Help for the Home Gardener from the Help Desk of the
UC Master Gardener Program of Contra Costa County
Situation: Client visited the Ask A Master Gardener (AAMG) Help Desk at a recent Wednesday morning program at MGCC's “Our Garden” asking for advice on the black spots on the fruit of his mature Meyer Lemon fruit tree. MGs on duty that morning couldn't give him a definitive answer at the time, but asked him to make some further observations about the tree and posed several questions about the health of the tree for him to answer and to send an email with his findings to the MGCC Help Desk.
Client's Response and Request: I appreciate your effort in determining the problems with my Lemon tree,
1. The tree is approximately 25 years old,
2. I bought it as a semi-standard tree. it's 18 feet tall and has a 15' canopy.
3. it's a great -year round producer of fruit.
4. The tree is located about 20' from a building, and it now gets sun all day.
5. I recently cut down a large olive tree that partly shaded the tree and blocked a lot of early morning sun.
6. I don't recall ever seeing spots on the rinds before, I have seen the inside of the fruit that looks darkened and not much juice before. I assumed that it was due to lack of water or fruit being old.
7. I fertilize the tree probably once a year with fertilizer spikes.
8. The bark looks fine.
9. The spotting on the fruit is about 20% of the total, and the leaves look good.
I'll examine the tree closer, but it's been a fantastic tree. I'll send you this now and if you need anything else from me let me know.
MGCC Help Desk Response: Thanks for coming to the UC Master Gardener Program Help Desk at Our Garden with your request for assistance with your Meyer lemon tree and fruit. Quite a few of us have spent time researching your inquiry in the past few weeks; unfortunately, we have been unable to pinpoint a specific disease or cause in order to give you a confident diagnosis.
Here's a list of what we think could be causes for your fruit decline based on our research:
- The change in the sun exposure is likely to have been a culprit, but we don't think that it is the only factor causing damage to the fruit. This problem may be resolved next year after the tree has had some time to adjust to the new light exposure.
- The high continual heat we've experienced this past summer may also have contributed to fruit decline.
- The cold wet winter last year may have caused some of the damage to the fruit.
- Oddly enough, actions you have taken to care for the tree may also have caused problems. See information in the attached link below.
We found an on-line UC article that includes many photos of various types of rind damage on citrus. There is mention in this article of many causes of fruit rind damage including: cold wet weather and frost, copper sprays, fertilizer sprays, wind damage, etc. Please take a look at this article to see if any of these causes may apply to your situation.http://ipm.ucanr.edu/IPMPROJECT/ADS/Fruit_disorders_in_citrus.pdf
We think that the best thing you can do now is to remove all the damaged fruit and give your Meyer lemon the very best cultural care you can and then you'll need to simply wait and see. Citrus are usually very hardy in our area and we think you may see recovery and improvement by next year.
Here are some tips on giving your citrus good cultural care:
- Citrus trees require moisture for growth and fruit production. Apply enough water at each irrigation to wet the soil three feet deep. This requires three to six inches of water depending on the type of soil. Here is a link to information on how to water citrus: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citruswatering.html
- A layer of organic mulch will help retain soil moisture and permits feeder roots to grow close to the surface. Mulch should not be placed close to the trunk of a mature tree.
- Mature citrus trees are given fertilizer to maintain their growth and fruit production. Nitrogen is the chief nutrient required by citrus and should be applied each year. Smaller quantities of phosphorus and potassium are required. These nutrients are held in the soil much longer than nitrogen. Here is a link to information on how to feed/fertilize citrus: http://ipm.ucanr.edu/PMG/GARDEN/FRUIT/CULTURAL/citfertilization.html
- Citrus may occasionally suffer from a deficiency of zinc or iron. When these nutrients are deficient, the tissue between leaf veins turns yellow, but the veins remain green, at least initially. Foliar sprays containing chelated zinc or iron can be used to correct these deficiencies. Iron deficiency can also be caused by excessively wet soil or by very alkaline soil (pH above 7).
- Citrus is ready to harvest when the fruit has colored and is mature. Your 25 year experience should suffice to know when the fruit is ripe... i.e. dark yellow. Fruit should be left on the tree until it attains a satisfactory "sweetness". Mature fruit should be carefully harvested. Any break in the rind will promote decay. Use sharp clippers to cut the stem close to the fruit. Fruit can be stored on the tree several weeks to several months, depending on variety, after it is mature. As you probably have experienced, fruit left on the tree too long will become overripe and can reduce the size of the following year's crop.
We hope you find this information helpful in bringing your lemon tree back to full production. Please let us know if you have any additional questions.
Help Desk of the Master Gardener Program of Contra Costa County (SLH)
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: email@example.com, 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/)./span>/span>
Advice for the Home Gardener from the Home Gardener from the
Help Desk of the UC Master Gardener Program of Contra Costa County
Help Desk Response: Thanks for contacting the UC Master Gardener Program Help Desk with your question about the “white spots” on your blackberries.
What you see happening on the fruit of your blackberry vine is an abiotic disorder (damage not caused by insects or disease) called “White Drupelet”. A “drupelet" is the individual seed on fruits like blackberries and raspberries (the “bump”).
White Drupelet will appear as a tan-to-white discoloration on the drupelets of caneberry fruit, and it can effect one drupelet or many. As you have described, the drupelet's often appear brown and hard at first, then become soft and take on a tan-to-white coloration.
This disorder happens when there is a sharp increase in the heat and a drop in humidity, often caused by wind. This is exactly the weather pattern we have had lately -- lots of wind with high heat and low humidity. Although this condition is weather related, the actual cause of the “whitening” is UV radiation. Ordinarily, cool, humid air scatters and absorbs UV radiation, while hot, dry air has the opposite effect and allows more direct UV rays to reach the fruit. You may be observing this condition more in the canopy of the vine, or on the berries exposed to the sun, while the fruit tucked in under the leaves lower on the vine may be unaffected. When the heat subsides, and the humidity increases the condition will correct itself. The berries are safe to eat but you will want to remove the damaged part of the fruit. This UC Pest Note provides some more detailed information on White Drupelet disease: http://ipm.ucanr.edu/PMG/r71800111.html.
There is some debate about shade cloth being used to protect the vines but we found no conclusive scientific information indicating that shade cloth will prevent this condition.
If you were to experiment using shade cloth you must be careful to leave a good space between the shade cloth and the vine for proper air circulation or the shade cloth will just exacerbate the problem, creating more of a greenhouse effect rather than a shade structure.
Note: If you were to see the pale colored drupelets ONLY on the back side of the fruit (away from the sun) this could be caused by thrips, red mites or stinkbugs. More information on growing caneberries can be found searching for “caneberries” at http://ipm.ucanr.edu/GENERAL/search.html
Thanks for contacting the Master Gardener Program with your question. If we can be of further help, don't hesitate to contact us.
Help Desk of the UC Master Gardener Program of Contra Costa County (BHD)
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: firstname.lastname@example.org, 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/)./span>
Advice From the Help Desk of the
UC Master Gardener Program of Contra Costa County
UC Master Gardener Help Desk: I did some research to determine possible causes for the reduced production of okra in your garden this year as compared to last year. I suspect that the high daytime temperatures that we've experienced on and off throughout the summer have contributed to the reduced production. My research also indicates that temperatures above 90° F (some sources say above 95°F) can interfere with pollination of okra and cause flowers and buds to drop. You reported in your latest message that you have noticed some encouraging signs that more pods may have started forming recently, which could be the result of the cooler temperatures that we had for several successive days last week.
Of course, we also experienced high temperatures from time to time last year when you report that production was much higher. So, there may be some other factors at work. You mentioned that you were doing some supplemental watering for the okra last summer to add to what was provided by your scheduled drip system. My research did indicate that water stress can also reduce pollination rates for okra. So perhaps the reduction in watering this year has also contributed to the reduced production rate.
One other consideration could be the fertility of the soil. Too much nitrogen will encourage lots of green growth but can suppress fruit development. Also, plants need adequate phosphorous which supports blooming and fruit production. If you have a soils test kit, it might be worth checking the fertility levels of the soils in the okra bed. If phosphorous is too low, you could supply a boost with a foliar spray or soil drench of a liquid fertilizer that is high in phosphorous. Just be careful not to supply more nitrogen if the current levels are already adequate.
One other fact I learned from my research is that you can prolong the production period of okra by cutting off about 1/3 of the plant top in late summer. This pruning allows plants to send out new growth and flower and fruit for a second time in the fall.
I hope this information is useful. You are welcome to contact our Help Desk if you have further questions.
Help Desk of the UC Master Gardener Program of Contra Costa County (TKL)
Editor's note: For more information on okra gardening, a Sonoma County MG article is recommended (click)... the pictures in this blog post came from that article.
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: email@example.com, 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/).