Panonychus citri

Panonychus citri (McGregor)

Taxonomic placing: Acari, Prostigmata, Tetranychoidea, Tetranychidae.

Common name: Citrus red mite.

Geographical distribution: The pest occurs wherever citrus is grown; in Israel since the late 1970s, mostly along the coastal plain.

Host plants: Panonychus citri was found on about 100 host plants, and is best known by its infesatation of all varieties and species of citrus.

Morphology: The tarsi carry a claw-like empodium with three pairs of ventrally-directed hairs. All stages of this mite, including the eggs, are dark red. The dorsum bears 13 pairs of mostly long and prominent setae set on reddish [tubercles(entry/Tubercle).

Life history: The mite is dispersed by “ballooning”, floating on air streams by holding on to a silken thread. A generation is completes in a fortnight at 26°C and each female lays about 40 eggs. The eggs, each with a prominent stalk, are placed along the main vein, usually on the upper side of young leaves. Pest populations are more numerous during early winter, least abundant in summer, but their reproduction is continuous, with no summer diapause. The mite is very susceptible to high temperatures and low humidities, causing a population decline during summer.

Economic importance: This mite is a major pest of citrus in California, Japan and South Africa. Feeding causes stippling spots that combine to cause yellow or silvery areas on the leaves. Heavy infestations result in leaf drop, twig dieback, low-quality fruit and even tree death. The expression of damage is enhanced by dry, hot winds.

Management

Sampling: Mites may be counted on entire leaves, usually 20 per tree (five from each aspect), ten trees/orchard. Alternately, only part of the leaves may be scanned. Mite presence on leaves collected in the same manner may be tallied in categories; no mites=0; 1-10 mites=1, 11-20 mites=2 and >21 mites=3. Infestation on fruit can be estimated in the same manner.

Chemical control: The pest was controlled with many conventional acaricides, but has developed much resistance to most pesticides. Pyrethroids encourage citrus red mite outbreaks.

Biological control: This pest is usually maintained below its economic injury level by natural enemies, and outbreaks often follow the application of indiscriminate pesticides. The use of selective pesticides, which do not harm the natural enemies would be the key to its management. Abroad the mite is controlled by various predatory Phytoseiidae and (in California) by a virus disease. Efforts to establish some of these natural enemies in Israel have so far been unsuccessful, but the pest is often kept below its economic injury threshold by indigenous predators. Species of the coccinellid genus Stethorus feed voraciously on the pest and pupate on the injured leaves. However, these beetles often begin to feed on the mites only after the latter had already caused some damage.

References

Gerson, U. and Cohen, E. 1989. Resurgences of spider mites (Acari: Tetranychidae) induced by synthetic pyrethroids. Experimental and Applied Acarology 6: 29-46.

Jeppson, L.R., Keifer, H. and Baker, E.W. 1975. Mites Injurious to Economic Plants University of California Press.

McMurtry, J.A. 1985. Citrus. In Spider Mites, Their Biology, Natural Enemies and Control, ed. by Helle, W. & Sabelis, M.W. Vol. II, pp. 339-347. Elsevier, Amsterdam.

McMurtry, J.A., Shaw, J.G. and Johnson, H.G. 1979. Citrus red mite populations in relation to virus disease and predaceous mites in Southern California. Environmental Entomology 8: 160-164.

Swirski, E., Gokkes, M. and Amitai, S. 1986. Phenology and natural enemies of the citrus red mite, Panonychus citri (McGregor) in Israel. Israel Journal of Entomology 20: 37-44.

Websites: https://www.google.co.il/search?q=panonychus+citri&biw=1024&bih=695&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCUQsARqFQoTCPXFs6n2tMgCFUFVFAodnjYKNQ&dpr=1.25