Polyphagotarsonemus latus
(broad mite)

The broad mite P. latus is spread worldwide. In the tropics and subtropics it reproduces the whole year round and has a wide host range. In temperate climates it is a serious pest on vegetables and ornamental plants in glasshouses. Due to its high reproductive potential, it can reach damaging densities within a very short time.

The generation time of P. latus is short. On chilli pepper (Capsicum sp.) the developmental period from egg to adult at 25°C averages 4.1 days for both males and females. Adult female and male longevity is 11.4 and 15.3 days, respectively. Each female lays 25 eggs. The female/male sex ratio is 2.8 in the laboratory, and 2.3 on seedlings in the greenhouse (Ho, 1991).

P. latus eggs are laid on the underside of leaves, tender stems, fruits, flower peduncles and flowers. Attack occurs during a short period of time. Discoloration of tissues is produced by mite feeding; fruits become deformed or fail to develop. Severely infected fruits fall. Leaves of attacked plants are stunted and yield is significantly reduced. Symptoms remain for a long period of time after control.

P. latus disperses by various means. Short-distance movement may be accomplished by walking. Mites may reach far-away uninfested plants by wind. Human transport of infested plants is another way of dispersal for this mite.

There is also evidence that P. latus disperses through insects living on plants. Females of P. latus were observed to have a phoretic relationship with Bemisia tabaci on Phaseolus vulgaris in Colombia and on watermelons in Venezuela. Females of P. latus were found attached to the tarsi and tibiae of B. tabaci (Flechtmann et al., 1990) and B. argentifolii (Fan and Petitt, 1998). The phoretic association between P. latus and insects is quite specific; whiteflies are most attractive to P. latus but other insects such as thrips and aphids are rarely used (Palevsky et al., 2001).

Waterhouse and Norris (1987) discussed the natural enemy records and pointed out that none are specific to P. latus. They recommended biological control experiments using Typhlodromus stipulatus and Amblyseius ovalis on chilli peppers.

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Chemical Control

P. latus may be difficult to control on certain plants. On the curly leaves of Psophocarpus tetragonolobus, dicofol, bromopropylate, azocyclotin and abamectin were not effective (Heungen and Degheele, 1986), presumably because the mites were protected in curly leaves; chinomethionat was more effective. On the more easily treated leaves of castor, all five pesticides tested virtually eliminated the mite population in 2 weeks, and abamectin remained effective for up to 3 weeks.

Dicofol and wettable sulphur were effective against all life stages of P. latus on chilli (Karmakar et al., 1996).

In Sao Paulo, Brazil, abamectin was the most efficient acaricide against P. latus in 12 applications at a range of rates and one application at a higher rate; the higher rate application maximized the production of beans (Scarpellini, 1999). Chlorfenapyr is recommended for the control of P. latus on cotton in Sao Paulo (Santos et al., 1999).

Greenhouse tests in China showed that liuyangmycin (an antibiotic preparation from Streptomyces griseolus) gave the most effective and economical control of P. latus on green chilli peppers (Capsicum). Introduction of female adults or nymphs to plants 5 days after treatment with liuyangmycin resulted in 71.1 and 83% mortality, respectively. The effect declined after 7 days, but mite control for the 3 weeks after treatment remained >98%, which was equivalent to a control by dicofol (Xie et al., 1992). Three applications liuyangmycin to Capsicum in the greenhouse in September-April gave satisfactory control of the pest, with no side-effects.

In India, leaf extracts of Lippia nodiflora and Aloe sp. were shown to significantly reduce the population density of P. latus on chilli when sprayed as 5% aqueous extracts (Palaniswamy and Ragini, 2000). In Brazil, Manipueira, a liquid extract from cassava roots, provided 100% control of P. latus on papaya plants when it was diluted in water (1:3) and sprayed three times at weekly intervals (Ponte, 1996).

Biological Control

In laboratory tests with chilli (Capsicum annuum) leaves, Amblyseius ovalis [Euseius ovalis] at predator-prey ratios of 1:25, 1:50 and 1:100 eliminated P. latus after 9, 12 and 17 days, respectively. Moutia (1958) reported similar results from Mauritius.

In the greenhouses in the 'Land' section of the EPCOT Center, Walt Disney World Vacation Resort, Florida, P. latus was controlled by releasing Neoseiulus barkeri. Fan and Petitt (1994) showed that releasing 10 or more predatory mites per plant of Capsicum cv. Hungarian Wax effectively reduced populations of P. latus from more than 100 mites per leaf to zero in a week. Influx experiments, in which there was continuous immigration of P. latus, showed that a single release of five N. barkeri adults per plant significantly reduced populations of P. latus, but failed to prevent all plants from mite injury, and that three releases of five predatory mites per main stem every 7 days provided adequate protection from mite injury for over 7 weeks.

On beans (Phaseolus vulgaris) and limes in greenhouses in Florida, USA, Neoseiulus californicus was more effective than N. barkeri. In the field, N. californicus, together with a complex of indigenous predaceous mites, kept the density of P. latus below economically damaging levels on lime fruits (Pena and Osborne, 1996).

In greenhouses in China, the release of predatory mites of Neoseiulus cucumeris successfully controlled P. latus on sweet pepper (Wang et al., 2000).

Several species of fungi were tested as possible biocontrol agents against P. latus (Pena et al., 1996). Mortality of P. latus caused by Beauveria bassiana occurred fastest at densities fluctuating between 65 and 125 mites per leaf.

Host-Plant Resistance

Plant resistance is not yet employed as a component in broad mite (P. latus) control, but there is some evidence that the potential exists (Gerson, 1992). In Cuba, a double haploid of sweet pepper (Capsicum sp.) that has higher mean fruit weight and yield per plant was tolerant of P. latus (Depestre and Gomez, 1995). Several chilli cultivars in India are resistant to P. latus (Rao and Ahmed, 2001).