the broad mite , polyphagotarsonemus latus ( banks ) ( acari : tarsonemidae ) , is a serious pest of several greenhouse crops worldwide , including pepper , cucumber and egg plants ( gerson 1992 ; palevsky et al . because of their small size ( 0.10.3  mm long ) , broad mites are not initially noticed in crops , but are detected when plants show damage symptoms ( venzon et al . broad mites attack young , growing plant parts and oviposit on the undersides of leaf surfaces . young pepper plants have a particular low tolerance for broad mite damage ( de coss - romero and pea 1998 ; jovicich et al . 2009 ) ; only five adult mites on a young pepper plant can result in lower fruit weight ( weintraub 2007 ) . a number of phytoseid mites , such as neoseiulus californicus ( mcgregor ) and neoseiulus barkeri ( hughes ) have been described to offer good control of broad mites ( fan and petitt 1994 ; pea and osborne 1996 ) . neoseiuluscucumeris ( oudemans ) was also described to control broad mites on peppers when releasing individuals on each plant or every other plant ( weintraub et al . 2003 ) . however , broad mites are still one of the major pests on greenhouse peppers in south - eastern spain ( e. vila personal observation ) . this is mainly due to high temperatures and low humidity during summers in this region and the prevalence of whiteflies , the vector of broad mites ( parker and gerson 1994 ) . this paper reports on a candidate natural enemy for biological control of broad mites , the generalist predatory mite amblyseius swirskii ( athias - henriot ) ( acari : phytoseiidae ) . it has been shown capable of suppressing populations of the tobacco whitefly [ bemisia tabaci ( gennadius ) ] , the greenhouse whitefly [ trialeurodes vaporariorum ( westwood ) ] ( hemiptera : aleyrodidae ) and the western flower thrips [ frankliniella occidentalis ( pergande ) ] ( nomikou et al . currently , a. swirskii is widely used to control thrips and whiteflies ( vector of broad mites ) in sweet pepper crops , also in south - eastern spain . in order to establish the suitability of a. swirskii to control broad mites , we measured oviposition and predation on broad mites in the laboratory and tested the ability of a. swirskii to control broad mites on pepper plants in a greenhouse . sweet pepper plants were grown , pesticide free , in pots ( 2  l ) with potting soil ( jongkind bv , aalsmeer , hol03/no.3 ) in a greenhouse compartment ( 3    7  m ) . amblyseius swirskii was reared on plastic arenas ( 8    15  cm ) , placed on a wet sponge in a plastic tray containing water ( nomikou et al . females were collected from infested pepper leaves with a fine brush , and a culture was started on intact pepper plants , which were grown as above , but kept in a box made of glass ( 45    45    55 cm ) inside a walk - in climate room ( 25c    1.5 and 60%    0.5 humidity ) , free of other herbivores . the oviposition and predation rate of a. swirskii were measured during 2  days on a diet of adult female broad mites . adult female broad mites are larger than adult males and relatively easy to detect . as a control , we measured oviposition rates without food and on a diet of pollen , which is known to be a good food source for this predator ( nomikou et al . young adult female predators ( 89  days old since the egg stage ) were tested individually on a pepper plant leaf disc ( diam . 24  mm ) with a supply of 15 broad mites per leaf disc per day . a pilot study showed that this density is high enough to ensure maximum prey consumption . predation was recorded as the number of broad mites consumed ( as judged by the presence of the remaining transparent cuticles ) after 24 and 48  h. because oviposition rates are affected by the previous food source of adult predatory mites , we used oviposition data from the second day of the experiment only ( sabelis 1990 ) . the distribution of oviposition data was non - normal due to zero inflation ( especially in the treatment without food ) , even after transformations ; we therefore used the more conservative nonparametric kruskal wallis test with post - hoc comparisons ( siegel and castellan 1988 ) to compare oviposition among diets . the capacity of a. swirskii to control populations of broad mites was tested on sweet pepper plants in a greenhouse . young plants without flowers were used because they produce no pollen that could be used as food by the predatory mites . twenty or forty adult female broad mites , collected from the culture with a fine brush , were released on each plant . after 1  h , two females of a. swirskii were released on each plant , except for the controls . this resulted in four initial predator : prey ratios ; 0:10 ; 0:20 ; 1:10 and 1:20 , ratios were replicated four to seven times . contamination of the plants with other herbivores was avoided by keeping the plant pots isolated in a water layer on tables inside the greenhouse compartments . the greenhouse compartments were free from flying herbivores such as whiteflies during the whole experiment . the replicates of different treatments of the experiment were performed in two different greenhouse compartments . the average temperature and relative humidity were similar for each treatment ( 25c    1.5 and 60%    0.5 humidity ) . the numbers of predatory mites and broad mites were assessed 3  weeks after introduction of the mites by collecting all leaves from each plant of each treatment . the leaves of each plant were put in a separate plastic bag and stored in a freezer . later , they were cut into strips of 5  cm and the number of all stages of predatory mites and adult female broad mites was counted using a binocular microscope ( magnification 40 ) . for similar reasons the oviposition and predation rate of a. swirskii were measured during 2  days on a diet of adult female broad mites . adult female broad mites are larger than adult males and relatively easy to detect . as a control , we measured oviposition rates without food and on a diet of pollen , which is known to be a good food source for this predator ( nomikou et al . young adult female predators ( 89  days old since the egg stage ) were tested individually on a pepper plant leaf disc ( diam . 24  mm ) with a supply of 15 broad mites per leaf disc per day . a pilot study showed that this density is high enough to ensure maximum prey consumption . predation was recorded as the number of broad mites consumed ( as judged by the presence of the remaining transparent cuticles ) after 24 and 48  h. because oviposition rates are affected by the previous food source of adult predatory mites , we used oviposition data from the second day of the experiment only ( sabelis 1990 ) . the distribution of oviposition data was non - normal due to zero inflation ( especially in the treatment without food ) , even after transformations ; we therefore used the more conservative nonparametric kruskal wallis test with post - hoc comparisons ( siegel and castellan 1988 ) to compare oviposition among diets . the capacity of a. swirskii to control populations of broad mites was tested on sweet pepper plants in a greenhouse . young plants without flowers were used because they produce no pollen that could be used as food by the predatory mites . twenty or forty adult female broad mites , collected from the culture with a fine brush , were released on each plant . after 1  h , two females of a. swirskii were released on each plant , except for the controls . this resulted in four initial predator : prey ratios ; 0:10 ; 0:20 ; 1:10 and 1:20 , ratios were replicated four to seven times . contamination of the plants with other herbivores was avoided by keeping the plant pots isolated in a water layer on tables inside the greenhouse compartments . the greenhouse compartments were free from flying herbivores such as whiteflies during the whole experiment . the replicates of different treatments of the experiment were performed in two different greenhouse compartments . the average temperature and relative humidity were similar for each treatment ( 25c    1.5 and 60%    0.5 humidity ) . the numbers of predatory mites and broad mites were assessed 3  weeks after introduction of the mites by collecting all leaves from each plant of each treatment . the leaves of each plant were put in a separate plastic bag and stored in a freezer . later , they were cut into strips of 5  cm and the number of all stages of predatory mites and adult female broad mites was counted using a binocular microscope ( magnification 40 ) . for similar reasons oviposition was significantly different among treatments ( fig .  1 , kw  =  44.4 , df  =  2 , p  <  0.0001 ) . the oviposition rate of a. swirskii on a diet of broad mites was lower than the oviposition rate on a diet of pollen ( difference in average rank  =  14.9 , p  <  0.05 ) , but higher than oviposition in the absence of food ( difference in average rank  =  36.9 , p  <  0.0005 , fig .  1 ) . the predators consumed on average 8.6 ( se  =  0.80 ) adult female broad mites per female during the first day and 10.2 ( se  =  0.70 ) during the second day.fig . 1average oviposition rate of young adult amblyseius swirskii on a diet of broad mites , pollen or without food . shown are average numbers of eggs ( + sem ) per female per day measured from 24 to 48  h since the predators were put on the diet or kept without food . different letters indicate significant differences among treatments average oviposition rate of young adult amblyseius swirskii on a diet of broad mites , pollen or without food . shown are average numbers of eggs ( + sem ) per female per day measured from 24 to 48  h since the predators were put on the diet or kept without food . different letters indicate significant differences among treatments amblyseius swirskii was very effective at controlling populations of broad mites ( fig .  2 ) . there was a significant effect of the initial predator  prey ratio on the numbers of broad mites at the end of the experiment ( kw  =  12.7 , df  =  3 , p  =  0.0053 ) . there was no significant difference in broad mite densities on plants without predators ( difference in average rank  =  3.75 , p  >  0.05 ) . also , the density of broad mites did not differ significantly between the two treatments with predators ( difference in average rank  =  4.2 , p  >  0.05 ) . this is probably due to the large variation between plants within the treatment with initial ratio 1:10 . sweet pepper plants without predatory mites had significantly more broad mites than sweet pepper plants with predatory mites ( kw  =  12.7 , df  =  1 , p  =  0.0015 ) . the release of predatory mites resulted in successful control of broad mites ( fewer than 4 broad mites per plant ) on plants with an initial ratio 1:20 . after 3  weeks , the average number of predators per plant did not differ between the two treatments with predators ( kw  =  0.135 , df  =  1 , p  =  0.71).fig . 2average number of polyphagotarsonemus latus females ( + sem ) per plant , 3  weeks after introducing broad mites and predators simultaneously ( 1:20 means 40 females of p. latus were introduced with 2 amblyseius swirskii females ; 1:10 means 20 p. latus females were introduced with 2 a. swirskii ) . different letters indicate significant differences among treatments average number of polyphagotarsonemus latus females ( + sem ) per plant , 3  weeks after introducing broad mites and predators simultaneously ( 1:20 means 40 females of p. latus were introduced with 2 amblyseius swirskii females ; 1:10 means 20 p. latus females were introduced with 2 a. swirskii ) . oviposition was significantly different among treatments ( fig .  1 , kw  =  44.4 , df  =  2 , p  <  0.0001 ) . the oviposition rate of a. swirskii on a diet of broad mites was lower than the oviposition rate on a diet of pollen ( difference in average rank  =  14.9 , p  <  0.05 ) , but higher than oviposition in the absence of food ( difference in average rank  =  36.9 , p  <  0.0005 , fig .  1 ) . the predators consumed on average 8.6 ( se  =  0.80 ) adult female broad mites per female during the first day and 10.2 ( se  =  0.70 ) during the second day.fig . 1average oviposition rate of young adult amblyseius swirskii on a diet of broad mites , pollen or without food . shown are average numbers of eggs ( + sem ) per female per day measured from 24 to 48  h since the predators were put on the diet or kept without food . different letters indicate significant differences among treatments average oviposition rate of young adult amblyseius swirskii on a diet of broad mites , pollen or without food . shown are average numbers of eggs ( + sem ) per female per day measured from 24 to 48  h since the predators were put on the diet or kept without food . amblyseius swirskii was very effective at controlling populations of broad mites ( fig .  2 ) . there was a significant effect of the initial predator  prey ratio on the numbers of broad mites at the end of the experiment ( kw  =  12.7 , df  =  3 , p  =  0.0053 ) . there was no significant difference in broad mite densities on plants without predators ( difference in average rank  =  3.75 , p  >  0.05 ) . also , the density of broad mites did not differ significantly between the two treatments with predators ( difference in average rank  =  4.2 , p  >  0.05 ) . this is probably due to the large variation between plants within the treatment with initial ratio 1:10 . sweet pepper plants without predatory mites had significantly more broad mites than sweet pepper plants with predatory mites ( kw  =  12.7 , df  =  1 , p  =  0.0015 ) . the release of predatory mites resulted in successful control of broad mites ( fewer than 4 broad mites per plant ) on plants with an initial ratio 1:20 . after 3  weeks , the average number of predators per plant did not differ between the two treatments with predators ( kw  =  0.135 , df  =  1 , p  =  0.71).fig . 2average number of polyphagotarsonemus latus females ( + sem ) per plant , 3  weeks after introducing broad mites and predators simultaneously ( 1:20 means 40 females of p. latus were introduced with 2 amblyseius swirskii females ; 1:10 means 20 p. latus females were introduced with 2 a. swirskii ) . different letters indicate significant differences among treatments average number of polyphagotarsonemus latus females ( + sem ) per plant , 3  weeks after introducing broad mites and predators simultaneously ( 1:20 means 40 females of p. latus were introduced with 2 amblyseius swirskii females ; 1:10 means 20 p. latus females were introduced with 2 a. swirskii ) . we studied the ability of a generalist predatory mite to control broad mites on sweet pepper plants . although the predators produced fewer eggs per day when offered a diet of broad mites compared to a diet of pollen , they successfully controlled broad mites on greenhouse - grown sweet pepper plants with an initial predator : prey ratio of 1:20 ( fewer than 4 broad mites per plant after 3  weeks ) . although the oviposition of a. swirskii on a diet of broad mites is not as high as on other arthropods food sources , such as thrips larvae or whitefly eggs ( messelink et al . 2008 ) , we expect an effective control of broad mites in greenhouses for two reasons.the predatory mites are generalists and prey on eggs of whiteflies . broad mites often co - occur with whiteflies because adult whiteflies are vectors of broad mites ( natarajan 1988 ; flechtmann et al . the predator will decrease the future vector population , thus reducing the dispersion of broad mites.besides feeding on broad mites and whiteflies , a. swirskii also feeds and reproduces on thrips and pollen and can therefore be released preventively in the crop . because a few individual broad mites can lead to substantial damage of sweet pepper plants , preventive release of biological control agents broad mites often co - occur with whiteflies because adult whiteflies are vectors of broad mites ( natarajan 1988 ; flechtmann et al . 1990 ) . by feeding on whitefly eggs , the predator will decrease the future vector population , thus reducing the dispersion of broad mites . besides feeding on broad mites and whiteflies , a. swirskii also feeds and reproduces on thrips and pollen and can therefore be released preventively in the crop . because a few individual broad mites can lead to substantial damage of sweet pepper plants , preventive release of biological control agents our results demonstrate the potential of amblyseius swirskii to control broad mites on sweet pepper plants . however , large greenhouse experiments are necessary to confirm its efficacy in reducing p. latus under commercial growth conditions . furthermore , experiments are needed to study the control of broad mites in the presence of whiteflies and other food sources for the predators ( messelink et al . if , for example , a. swirskii has a strong preference for feeding on whiteflies over broad mites , this could lead to temporarily reduced predation in the presence of whiteflies , but at the same time to reduced dispersal of broad mites through phoresy on whiteflies .
the broad mite is a serious pest of a variety of crops worldwide . 
 several phytoseiid mites have been described to control these mites . 
 however , broad mites are still one of the major pest problems on greenhouse pepper in south - eastern spain . 
 the generalist predatory mite a. swirskii is widely used against other pests of pepper plants such as thrips and whiteflies , the latter being a vector of broad mites . 
 we assessed the potential of a. swirskii to control broad mites . 
 the oviposition rate of a. swirskii on a diet of broad mites was lower than on a diet of pollen , but higher than oviposition in the absence of food . 
 population - dynamical experiments with a. swirskii on single sweet pepper plants in a greenhouse compartment showed successful control of broad mites .