Advice from the Help Desk of the
UC Master Gardeners Program of Contra Costa County
Client: I'm having some early summer problems in my garden. I'm reluctant to use pesticides in my garden since I have several small children. Would you please provide some recommendations to either cure and/or minimize the problems:
- Tomato plants are doing reasonably well but there are some funky looking lower leaves that I'm concerned about.
- My roses' leaves are mottled with brown-red markings.
- The flowering pear tree's leaves are mottled and dropping; an arborist recommended injecting a chemical into the tree to cure the problem
- I suspect that my garden soil is too alkaline (i.e. previously tested pH@7.1). How can I test it and what can I do to reduce pH? Will just adding compost reduce pH?
UCMGP's Help Desk Response: Thank you for the photographs, which were very helpful. Our responses follow:
Tomato Early Blight Infection
Tomatoes: Your tomato plants look mostly healthy, but do have a very common disease called early blight seen on a lower leaf. This disease is caused by a fungus, and is spread by wind and splashing water. Disease development is favored by cool, humid conditions. To reduce the spread of the disease, avoid overhead irrigation. You may want to cut off the diseased leaf at the bottom of the plant to reduce spore production. These cultural methods should be sufficient to reduce the impact of the disease on your plants. Since you have small children and are concerned about the toxicity of pesticides, you probably will not want to use any pesticides on your tomato plants. Additional information about early blight can be found here http://ipm.ucanr.edu/PMG/GARDEN/VEGES/DISEASES/tomearlyblight.html.
Roses: Your roses are infected with rust, another common fungal disease in our county. Rust is favored by mild, moist conditions, and is less common during hot weather. However, once a leaf has become infected, it will not recover, and many infected leaves will drop prematurely. Avoid overhead watering or splashing onto leaves. Fungicides can protect new growth but do not eradicate the fungus from leaves that are already infected. Commercial products (when labeled for the care of rose rust) as well as Neem oil should be effective as a preventive when used before infection starts. Clean up all fallen leaves and put them in your green waste container (i.e. do not add to the compost pile). Since one of your roses is almost completely defoliated, you may want to consult with a rose specialist. You can find one here: http://www.ncnhdistrict.org/CRs/districtcr.html. Rust resistant roses are available. Additional information on rusts can be found here: http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/rusts.html.
Flowering Pear Tree: The photograph from the flowering pear confirms that it is infected with Entomosporium, another fungus that is spread by splashing rain. http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/entomoslfspt.html. We do not think that this disease warrants fungicide treatment. I do not know what chemical the pest company was Infected Evergreen Flowering Pear
all pictures from ucanr.edu
recommending for injection, but any chemical that has systemic activity would be transported to the leaves. The infected leaves do fall prematurely, but the tree grows a new set of leaves later. Hot dry weather protects the new leaves from infection. The fungus survives from season to season in the fallen leaves, so it is recommended to clean up all the fallen leaves and put them also in your green waste container (i.e., again do not compost). This cleanup is made easier if there is no other vegetation under the tree and the soil is left bare. The University of California says that in special cases fungicides can be applied, but neither of the UC recommended fungicides have activity when injected, only when sprayed on the leaves. Generally, we do not recommend spraying any type of pesticide on large trees, because the chemical, applied under pressure, is bound to drift onto other plants where children, pets, beneficial insects and wild animals can be exposed. Further, since this disease is mostly a cosmetic problem and not likely to kill the tree, using fungicide is hard to justify.
Soil pH: Home test kits for soil are fairly reliable as long as the instructions are followed carefully. A pH of 7 - 7.5 is borderline satisfactory, but may go up over time because our municipal water tends to have high pH. We recommend that you wait until the plants have been harvested and then add garden sulfur to the soil in the fall according to label directions. Lowering the pH with sulfur takes time (i.e., months), so you must be patient. Adding compost will not lower the soil pH.
I hope that this information is helpful. Please do not hesitate to contact us again. Good luck on a successful summer garden.
Editor's Notes: It is likely that the tomato, rose, and flowering pear tree problems may have been caused by the late rains creating conditions conducive to fungus: cool, humid conditions. Warmer, drier weather should minimize these types of fungus infestations provided there is adequate air circulation and not overhead watering early evening.
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 (//ucanr.edu/blogs/CCMGBlog/).
Posted on
Monday, June 20, 2016 at
12:07 AM
Request from Client at Master Gardener's "Ask a Master Gardener" Help Desk tomato leaf w/early blight
I bought this tomato from your Great Tomato Plant Sale in April. It's now late May and while the tomato is alive it sure is not looking good. It looks like it's diseased with spots on the leaves and "sores" on the main stem. It's.not looking good and I don't think it's going to survive or produce tomatoes. What should I do? (
Note: Due to time constraints, the tomato specimen was subsequently transported to the MGCC office for further diagnosis and the promise to get back to the client via email.)
Response from MGCC's Help Desk: After further examining the tomato specimen that you brought to Our Garden' AAMG Help Desk yesterday in our Pleasant Hill Help
tomato stem w/early blight
Desk office, we believe that the plant may have been attacked by Early Blight. Early blight
(Alternaria solani) is a fungal disease. The early symptom of the disease are round leaf spots that first appear on the older leaves. Stem lesions also develop on the stem at the base of the plant. We could observe both the leaf spotting and the stem lesions on your specimen. Had the plant been mature enough to have set fruit, you may also have observed spotting on the tomatoes.
A common source of the fungal spores that cause early blight is debris from infected plants left in or on the soil (where it can survive at least 1 year), and spores from other affected plants dispersed by wind, water, insects, or animals. As explained in this University of California website,
http://www.ipm.ucdavis.edu/PMG/GARDEN/VEGES/DISEASES/tomearlyblight.html the fungal spores require moisture for germination and infection. We also observed that the compost in which your tomato was planted was very wet. The wet planting medium, coupled with the cool and often cloudy weather we have experienced for the last few weeks, probably combined to create an environment favoring the development of the disease.
As noted above, the spores from affected plants can survive in soil for at least a year. The spores can also survive in a compost pile unless the pile is managed in a manner that allows the compost to develop very hot temperatures for a sustained period of time. Most home gardeners are not able to manage their compost piles in that manner. Although good compost is created, the pile doesn't get sufficiently hot to kill fungal spores. For that reason, you may want to avoid putting any plant material that shows signs of fungal disease in your compost piles.
Since the spores can survive in soil for at least a year, you will want to be sure that you do not attempt to grow any other tomatoes or other plants in the same plant family (Solanaceae, or nightshade family) including peppers, eggplants, potatoes, and tomatillos in the soil from the container in which you were growing the diseased tomato. All of the plants in this plant family can suffer from early blight. Also be sure to clean the container thoroughly before using it for another plant. After washing the container well, you can use a solution of 10% bleach and 90% water to rinse the container to increase your chances of killing all the pathogen spores.
In examining the tomato, we also noted that the root zone of the plant was very poorly developed. I understand that you purchased the tomato at our tomato plant sale in early April and had potted it in a container that was about a five gallon size. We would have expected the root system to have grown much larger by now. The compost in which the tomato was growing was very heavy and dense. You may have better luck with your tomatoes if you alter the potting soil medium you use. I also use compost in the containers in which I grow tomatoes, but before using it I mix the compost with equal amounts of perlite or vermiculite as well as some coconut coir. The perlite or vermiculite helps keep the mixture much lighter and creates better conditions for the roots to get the oxygen that the plant requires. The coconut coir increases the moisture holding capacity of the soil without allowing the soil mixture to become overly saturated with water.
Also, you may want to reduce the amount of water you give the tomatoes. When I examined the tomato this morning, the soil was so wet it was soggy and a significant amount of water had collected in the plastic bag in which the tomato was stored. I wouldn't expect to find such wet soil in a container in which a tomato was being grown except perhaps for an hour or so immediately after the plant had been well watered. After that time, the soil should dry out much more. Soggy soil prevents the roots from getting the oxygen the plant needs.
You might want to use the “squeeze method” to test the moisture level in the soils in your containers before giving your plants more water. Squeeze a handful of soil from the container firmly to do the test. If you squeeze the soil and it releases free moisture, you definitely do not need more water. In fact, you should not observe such conditions except immediately after you have watered or after a heavy rain. If you squeeze the soil and it readily forms and maintains a ball but does not release free moisture, the plant still has sufficient water and you can wait before adding more. If the soil won't form a ball or if it forms a ball only with much pressure and the ball falls apart readily, it's time to water again.
Finally, if you want to reduce the chances of having a recurrence of early blight next year, you might want to look for a variety that has better resistance to blight. I've listed below some tomato varieties (both heirlooms and hybrids) with some resistance to blight. Keep in mind, however, that even resistant varieties can suffer from blight if conditions are favorable for its development.
Hybrid, indeterminate, 60 days, red, elongated cherry (1 ounce), resistance: cracking, blight
Legend Tomato
OP (open-pollinated), determinate, 68 days, red, beefsteak (14-16 ounces), resistance: early blight, late blight (We had this variety at our tomato sale this year.)
Manalucie Tomato
Hybrid, indeterminate, 82 days, red, globe, resistance: blossom end rot, gray leaf mold, early blight, fusarium wilt
Matt's Wild Cherry Tomato
Heirloom, indeterminate, 70 days, red, cherry (1/2 inch), resistance: early blight
Mountain Fresh Plus Tomato
Hybrid, determinate, 77 days, red, globe (12 ounces), disease resistance: VFFN, blossom end rot, early blight
Mountain Supreme
Hybrid, determinate, 69-70 days, red, globe, resistance: VF, blight
Old Brooks Tomato
Heirloom, indeterminate, 78 days, red, globe (6-8 ounces), resistance: blossom end rot, early blight, late blight
Tommy Toe Tomato
Heirloom, indeterminate, 70 days, red, cherry (1 inch)
Hope this information is helpful. You are welcome to contact us at our Help Desk or at Our Garden if you have additional questions.
Master Gardeners of Contra Costa Help Desk
Note: The Contra Costa Master Gardener 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/
Posted on
Wednesday, June 10, 2015 at
12:05 AM