PROTECTING DECLINING TREES & PLANTS FROM SECONDARY PESTS
SUCKING AND CHEWING INSECTS (FEED ON LEAVES AND STEMS)
Chewing and sucking insects – Systemic insecticides can be applied and usually only require one application. These insecticides localize in the leaf and/or xylem and protect the tree throught the growing season. Alternative treatments should be applied were bees may pollinate such as fruit trees and other flowering trees. There are organic dormant oils and summer oils as well as insecticidal soaps that can be applied. These treatments will require more applications throughout the active season.
Broad spectrum sprays should not be applied because they kill beneficial insects as well. Also more than one application is required, so they are not financially or environmentally beneficial. If they must be done plan on repeating every thirty days throughout the active season.
Aphid– there are more than 1200 species of aphid which come in all sorts of shapes and color they are the most common of all pests, they cause damage by extracting sugars from leaves, in doing so the leaves are less capable of manufacturing sugars and in time become smaller in size thus reducing the amounts of sugars that can be created. Aphids excrete a sugary substance called “honey dew” that attracts ants, wasps and some scale. Honey dew that collects along branches and trunks becomes colonized by sooty mold, a blackish gray mold that discolors bark. This can be used to identify infestations during the dormant season. Some species of aphid are more damaging than others and many have built natural tolerances to foliar sprays. Even more impressive are the wholly aphid that have a waxy coating that resembles thin strands of cotton which actual repel pesticides and fluids. Aphids along with all leaf chewing and sucking insects should be controlled systemically so only the target insect is eliminated and beneficial insects are allowed to remain and aid in natures process.
Super family: Coccoidea
Scale– Scale insects are made up of many families, genus, and species from hard scale to soft scale and even cottony scale they all have a very effective defense system in the form of a waxy coat that protects them from insecticides and the elements. Scale insects are far less mobile then aphids and as they are mostly larger in size they are also more serious a threat to your tree, using a rasping mouth part they draw sugars from the twigs just below the leaves, some species attach themselves to the leaves. Scale insects should be sprayed with dormant oil in November, December and February. Or timed during crawler stage (spring) with insecticide. Some heavy infestations may need to be sprayed additionally with superior oil in the spring and summer months; in all cases Pruning to introduce more light into canopy along with fertilization is helpful to reduce populations.
Pit scale- Probably the smallest of the deadly insects it is often overlooked or misdiagnosed. When this tiny scale insect grows to populations of more than 8-10 per sq. inch it can cause defoliation. This is especially dangerous during the summer months when leaves are needed most and it predisposes the tree to other secondary insects or diseases. Treatment is difficult and takes dedication, in smaller trees physically sanding the infected bark with fine grit sand paper combined with trunk and limb spray of insecticide and oil should be done as soon as identified and then twice again within 2 to 3 weeks. A preventative schedule of dormant oil should be applied November, December and February. Ensure ample amounts of water and fertilizer are introduced into cultural habits.
Common California scales and susceptible plant species: http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7408.html
Red gum lerp psylid _Glycaspis brimblecombei: is an insect that attacks only red gum eucalyptus. The small psylid extracts sugars from leaves and excretes it to create a sugar based “shell” which appears somewhat like a cone. Once populations grow, they can completely defoliate a giant eucalyptus within three years and either predispose it to attacks from long horned eucalyptus borer or outright kill it. In the interim they are easily controlled with the systemic insecticides, increased watering, and fertilizer to create balanced new growth of foliage.
Oak Leaf roller_ Archips semiferanus [Walker]: also known as web worms, is a moth that chews leaves, in the caterpillar stage, creating clusters of webbing which resembles that of a spider. Mostly found in live oak and valley oak, damage is seen as “flagging” of dead branches throughout the crown of the tree.
A foliar application of BT (Bacillus thuringiensis) in March and again in April, during the leaf rollers larval stage, is the best control. BT is a bacterium that produces crystals that are toxic to caterpillars only. Once eaten, these crystals destroy the stomach lining of the caterpillars and they stop eating and soon die. BT should be applied twice within fourteen days of each application.
As caterpillars, Western tussock moth _Orgyia vetusta, chew on the leaves of most oak species but are predominantly found on live oak. The adult moth lays its eggs in the cocoon it molted from. The cocoons are brown and “fuzzy” with exit holes at the apex. They are mostly found on the underside of limbs or places protected from weather. The tussock moth is relatively harmless but a large population is easily capable of defoliating trees. Natural predators of the moth generally prevent such large out breaks. Bt should be applied during the caterpillar stage. For best results two applications should be made, within fourteen days of each other.
Thrips that are pest are often in the Family: Thripidae
Lace bugs Family: Tingidae
Thrips and lace bug– Thrips feed on both the upper and lower sides of leaves. Lace bugs only from the underside. You can identify lace bugs by stippling on the top of the leaves and excrement on the bottom. Both sides of the leaf have stippling and excrement in the case of Thrips. Common species infected are Photinia, Azalea, and Rhododendron. Possible treatments include a systemic soil drench or foliar spray with a contact insecticide.
WOOD BORING INSECTS-(BORERS)
Borers– the Order coleoptra contains 1/5 of all described species in the animal kingdom. There are hundreds of thousands of species and they discover more every year. Beetles are extremely important to ecosystems because of their proficiency at facilitating decomposition of organic matter. However this is also why they can be pests. Some species feed and/or breed inside living trees. They are opportunistic and generally a secondary illness, which means they are infesting your tree because your tree has a primary contagion and is not healthy. The most damage is done during the larval stage of the beetle. Many beetles are attracted to one or two genus of tree and thus are named after what they infect.
The following are some common borer in the Sacramento valley and their habits. Keep in mind that a healthy tree that is fertilized and receives proper watering and mulching is far less likely to be infected if at all.
Bronze birch borer (BBB) _ Agrilus anxius: Unlike most other borers, the BBB is not organ specific it may enter any part of the tree and begin breeding. Often aerial inspections are necessary to identify, exit holes have very little Fras but are distinctively “D” shaped with one flat side. Infection is not a death sentence. Populations can be managed with proper fertilization, pruning of infested limbs, and spraying with a systemic insecticide twice annually during breeding season.
Trunk/bark applications are done to poison the beetle as it enters bark and exits. They should be administered during the breeding season and combined with low nitrogen fertilization.
Pacific flat headed borer _Chrysobothris malis: is also referred to as flat headed apple borer or flat headed borer. These beetles prefer damaged and or weak trees/limbs to infest and lay eggs. The larvae feed on the cambium tissue and can girdle a young tree in a short span of time. This pest is generally not the primary cause of decline but a secondary cause. Fertilize with a low nitrogen amendment, maintain good cultural habits, and apply foliar systemic insecticide throughout spring and summer months.
Long horned eucalyptus borer _Phoracantha semipunctata & Phoracantha recurva: is a rare insect to find in the adult stage, however they can be devastating. Adult borers are speckled gray with antennae that are 1 1/2 to 2 times the size of the body. Long horned borers are attracted to freshly cut wood, dying limbs, and trees suffering from stress, especially drought stress. Control starts with the removal of all dead wood including surrounding firewood. The next step is a sequence of applications including foliar sprays of oil in conjunction with wedgle injections of a systemic insecticide, and soil injections of merit. This should all be followed by fertilization for two or more seasons.
Sequoia pitch moth_ Synanthedon sequoiae : often confused for a borer pitch moth is identified by a large pitch mass found on pines throughout the bole and trunk of the tree. The adult stage of the moth lays its eggs in the fissures of the bark. As the eggs pupate they agitate the cambium creating a pitch cocoon that protects them until their adult stage when they fly away. They do limited damage to the tree but may draw the attention of red turpentine beetle (Dendroctonus valens LeConte), especially in susceptible species. Treatment is good cultural habits along with fertilizing and monitoring for RTB.
Anthracnose results from infection by any of several different, host specific, fungi species. Infections worsen when prolonged rain occurs after new shoot growth. Two applications of a contact and systemic fungicide mix should be sprayed at bud break and then ten to fourteen days after. Or a wedgle application in November can be used for large hard to reach trees. Trees should be fertilized to help strengthen their own defenses.
Wilts should be pruned out by sterile tools and either root infusion or trunk application of Pentrabark and Agraphos.
Armillaria _ Armillaria mellea: is a soil borne fungus that causes root rot in many species of tree. Mycelium can persist for year in infected soil, roots, and wood. Presence of armilleria should receive 42lbs of Ca per 1000sqft along with water management and a TGR mixed with beneficial bacteria. This is not a cure only a management plan.
Verticillium wilt _Verticillium dahliae and V. albo-atrum: is a wilt that can be spread through pruning tools and root graphs. If infection starts from root graphs or infected soil you may see lowest limb from the ground affected first and then others successively up trunk. In some instances you may need to remove a tree to prevent the spread to others if planted in line or a row (remove a link in the chain.) Cures include sterile pruning of infected wood and balancing cultural habits in combination with soil sampling and prescription fertilization. Some cases may require fertilization with PHC while waiting for results.
Phytophthora _Phytophthora spp.: can be treated in all stages except the resting stage (near death) with trunk sprays of pentrabark and Agraphos, applications should be done at leaf set, on deciduous trees.
Fusarium canariensis: The fungi that cause Fusarium wilt diseases are composed of a group of host-specific forms (forma specialis) abbreviated f. sp. Thus, the fungus that causes wilt of canary island palms is Fusarium oxysporum f. sp. canariensis. It can be spread through contact with infected pruning tools. Infected trees should be removed using tarps to collect dust and protect other palms around them. Responsible cleaning of all tools used during the process should be done immediately after job completion.
Botrysphaeria spp.: Several species of the fungus Botryosphaeria cause cankers on branches and stems of trees and shrubs with low vitality. Branches turn reddish brown and die back and often exude drops of yellowish pitch. Giant Sequoias are common host species for this fungus. Often you will find one dead branch on a redwood that is associated with a canker, a sunken area containing dead tissue. This should be removed back to the trunk with sterile tools and the tree should be fertilized and monitored.
Entomosporium spp.: is a fungal disease that spots the leaves of apple, flowering crab apple, evergreen pear, hawthorn, pear, photinia, pyracantha, quince, Rhaphiolepis, and toyon. Infected trees can be treated with high nitrogen fertilizer combined with two applications of a contact and systemic fungicide mix in November and again at bud break.
Diamond scale _Sphaerodothis neowashingtoniae: primarily affects California fan palm, Washingtonia filifera. It causes yellowing, dark mottling, and necrosis of fronds. Black or greasy, diamond-shaped or elongate fungal bodies occur on fronds, resembling scale insects. It can cause considerable damage when its population grows large enough. Treatment is a foliar application of a contact fungicide. Proper management May require 3 to 4 applications.
Bacterial infections- should be treated by addressing the primary causes such as watering habits, soil fertility, and available organics. A half rate fertilization and bio package combined with vertical/horizontal mulching for soil peculation should be considered
Fluxing/Wet wood– Bacterial fluxing is normally not serious in most trees but as a chronic disease it can contribute to a general decline in tree vigor, especially of older trees growing under adverse conditions. Bacterial fluxing in landscape trees is usually unimportant except for the disfiguring appearance of light or dark streaks where liquid seeps out of cracks and wounds and flows down the bark. The liquid on the bark surface becomes contaminated with mixed populations of many different kinds of airborne bacteria, yeasts, and filamentous fungi that give it a slimy texture and often a fetid odor. Bacterial fluxing should be treated with fertilization and incorporation of fungal based mulch.
Fire blight _caused by bacteria Erwinia amylovora: Prune branches showing dieback and severe blight. Space plants to provide good air circulation. Prune during the dry season when infection is less likely to occur. Do not wet foliage with overhead irrigation; do not over fertilize. For severe cases you may soil drench with table salt at rate of 1lb per 8”diameter and water heavily.
Bacterial knots- several bacterial knots exist in such species as olive, oleander, sycamore, and Hollywood juniper. Pruning should be done, using a sterile tool, at least 18” before canker or between the tree and the canker. Fertilize, irrigate without broadcasting water so as not to transmit bacteria, and mulch to at least 3” depth.