Tuesday, January 19, 2010

The Pests of Citrus

When compared to other fruit trees, citrus are basically carefree. They tolerate an amazing amount of neglect and still fruit reliably. Keeping citrus in optimal health will require some vigilance though as they are prone to a myriad of pests.
Scale, spider mites, aphids, citrus leaf miners and whitefly all attack citrus. If you want to look at the bright side, more times than not, you will not have to fight all of these critters at the same time. One year may be bad with aphids, the next year will be bad with whitefly. Doesn’t that make you feel better?
SCALE are white, brown or orange stationary insects that suck plant juices. They are most common on the undersides of leaves. Scale can be controlled with horticultural oil and or a non-systemic insecticide. NEVER use a systemic insecticide on a plant that you are planning on eating some part of and ALWAYS follow the label directions. The label is the law!
SPIDER MITES are tiny red or orange arachnids that also feed on plant juices. Spider mites can reproduce very quickly. The effect of spider mites usually is evidenced by yellow or orange speckles on the leaves. They can be controlled with horticultural oil and insecticidal soaps. If you use a type of pesticide, make sure the label reads for use on spider mites or miticide. Because they are arachnids, spider mites are not effected by certain insecticides.
APHIDS are another type of sucking insects. They like young new growth and can severely damage emerging growth in the Spring. Aphids are usually in the presence of ants. They get along with each other in a loving way. Ants feed on the sticky honeydew that aphids produce and ants protect and help move around the aphids. Introducing lady bugs to the area will go along way in controlling aphids. Insecticidal soap will also help.
CITRUS LEAF MINERS are a recent introduction to the United States. CLM’s are a nocturnal moth that lay their eggs on young flushes of growth. After hatching in 4-5 days, the larvae begin tunneling just underneath the leaf surface, creating a squiggly pattern on the leaf. Once in the leaf, the miner is impossible to control. Horticultural oil seems to help in discouraging the moth from laying her eggs.
WHITEFLY are particularly bothersome because the damage they cause shows up long after they are gone. They live and breed on the undersides of leaves and feed on the juices of the leaves. Insecticidal soap seems to be the best defense.
ORANGE DOGS & GRASSHOPPERS are leaf chewing pests. Orange dogs are the larvae of the Swallowtail Butterfly. Both of these pests can defoliate a young citrus tree in a matter of days if not hours.
These are your more common pests, I saved the biggie for last:
ASIAN CITRUS PSYLLID are the ones that spread Citrus Greening Disease (Watch for a new posting on this disease alone in the future) The female only lives for several months, but will lay up to 800 eggs, which will develop in 15 to 47 days, depending on the time of year. As long as the ACP has not been on an infected tree, they are no worse than an aphid. If it has been on an infected tree, your tree can become infected in 15 minutes of the start of feeding. All the normal controls used above will help, but be careful of insecticide resistance. Again, I will cover that in another posting also.
Do a Google search on any of these to see what they look like.
Happy Growing!

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