We hope by now most people have heard about and are aware of the Asian citrus psyllid (ACP), a small brown insect that carries a deadly citrus disease called huanglongbing (HLB), threatening all backyard citrus trees as well as the statewide citrus industry.
This insect feeds on newly developed leaves of all varieties of citrus trees and can spread the bacteria that causes HLB. The HLB disease can kill a citrus tree in as little as 5 years and there is so far no cure or remedy.
Learn more about ACP and HLB by joining the free UC Ag Experts Talk on December 5 from 3:00pm to 4:30pm. Dr. Elizabeth Grafton-Cardwell, Director of Lindcove REC and Research Entomologist at UC Riverside, will address monitoring for these insects and the disease, as well as what Californian residents and backyard gardeners can do if they're in an HLB-infected area.
Register in advance at http://bit.ly/webinarACP
For PCAs and commercial growers, a separate webinar will take place on December 4, from 3:00pm to 4:30pm. Register here for the PCA and commercial grower webinar.
Additional information about ACP and HLB can be found in our Pest Notes: Asian Citrus Psyllid and Huanglongbing Disease.
- Author: Elizabeth E Grafton-Cardwell
[This post has been modified from the article originally published in the Fall 2018 issue of the Retail Nursery and Garden Center IPM News.]
Citrus trees remain a popular choice for home gardeners in California, largely due to their ease of care, beauty, and functionality for food and shade. However, backyard citrus can also be plagued by pests such as psyllids, leafminers, cottony cushion scale, and mealybugs.
Longtime readers of this blog will know that we have covered the Asian citrus psyllid many times over the years. While the Asian citrus psyllid (ACP) is currently the most problematic pest on California citrus, there are a few other common insect pests you might be dealing with.
The next four blog posts will briefly describe these insects, their damage, and management, and where you can find more information to manage citrus pest problems with careful, research based practices.
- Citrus leafminer
- Mealybugs and cottony cushion scale
- Asian citrus psyllid
- Ant control for Asian citrus psyllid
For more details about these and many other citrus pests, visit the Citrus page on the UC IPM home and garden website.
/span>- Author: Elizabeth E Grafton-Cardwell
- Editor: Elaine Lander
[This post has been modified from the article originally published in the Fall 2018 issue of the Retail Nursery and Garden Center IPM News.]
Citrus leafminer is a moth that arrived in California in 2000 and has invaded citrus throughout the state. This small moth lays its eggs on new, succulent citrus leaves. The larvae burrow through the soft leaf tissue, creating shallow meandering tunnels, or mines (Figure 1). Larval feeding causes the leaf to curl and distort. Mature citrus trees are less frequently attacked since most of their tough leaves are resistant to the leafminer, but very young trees with their higher proportion of young, tender leaves, are more susceptible. This can slow growth of young trees but even those with heavy leafminer damage are unlikely to die.
In home landscapes, citrus leafminers are killed by many natural enemies—other insects and spiders that attack pest insects. Insecticides don't work very well on this pest because it is inside the leaves. If you can, try to ignore leafminer damage since citrus can tolerate it. The leaves damaged by leafminers will continue to produce food for the tree, so they do not need to be removed. If you remove them, it will stimulate the tree to produce more new leaves, which will be attacked by the leafminer and more damage will appear.
For more information about management techniques, see the Pest Notes: Citrus Leafminer.
Looking for other citrus insect pests? Check out our related posts on mealybugs and cottony cushion scales, Asian citrus psyllid, and ant control for Asian citrus psyllid.
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- Author: Elizabeth E Grafton-Cardwell
- Editor: Elaine Lander
[This post has been modified from the article originally published in the Fall 2018 issue of the Retail Nursery and Garden Center IPM News.]
As a home gardener, you may find big white bugs clinging to the twigs and leaves of your citrus trees and need help with identifying and managing these pests. At first glance, they may look similar but in order to have effective pest management, it's important to first determine what they are. Mealybugs and cottony cushion scale are common pests on backyard citrus trees that can easily be mistaken for one another.
Mealybugs
Mealybugs (Figure 1) are soft, oval, wax-covered insects that feed on many plants in garden, landscape, and indoor settings. These insects suck plants juices as they feed and can produce abundant honeydew which can in turn lead to sooty mold. Mealybug feeding can also reduce tree vigor and damage fruit. Colonies of mealybugs hide in crevices so light infestations might be missed.
Mealybugs are very difficult to control with insecticides. Instead encourage, conserve natural enemies by reducing ant numbers and dust. As with citrus leafminers, many natural enemies feed on and kill mealybugs. Some include common predators such as mealybug destroyers, lacewings, and spiders.
Clusters of mealybugs can be physically removed by handpicking or pruning them out. A high-pressure water spray repeated daily can also reduce populations.
The Pest Notes: Mealybugs contains more information about citrus mealybugs and other common mealybugs.
Cottony Cushion Scale
Cottony cushion scale (Figure 2) is most easily recognized by the female's elongated, fluted white cottony egg sac which can be about ½ inch long. These insects can infest both citrus and some woody ornamentals. Like mealybugs, they suck plant juices and produce profuse amounts of honeydew which attracts ants and allows growth of sooty mold. Cottony cushion scale decreases the plant's health by sucking sap, and heavy infestations can cause branches to die.
In most regions of California, cottony cushion scale is well controlled by natural enemies; the red and black lady beetle called the vedalia beetle, or a parasitic fly. Insecticides don't control adult cottony cushion scale very well and may kill their natural enemies, allowing even more growth of the scale insect.
See the Pest Notes: Cottony Cushion Scale to learn more about this pest.
Looking for other citrus insect pests? Check out our related posts on citrus leafminer, Asian citrus psyllid, and ant control for Asian citrus psyllid.
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- Author: Elizabeth E Grafton-Cardwell
- Editor: Elaine Lander
[This post has been modified from the article originally published in the Fall 2018 issue of the Retail Nursery and Garden Center IPM News.]
The Asian citrus psyllid, Diaphorina citri, is a tiny, mottled brown insect about the size of an aphid (Figure 1). This psyllid feeds on all varieties of citrus and some related ornamental plants like orange jessamine. It damages citrus leaves by feeding on new leaf growth, causing the leaves to twist or notch as they mature. More seriously than this plant damage, ACP can infect citrus trees with the bacterium Candidatus Liberibacter asiaticus, which causes huanglongbing disease. Huanglongbing (or HLB) can kill a citrus tree in as little as 5 years. There is no known cure, and all commonly grown citrus varieties are susceptible to the disease.
Controlling ACP infestations is the only way to save citrus trees from this disease. To keep ACP and the disease it can carry from spreading, quarantines have been established in California. Citrus trees sold within an ACP quarantine area will have a blue or yellow tag indicating they must stay within the quarantine area.
Best Practices for ACP Within the Retail Nursery
Citrus trees in wholesale nurseries are treated with insecticides before sale but this protection only lasts for three months. In retail nurseries and garden centers, trees are protected from ACP infestations by placing them inside a screened-in structure or in shaded areas of the store. This is especially important in ACP quarantine areas but is prudent in other nearby areas. It's important to know where the quarantine boundaries are, so refer to the California Department of Food and Agriculture (CDFA) for information.
As you are shopping for citrus trees, carefully check for psyllids. Be sure to inspect new leaves that are forming on the trees. If you see ACP in a retail setting, notify the nursery and have them contact your county agricultural commissioner as soon as possible.
Best Practices for ACP in the Home Garden
Once you purchase your citrus trees, you can help minimize spread of the ACP and HLB disease from your garden. Be sure to plant the trees locally, near where you purchase them.
Home gardeners should treat for ACP and control ants on your citrus trees. Anyone growing citrus trees must watch for HLB symptoms and if you suspect that a tree is infected, you must report it to your county agricultural commissioner's office or call the CDFA Exotic Pest Hotline at 1-800-491-1899. Home gardeners need to support ACP treatments and removal of HLB-infected trees if you are in an area with HLB.
See the recently revised Pest Notes: Asian Citrus Psyllid and Huanglongbing Disease for more information on identification and management.
Looking for other citrus insect pests? Check out our related posts on citrus leafminer, mealybugs and cottony cushion scale, and ant control for Asian citrus psyllid.
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