Common Tree Insects for the South Bay Area

Arbortek’s certified arborists not only work here in the South Bay are, but live here as well. They see and treat numerous native tree insects day in, and day out. Here are a few common tree insects you can watch out for yourself. If you see these little critters, it’s time to call Arbortek Trees.


Aphids are fairly small (smaller than most ants), somewhat pear-shaped, and come in a variety of colors. They are most commonly green, but some are white, brown, black, orange, green, or red while others are woolly, spotted or bull-legged.

Aphids feed on tree or other plant sap by sucking it out with their straw-like mouths. They often bunch up in clusters, feeding together on the underside of leaves, around stem joints, or on new shoots and flower buds.

They feed off deciduous trees’ leaves and evergreens and cluster in large colonies to attack new growth.

Early season aphids cause leaf curling and new growth distortion similar to broadleaf weed herbicide damage. If there is a large aphid colony, twig dieback and stunting may occur.

Prevention, especially the biological variety, is best done in late winter or early spring. However, if you missed that window, treatment can still be effectively applied. There are a number of pesticides that can tree aphids – head over to our blog Honeydew and You: How to Treat Tree Aphids for more detail.

If it’s too late and your biological measures were missed (or didn’t work effectively) Arbortek Trees regularly provides safe and effective pesticide treatments for trees and garden plants. Contact us for an assessment today.

California Oakworm

These California caterpillar natives love to munch on oak trees. Damage is very common on the coast live oak and most often seen in the San Francisco Bay area.

California Oakworm

During the fall, females lay eggs that hatch and overwinter into pupae late Spring. Overwintering typically does not occur on deciduous oaks, which lose their leaves during autumn. The Oakworm pupae emerge mid-summer as moths – you may see them flying around trees.

The young larvae skeletonize the leaves while the more mature larvae eat the entire leaf.

Inspect your trees regularly for oakworms during the active seasons. Arbortek can recommend the proper treatment option for your landscape. We also recommend fertilization of trees showing stress from defoliation.

If you are concerned about your oak trees, contact us for a consultation and learn how to keep your oak trees healthy and bug-free.

Lace Bugs

Lace bugs attack deciduous plants and evergreens. Infested leaves will present whitish flecked damage called stippling (similar to a “bleached” look). Large populations cause premature leaf drop and weaken plants by removing nutrients from their leaves.

Look for blackish, shiny droplets of lace bug excrement on the bottom of the leaf to pinpoint lace bug activity. A grouping of young lace bugs looks like a dark smudge on the leaf.

Their favorite hosts include deciduous plants (hawthorn, oak, pyracantha, quince, and sycamore) and evergreen plants (azalea, mountain-laurel, and rhododendron).

Lace Bugs

Monitor leaves in late May at three-to-four-week intervals. An insecticide application may be necessary from late May through mid-August. When planting a tree, choose a cool and shady site where naturally occurring fungal diseases will attack lace bugs and reduce their population.

If lace bugs are negatively affecting your landscape, contact us to get an inspection.

Honeydew and You – How to Treat Tree Aphids

Is there a tree dripping sap on your property – possibly staining sidewalks or other areas with sticky residue? Unfortunately, that is generally a sign of tree aphids. There are thousands of types of aphids who live in relatively temperate climates worldwide. They can cause severe stress to trees and other plants (roses are a prime target on the West Coast) and sometimes introduce fungal diseases.


What exactly are Tree Aphids?Honey Dew and You - How to Treat Tree Aphids by Arbortek Trees

Aphids are fairly small (smaller than most ants), somewhat pear-shaped, and come in a variety of colors. They are most commonly green, but some species are white, brown, black, and many other colors. Aphids feed on tree or other plant sap by, essentially, sucking it out with their straw-like mouths. They often bunch up in clusters, feeding together on the underside of leaves, around stem joints, or on new shoots and flower buds.


Aphid Tree Damage

Infestations of aphids pose a number of risks to trees and other plants. To start, their feeding weakens the tree, draining the sap the tree needs to remain vital and healthy. In plants affected by aphids, you may observe slowed growth rates, spotted or yellowed leaves, curled leaves, browning, wilting, lower yields of fruit or flowers and potentially the death of the plant.

Aphids also spread plant-based diseases. Weakened trees become more likely to succumb to the infections they spread. Fungal infections are common, as well as plant viruses. These diseases are usually much more harmful than the aphids themselves, the viruses in particular. Because of these risks, it is important to actively control aphid populations.


What is Honeydew?

As aphids feed on a plant’s sap, they secrete a sugary fluid called honeydew from their abdomen. When an aphid population grows large enough, the honeydew begins dripping down from the tree (and potentially making a mess of your sidewalk).

The honeydew that aphids produce is collected by certain birds, wasps, stingless bees, and honey bees. Honey bees process the honeydew into a darker, stronger honey which is highly sought after in Europe and Asia due to its purported medicinal value.


Biological Aphid Control

Other insects also harvest the honeydew. Some types of ants actually protect aphids from their natural predators because the ants essentially “farm” the aphids for the honeydew they produce. Deploying ant traps to reduce tree ant populations may help reduce aphid populations once their defenders are gone. Ladybird beetles (ladybugs) and their larvae feed on aphids, so encouraging the beetles can help balance out the aphids.


Chemical Aphid Control

Prevention, especially the biological variety, is best done in late winter or early spring. However, if you missed that window, treatment can still be effectively applied.

A number of pesticides, including surface sprays as well as systemic pesticides (chemicals that are absorbed into the system of a plant) may be used to treat aphid infestations. The systemic pesticides circulate through the plant, reaching the aphids as they feed and leaving other beneficial fauna undisturbed. Sprays like neem oil or insecticidal soap may also be effective, but they have to coat the tree thoroughly to insure that they actually make contact with the aphids and may impact beneficial residents.

If it’s too late and your biological measures were missed (or didn’t work effectively) Arbortek Trees regularly provides safe and effective pesticide treatments for trees and garden plants. Contact us for an assessment today.

Fruit Tree Selection Guide

Fruit Tree Selection Guide for San Jose Area

Fresh fruit from your own backyard is everyone’s dream. But many find the idea of planting and successfully growing fruit as a insurmountable task. Not so! Pick the right tree and plant at the right time – and you will be enjoying ripe and healthy snacks straight from the vine in no time!

First, what type of soil do you have? Certain soils are best for certain trees:

Sandy: peaches, pomegranates, apricots, plums, almonds, grapes, ad nectarines.
Loam: All trees, especially walnut and cherries.
Clay: Apples, plums, pears, apricots, almonds and peaches (grafted on plum rootstock).

Next, determine climate:

Here in the San Jose area, November through February the temperature will drop. To determine your climate (climates vary across Bay Area, especially Inland), count or estimate the number of chill hours your area receives. Chill hours are the total number of hours the temperature will dip below 45 degrees. Fruit trees require different levels of chill hours to produce the best fruit.

High – Trees that require 800 to 1,200 chill hours are apples, some apricot varieties, cherries, and pears

Moderate – 500 to 800 chill hours; some apricots, nectarines, plums, peaches, and some varieties of apples

Low – 500 hours or less; almonds, persimmons, pomegranates, figs, and some varieties of apples

Third, consider pollination requirements:

Some trees are self-pollinating, others require cross-pollinaters to be planted nearby. If the fruit tree requires a cross pollinator, and you don’t have one, you likely won’t get fruit.

Self-pollinating: Figs, peaches, nectarines, pomegranates and most varieties of apricots.

Needs cross-pollination- Almonds, apples, pears, plums, pluots and cherries. However, there are some varieties of these that do not need pollinators. If you are purchasing your own trees from a nursery, ask a nursery professional for assistance.

If a cross pollinator is needed for the fruit tree, you need space to plant both of them. Since space may be an issue, a suggested alternative is to plant fruit trees that have multiple grafts on them. You can purchase an apple tree that has up to 4 different varieties grafted onto the same tree. Again, ask your nursery professional to point you in the right direction for these trees, or contact your Arbortek Trees team of arborists for advice.

Will you have enough room when the trees are mature?

Walnuts – trees grow up to 30’ tall
Peaches – up to 15’ tall
Nectarines – up to 15’ tall
Figs – up to 30’ tall
Pomegranate – up to 20’ tall
Apples – up to 20’; dwarfing at 14’
Pears – up to 20’; dwarfing at 15’
Cherries – up to 20’, dwarfing at 12’
Apricots and plums – up to 18’; dwarfing at 14’

If you live in an urban area, you must consider city or county restrictions. Learn more about San Jose tree planting restrictions, in our Dummies Guide to Tree Planting in the Bay Area.

Lastly, make sure you have enough light.

Fruit trees need six hours a day during the growing season (when leaves are on).

Now you’ve determined the tree, it’s time to plant. Call San Jose tree experts, Arbortek Trees if you’d like to leave the planting to the professionals. Be sure to plant in winter, before the trees break dormancy.

The Hard Facts About Growing (and Spraying) Olive Trees

Spraying Olive Trees in San Jose

These blooming Mediterranean natives are true beauties, growing up to 30’ tall and spreading out nearly as far. It’s no wonder that olive trees have become California landscape mainstays, thriving in the plentiful sunshine and temperate climate that California offers up.

While we never complain about olives in a delicious tapenade or Niçoise salad, unless you have a sprawling property or plan on committing lots of time to jarring homemade olive oil – olive trees can be a major headache.

Olive fruit can be bad news for walkers – and your indoor flooring

Moderation is key, but olive trees didn’t get that memo. They produce an abundance of fruit that’s challenging to keep up with. When the olives ripen and fall from the tree, they can quickly cover the ground and sidewalks, posing a major, oily threat to those walking over them. Not only does the fruit create an increased potential for falls, but their color and oil can quickly be transferred from the soles of shoes to light-colored living room carpet.

The olive fruit fly is a serious pest of California olive trees

The olive fruit fly has been around for thousands of years, but have surfaced only the last couple decades in California. And in those couple of decades, they have cost olive farmers quite a bit! The adult fly is rarely seen, and the larvae feed on the fleshy olive underneath the skin. The damage makes olives prone to rot and premature dropping. For commercial growers, this is a serious issue. In order to produce olive oil, damage level must be below 10%.

Olive tree blooms are an irritant for allergy sufferers

Many people suffer from an allergic reaction to olive tree pollen, and their symptoms can be anywhere from mildly irritating to severe. When the pollen is released – typically in May and June – those with allergies can experience respiratory symptoms like runny, itchy, and watery eyes and noses, as well as sneezing, coughing, wheezing, and all sorts of olive tree-induced discomforts. Those with asthma must exercise extra caution even in the general vicinity of blooming olive trees.

If you are a homeowner with olive trees on your property, follow these suggestions:


  • First off, plant fruitless olive trees such as the ‘Swan Hill,’ ‘Wilsoni,’ ‘Majestic Beauty,’ or ‘Little Ollie’ types. These olive trees have little or no fruit. If you are looking for landscape appeal of an olive tree, without the fruit, these are your best options. Visit Bayscape Landscape’s planting page to learn ore about our planting services.
  • Second, let’s face the facts – timing is everything. In order for spraying to be effective, olive trees must be sprayed annually, in the first quarter of the year, and well before the flowers begin blooming in late spring and early summer. It’s sometimes necessary for trees to be sprayed more than once (and during extended bloom periods, two applications may be necessary). We advise to schedule your tree care experts for olive spray treatments in January.  At Arbortek Trees we have access to the most effective treatments, at the correct time of year (which is January for us in the San Jose or Bay Area, CA).

**If you intend to use your olives for making oils or table fruit, read this article from University of California (Cooperative Extension – Santa Rosa, CA) on “Controlling Olive Fruit Fly at Home” and learn about the various treatments available.

**For more information on the Olive Fruit Fly, we site “Olive Fly Control” from

**To schedule a olive oil treatment, call Arbortek Trees at 408-288-2942 or email us to schedule an appointment at


Growing Fruit Trees in San Jose


How To Spot Tree Disease, Before It’s Too Late!

Do you know how to spot tree disease?Arbortek Trees, Spotting Tree Disease

You probably already know many of the benefits of trees: that they’re a crucial part of the environment – providing shade, oxygen, and animal habitats; that they bring beauty and fullness to most any landscape; and of course, that they can add dramatically to both the curb appeal and value of your home and property.

It would be more than unfortunate to lose all of that to tree disease – especially since it’s often preventable or treatable, and since saving a tree is less costly and more efficient and desirable than removing it after it’s dead.
Proactive maintenance and preventive care are key to keeping your trees healthy. Do you know how to spot the warning signs of possible tree disease?

Check your trees regularly, and look for these (and other) red flags of tree disease:


  • Brown black “scorches” on leaves: a possible sign of the fungal disease anthracnose.
  • Rot on branches or trunks: could signify the presence of a soil fungus called crow rot.
  • Sunken or crumbling bark: might point to a canker
  • Yellowish/brownish foliage: Dutch elm disease could be present.
  • Sudden limb drop: While the sudden dropping of limbs from an otherwise healthy-looking tree may not necessarily be a sign of disease, it is, however, a concern as it has been happening with some regularity in the Bay Area. (Read more about this phenomenon on our website here.) Trees – most frequently quercus, populous, salix, eucalyptus quercus, ulmus procera, fagus sylvatica, and cedrus – can drop without warning and in the absence of disease symptoms.

It’s important to keep an eye on your trees, but nothing can take the place of a trained professional with the education and experience to know exactly what to look for. Call us to set up a tree inspection appointment with one of Arbortek’s ISA-certified arborists today.

How To Be Unpopular in the Tree Trimming World

Bad Tree Trimming | How to Be Unpopular in the Tree Trimming WorldPoor Rodney Dangerfield. The late “I can’t get no respect” comedian apparently found he wasn’t popular close to home, either.

“I looked up my family tree,” he said, “and found out I was the sap.”

In the tree-trimming world, nobody cares if you’re the sap in your family: what makes you unpopular has a lot more to do with blunders that hurt, even kill, the trees that you’re supposed to nurture to health. Consider hiring a certified arborist, otherwise you might be dealing with tree-harming issues like this:

  • Overdoing It: Too much of a good thing – whether watering or thinning – can quickly become a healthy tree’s downfall by opening the door to injuries, disease, and insects. Over-watering can weaken soil and inviting root problems and decay; over-thinning can take away a tree’s natural shade and let in too much sunlight, which can lead to splitting bark.
  • Topping: Not many living things can thrive when they lose 50 (or more!) percent of their source of nourishment – in a tree’s case, its photosynthesizing crown. That’s just one of many reasons that topping (removing the top of a tree’s leader stem) is dangerous to both the tree and a trimmer’s reputation. Not to mention, 50% of the Earth’s land biology lives in the tops of trees! Meg Lowman, also known as “Canopy Meg,” from the California Academy of Sciences wrote a blog about this rather unknown study here.
  • Damaging Bark or Soil: Carelessness isn’t smiled upon in almost any industry, and in tree-trimming, it’s no different. Parking your truck too close to the tree or using automated tools carelessly can cause a lot of damage, from compacted soil (that doesn’t allow water or air in) or injured bark.
  • Stubbing Out: Stubbing out, or snipping the tips of a branch, is no good, either – it often results in a single branch being replaced by several more. When that happens all over the tree, you’re looking at excessive regrowth, which is neither attractive nor healthy.

Well, there you have it. Hopefully this article has saved you from being unpopular in the tree-trimming world!

Tree Hollows: One Big Myth, One Big Truth Uncovered

The Tree Hollow Myth

In our popular imagination, there’s hardly a place as idyllic as the hollow of an old tree – even better if it’s in the middle of a mossy forest, surrounded by chirping birds and squirrels.

The romantic association makes sense: Winnie the Pooh, after all, lived in a cozy hollow in the Hundred Acre Woods with his “hunny” pot, and the Keebler elves have been churning E.L. Fudge cookies out of their hollowed tree with the magical oven for more than four decades.

Tree Hollow Myths | Arbortek Trees

But the biggest myth surrounding tree hollows isn’t quite so pretty: that some ugly disease must’ve caused it, thus, the tree needs to be destroyed and/or removed.

The truth? Tree hollows can be caused by a number of things, and they can be a perfectly natural part of a tree’s aging process. But hollows – even in dead trees – are an invaluable part of our ecosystem.

Hollows are generally a mark of age. You can safely surmise that a tree has been around for at least a hundred years, maybe even many centuries, if there are hollows present.

In that time, normal “wear and tear” takes place, and a hollow forms. Here are just a few ways that can happen:


  • Weather elements: Fire, rain, wind, a lightning storm – all are natural forces that might injure a part of the tree’s bark, even though the tree as a whole remains healthy.
  • Insects: Beetles and termites can make a quick snack of tree bark.
  • Fungi and bacteria: Various bacteria and fungi can enter through a part of the tree’s protective bark that’s already injured.
  • Overpruning: When you prune too much, it can eventually create wounds in a tree that are difficult to heal.

Regardless of how the hollow forms, it will likely become a perfect spot for birds, squirrels, and many other animals to nest, rest, or find protection from predators. When trees with hollows are removed, cleared, or logged, those animals lose their habitat and sometimes die. If you think pests may be invading surrounding trees, contact one of our specialists to visit your property and diagnose.

Why Spraying for Peach Leaf Curl Now, Can Save Fruit & Money Later!

You have probably seen a nearby peach or nectarine tree that is suffering greatly from peach leaf curl……

How does it happen? Peach leaf curl causes leaves of peaches and nectarines to discolor, pucker, distort, and eventually fall off. Peach leaf curl is a fungal disease which overwinters in the tree bark and around the buds. The fungus is seen in the trees as spores, usually in the new buds. Rain and abnormal wet weather splashes spores onto the emerging leaves causing more problems and emerging shoots to die.


Fruit production (thus income for farmers) can be reduced in severe infestations of peach leaf curl. Only    rarely do the reddish, curled, wrinkled areas develop on fruit surfaces, but later on in the season infected areas become corky and crack. Airborne fungal spores land on buds and infest newly-emerging leaves in spring. The fungus feeds on the young leaves and affects their development so that they become curled and distorted. The smaller leaf size makes them less efficient at making food for the tree.

Can the tree recover? Yes, trees can recover to make a second flush of growth and the leaves are usually unaffected by the fungus, but peach leaf curl fungus survives on fallen leaves and branches to re-infect next season’s new buds. Leaves finally turn brown, shrivel up, and drop from the tree. Fruits may drop early or turn a reddish purple color with bumpy growths on the surface. The cycle can repeat for years!

Is there any good news? Yes, the second set of leaves and buds emerge and can develop normally when the rains stop and daytime temperatures warm up. Fungal applications for most fruits on schedule should control the disease.

According to the experts, there are solutions to decrease problems created by peach leaf curl:

1. Rake up any fallen leaves and pull weeds that are growing beneath the drip line of the trees. Fertilize the area under the trees thoroughly.

2. Before the weather heats up, spread four inches of fresh organic mulch around the base of trees to maintain general tree health.

3. Water trees well on dry days and in summer seasons.

4. Remove any infected leaves as soon as they are seen, together with flowers and fruit.

5. Cover trees with polythene sheet in winter to prevent development of fungus.

6. Prune infected trees in the fall before spraying. Avoid over-feeding with nitrogen fertilizer.

7. Spray trees with Bordeaux mixture. Late January  or early February would be a good time and then repeat two weeks later before the leaves emerge from the buds.

8. Applications of fertilizers with seaweed can stop the spread of fungus.

treatpeachleavesIf your trees are showing signs of leaf curl now, the best thing you can do is follow the suggestions above to assist your trees through the stressful seasonal growing periods. Good Luck and please let us know if Arbortek helped you saved your fruit this year!


Sudden Limb Drop……

sudden limb dropLimbs can fail due to heavy and unnecessary loads of foliage or genetic defect, but there is another cause happening all around the Bay Area. It is called “sudden limb drop phenomena,” or sometimes referred to as “sudden branch drop.”

The phenomena causes limbs to break commonly on hot and windless days, with no obvious external signs of defect or trauma to the tree. The inner wood is broken bluntly (round and flat breakage), as opposed a breakage with sharp splintering.

Arborists studying sudden limb drop, or sudden branch drop, have found no consistent causes or visible warning signs. Some arborists theorize that sudden branch drop may be caused by change in branch movement, moisture changes, ethylene gas released inside the branches, however there are still no definitive answers.

So what can you do about it? First understand which trees commonly suffer from sudden limb drop. They include, but not limited to:

Eucalyptus Quercus
Ulmus Procera
Fagus Sylvatica

Next, reduce the risk. Trees are living organisms and arborists can not always detect when, and which limbs will fall. But we can imply measures for prevention of sudden limb drop the best we can.

1) Prune at risk tree limbs for crown thinning.
2) Install a cable system to limit motion and share the load with other limbs or nearby trees.
3) Request an Arbortek Arborist to visit your property to identify at-risk trees.