Black leaves on citrus trees

How To Manage Citrus Trees

SERIES 16 | Episode 26

Citrus trees are common in backyards all over Australia, but the challenge is that they suffer from many pests and diseases. It’s important to know what signs to look for, how to treat them and how best to feed citrus for a healthy tree and great fruit crops.

A lemon tree that has lost many leaves and has dead wood might well be sick. Prune any dead wood off to encourage new growth. Problems can also be caused by a severe lack of water. Citrus trees need lots of water. In Adelaide apply about 3 to 4 centimetres of the equivalent of rain each week from spring until autumn. The way to see whether you’re doing this correctly is simply to use a cup, turn on a sprinkler and see how long it takes to get 3 to 4 centimetres of water in the cup. Elsewhere around Australia use commonsense. Feel the leaves. If they feel cool and thick, the tree is fine, but in hot weather, if they feel dry and leathery, the citrus probably needs a drink.

A hole in a citrus tree indicates a more serious problem. It’s caused by a borer. Borers are the schoolyard bullies of the plant kingdom. They attack the weakest plants and those under stress. It does not mean they will spread to other trees. For recent holes take a piece of wire, and jam it down the hole to skewer the borer. But for a tree riddled with borers and other problems it might be better to remove the tree and plant a healthy, new one. Plant it a little away from the old tree and in a couple of years you’ll have a great crop of lemons.

If your orange tree has yellow leaves, with darker, green veins, this indicates an iron deficiency commonly known as chlorosis. It’s particularly common in alkaline soils like those around South Australia. Treat this with iron chelates. (Mix it according to the packet instructions). Put in a sprayer and spray the foliage. In the warmer weather you should see a difference in about three to four days. For a large tree apply with a watering can and water around the tree’s root zone. Always remove ground covers, such as ivy, from around the roots of the tree before applying the iron chelates.

Another problem to watch for is sooty mould. It’s a fungal problem but it doesn’t need to be treated with fungicide. Sooty mould actually indicates there is an insect pest, such as white fly. These are sap sucking insects, often found on the undersides of leaves, especially during the cooler weather. These suck sap from the leaves and secrete a sweet honeydew which drips onto the foliage and the sooty mould grows in the secretion. To treat white fly use an oil based spray. Commercial products are available but Peter Cundall’s recipe works well. Use about a cup of ordinary cooking oil, a half a cup of water and a tiny amount of ordinary washing-up detergent. This is known as white oil. Put it in water, so it’s about 40 parts water to one of this mixture. Stir it up and spray it on.

Remember to get good coverage of the leaves so that you get the white fly. It smothers them and they die. For a smaller white fly problem, try a commercially available yellow white fly sticky trap. White fly are attracted to yellow and they stick onto the trap. To make your own use a yellow ice cream container and smear it with Vaseline or cooking oil.

Another common problem on citrus is wiggly lines. It is caused by the citrus leaf miner, a tiny moth that lays its larvae into young leaves and causes distortion of the leaves. Simply control by using a routine oil spray similar to what was used for the white fly.

Weird looking, twisted, deformed fruit with almost finger like growth is the result of citrus bud mite. It’s a microscopic sap sucking insect that affects the leaves, flowers and fruit. If you’ve got trees with deformed fruit don’t worry it will not hurt the tree. Routine oil sprays will keep the mite population under control.

Keep citrus trees happy and healthy by using organic based fertilisers. These products do more than feed the plants – they also feed the soil and encourage earthworm and soil microbial activity. Add about a handful of fertiliser per square metre once a season and cover with mulch. Follow these basic principles for happy, healthy citrus, which produce loads of fruit.

Citrus Sooty Mold Info: How To Get Rid Of Sooty Mold On Citrus Trees

Citrus sooty mold isn’t actually a plant disease but a black, powdery fungus that grows on branches, leaves and fruit. The fungus is unsightly, but it generally does little harm and the fruit is edible. However, a severe coating of fungus can block light, thus affecting plant growth. Most importantly, citrus with sooty mold is a sure sign that your citrus tree has been invaded by harmful insects. Read on for tips on controlling citrus sooty mold, along with the insects that create conditions ripe for fungal growth.

Citrus Sooty Mold Info

Citrus with sooty mold is the result of an infestation of aphids or other types of sap-sucking insects. As the pests dine on the sweet juices, they excrete sticky “honeydew” that attracts the growth of ugly black mold.

Sooty mold fungus can grow wherever the honeydew drips – on sidewalks, lawn furniture, or anything else under the tree.

Citrus Sooty Mold Treatment

If you want to get rid of sooty mold on citrus, the first step is to eliminate the honeydew-producing insects. While aphids are often guilty, honeydew is also left behind by scale, whiteflies, mealybugs and various other pests.

Neem oil, horticultural soap or insecticidal sprays are effective ways of controlling pests, although eradication generally requires more than one application.

It’s also important to keep ants in check. Ants love the sweet honeydew, and they will actually protect the honeydew-producing insects from ladybugs, lacewings and other beneficial insects, thus ensuring a continual supply of the gooey stuff.

Control ants by placing ant bait under the tree. You can also wrap sticky tape around the trunk to prevent the ants from crawling up into the tree.

Once the pests are controlled, the sooty mold will usually wear away on its own. However, you may be able to speed the process by spraying the tree with a strong stream of water, or water with a little detergent mixed in. A timely rainfall will do a world of good.

You can also improve the appearance of the tree by pruning damaged growth.

How to Manage Pests

Pests in Gardens and Landscapes

Sooty Mold

Revised 7/11

In this Guideline:

  • Management
  • About Pest Notes
  • Publication
  • Glossary

Sooty mold on an orange. Citricola scales on the stem produced the honeydew.

Sooty mold growing on honeydew on a citrus leaf.


Sooty mold is the common name applied to several species of fungi that grow on honeydew secretions on plant parts and other surfaces. The fungi’s dark, threadlike growth (mycelium) gives plants or other substrates the appearance of being covered with a layer of soot.

Sooty molds don’t infect plants but grow on surfaces where honeydew deposits accumulate. Honeydew is a sweet, sticky liquid that plant-sucking insects excrete as they ingest large quantities of sap from a plant. Because the insect can’t completely utilize all the nutrients in this large volume of fluid, it assimilates what it needs and excretes the rest as “honeydew.” Wherever honeydew lands—e.g., leaves, twigs, fruit, yard furniture, concrete, sidewalks, or statuary—sooty molds can become established.

Although sooty molds don’t infect plants, they can indirectly damage the plant by coating the leaves to the point that it reduces or inhibits sunlight penetration. Without adequate sunlight, the plant’s ability to carry on photosynthesis is reduced, which can stunt plant growth. Coated leaves also might prematurely age (senesce) and die, causing premature leaf drop.

Fruits or vegetables covered with sooty molds are edible. Simply remove the mold with a solution of mild soap and warm water.

Fungi that most commonly cause sooty molds in garden and landscape situations are in the genera Capnodium, Fumago, and Scorias. Less common genera include Antennariella, Aureobasidium, and Limacinula. The species of sooty molds present are determined by a combination of the environment, host, and insect species present. Some sooty mold species are specific to particular plants or insects, while others might colonize many types of surfaces and use honeydew produced by several kinds of insects.

A number of insects can produce the honeydew sooty molds need for growth. Their common characteristic is that they all suck sap from plants. The insects include aphids, leafhoppers, mealybugs, psyllids (including eucalyptus lerp psyllid), soft scales, and whiteflies. Both the immature and adult stages of these insects feed by sucking sap from plants, producing honeydew.


Most plants will tolerate a small insect population and light amounts of sooty mold. When sooty molds are present on any surface in the landscape, it indicates there is, or has been, a sucking insect population present in the vicinity. Control of sooty molds begins with managing the insect creating the honeydew. For example, populations of aphids usually are highest on succulent, new growth. In some situations a strong stream of water can dislodge the insects. Also fertilize and water to keep plants healthy but not excessively vigorous.

Another important consideration can be ant management. Ants are attracted to and use honeydew as a source of food. Because of this, they will protect honeydew-producing insects from predators and parasites in order to harvest the honeydew. In many cases, predators and parasites are sufficiently abundant and quickly begin feeding on and reducing populations of scale insects, aphids, psyllids, whiteflies, or mealybugs once ants have been eliminated. If populations fail to decline, apply horticultural oils, neem oil, or insecticidal soap to suppress the problem insects. One or more applications might be needed. For detailed information on managing these pests see the appropriate Pest Notes listed in References.

Sometimes judicious pruning can be helpful in removing most of the infested plant parts. Also, keep ants out of trees and away from honeydew-producing insects by applying a sticky compound around the trunk and trimming limbs touching buildings or other access points. Baits, such as ant stakes placed under trees and shrubs, may help reduce ant foraging in some cases. More information on ant management can be found in Pest Notes: Ants.

Once honeydew-producing insects are suppressed, sooty molds will gradually weather away. In some instances, if necessary, sooty molds can be washed off with a strong stream of water or soap and water. However, it can be difficult to remove sooty mold even with soap and water.

Table 1. Some common honeydew-producing insect groups.

(Green peach aphid)

(Eucalyptus redgum lerp psyllid)

(Rose leafhopper)

Soft scales
(Brown soft scale)

(Obscure mealybug)

(Silverleaf whitefly)


Dreistadt, S. H., J. G. Morse, P. A. Phillips, and R. E. Rice. March 2007. Pest Notes: Scales. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7408.

Dreistadt, S. H., and E. J. Perry. Aug. 2006. Pest Notes: Lace Bugs. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7428.

Flint, M. L. May 2000. Pest Notes: Aphids. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7404.

Flint, M. L. Sept. 2002. Pest Notes: Whiteflies. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7401.

Grafton-Cardwell, E. E.. Dec. 2003. Pest Notes: Cottony Cushion Scale. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7410.

Paine, T. D., and S. H. Dreistadt. Aug. 2007. Pest Notes: Psyllids. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7423.

UC Statewide IPM Program. Feb. 2007. Pest Notes: Ants. Oakland: Univ. Calif. Agric. Nat. Res. Publ. 7411.


Pest Notes: Sooty Mold
UC ANR Publication 74108

Author: F. F. Laemmlen, UC Cooperative Extension (emeritus), San Luis Obispo Co.

Produced by UC Statewide IPM Program, University of California, Davis, CA 95616

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Sooty Mold

Sooty Mold (fungi – Capnodium spp., Fumago spp., and others): Sooty mold is a name commonly given to a condition that is not truly a disease, but a black coating on leaves, branches and fruit made up of fungal growth. The fungus is usually dark colored and powdery-like, hence the name sooty mold. The fungi associated with this condition are saprophytic, that is, they do not feed on live plant tissue, but rather thrive on insect secretions with a high content of sugars. These secretions, known as honeydew, are particularly common with aphids, scales, white flies, and other insects. The insect honeydew provides nourishment for the fungus, and under proper conditions, the entire plant may be covered with the sooty mold.

A black velvety coating made up of the fungal strands is formed on the surface of leaves, twigs and fruit. If the honeydew is light, it may appear only in spots. As a general rule, the black fungus coating usually can be rubbed off easily from the surface of leaves, fruit or branches. With time, the fungus may dry-off, become flaky, and fall off. If for some reason the insect infestation decreases, the amount of sooty mold also will decrease. If no insects are present to cause a re-infestation, rains will usually wash off most of the sooty mold. The fungi causing sooty mold are known to occur on citrus, oleander, gardenia, fig, crapemyrtle, azaleas, pittosporum and many other ornamental bushes and trees. Control can be obtained by applying insecticides that reduce insect populations. Using oil formulations as insecticides is effective, since oil gets rid of many of the insect pests and also softens the black fungus so it can be washed off easier by rain or other means.

Why does my lemon tree have black scabs on the lemons and yellow spots on the leaves?

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Are ants on Citrus trees OK?

Is your citrus tree looking ok? I often visit gardeners with citrus and they often have problems. The first thing I look for is ants tracking up and down the tree.

While lots of flowers is promising for a new harvest in a few months, and you may think the ants are drawn to them for the nectar, the ants are a real problem. Actually, the ants themselves are not the issue, but the reason they are in the tree is a problem.

Pictured: Scale insects on an ornamental shrub Courtesy of wikimedia commons

Ants can often be found tracking up and down in citrus, gardenias, bay trees and many more shiny-leafed trees and shrubs.

They are doing their job of cultivating waxy scale insects so they can collect the sweet exudates from the scale and feed it the ant young back in the nest.

Look closely at your citrus leaves and you may find you have a black dusty film on the leaves too. This is the black sooty mould so often associated with scale insects. It is harmless, but the scales will be small round raised lumps on the underside of the leaves near the veins.

Their are sucking the life out of your tree and have to be stopped.

Here are the top 4 organic things you can do to treat it:

1. If the tree is tiny, just wipe the scale off with a moist cloth.

2. Ensure the tree is in a moist and well fertilised spot with its roots covered by soil then mulch and that it is not stressed and weakened.

3. If the tree is larger, spray the entire tree, including branches and underside of leaves, with an organic oil such as Eco Oil. It works to smother the scale. Do a follow up a couple of weeks later to ensure you have all the scale covered.

4. If your tree is still suffering from scale after this treatment, cover the tree branches and as many leaves as possible with biodynamic tree paste. This is available from the Biodynamic association to kill all scale nymphs and smother scale hiding in bark etc..

UC Pest Management Guidelines

| All citrus pests | All crops | About guidelines |



Scientific Names:
Argentine ant: Linepithema humile
Native gray ant: Formica aerata
Red imported fire ant: Solenopsis invicta
Southern fire ant: Solenopsis xyloni

(Reviewed 2/17, updated 2/17, corrected 1/19)

In this Guideline:

  • Description of the pests
  • Damage
  • Management
  • Publication
  • Glossary

Description of the Pests (View Ant Identification Key) (PDF)

There are numerous species of ants present in citrus orchards, however, the most common are the Argentine ant (Southern and Coastal California), the native gray ant (San Joaquin Valley) and the southern fire ant (statewide). The red imported fire ant has been found in Southern California, but is not yet established in citrus orchards. It is important to identify the primary ant species in the orchard, because management tactics depend on which ant species is present.

The Argentine ant is a small, uniformly deep brown ant. Worker ants travel in characteristic trails on trees, the ground, or irrigation lines and build their nests underground. Ant numbers peak in mid-summer through early fall.

The southern fire ant is light reddish brown with a black hairy abdomen. They usually swarm in late spring or early summer. These ants build nests of loose mounds or craters near bases of trees, do not aggregate in colonies as large as those of the Argentine ant, and will sting and bite.

Native gray ants are gray and considerably larger than the other two species. They nest in topsoil or under rocks and debris and move in irregular patterns. In contrast to Argentine and fire ants, the native gray ant is solitary and its importance in disrupting biological control is often underestimated.

Red imported fire ant is new to California and can make large, dome-shaped mounds. They feed on almost any plant or animal material.


Most ant species feed on honeydew excreted by various soft scales, mealybugs, cottony cushion scales, whiteflies, psyllids, and aphids. As part of this relationship, they protect these pest insects from their natural enemies, thus interrupting biological control. They also protect some non honeydew-producing pests, such as California red scales.

Argentine and native gray ants are the most common ant species that aggressively protect pest insects. In addition, Argentine ants and fire ants can plug up irrigation sprinklers. Fire ants directly damage citrus by feeding on flowers and damaging young developing fruit. They chew on the bark and cambium of young trees to feed on sap; this can girdle and kill young newly planted trees. They also sting people working in the orchard and may cause allergic reactions.


Ants can be extremely disruptive to an IPM program. The Argentine, native gray, and fire ants can be prevented from climbing trees by skirt pruning and the use of sticky materials applied on top of a tree wrap to the bark as well as with insecticides.

Biological Control

No effective natural enemies of the ants are known.

Cultural Control

Skirt prune trees, i.e., remove branches within 12 to 30 inches of the ground, and apply sticky material to the trunk to prevent access to the trees by ants. Use polybutenes, as oil-based materials may cause phytotoxicity and should not be used.

The application of sticky polybutene materials directly to the trunk of citrus trees can cause bark cracking, especially if multiple applications are applied to the same area of the trunk, the area is exposed to sunlight (topworked trees), or both. The sticky material can be applied on top of a tree wrap, but this is both laborious and expensive. Young trees, which have a very thin cambium layer, are most susceptible to damage.

Sticky material should last from 2 to 10 months and will also prevent the access by Fuller rose beetles. If the sticky material contains tribasic copper sulfate, it will also control brown garden snails. Apply it higher above the ground to increase the persistence of sticky material, to reduce dust and dirt contamination, and to decrease irrigation wash-off.

To prevent bark damage by fire ants, plant trees with the bud union about 6 to 8 inches (14–19 cm) above the soil surface. Irrigate as needed, but avoid applying water to the trunk and do not allow water to pond near the trunk. Periodically examine bark under trunk wraps of young trees. When trees are large enough, remove the trunk wraps, which provide protection for ants.

Ants are attracted to trunk gumming. If gum is observed, inspect and if necessary, treat for Phytophthora gummosis (see DISEASE section). Bordeaux whitewash helps prevent gumming.

Cultivation reduces ant numbers but may create so much dust that it disrupts biological control of other pests.

Organically Acceptable Methods

Use cultural controls, including banding trunks with sticky materials in combination with skirt pruning, in organically managed citrus groves.

Monitoring and Treatment Decisions

Monitor the orchard in spring when honeydew-producing insects, such as aphids, appear. Check the abdomen of ants descending the tree trunks to see if they are swollen and translucent; this identifies them as honeydew-collecting species. Periodically inspect for ants and bark damage under the trunk wraps of several young trees.


Baits are the preferred chemical method for ant control whenever feasible. Effective bait insecticides have slow-acting toxicants that worker ants collect and feed to other ants, including nest-building immatures and queens. For the most effective and economical ant control, apply insecticides in early summer when ant numbers are just beginning to increase and are becoming active on the ground surface. To determine which bait to use, identify your primary ant species; fire ants are predominantly protein feeders (preferring oil based baits) whereas most gray and black ants are sugar feeders (preferring liquid sugar baits).

Corncob Grit and Oil Baits

Solid baits utilize treated corncob grits mixed with soybean oil as the food attractant plus an insecticide. These are effective for the primarily protein-feeding fire ants. The toxicants tend to degrade in light, so apply baits early in the morning or late in the day when ants are most active and will rapidly take the bait into the nest. Generally, corncob grit type baits are broadcast over the acreage that needs to be treated. However, spot application of baits at the location of the ant nest is preferred over widely spreading the bait because it concentrates the food where the ants are.

Sugar-water-based Baits

Liquid baits use a toxicant mixed in sugar water, which disguises the toxicant as well as helps attract the ants. These baits are most useful for the liquid sugar-feeding Argentine and native gray ants. Evaporation of the bait can cause the concentration of the toxicant to increase to a level in the bait that becomes repellant to ants. All liquid baits must be used in an EPA-approved bait station. Currently, there are no registered products that have been proven to fully control ants in citrus orchards.

Broad-spectrum Insecticide Sprays

The alternative to liquid sugar-bait stations or corncob grit baits is to use a broad-spectrum chlorpyrifos insecticide sprayed at the trunk and soil interface or inside the wraps of young trees. It is quicker acting than a bait, but not as long-lasting because the residue breaks down quickly. In addition, chlorpyrifos sprays kill only the worker ants that contact it on the soil surface, while baits are carried into the mound and fed to other ant stages.

Common name Amount to use REI‡ PHI‡
(Example trade name) (type of coverage)** (hours) (days)
Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide’s properties and application timing. Always read the label of the product being used.
(Tanglefoot) NA NA
RANGE OF ACTIVITY: Pests: narrow (trunk climbers); Natural enemies: few, if any
PERSISTENCE: Pests: long; Natural enemies: long
COMMENTS: For use on all varieties. Use polybutene-based products only. Do not apply sticky materials directly on the trunk; use a 6- to 18-inch wrap under the sticky material to protect the tree from sunburn. Exercise caution in applying multiple applications (more than 3 or 4); watch for symptoms of bark cracking. Apply the sticky band high enough to avoid sprinklers, dust, and direct sunlight. Reactivate periodically by rubbing with a stick to remove dust. Check to ensure that hanging branches, sticks, weeds, etc. are not allowing ants access to trees.
A corncob grit and soy oil bait. For use on all citrus varieties. Effective only against fire ants because they are attracted to the soy oil mixed with corncob grits bait. Apply when fire ants are most active during the season (especially early summer and fall) and when they are most active during the day (early evening and early morning when soil temperature is above 60°F). Treatments are most effective if applied 2 days after an irrigation, when ant activity is at a maximum. Do not irrigate again until at least 24 hours after application. Do not apply if rainfall is anticipated with 4 to 6 hours after application. While these baits can be broadcast using properly calibrated ground equipment to assure proper dosage and uniform distribution, spot applications at the location of the ant nest are preferred. Retreatment may be desirable after 3 to 4 months.
(Clinch bait 0.011%) 1 lb/acre 12 0
RANGE OF ACTIVITY: Pests: narrow (fire ants); Natural enemies: other ants
PERSISTENCE: Pests: intermediate; Natural enemies: intermediate
(Esteem Ant Bait 0.5%) 1.5–2 lb/acre 12 1
RANGE OF ACTIVITY: Pests: narrow (fire ants); Natural enemies: other ants
PERSISTENCE: Pests: intermediate; Natural enemies: none
COMMENTS: This insecticide takes several weeks to begin to kill the colony because it is an insect growth regulator. It does not kill the workers, but instead stops the growth of the immature ants and breaks the reproductive life cycle of the gueen. This causes colony death as the worker ants age and die and are not replaced.
(Altrevin Fire Ant Bait) 1.5 lbs/acre 12 5
RANGE OF ACTIVITY: Pests: narrow (fire ants); Natural enemies: other ants
PERSISTENCE: Pests: intermediate; Natural enemies: none
(Lorsban Advanced) 1–3% solution
(3–8 fl oz/gal water)
120 (5 days) See comments
RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
PERSISTENCE: Pests: short (low rates), intermediate (high rates); Natural enemies: short (low rates), intermediate (high rates)
COMMENTS: For use on all varieties. Registered for ant control under a supplemental (24c) label when temperatures are warm and ants are most active. Apply by thoroughly spraying base of skirt-pruned tree trunks and ant nests on the ground. Repeat applications are needed. Preharvest interval is 21 days for up to 7 pt/acre or 35 days for over 7 pt/acre and 28 days for ant control. Certain formulations emit high amounts of volatile organic compounds (VOCs); use low-VOC formulations. Regulations affect use for the San Joaquin Valley from May 1 to October 31, 2018 and 2019. Review the Department of Pesticide Regulation’s updated fact sheet. Additional application restrictions may apply; for more information on current California permit restrictions, see the Department of Pesticide Regulation’s Chlorpyrifos Interim Recommended Permit Conditions.
. . . or . . .
(Lorsban 15G) 6.6 lb/acre 120 (5 days) 28
RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
PERSISTENCE: Pests: short (low rates); intermediate (high rates); Natural enemies: intermediate (low rates), long (high rates)
COMMENTS: Apply with ground equipment to control foraging ants and suppress mounds. Do not apply where weed growth or other obstructions would impede uniform coverage of the orchard floor. Certain formulations emit high amounts of volatile organic compounds (VOCs); use low-VOC formulations. Regulations affect use for the San Joaquin Valley from May 1 to October 31, 2018 and 2019. Review the Department of Pesticide Regulation’s updated fact sheet. Additional application restrictions may apply; for more information on current California permit restrictions, see the Department of Pesticide Regulation’s Chlorpyrifos Interim Recommended Permit Conditions.
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
# Acceptable for use on organically grown produce.
* Permit required from county agricultural commissioner for purchase or use.
1 Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).
NA Not applicable.


UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441

Insects, Mites, and Snails
Acknowledgments for contributions to Insect, Mites, and Snails:

J. Barcinas, E.S.I., Corona, CA
R. Dunn, Badger Farming Co., Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
H. Griffiths, E.S.I., Corona, CA
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
T. Roberts, E.S.I., Corona, CA
T. Shea, UC Cooperative Extension, Riverside County
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA

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