and for how many days in a row can they safely stay on the tree without harming the tree? Can the same covers be used in the springtime when my mandarin is flowering to keep bees off and keep the fruit seedless? Thank you so much for your advice! Happy Holidays.
You probably noticed that the covers at Our Garden are white, and are designed to let some light through so they can be left on for several days at a time. You can buy such “frost blankets” at garden centers or online- one brand that I know of is called 'Agribon' They are a lightweight, non-woven material, and come in different weights. You also asked about using this for keeping bees off your mandarins: I would not use the heavier frost blanket for this, but you could use the lighter weight 'row cover' which is often used to keep various moths and bugs off vegetables. Most nurseries and/or hardware stores should stock this or similar types of frost cloth.
Here is a link to an online source which sells these “cloths”, and it has some good information on its use. This is a commercial link, and we do not endorse any particular business, but I include it as it may be helpful to you. https://www.groworganic.com/frost-and-sun-protection/frost-protection/frost-blankets.html. There are many other online suppliers that can be found by Googling “frost protection cloth”.
For now, the covers that you have been using most likely are doing a good job, but being dark in color need to be removed during the day to let light to the plant. If you can provide a frame around the plant to keep the cloth from touching the leaves, that will work best. Here is a UC link with helpful information: http://homeorchard.ucdavis.edu/8100.pdf
You also asked how long the covers can be left on. I can't give you an exact number of days, but the plant should be fine for a few days at a time. I personally use these covers, and I generally leave them attached to the framework, and try to pull them back on warm days to get some airflow and/or sunlight to the plant. I make hoop structures out of re-bar and PVC pipe, and find that kitchen clips (such as you would use for chip bags) are a quick and easy way to attach the cloth to the frame. You can see pictures of such a structure here: http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=22776 You can anchor the PVC hoops with 2 foot lengths of re-bar pounded into the ground (make sure the diameter of the re-bar is less than the internal diameter of the pipe!)
I hope this is helpful, and if you have further questions please don't hesitate to get back to us.
Happy Holidays to you, and good luck with your citrus.
Help Desk of the UC Master Gardener Program of Contra Costa County (SMW)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round (except the last two weeks of December) 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/)
Advice for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Response from the Help Desk: Thank you for sending the photo of your citrus leaf with what clearly looks like a whitefly infestation. Whiteflies are tiny, flying insects that derive their name from the mealy white wax covering their wings and body. They suck the leaf's sap, which in some cases can cause leaves to curl and/or wilt and drop when populations are large. Whiteflies can be abundant in vegetable, fruit, and ornamental plantings, especially during warm weather.
However, the primary concern with whiteflies is the honeydew they produce. Honeydew excreted by nymphs collects dust and supports the growth of sooty mold, which is the black stuff you see on the leaf in your photo. (Sooty mold does not cause damage to the plant unless it's so heavy it blocks all sunlight from reaching the leaves.) The honeydew however attracts ants, which can "protect" the whiteflies from natural predators which would usually keep the whitefly population under control. These natural predators can also be harmed by the home gardener spraying with broad-range products such as insecticidal soaps.
Management of heavy whitefly infestations is difficult so prevention is best. Removing heavily infested leaves or hosing them with “sharp” water sprays is a good way to get a handle on an infestation. You will need to be vigilant in watching for whiteflies in the future. Since dusty leaves are more attractive to these insects, regularly washing off the plants with water should help a lot. Also, controlling ants will go a long way to allowing the natural predators to do their job. Placing sticky yellow traps (available at garden stores) on the trees (or plants or nearby) can also be used to monitor for whiteflies and will give you a warning that you need to increase your inspections and controls.
Here is more information from UC about whiteflies and their control: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7401.html and also information about ants and their control: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7411.html.
Please do not hesitate to contact us again if we can be of help in your gardening.
Happy gardening!
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/).
Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County
MGCC Help Desk Request:I am located in Central County. I am having issues with my lemon tree. I have attached some photos. I was hoping you could give me some advice.
I have never sprayed pesticides. I am hoping for a more organic solution to the issues. I know it might not be possible.
I have not fertilized it this year. It is on our sprinkler system so it gets water daily. Some of the leafs have spiderweb looking substance under the leafs. Some leafs are yellow. I have also noticed the spikes are very large. Thank you so much for your help.
MGCC Help Desk Response: Thank you for contacting UC Master Gardener Program with your lemon tree questions and for sending the photos. The symptoms you are seeing could be the result of various minor problems that occur on citrus. The curled leaves show signs of citrus leaf miner. Citrus leaf miners are moth larvae that create shallow tunnels in young leaves. They can distort the leaves but are generally not harmful to the tree. You are probably seeing the end result of leaf miner damage that was done previously. For more information on citrus leaf miners, see: http://ipm.ucanr.edu/PMG/PESTNOTES/pn74137.html.
We are not sure about the spiderweb type substance. It could be from an insect, e.g., whiteflies, but if so you should also find sticky areas on the leaves. Also, any pictures of the insect would be helpful. It is also possible that there are spiders on your tree. If that is the case, I would not worry. If you want the spider identified, see if you can get a photo and we will try to identify it.
The fruits look like they may have been damaged by the thorns which you indicated are very large. That would happen if the fruits were rubbing against the thorns. Is that possible? If not, another possibility would be herbicide damage. Is it possible that herbicides were used anywhere near the citrus tree? Even your neighbors? Make sure you remove the damaged fruits from the tree before we have any more rain. The damaged areas provide an opening for fungi and other diseases to get into the tree. Also, large thorns might indicate that the branch is a juvenile branch or is coming from below the graft, the "bump" near the bottom of the trunk. If from below the graft, you should consider removing that branch as it probably will not produce edible fruit.
The spots on the leaves may be from a fungus. The fungus may be the result of the watering, especially if the sprinkler system is putting water on the leaves. Make sure that the sprinkler is set low and also make sure that the sprinklers are not dampening the tree trunk. Wet tree trunks can lead to root or crown rot from fungus growing around the roots and crown (where the roots and trunk meet). Root and crown rots are serious diseases that are difficult to treat and can ultimately kill the tree.
The daily sprinkling may also be causing other problems for the overall health of your tree. Daily watering might not be supplying the citrus with enough water. Citrus, like most trees, do best with less frequent, and deep watering to promote stronger roots. To give you an example of how infrequent the watering should be, watering in the heat of summer should be done about every seven to ten days. This would be for citrus planted in the ground and with several inches of mulch under the tree out to drip line. In a pot you would need more frequent watering as they dry out faster. If other plants on your irrigation system need frequent watering, you should consider setting up a separate irrigation system on a different timer for the lemon. For more information on watering citrus, see: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citruswatering.html.
You mentioned that you had not fertilized the tree this year. Yellow leaves are a common sign of a lack of nitrogen. Citrus trees require regular fertilization, especially with nitrogen. The fertilizer should be applied in January or February (prior to bloom) with a second application in May and perhaps a third in June. This link has more information on fertilizing citrus: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citfertilization.html.
Finally, I thought that you might be interested in this general write-up on growing citrus in Contra Costa County: http://ucanr.edu/blogs/slomggarden/blogfiles/4260.pdf
Please let us know if you have any remaining questions. You are also welcome to bring plant samples into our office if you want more information. We are open Monday to Thursday, 9am to 12 noon.
Good luck with your lemon tree..
Help Desk of the UC Master Gardener Program of Contra Costa County (ECS)
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/).
Advice from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Client: I wondering if you could help identify the issue with some of the leaves on my Lisbon lemon tree? I typically water once a week and not again until it dries out.
MGCC Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk with your question about your lemon tree. Thank you for the photograph which was very helpful.
The vein yellowing evident in the photograph you sent could be due to several factors:
- There is a virus that can cause vein yellowing, but it is not common in our area, and so is probably not the cause.
- Herbicide toxicity can cause this type of symptom. If you have used an herbicide containing either diuron or bromacil, that could be the cause. If you have not used herbicides, then the cause is probably nitrogen deficiency.
- Although nitrogen deficiency symptoms usually present as more general yellowing rather than prominent vein yellowing, nitrogen deficiency can cause vein yellowing when the soil is cold (usually during the winter months), or if stems or the trunk are girdled (mechanically constricted). If there are any ties around your tree, you should remove them.
Lemon trees need regular fertilization, particularly with nitrogen, to remain healthy and productive. If you have not fertilized your tree this spring, we recommend that you do so now. You can either use ammonium sulfate or a standard citrus fertilizer. Information on proper nitrogen fertilization of citrus, based on the age of the tree, can be found at this University of California website http://ipm.ucdavis.edu/PMG/GARDEN/FRUIT/CULTURAL/citfertilization.html.Or you can just follow the directions on the fertilizer label.
Citrus has many roots near the soil surface. Lemon tree roots should not be disturbed by digging or cultivating, since damaged roots will negatively impact water and nutrient absorption. At least several inches of mulch under the entire tree is usually also recommended to protect the roots, keep the roots cool, retain Irrigation moisture, and minimize competing weeds. Keep the mulch at least 6” from the trunk.
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Citrus should be watered every 7 - 10 days during the dry season. Additional information on how to water citrus can be found (and/or downloaded free) at the University of California's website http://ipm.ucdavis.edu/PMG/GARDEN/FRUIT/CULTURAL/citruswatering.html .
I hope that this information is helpful. If you water and fertilize the lemon tree properly but the leaves do not green up with 4 weeks, please feel free to contact us again.
Help Desk of the UC Master Gardener Program of Contra Costa County (JL)
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/).