Polyphagotarsonemus latus

Scientific Name Polyphagotarsonemus latus Banks
Common Names English: Broad mite; German: Breitmilbe; Spanish: Acaro amarillo; French: Acarien jaune; Portuguese: Ácaro-branco
Description The oval body of the adult female of P. latus is about 0.2-0.3 mm (0.008 - 0.01 inch) long, translucent, and of whitish to pale green or yellowish-brown color. Males are similarly colored, but are only about half that size.
In the female, the ends of the last pair of legs are reduced to a long hair each, in the male they bear strong claws.The characteristic eggs are colorless, translucent and speckled with numerous circular whitish tufts.

Biology

Damage

Broad mites puncture plant epidermis cells and suck out their contents, preferably on the shaded side of young leaves, fruits or growing points. The sap loss and reduction in photosynthetically-active surface damage the plant; they are negligible, however, in comparison with the effects of the toxic saliva. This contains substances that act as phytohormones and cause physiological changes in the tissue layers beneath the feeding site that lead to severe dysfunction of the affected parts, resulting in growth distortions, discoloration (bronzing) or corking, stunting and other symptoms, depending on the crop. In general, leaves will shrivel or curl and will eventually be shed; fruits will be heavily deformed or crack and will sometimes drop. When growth points are attacked, flowers or buds will fail to open or will be killed off. Young shoots may die back. The symptoms of broad mite infestation on citrus are very similar to those caused by the citrus rust mite, Phyllocoptruta oleivora. The changes induced by their feeding may persist for many weeks, therefore by the time the damage becomes apparent, the mites may already have disappeared.

Lifecycle

During its lifetime of about 1-2 weeks, a female broad mite lays c. 25-75 eggs (2-5 per day) singly on the undersides of young leaves (near the veins), on flowers, or in depressions on fruits. After 2-3 days, the larvae hatch and begin feeding. They move only slowly with their six legs and scarcely disperse. After 1-3 days, they enter a quiescent nymphal stage. This „pupa“ is almost transparent, and pointed at both ends. The adult emerges another 1-3 days later. After a pre-oviposition period of about 1 day, the females start laying eggs. Without mating, they will produce only males; otherwise the sex ratio is one male to 3-4 female eggs.
Under optimal conditions (temperatures of 21-27°C; 69.8°F and high relative humidity) P. latus can complete its life cycle in less than one week. However, reproduction ceases at below 13°C (55.4°F) and above 34°C (89.6°F).
Broad mites avoid direct sunlight and often hide in crevices, buds or other dark places. Both sexes are very active. P. latus uses two interesting methods of dispersal, besides those common for all phytophageous mites (e.g. wind transport). The adult males are attracted to female pupae, take them up with their specialized hind legs and carry them to new feeding sites. As soon as the female emerges, mating occurs. Furthermore, there is a phoretic relationship of this species with whiteflies, especially Bemisia sp., by which female broad mites will attach themselves to adult whiteflies, using them as a carrier to reach other plants.

Occurrence

Additional Crop Information

This mite is extremely polyphagous. It is a serious pest on bell pepper, chili, citrus, tomato, eggplant, cucumber, papaya, potato, tea and numerous ornamentals. It is also found on apple, avocado, beans, beet, cantaloupe, cocoa, coffee, cotton, grapevine, guava, jute, mango, passion fruit, pear, sesame, string bean and watermelon.

Agricultural Importance

The broad mite is spread worldwide and considered a very serious pest. In the tropics and subtropics it reproduces the whole year round. In temperate climates ist is a serious pest on vegetables in greenhouses. Due to its stupendous reproductive potential, it can reach damaging densities within a very short time. Moreover in some crops significant damage can occur at a very low infestation level.
Losses of almost 100% have been reported.

Control

Integrated Crop Management

Mites are easily spread with tools, on clothing, or on the hands of workers. As broad mites are very sensitive to heat, hot water treatment (45-50°C; 113 - 122°F for 15 minutes) of plants before they are transferred into a greenhouse may prevent the introduction of the pest.
Treatments with selective products should be preferred, if feasible.
To discover infestations as early as possible, monitor regularly and carefully using a hand lens. The characteristic eggs are the only reliable criterion for distinguishing P. latus from other, mostly harmless tarsonemid mites.
Broad mite infestation symptoms may resemble herbicide injury, and nutritional or physiological disorders.

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