Sweetpotato spider mite

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Scientific name: Tetranychus marianae McGregor

Other name: Vine spider mite

Taxonomy

Class

Arachnida

Order

Acarina

Family

Tetranychidae

 

Economic importance

Tetranychus marianae is a pest of several annual crops and perhaps certain perennials. This mite could also become important in pasturelands and rangeland.

Geographical distribution

Widespread in the Pacific islands, like the Marianas, from where it was first discovered. It is also found in the West Indies, Bahamas, Southern Florida, Nicaragua, Argentina, Brazil and Southeast Asia.

Damage

Adults and nymphs of spider mites suck the sap from the leaves, causing the area around the feeding punctures to become chlorotic and appear as conspicuous whitish to yellowish stippling on the upper surface of the leaf. Under heavy infestation, photosynthesis is greatly reduced and the chlorotic areas may coalesce forming mottled yellowish interveinal patches. The leaves eventually turn yellow and may become brown and scorched and drop prematurely.

Morphology

Egg. The microscopic spherical egg is hyaline turning translucent white when about to hatch.

Larva. The newly hatched larva is small, round, pale yellow with three pairs of legs and distinct red eyes. Upon feeding, its body turns yellowish green with black side to side marks on its back.

Nymph. The protonymph has four pairs of legs and a greenish oval body. The deutonymph appears like the protonymph but is bigger.

Adult. The adult is similar in shape as the deutonymph but bigger (about 0.5 mm) and has relatively longer legs. The newly emerged adult is pale orange and becomes carmine red with dark lateral markings  as it grows older. Female adults are ovoid while the male adults are tapered towards the abdominal tip and remain yellowish green like the proto- and deutonymphs.

Biology and ecology

The eggs are deposited singly and scattered on the lower surface along or near the midrib or veins. The incubation period lasts 3-5 days. Protonymphal and deutonymphal periods range from 1-2 and 1-3 days, respectively. The total developmental period takes about 7-10 days for both sexes. Females are capable of parthenogenetic reproduction with unfertilised eggs developing into males exclusively. Mated females lay more eggs than the unmated ones. The former is capable of laying an average of 134 eggs and the latter 61 eggs during their entire lifetime. The colony  produces webbing located on the undersurface of the leaf.

Detection and inspection

These mites may be found on the underside of leaves, with the help of a magnifying glass. Close inspection would also show tiny spider webs on stems and leaves. Applying mist on the plants before inspection will make the webs more visible.

Host range

Sweetpotato spider mite is a polyphagous species (i.e. it feeds on a wide range of plant species).  Its common hosts are Maxima cucurbita, Passiflora edulis, Centrosema pubescens, Ipomea triloba, Merremia vitifolia, Acalyphaa wilkesiana, Ricinus communis, and many more.

Management

Biological control

Several species of coccinellid beetles, and phytoseeid mites (Amblysieus linearis Corpus and Amblysieus longispinosus Evans) prey on all stages of development.

Chemical control

Several insecticides/acaricides available for mite control.

References

Amalin, D.M. and Vasquez, E.A. 1993. A handbook on Philippine sweetpotato pests and their natural enemies. International Potato Center (CIP), Los Baņos, Philippines. 82 p.

Baker, E.W. 1975. Spider mites (Tetranychidae: Acarina) from Southeast Asia and Japan. U.S. Dept. Agr. Coop. Econ. Inst. Rpt. 25(49-52): 911-921.

Mata, I.C. 1984. Biology of sweetpotato spider mite, Tetranychus mariannae McGregor (Tetranychidae, Acarina). Unpublished BSA Thesis, Visayas State College of Agriculture, Baybay, Leyte, Philippines.

Gapud, V.P. and  Raros, L.C. 1986. Guide to Philippine Flora and Fauna - Water Bugs and Mites. Vol. VII. Natural Resources Management Center , Ministry of Natural Resources and University of the Philippines. 204 p.

Vasquez, E.A. and Sajise, C.E. . 1990. Pests of sweetpotato: Insects, mites and diseases. Philippine Root Crop Information Service, Philippine Root Crop Research & Training Center. 65 p.

 

 

Contributed by: Erlinda Vasquez and Vilma Amante

Taxonomy

Economic importance

Geographical distribution

Damage

Morphology

Biology and ecology

Detection and inspection

Host range

Management

References

White feeding punctures on leaves due to sweetpotato spider mite (E. Vasquez).

 

 

Sweetpotato spider mites produce webs between leaf lobes and petiole (E. Vasquez).

 

 

Adult female sweetpotato spider mite (E. Vasquez).

Sweetpotato spider mite eggs (E. Vasquez).

Sketch of adult sweetpotato spider mite.