Oligonychus, Berlese, 1886

Bustillo, Alex, 2015, Part II. Pests, Compendium of Coffee Diseases and Pests, United States of America: The American Phytopathological Society, pp. 45-60 : 46

Several spider mites of the genus Oligonychus (Acari: Tetranychidae )

are recorded on coffee plantations, but the most prevalent species in South and Central America are O. yothersi (McGregor) and O. ilicis (McGregor) . O. coffeae (Nietner) is an important pest of coffee in Africa and Asia. All of these species are very similar. The adults are oval and 0.4-0.6 mm long. In general, the life cycle for these spider mites is around 20 days long and the adult lifespan may be as long as 1 month. All of these species are characterized by their red color in the adult stage. They are normally found on the lower side of the leaves along the veins. Adult females can lay up to 30 eggs in about 8 days.

O. coffeae , commonly called the coffee red spider mite, also attacks tea, cotton, and several other plants. Eggs are bright red, spherical, and invisible to the naked eye. The anterior part of the adult is red and the posterior part is lightly colored ( Fig. 80 ). The nymphal stages are similar but smaller. O. ilicis is also red and lives on the upper surface of leaves, covering itself with webbing. The mites descend on threads from leaf to leaf and are carried by wind. O. yothersi is also a serious pest of avocado in several regions of the Americas. The life stages last 14-15 days. Females are capable of laying 40-50 eggs during their lifespan.

Damage

Nymphs and adults feed by sucking the sap from the leaf tissue. Feeding is initially confined to the upper surface of leaves and is found first along the midrib and secondary leaf veins. The areas along the veins become reddish brown ( Fig. 81 ). Damage by spider mites reduces photosynthesis up to 30%. Infested leaves often abscise prematurely.

Population Management

Spider mites are especially abundant during dry seasons, increasing populations and causing alarm among the farmers. However, populations decrease as soon as the rainy season arrives. They are very common in coffee plots near dusty roads. Control is exerted by several natural enemies, such as members of the family Coccinellidae , Stethorus sp. , Scymnus sp. , Coleomegilla sp. , and fungal entomopathogens, such Beauveria bassiana (Bals.-Criv.) Vuill. and Paecilomyces spp. They are also preyed upon by mites in the family Phytoseiidae .

Figures

Fig. 80. Oligonychus coffeae adult. (Courtesy J. C. Ortiz, Cenicafé)

Fig. 81. Reddish brown areas along the leaf veins in plants attacked by red spider mites. (Courtesy A. Bustillo, Cenicafé)