Master Gardener News Blog
By Leslie E. Stevens UCCE Master Gardener
I have little trails all over my lemon leaves. What do I do? Karen P. San Luis Obispo
Leafminers are best identified by what they leave behind – tiny, meandering trails on the undersides of young leaves. These mines are marked by thin dark lines of frass (feces) formed by newly hatched larvae feeding beneath the upper surface of leaf tissue. C
Citrus leafminer (Phyllocnistis citrella), a resident of California since 2000, confines itself to citrus trees (oranges, mandarins, lemons, limes, grapefruit) and close releatives such as kumquat and calamondin. Conversely, the serpentine leafminer attack a variety of flower and vegetable plants such as beans, peas, cole crops, tomatoes; begonia, dahlia, impatiens, petunia, and marigolds.
Adult citrus leafminers are tiny, light-colored, ¼-inch moths. The adult serpentine leafminer is a small black-and-yellow fly (Liriomyza species). Despite these differences, leafminers share many common traits.
They are most active in spring and summer months when tender new growth is abundant. Hot, inland temperatures tend to suppress populations, while mild coastal climates may extend leafminer seasons. The entire life cycle takes 3-7 weeks. Adults lay eggs on the underside of leaves. Eggs hatch after one week; larvae emerge and begin to feed just beneath the surface cells of leaf tissue, creating the telltale mines. Larvae molt, exit the mines, and roll the edge of the leaf. Within this curled leaf, larvae develop into pupae and emerge as adult moths.
Although leaf damage is unsightly, leafminers rarely threaten crops or overall plant health. Damage tends to be greatest on young trees, but will gradually decline as natural enemies become established. Insecticides are not recommended for leafminers. Young citrus trees may be the exception. Insecticides may be applied to new foliage when adult moths are present and laying eggs. Timing is important because chemicals are ineffective if applied when mining larvae are protected within leaf tissue. Manage leafminer populations the first couple years until the trees have sufficient leaf growth and are able to withstand pest damage. Other control strategies include removing water sprouts from trees to reduce leaf sites for leafminers to lay eggs and feed on. Also avoid applying leaf-stimulating nitrogen fertilizer when leafminer populations are high.
Always inspect plants for pests and disease prior to purchasing and planting.
Master Gardener Helpline
By Jutta Thoerner UCCE Master Gardener Volunteer
I used to call the UC Master Gardner Program in Orange County for advice with my plant and insect ID questions. Is this service available in this area? Christian, SLO.
Yes, these services are available through the UC Master Gardener helpline. We have three helpline locations in the county - San Luis Obispo, Templeton and Arroyo Grande.
There are four ways of accessing the Helpline.
1. Visit the MG helpline office
2. Call the helpline office number and talk to a MG or leave a voicemail
3. Drop off a sample and fill out a questionnaire when MGs are not in
4. Email MGs and include information and photos of your plant or insect issue, using firstname.lastname@example.org,
Tips on how to collect samples:
FOR PLANT PROBLEMS: Its ideal for the sample to be collected just before it is brought into the Helpline Office. If that's not possible, store the sample in the refrigerator until you can bring it in (don't add any water to the sample bag). Select a sample showing distinct disease or insect symptoms. Include plant parts to show various stages of the problem with diseased and healthy plant tissue for comparison.
FOR PLANT IDENTIFICATION: Collect as many parts of the plant including flowers and leaves attached to the stems, and any fruit or berries. Flowers are especially crucial in plant and weed identification. If submitting a root sample, place it in a paper bag separate from any other plant samples. Dig roots carefully; don't pull as diseased roots are fragile.
FOR PEST IDENTIFICATION: Handle the insects gently as not to damage them. Include any leaves with evidence of damage caused by the insect.
No problem is too small for the MG helpline!
San Luis Obispo: 2156 Sierra Way, 805-781-5939. Helpline is staffed on Monday and Thursday 1-5pm. Drop off samples anytime M-F, 8 am-5 pm.
Templeton: 350 N. Main St B, 805-434-4105. Helpline is staffed on Wednesday 9am -12 pm. Drop off samples anytime M-F, noon-2:30pm.
Arroyo Grande: 810 West Branch St, 805-473-7190. Helpline is staffed on Wednesdays, 9am -12pm. Drop off samples anytime M-F, 8 am-2:30pm.
Citrus and Avocado
By Jackie Woods UCCE Master Gardener
So you're thinking of adding a citrus or avocado tree to your garden repertoire. Great idea! I mean, who wouldn't want healthy, fruit-laden trees to provide delicious citrus and avocados? With the idea firmly seeded in your mind, what's the next step? What should you know before you start? What do these trees need to grow? With just some basic knowledge in hand, you too can successfully grow your own citrus and avocados!
Citrus and avocado trees are not drought tolerant plants. They like their food (nitrogen) and water. They are also particular about their living environment, preferring well-drained soils rather than heavy clay soils. Avocado trees don't appreciate excess water and are susceptible to root rot. Citrus trees love the heat, but they are susceptible to the dastardly Asian citruspsyllid, a pest that is a carrier of the devastating disease known as HLB or huanglongbing. Both citrus and avocado are not fond of severe freezing conditions either. Remember the devastating frost of 2007? Avocado orchards in Cambria, Morro Bay, Arroyo Grande and the Nipomo Mesa suffered greatly. By mid-January of that year, approximately 50-60% of SLO county's avocado crops worth an estimated $11.5 million was lost. The citrus crop also took a 50% hit with an estimated loss of $2 million.
Fear not! Help is on the horizon. Lucky for all of us, the UCCE Master Gardener Program of San Luis Obispo County offers free Advice to Grow by Workshops in their demonstration garden. And, guess what their next topic is? Citrus and avocados! The UCCE Master Gardener Program is a public service and outreach program whose mission is to extend research based knowledge and information to the public on home horticulture, pest management and sustainable landscape practices to the residents of California. How cool is that?
The Citrus and Avocado Workshop will be held on Saturday, July 16th located at Garden of the Seven Sisters, 2156 Sierra Way, San Luis Obispo. The workshop starts at 10:00 am and goes till noon. After the workshop, docents will be available until 1:00 if you have any gardening questions. It's going to be a warm one so bring your hat, sunscreen, and a water bottle!/span>
Bordered Plant Bug
By Andrea Peck UCCE Master Gardener
My plants are covered in black and orange bugs—should I be worried?
Your plants may be experiencing life with the bordered plant bug (Largus cinctus). The bordered plant bug is often confused with the boxelder bug and a number of other true bugs, but the dramatic coloring is a dead giveaway. Adults sport a deep gray-blue body color with an orange trim outline. Their “tail end” is dark black and semi-diamond shaped. When full grown, the bug can reach up to 1/2” in length, so you won't need your magnifying glass for this insect. The nymphs are smaller and similarly eye-catching, with a metallic blue body and one red dot in the center of their back. Certainly, they are striking to behold, but are they problematic?
This insect is generally not a major menace, particularly when it comes to your ornamentals. But, you may keep a sharp eye on them when it comes to your fruits and flowers. The bordered plant bug is a gourmand when it comes to homegrown delicacies such as strawberries, peaches, plums and, well, anything else that is juicy. In general, true bugs come with standard-issue mouthparts that include the capability of piercing their next meal, making a slushie of sorts, then sucking it up with their bring-your-own straw apparatus. Despite their MacGyver-type ingenuity, these pests are not considered enough of a threat to warrant chemical control.
You may notice a proliferation of this bug in the summertime. After overwintering, females lay eggs in the spring. Eggs hatch in about 14 days and nymphs typically reach adulthood during the summer. Should the bordered plant bug become a nuisance, hand-picking, or shaking them off into a container is recommended. A sharp spray of water may discourage the little creatures as well. For those who prefer machinery, try using a shop-vac especially on hardscape or where more sturdy flora such as trees and bushes are concerned. More cautious types may prefer exclusion methods, such as row covers or netting material.
By Lee Oliphant UCCE Master Gardener
I've found a bug that looks like a twig with legs. Is it harmful? How do I get rid of it? Pat M., Cambria.
Looks like you've found an “exotic” (not native to the region) Indian walking stick insect (Carausius morosus). While there are native walking sticks, they are not usually found in the garden. They live in native grasslands.
This strange looking insect arrived from tropical climates and was first found in Southern California in 1991. This species is a popular pet and likely escaped. They've been eating their way north and are now becoming a pest in central coast gardens, especially along the coast.
The Indian walking stick is greenish brown in color and grows to be about 3 inches long, but can appear much longer when the front legs are extended. Walking sticks are masters of camouflage. Their shape and color is similar to twigs and branches and their behavior can mimic plant material swaying in the wind. When disturbed, the walking stick retracts their legs and holds perfectly still making them look even more sticklike.
Walking sticks reproduce without mating, laying several hundred eggs over their lifetime. Eggs hatch in 10-12 weeks and nymphs begin to wander about. Nymphs develop into adults in about 4 weeks.
No research has been conducted on natural enemies of Indian walking sticks. They hide inside host plants during the day and are difficult to see because of their shape and color.
Both nymphs and adults have an appetite for foliage of azalea, bramble, camellia, geranium, hawthorn, hibiscus, ivy, jasmine, oak, privet, pyracantha, rose and some garden vegetables. They're most active at night, chewing around the margin of leaves making ragged edges.
Spraying insecticides for walking sticks is not recommended and is likely to disrupt beneficial insects. Instead, handpick them off at night, dropping them into a bucket of soapy water.
If you keep Indian walking sticks as pets, use caution when cleaning out the cage. The eggs look like frass and will survive the trash and later hatch. Bag all cage debris and freeze for at least 48 hours before placing in the trash.
For more information on Indian walking sticks visit- http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn74157.html