Brevipalpus phoenicis (Geijskes)
Taxonomic placing: Acari, Prostigmata, Tetranychoidea, Tenuipalpidae.
Common name: Reddish black flat mite.
Geographical distribution: Almost cosmopolitan.
Host plants: Although collected from almost 500 host plants, the recent discovery of several cryptic species that masquerade under the specific name phoenicis suggests that the host list (and biological as well as morphological data) should be revised.
Morphology: The body is oblong, red, about 0.25-0.30 mm in length. The entire dorsum, an area that shows some variability, is covered by irregular, rounded striae and dark-red color patterns, but no reticulations. The opisthosoma bears six pairs of short lateral setae and tarsus II has two sensory setae (solenidia).
Life history: The mite completed ten annual generations on citrus in Egypt, a generation requiring about three weeks at 27°C. Besides temperature, duration of development and fecundity also depend on the host plant: on citrus fruit a generation was completed in 19 days, but took 29 days on papaya fruit. On the latter host it produced an average of 57 progeny per female, compared to ca 12-16 on citrus. The mite prefers the lower sides of mature leaves and aggregates in protected invaginations and the pedicle, and around the button of fruit.
Economic importance: During feeding the mite injects a toxin into the host tissues, causing a variety of symptoms on different plants, including citrus. Oranges attacked by B. phoenicis are usually smaller, their weight being inversely proportional to the extent of infestation; and affected trees may lose 50% of their yield. In Italy pest feeding resulted in greyish scabby patches and in medial cracks on the apical epidermis of mandarins. Many lesions were located on the oil glands, which were emptied and dried; affected oranges show rounded reddish patches. In heavy attacks the mite infests all above-ground citrus parts, causing the leaves to turn brownish, dry and drop. In South and Central America the mite transmits several plant viruses, the most dangerous to citrus being leprosis. In Brazil its damage, including yield reductions and the cost of acaricide applications, was recently calculated to cost the citrus industry $62 million annually, coming to 35% of total agrochemical costs. These data probably represent only part of the total cost. No such damage has yet been reported in the Mediterranean region. This mite is also a major pest of tea in south-eastern Asia.
Management: In Brazil outbreaks of B. phoenicis on citrus were controlled by the acaricides hexythiazox and fenbutatin oxide, but the large number of necessary applications is promoting the development of resistance to these chemicals. Neem oil, at 1.5% v/v, successfully controlled the mite on orange fruits there. Another option, intended to reduce the damage caused by leprosies, is to explore the tolerance or resistance of citrus species and varieties to the disease. The large numbers of B. phoenicis that occur on hedges, windbreak plants and weeds near or around citrus groves suggests that such plants represent threats to the crop.
Biological control: Many entomopathogenic fungi were assayed against B. phoenicis infesting citrus fruit in the laboratory, but only Hirsutella thompsoni Fisher provided over 90% mortality. Several acarine predators of the families Phytoseiidae and Stigmaeidae reproduced best and survived longest when feeding on B. phoenicis in laboratory experiments in Brazil. Diverse predatory mites feed on the pest in the field, but usually only after its populations have reached large numbers and damage has already been done.
References
Beard, J.J., Ochoa, R., Braswell, W.E. and Bauchan, G.R. 2015. Brevipalpus phoenicis (Geijskes) species complex – a closer look. Zootaxa 3944: 001–067.
Childers C.C., French, J.V. and Rodrigues J.C.V. 2003. Brevipalpus californicus, B. obovatus, B phoenicis and B. lewisi (Acari: Tenuipalpidae): a review of their biology, feeding injury and economic importance. Experimental and Applied Acarology 30: 5-28.
Childers C.C. and Derrick K.S. 2003. Brevipalpus mites as vectors of unassigned rhabdoviruses in various crops. Experimental and Applied Acarology 30: 1-3.
Navia, D. (and 6 co-authors). 2013. Cryptic diversity in Brevipalpus mites (Tenuipalpidae). Zoologica Scripta 42: 406-426.
Vacante V. and Gerson, U. (eds) 2011. Integrated Cotrol of Citrus Pests in the Mediterranean Region. Bentham E-book, Science Publishers.
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