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Citrus Pest Management

There is a wide range of pests and diseases that can damage citrus and threaten tree health. Since the early 1900s when the Vedalia beetle was introduced to control Cottony Cushion Scale, California citrus growers have utilized biological control as part of an Integrated Pest Management (IPM) approach to controlling pests and diseases in their orchards. This sustainable approach to pest management helps assure maximum effectiveness and less pesticide applications.

Major Citrus Pests of Concern in California

Asian citrus psyllid – Diaphorina citri

The Asian citrus psyllid (ACP) is an invasive insect that can carry the lethal citrus plant bacteria Huanglongbing (HLB). A majority of California counties, predominately in the Southern part of the state, are currently under federal quarantine for this pest.

The Asian citrus psyllid only attacks citrus and closely related plants in the Rutaceae family. When the psyllid feeds, it injects a toxin that causes leaves to twist and die. More importantly, it is an efficient vector of the bacterium Candidatus liberibacter asiaticus that causes Huanglongbing disease (HLB). This disease is one of the most devastating diseases of citrus; causing leaves to yellow, fruit to become bitter and eventually death of the tree.

The only defense against HLB is to control the Asian citrus psyllid. Citrus growers are highly encouraged to participate in localized area treatments to keep populations from spreading. A recent study by Dr. Beth Grafton-Cardwell, Neil McRoberts, and Carla Thomas has indicated the movement of the Asian Citrus Psyllid along major transportation routes. Extra precaution is encouraged when moving fruit, equipment, or crews between regions in California.

Asian citrus psyllid females lay their eggs on the tips of growing shoots or in the crevices of unfolded leaves. The eggs will pass through five nymphal instars.

Resources
University of California KAC Citrus Entomology
Asian Citrus Psyllid Distribution and Management
UC Pest Management Guidelines – Controlling the Asian citrus psyllid
For more information on the biology of the psyllid, see ANR Publication Asian Citrus Psyllid and Huanglongbing.

Adult Asian citrus psyllid

Adult Asian citrus psyllid.

Asian citrus psyllid nymphs

Asian citrus psyllid nymphs.

Fuller Rose BeetleNaupactus (Asynonychus) godmani

Fuller rose beetle adult females emerge from the ground year round, but the heaviest emergence is from July to October. There are no males. Female beetles lay eggs under the calyx of citrus fruit and other cracks and crevices. The neonate larvae drop to the ground and feed on roots for 6-8 months, after which they pupate and then emerge as adults the following year.

Resources
University of California KAC Citrus Entomology
UC Pest Management Guidelines – Controlling Fuller Rose Beetle

Fuller rose beetle leaf damage

Characteristics of Fuller rose beetle damage

Fuller rose beetle adult

Fuller rose beetle adult

California red scaleAonidiella aurantii

California red scale starts its life cycle as a crawler that emerges from a female scale. The crawler finds a leaf, twig or fruit to settle down on and inserts its threadlike mouthpart. If female, the scale molts twice and matures through 2 nymphal instars into the virgin female stage that is receptive to mating with a male. If male, the scale molts from 1st to 2nd instar, then prepupa, pupa, and finally becomes a winged adult. The entire lifecycle takes six weeks to complete.

Resources
University of California KAC Citrus Entomology
UC Pest Management Guidelines – Controlling California Red Scale
For more information on the lifecycle, see ANR publication 21529 CRS lifecycle Pub 21529.

California red scales infesting citrus fruit

California red scales infesting citrus fruitt

Bean thrips – Caliothrips fasciatus

Bean thrips lays its eggs and completes its lifecycle in weeds and other plants near citrus orchards. The adult bean thrips migrate into citrus orchards in October-November, when the weed hosts die or the field crops it infests are harvested. Bean thrips seek out well-protected areas to overwinter, such as the navel of oranges where they contaminate harvested fruit. Bean thrips is not considered a pest of citrus in California. However, other countries such as Australia that do not have this pest consider it a quarantine pest of significance, requiring a preclearance program and fumigation of infested loads. Bean thrips are found throughout California citrus.

Resources
UC Pest Management Guidelines – Controlling Bean Thrips

Bean thrips adult

Bean thrips adult

Bean thrips burrow into orange navels and overwinter

Bean thrips burrow into orange navels and overwinter