Master Gardener News Blog
11th Annual Tomato Extravaganza and Plant Sale
By Tami Reece UCCE Master Gardener
Did you know there are over 7,500 tomato varieties? Hybrids and heirlooms are most commonly found in home gardens. Hybrid tomatoes are a cross between two genetically different tomato varieties and give the best qualities of two or more parents. The most sought after qualities include increased productivity, disease resistance, cold tolerance, consistent size and fewer blemishes. Hybrids are firm and bruise less easily than other tomatoes. However, many do claim that hybrids just don't have the luscious flavor of an heirloom tomato. Seed saving is also not a viable option as the plant will never be true to its parent.
Heirloom tomatoes, or “open pollinated” tomatoes, are varieties that can be grown from seed and will be true to their parents. Some seeds have been passed down through generations, from gardener to gardener, for hundreds of years. Heirlooms generally have lots of seeds, are unique in shape and size, and oh the flavors you will find!
When buying tomato plants, it's helpful to know the difference between indeterminate and determinant varieties. Determinant varieties will give you all their fruit at once. If you plan to preserve tomatoes, this will allow you to water bath can or dry your harvest in a day or two. Indeterminate varieties will give you tomatoes all season, so you can enjoy them in salads all summer long.
Join us at the 11th annual Tomato Extravaganza on Saturday, August 19, 10:00 am to 2:00 pm at 2156 Sierra Way in San Luis Obispo. Presentations include “Growing Your Best Tomato”, “Rid Your Yard of Gophers and Ground Squirrels”, and “Preserving Your Tomato Harvest”. Landscape plants, herbs, and basil will be for sale and the California Rare Fruit Growers will be on hand selling trees. The UCCE Master Food Preservers will be available for your food preserving questions and there will be children's activities, informational booths, and a food truck from 11:00 to 1:00 pm. Admission is free and seating for the presentations is limited. Visit our website to register - http://ucanr.edu/sites/mgslo/. Stop by, learn something new and stroll the beautiful demonstration garden.
Are you interested in being a UCCE Master Gardener but need more information? Join us at the New Master Gardener Class Informational Meeting on Thursday, September 14th from 1-3 in the UCCE auditorium at 2156 Sierra Way, San Luis Obispo.
By Linda Lewis Griffith UCCE Master Gardener
What are those brown, squiggly lines on the underside of my lemon tree's leaves? James T., Oceano
Your tree probably has an infestation of citrus leafminer, a very small, light colored moth most commonly found on citrus and closely related trees, such as kumquats. The pest arrived in California from Mexico in 2000 and has spread throughout most of the state.
Citrus leafminer moths are seldom seen. They're most active from early morning to evening and spend days resting on the back of leaves.
Females lay eggs on the undersides of a tree's newest growth. The eggs hatch in 4 to 5 days and the larvae immediately begin feeding and create shallow, meandering mines. As larvae increase in size, the mines become more visible and fill with larval excrement, creating the telltale trails. Larvae molt 4 times over the next few weeks, eventually emerging from the mine as a prepupa, rolling the edges of the leaf to complete pupal development. The entire life cycle takes 3 to 7 weeks, depending on the temperature and weather conditions. Citrus leafminer is most common from mid-summer through fall and early winter.
Mature citrus trees can tolerate leafminer damage without any effect on tree growth or fruit yield. Nurseries and new plantings are more susceptible because their growth is slowed by the infestation. However, even when infestations are heavy, the trees are unlikely to die.
Because citrus leafminer are attracted to new flush of leaves, gardeners are advised to limit pruning to once a year, ensuring that cycles of flushing are uniform and short. Once citrus leaves have hardened, they're imperious to further leafminer damage. Do not prune off leaves afffected by citrus leafminer; undamaged areas of the leaves continue to produce food for the tree. In addition, avoid applying nitrogen fertilizer when leafminer numbers are high and new growth will be severely impacted.
Vigorous shoots known as water sprouts often develop on branches and above the graft union on the tree's trunk. These shoots grow rapidly and produce new leaves for a prolonged period of time. Remove water sprouts that serve as sites on which moths can lay eggs.
For more information, go to: http://ipm.ucanr.edu/PMG/PESTNOTES/pn74137.html
Don't miss our 11th annual Tomato Extravaganza and Plant Sale on Saturday August 19, 10:00 to 2:00 p.m. at 2156 Sierra Way, San Luis Obispo.
This week's insect is a fairly impressive predator. Dobsonflies are aquatic insects in the family Corydalidae, order Neuroptera - same order that includes Green and Brown Lacewings, Ant Lions, and Snake Flies. Only the larval stage is aquatic, but it may last several years. The larvae are known as “hellgrammites”, and are also very impressive predators, often catching and feeding on small fish. This is something that you don't see too often, a lower form of animal life, an insect, predating on a higher form, a fish. You do see it once in a while though. I have seen large tropical tarantulas kill and eat young birds in the nest. I had a person tell me they had seen a large Chinese mantid catch and try to eat a hummingbird, but the bird died after being caught and the mantid dropped it.
As you can see from the picture it is a large insect, some of the largest being nearly 5 inches in length. Adults are highly attracted to lights at night. The males have the very impressive large mandibles, but these are not meant to bite humans. They are most likely used on other male dobsonflies, to pick them up and throw them off to the side when competing for a female's attention. Mandibles this large are seldom functional for anything else, and you can feel a strong poke when they try to bite but it seldom breaks the skin. Now the females are a different story. Their mandibles are very functional. While trying to pick some females off our backlight sheet on a tropical collecting trip, I had to be very careful to grab them close to their head. Grab them closer to their body, and they can turn their head and bite. It does hurt and it drew blood.
The female's highly functional mandibles indicate that it probably is a predator as an adult. I'm not sure what they would eat, but anything smaller than it is, would probably be fair game. I don't believe the males predate as adults. Dobsonflies do occur in California, especially in rivers and streams coming down through the Sierra Nevada foothills. But the local males don't have mandibles quite as large as those from the tropics.
This will be my last article for two weeks. I am leaving the country for a tropical collecting trip to French Guiana. One of our collecting sites is next to a good sized river so perhaps we will be able to attract a few Dobsonflies to our black light sheet. Wish me luck.
Norman Smith, UC Master Gardener, San Luis Obispo County
About Norman -
I was the Fresno County Entomologist for 30 years. I fielded calls from the general public, pest control companies, farmers, PCA's, etc., ran our insect trapping program, and gave presentations on insects to many different groups, but especially schools. I developed a 100,000 insect specimen collection for the county over the 30 years that I was there. I received my Ph.D. in Entomology at UC Davis in 1979.
I now enjoy working in my garden, traveling with my wife, golfing and bowling, take insect collecting trips in the US and overseas in the tropics, and work on some personal research of some small wasps. I also enjoy working with and for the Master Gardener program in SLO.
By Polly Nelson UCCE Master Gardener
What are the silky spots on the back side of my avocado leaves? F.B., Arroyo Grande
Persea mites (PM) cause spots to form on the underside of the leaves of avocado tree. Classic damage presents as distinct circular, yellow or brown spots along veins on the undersides of leaves, and the mites feed under dense silvery, silken patches. The spots become visible through the upper leaf surface as their numbers increase. Avocado Brown mites and Sixspotted spider mites can also feed on avocado leaves; the former mainly on the upper leaf surface, causing the upper leaf to appear bronzed or scorched, and damage is not in circular spots. Sixspotted spider mite damage is primarily on the underside of leaves and produces brown to purplish irregularly-shaped blotches along the veins, not distinct circular spots.
Persea mites (Family Tetranychidae) are yellow to green with two or more dark spots on its body. Adults have eight legs (six in the nymph stage). Each female lays 2 to 4 dozen round, pale yellow eggs in her lifetime; egg to adult development time is 2-3 weeks during temperatures of 63˚-77˚F. Densities of mites are lowest around March and gradually increase through spring as they feed on new leaf growth. Populations peak in July and August, but are suppressed when humidity is low and the daily high temperature is 100°F or greater for several consecutive days.
Persea mites are most damaging to Hass, Gwen, and a few other avocado varieties. Bacon, Fuerte, Lamb Hass, and Zutano varieties are much less affected.
High PM numbers can severely stress trees and cause premature leaf drop and defoliation, which results in sunburned bark, dropped fruit, and reduced yields. Lessen the effects of persea mites by maintaining healthy trees. Avoid over-watering and over-fertilizing. Avocado trees are susceptible to root rot diseases, a problem that is exacerbated by improper watering practices. Excess nitrogen will promote leaf flush and attract more mites. In the home garden, low numbers of mites can be tolerated without causing detrimental affects to otherwise healthy trees. If numbers get too high, washing the leaves, especially the undersides, with a stronge stream from the garden hose, to remove mites and destroy nests. Insecticidal oil can be applied if water alone doesn't work, although it may not be practical with a large tree.
Additional information may be found at http://ipm.ucanr.edu/PMG/r8400211.html
Don't miss our 11th annual Tomato Extravaganza and Plant Sale on Saturday August 19, 10:00 to 2:00 p.m. at 2156 Sierra Way, San Luis Obispo./span>
By Leslie E. Stevens UCCE Master Gardener
Stumped by what's devouring your prized tomatoes? Or what's causing all those squiggly lines on your citrus leaves? Contact your local UC Master Gardener Helpline.
Trained volunteers are available Mondays, Wednesdays or Thursdays at Helpline offices in Arroyo Grande, San Luis Obispo and Templeton to aid home gardeners in solving their plant or plant related pest or disease problems. UC Master Gardeners will listen to your gardening problems, ask pertinent questions, and analyze pest and plant samples when provided.
Frequently, Helpline volunteers may not be able to identify a pest or diagnose a disease on the spot, but they have access to multiple, science-based resources to help nail down your gardening issues and offer possible solutions. All UC Master Gardeners have completed a comprehensive home horticulture training program under the supervision of the UC Cooperative Extension horticulture advisor. They participate in continuing education workshops and other trainings in order to maintain their UC Master Gardener certification.
Home gardeners can call, email or drop off samples at any of the Helpline offices Monday through Friday. If volunteers are not available at the time of contact, a UC Master Gardener will get back to you during regular Helpline office hours. Please provide your name, home city and contact information (including telephone number and email), along with a brief description of your gardening question. Include names of plants and pests involved if known. Detailed photos may also be submitted via email at firstname.lastname@example.org.
To aid Helpline volunteers in analyzing your plant and pest samples, it's important the specimens be fresh and undamaged. Try to provide live bugs, for instance. Submit samples in a clear plastic bag or container. Do not add water. If samples cannot be brought in on the same day you collect them, store them in a refrigerator. Include multiple plant samples to show the extent and type of damage or infestation.
For specific information on UC Master Gardener Helpline offices, locations and office hours, visit our website at http://ucanr.edu/sites/mgslo/Master_Gardener_Helpline/ The website includes a link with detailed instructions on submitting pest and plant specimens to the Helpline.