Polyphagotarsonemus latus Banks Broad mite

In temperate regions, this tropical or subtropical mite infests a wide range of glasshouse-grown plants, including various ornamentals (e.g. begonia, chrysanthemum, cyclamen and gerbera) and vegetable crops (e.g. aubergine, cucumber, sweet pepper and tomato). Affected plants are stunted and discoloured, and the new growth often becomes brittle, distorted and shiny. Fruits of infested vegetable crops are small, deformed and discoloured, and often develop a corky, reticulated pattern (Plate 16e). Broad mite is a persistent pest and heavily infested plants may be killed.

BIOLOGY

Broad mites breed continuously under favourable conditions, development including an egg, a larval and a quiescent nymphal stage, the latter being passed within the cast-off larval skin. At normal glasshouse temperatures, eggs hatch in 2-3 days and larvae feed for about 4 days before moulting into 'resting nymphs'. The adult stage is reached a day or so later. Female nymphs are often carried around by adult males which, unlike other motile stages (e.g. larvae and adult females), frequently wander over host plants. Colonies of mites occur on the underside of young, expanded leaves and amongst still furled tender growth; leaves, however, become unsuitable as they mature and are then abandoned. All stages may be found together on infested plants, and adult females usually greatly outnumber males.

DESCRIPTION

Adult female 0.2 mm long, broad-bodied, whitish and translucent to greenish or yellowish; hindlegs each with a long whip-like seta (see Fig. 170). Adult male 0.14mm long, long-legged; body tapered posteriorly and with a genital sucker; hindlegs stout but unflanged (Fig.

339) (cf. cyclamen mite, Phytonemus pallidus, p. 260). Egg 0.11 x 0.07 mm, oval and translucent, with several rows of white, mushroom-like tubercles on the exposed surface (Fig.

340). Larva similar in appearance to adult but smaller and 6-legged; tip of body triangular (Fig.

Fig. 339 Hindleg of male broad mite, Polyphagotarsonemus latus.
Infested Plants

Fig. 340 Egg of broad mite, Polyphagotarsonemus latus (x550).

Fig. 341 Larva of broad mite, Polyphagotarsonemus latus (x400).

Fig. 340 Egg of broad mite, Polyphagotarsonemus latus (x550).

Fig. 341 Larva of broad mite, Polyphagotarsonemus latus (x400).

torted; they are also frequently bright green, lacking the greyish bloom of healthy tissue. Furthermore, leaves may become scarred and may develop yellow streaks and characteristic sawtooth edges (see also damage caused by bulb mites, Rhizoglyphus spp., p. 269). Infestations have an adverse effect on flower production. On some host plants, such as amaryllis, the mites induce the formation of reddish spots or streaks on the emerging leaves.

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