Induced feeding preferences in dicofol-resistant two-spotted spider mites (Acari: Tetranychidae)

Preadult rearing conditions affected the behavior of dicofol-resistant two-spotted spider mites (Tetranychus urticae). Resistant spider mites reared on dicofol-treated leaves initiated a significantly greater number of feeding bouts on dicofol-treated leaves than did genetically identical spider mites reared on residue-free leaves. Therefore the prior exposure of resistant spider mites resulted in induced feeding preferences that could exacerbate the potential outcome of the resistance by resulting in greater amounts of feeding by resistant individuals on dicofol-treated areas. Since resistant individuals that had not experienced dicofol in their lifetime did not display this feeding preference, avoidance of this phenomenon of induced feeding preference may be an undescribed value of rotations of pesticides.     

Climbing of Leaf Trichomes by Eriophyid Mites Impedes Their Location by Predators

Eriophyid mites are plant parasites that are well adapted to hide away from predators. Tiny and wormlike, they can invade very narrow spaces in plants or form galls that, apart from other functions, serve as a shelter from predation. Previous observations showed that some free-living eriophyids as well as tetranychid mites spend their quiescence on the top of leaf trichomes. Here, I investigated climbing leaf trichomes by the eriophyid, Rhinophytoptus concinnus, and tested whether it enables the herbivores to avoid phytoseiid mites. Climbing behavior took place just prior to the quiescent period of juveniles. Larvae and nymphs raised the hind part of their stiffening bodies and walked, turning around on their axis. Having found a hair, juveniles attached their anal suckers to its tip, and, pushing back from a leaf surface or the base of the hair, they lifted their bodies up to become motionless. As revealed by the playback experiments with the phytoseiid mite, Typhloctonus tiliarum, predatory females needed much more time to find quiescent nymphs perching on hairs than those placed on a leaf surface. The time of nymph handling was similar in both situations. Also, a similar number of predators gave up feeding on nymphs in both locations. I conclude that climbing leaf trichomes enables the herbivorous mite to hide from predators. After detection, however, placement on trichomes does not give the quiescent juveniles any advantage over those placed on a leaf blade.     

Lethal and sublethal effects of spiromesifen,spirotetramat and spirodiclofen on Tetranychus urticae Koch (Acari: Tetranychidae)

Lethal and sublethal effects of spirotetramat, spiromesifen and spirodiclofen were assessed on Tetranychus urticae Koch. Leaf disc bioassay was used in all experiments. In this study, toxicity of these compounds was tested on T. urticae eggs and adults. Ovicidal activity was observed in all of the compounds tested, but only spirodiclofen was considerably effective against adult mites. Up to 24?h-old adult females were placed on leaf discs treated with sublethal concentrations (LC₁₀ or LC₂₅). Twenty-four hours after exposure to treated discs, 20 females showing no visible symptoms of poisoning were transferred to untreated leaf discs. The leaf discs were changed daily for up to five days. The number of eggs laid during this period was recorded. The survival rate, total number of laid eggs per female and egg hatching rate were calculated. All above-mentioned parameters were slightly lower in treated females compared with controls.     

Life-cycle variation inPanonychus akitanus Ehara (Acarina:Tetranychidae)

The life history ofPanonychus akitanus Ehara was studied in two Hokkaido populations on dwarf bamboos. The Sapporo population overwintered both as egg and female adult onSasa senanensis, and the Tomakomai population overwintered as egg onSasa apoiensis. Mites of the Sapporo population produced four or five generations from late April to late November or early December. The eggs that had overwintered began to hatch in mid-May, and this hatching period overlapped with that of eggs laid in late April by females that had overwintered. Therefore, mites with different overwintering stages would interbreed. Most eggs that had overwintered in the Tomakomai population hatched in mid-May, and about four generations were produced before early December, when only eggs were found. The density of mites per leaf of the Sapporo population reached a maximum in early May on old leaves and in late June on new leaves, and thereafter gradually decreased. The Tomakomai population initially decreased in density after hatching in the spring, but rapidly dispersed to new leaves, reached a peak in early September, and then gradually decreased. The maximal density was about 10 times higher and the distribution was less clumped (lower values of the aggregation index,m/m) than that of the Sapporo population. This was probably because the Sapporo mites could utilize only the underside of sporadically distributed leaves which were curled by spiders, whereas the Tomakomai mites inhabited any part of the leaf undersurface of the hairy host plant. Predators observed were phytoseiid mites and larvae of gall midges. The predatory effect on the Sapporo population was not clear. In the Tomakomai population, the number of gall midges correlated with the number of spider mites better than that of phytoseiid mites.     

Phytophagous Mite Populations on Tahiti Lime, Citrus Latifolia, Under Induced Drought Conditions

In the nort-western region of Venezuela, Phyllocoptruta oleivora, Tetranychus mexicanus and Brevipalpus phoenicis are common plant-feeding mites on leaves, fruits and branches of Tahiti lime, Citrus latifolia. The population dynamics of these herbivores are affected by many factors, such as weekly treatments with wettable sulphur, particularly during the wet season, maintenance pruning of plants, irrigation with microsprinklers, induction of water stress by withholding irrigation and biotic and abiotic environmental factors. During October 1994-January 1995, 31 trees in a commercial orchard were sampled weekly in order to describe population fluctuations of plant-feeding mites (mean number of mites per leaf or fruit), before (4 weeks) and after (4 weeks) a period of 6 weeks of drought stress (no irrigation). The population density of P. oleivora increased progressively during the last 3 weeks of the irrigation period and reached a maximum of 24 mites per fruit. In contrast, the populations of the other two species, T. mexicanus and B. phoenicis, remained at the same low density as before the withholding-irrigation period. After 6 weeks without irrigation, only T. mexicanus increased, to a high mean value of 11 mites per leaf. The withholding-irrigation practice appears to affect the population size of P. oleivora towards the end of this period and that of T. mexicanus at the beginning of the re-establishment of the water supply. The highest proportion of trees (32%) was infested by T. mexicanus after the withholding-irrigation period, when irrigation was resumed, whereas the highest levels of infestation of trees by P. oleivora and B. phoenicis were 16 and 10%, respectively, during the last week of the water-stress period. Although factors affecting the dynamics of the mites in the orchard are likely to be complex, irrigation management apparently plays an important role.     

Influence of dispersal from almonds on the population dynamics and acaricide resistance frequencies of spider mites infesting neighboring cotton

Neighboring almond and cotton fields were sampled for spider mites in four locations in the San Joaquin Valley of California. The dominant species in the almonds wasTetranychus pacificus McGregor. In three cotton sites.T. pacificus was present in significantly higher densities near the almonds on at least one sampling date. In contrast.T. urticae Koch andT. turkestani Ugarov & Nikolski were equally abundant across the cotton fields. Almonds appeared to act as a continuous early-season source ofT. pacificus for cotton, with peaks in aerial dispersal from almonds occurring due to overcrowding, plant water stress, and applications of repellent acaricides. Cotton, which experienced little water stress, supported very high densities of spider mites and so acted primarily as a sink for spider-mite dispersal from almonds and other field crops throughout the growth-season. The frequencies of resistance expressed byT. pacificus andT. urticae were similar between neighboring crops, even if the acaricide had been registered for use only in almonds (cyhexatin) or cotton (dicofol). Thus, longterm acaricide selection and movement of spider mites between the two crops resulted in similar proportions of resistant individuals. In these study sites, large-scale dispersal ofT. pacificus from almonds rarely directly affected acaricide efficacy in cotton, because resistance frequencies were similar for spider mites from the two crops and because acaricide applications were usually made in cotton after dispersal from almonds was completed. In two cotton sites, field selection with dicofol was reversed by subsequent immigration of spider mites from neighboring field crops.     

Behavior of varroa mites in worker brood cells of Africanized honey bees

The ectoparasitic mite Varroa destructor is currently the most important pest of the honey bee, Apis mellifera. Because mite reproduction occurs within the sealed cell, the direct observation of varroa activity inside the cell is difficult. A video observation method using transparent polystyrol cells containing infested brood was used to analyze the behavior of varroa mites in worker brood of Africanized honey bees. We recorded how mites feed on the larva and pupa, construct a fecal accumulation site and how the bee larva carried out some longitudinal movements around the cell. The feeding activity of the foundress mite varies during the course of the cycle. On the prepupa mites were found to feed often (0.3 ± 0.2 bouts h⁻¹) for a period of 8.7 ± 8.4 min h⁻¹ and there was no preference for a specific segment as feeding site. On the opposite, during the pupal stage mites fed less often (0.1 ± 0.1 bouts h⁻¹) for a period of 6.2 ± 4.0 min h⁻¹ and almost always at a particular site (92.4%). On pupa, 83.7% of the feeding was on the 2nd abdominal segment (n = 92), and only few perforations were found on the thorax. Varroa shows a preference for defecation in the posterior part of the cell (cell apex), close to the bee′s anal zone. We found a high correlation between the position of the feeding site on the pupa and the position of the fecal accumulation on the cell wall. Most infested cells have only one fecal accumulation site and it was the favorite resting site for the mite, where it spent 24.3 ± 3.9 min h⁻¹. Longitudinal displacements were observed in 28.0% (n = 25) of the analyzed bee larvae. Turning movements around the cell, from the bottom to the top, were carried out by these larvae, mainly during the second day (47.7 ± 22.5 min h⁻¹), just before pupation, with a total time of 874.9 ± 262.2 min day⁻¹ (n = 7 individuals). These results in worker brood of Africanized bees demonstrate adaptations of varroa mites to parasitizing the developing bee inside the capped brood cells.     

Effect of avermectin and dicofol on the immatures of the predacious miteAmblyseius gossipi with a special reference to the secondary poisoning effect on the adult female [Acari: Phytoseiidae]

Avermectin at 1 ppm was slightly toxic by contact to the different immature stages of the predacious miteAmblyseius gossipi El-Badry. When immatures ofA. gossipi ingested treated prey on clean leaf discs, the toxicity increased and the resulted ΦΦ oviposited at a significantly lower rate. In contrast, dicofol at 250 ppm was extremely toxic by contact and caused a significant mortality to the immatures when it was ingested. Female mortality increased and fecundity decreased as the time of feeding treated prey increased from 24 h to 192 h. In case of dicofol a permanent depression in reproduction was recorded after feeding treated prey for 144 h. Females ofA. gossipi suffered a depression in reproduction when fed on prey formerly kept on plant leaves treated with avermectin. This depression was reported, only, after 192 h of feeding on prey previously reared on leaves treated with dicofol.      

Behavioral aspects of dicofol resistance in the twospotted spider mite Tetranychus urticae

Behavioral analysis of near-isogenic dicofol-resistant and dicofol-susceptible spider mites did not uncover behavior patterns, present in resistant individuals yet absent in susceptible individuals, that would have reduced exposure to dicofol. On the contrary, homozygous resistant individuals were more likely than homozygous susceptible individuals to remain in contact with treated leaf areas. In the case of dicofol resistance in twospotted spider mites, resistance appears to have resulted in the loss, rather than the acquisition, of behavioral traits that lessen exposure to pesticide. Therefore, we conclude that behavioral resistance does not play a major role in twospotted spider mite resistance to dicofol.Deux génotypes de T. urticae Koch (un sensible et un résistant) ont servi à étudier les aspects comportementaux de la résistance aux pesticides: la durée et la fréquence des comportements de nutrition, de marche et d'attente ont été mesurés chez cet acarien. Dans toutes les expériences, des femelles de mêmes âges avaient été placées sur des feuilles jeunes de haricot (Phaseolus vulgaris) portant des résidus de dicofol.3 séries d'expériences ont été réalisées pour examiner:

Species diversity and seasonal dynamics of Acari on abandoned apple trees in southern Ontario,Canada

Foliage-inhabiting mites and associated insects were observed over a 3-year period on abandoned apple trees at two sites in southern Ontario. This study included species diversity and seasonal dynamics as well as the total habitat size and its seasonal fluctuations. Due to heavy feeding on the leaves in the early season by the fall cankerworm, at one observation site, the habitat available for foliage-inhabiting mites was regulated so that both the total number and the area of leaves on the tree did not increase significantly until early July. However, the influence of this on the population of the dominant mite species was minimal. The mite community was relatively stable over time. Four phytophagous species, representing a basic trophic level, were fed upon by a group of predacious mites. The phytophagous mites consisted of two rust-mite species (Diptacus gigantorhynchus sp. complex andEriophyes pyri sp. complex) and two tetranychid species (Bryobia rubrioculus andEotetranychus uncatus). On the basis of consistency in seasonal abundance,D. gigantorhynchus was the only prey species which could support the early-season population increase of the predacious mites. Ten species of predacious mites were recorded on the apple trees, nine phytoseiids and one stigmaeid; two separate species of these were common at each of two observation sites:Typhlodromus pomi and the stigmaeidZetzellia mali at one site; and two phytoseiid species,Phytoseius macropilis andAmblyseius finlandicus, at the other. There seemed to be a rather simple and stable prey/predator system at each site throughout the three seasons. Species dominance on these apple trees was investigated for the phytoseiids, especially from the perspective of the issue of one-species dominance.     

Overwintering phenology of a predacious mite, Typhlodromus vulgaris (Acari: Phytoseiidae), on Japanese pear trees, observed with Phyto traps

Phyto traps were attached to twigs, main branches and trunks of Japanese pear trees in central Japan in autumn of 2004, to evaluate the effectiveness of the trap as a tool to study overwintering phenology of arboreal phytoseiid mites. A subset of the traps was inspected and replaced at two-weeks intervals (“short-term Phyto trap”), in order to evaluate movement of phytoseiid mites on the trees in a short-term. The remaining traps were left undisturbed and collected monthly from January to May 2005 (“long-term Phyto trap”), to know what species overwinter in the traps and when they leave them. Most phytoseiid mites were collected in the traps on twigs. The most abundant phytoseiid species was Typhlodromus vulgaris Ehara. In the short-term traps on twigs, adult females and males of T. vulgaris were collected until mid-November 2004, when the pear trees became completely defoliated, but few mites were collected from December to April. On the other hand, adult females of T. vulgaris were abundant in the long-term traps on twigs sampled from January to April, but other stages of mites were never collected. These results indicate that T. vulgaris had moved to the long-term traps by late November, and that only adult females had overwintered in the traps. These females began to move and reproduce in early May. By that time immature developmental stages of T. vulgaris were also recorded in the short- and long-term Phyto traps. Our results confirmed that the Phyto trap was a useful tool for estimating overwintering phenology of phytoseiid mites on trees.     

Pest species diversity enhances control of spider mites and whiteflies by a generalist phytoseiid predator

To test the hypothesis that pest species diversity enhances biological pest control with generalist predators, we studied the dynamics of three major pest species on greenhouse cucumber: Western flower thrips, Frankliniella occidentalis (Pergande), greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and two-spotted spider mites, Tetranychus urticae Koch in combination with the predator species Amblyseius swirskii Athias-Henriot. When spider mites infested plants prior to predator release, predatory mites were not capable of controlling spider mite populations in the absence of other pest species. A laboratory experiment showed that predators were hindered by the webbing of spider mites. In a greenhouse experiment, spider mite leaf damage was lower in the presence of thrips and predators than in the presence of whiteflies and predators, but damage was lowest in the presence of thrips, whiteflies and predators. Whitefly control was also improved in the presence of thrips. The lower levels of spider mite leaf damage probably resulted from (1) a strong numerical response of the predator (up to 50 times higher densities) when a second and third pest species were present in addition to spider mites, and (2) from A. swirskii attacking mobile spider mite stages outside or near the edges of the spider mite webbing. Interactions of spider mites with thrips and whiteflies might also result in suppression of spider mites. However, when predators were released prior to spider mite infestations in the absence of other pest species, but with pollen as food for the predators, we found increased suppression of spider mites with increased numbers of predators released, confirming the role of predators in spider mite control. Thus, our study provides evidence that diversity of pest species can enhance biological control through increased predator densities.     

Threshold‐based spraying decision programmes for the red spider mite Tetranychus marianae on eggplant

The red spider mite, Tetranychus marianae McGregor (Acari: Tetranychidae), has been an important pest of eggplant Solanum melongena L. (Solanaceae) and other vegetables in the Mariana Islands. The damage due to T. marianae has been severe and caused huge economic losses. Because no threshold levels are available for T. marianae, many growers are applying up to 12 chemical applications per eggplant cropping period. This is not only expensive, but also results in lower yields because of extensive foliar damage and development of resistance in mites to chemicals. To diminish the calendar‐based chemical applications and to preclude damage to foliage and fruit quality, this study was undertaken for the development of a threshold level for optimum timing of chemical applications for T. marianae. In the direction of this aim, an attempt was made to generate different threshold levels by applying chemical spray (Sun‐spray 6E, 5 ml/l) within 12 h after reaching the threshold levels at 2, 4, 6, 8 and 10 mites/leaf, as well as current recommended calendar‐based sprays and non‐sprayed control in a replicated block design for the dry and wet seasons of 2010 at two locations (Yigo and Inaranjan) in Guam (USA). Based on T. marianae‐infested leaves, incidence of T. marianae and yield levels, the plots sprayed at 2 or 4 mites/leaf in the dry season and 2–8 mites/leaf during the wet season had significantly lower leaf damage and incidence of T. marianae compared with a greater number of mites/leaf in calendar‐based sprays and control plots. At the greater threshold levels, the mean yield was significantly reduced in comparison with the mean yield obtained when plots were sprayed at a threshold of 2–8 mites/leaf. Therefore, it is concluded that the optimum threshold chemical spray for T. marianae on eggplant is 4 mites/leaf during the dry season and 8 mites/leaf in the wet season.     

Studies on the feeding behaviour of the eriophyid mite Abacarus hystrix, a vector of grass viruses

On Italian ryegrass (Lolium multiflorum cv. S 22), the eriophyid mite Abacarus hystrix usually fed on the bulliform epidermal cells at the base of the grooves on the adaxial leaf surface. Scanning electron micrographs illustrate (1) the external morphology of the mouthparts of the mites, (2) how, prior to feeding, they remove cuticular leaf wax with their rostra and (3) feeding punctures in epidermal cells made by the styliform chelicerae. Of eleven graminaceous species tested, A. hystrix only settled on Festuca pratensis, L. perenne and L. multiflorum. On L. multiflorum, the mites preferred the youngest leaves and on mature leaves, preferred the youngest part.     

Do plant mites commonly prefer the underside of leaves?

The adaxial (upper) and abaxial (lower) surfaces of a plant leaf provide heterogeneous habitats for small arthropods with different environmental conditions, such as light, humidity, and surface morphology. As for plant mites, some agricultural pest species and their natural enemies have been observed to favor the abaxial leaf surface, which is considered an adaptation to avoid rain or solar ultraviolet radiation. However, whether such a preference for the leaf underside is a common behavioral trait in mites on wild vegetation remains unknown. The authors conducted a 2-year survey on the foliar mite assemblage found on Viburnum erosum var. punctatum, a deciduous shrub on which several mite taxa occur throughout the seasons, and 14 sympatric tree or shrub species in secondary broadleaf-forest sites in Kyoto, west–central Japan. We compared adaxial–abaxial surface distributions of mites among mite taxa, seasons, and morphology of host leaves (presence/absence of hairs and domatia). On V. erosum var. punctatum, seven of 11 distinguished mite taxa were significantly distributed in favor of abaxial leaf surfaces and the trend was seasonally stable, except for Eriophyoidea. Mite assemblages on 15 plant species were significantly biased towards the abaxial leaf surfaces, regardless of surface morphology. Our data suggest that many mite taxa commonly prefer to stay on abaxial leaf surfaces in wild vegetation. Oribatida displayed a relatively neutral distribution, and in Tenuipalpidae, the ratio of eggs collected from the adaxial versus the abaxial side was significantly higher than the ratio of the motile individuals, implying that some mite taxa exploit adaxial leaf surfaces as habitat.     

Does time spent on adult bees affect reproductive success of Varroa mites?

Reproduction ofVarroa jacobsoni Oudemans (Acari: Varroidae) and the number ofVarroa mites that were found dead on the bottom board of the hive, were studied in relation to the period the mites spent on adult honey bees,Apis mellifera L. (Hymenoptera: Apidae), prior to invasion into brood cells. The maximum period on adult bees was 23 days. To introduce mites, combs with emerging worker brood, heavily infested with mites, were placed into a colony and removed the next day. At the beginning of the first day following emergence from brood cells, 18% of the mites introduced into the colony was found on the bottom of the hive. Part of these mites may already have died inside the capped brood cells, and then fallen down after cleaning of cells by the bees. At the second and third day following emergence, respectively 4% and 2% of the mites on adult bees at the previous day was recovered on the bottom, whereas from the fourth day on only 0.6% of the mites on adult bees was recovered on the bottom per day. After invasion into brood cells, 8–12% of the mites did not produce any offspring. Of the mites that did reproduce, the total number of offspring was 4.0–4.4 per mite during one reproductive cycle, part of which may reach maturity resulting in 1.2–1.3 viable daughters, and 8–10% of the mites produced only male offspring. Reproduction was independent of the period the mites had spent on adult bees prior to invasion into brood cells.     

Euseius addoensis addoensis,an effective predator of citrus thrips,Scirtothrips aurantii,in the eastern Cape Province of South Africa

The predacious mite,Euseius addoensis addoensis (McMurtry) (Acari: Phytoseiidae), significantly (P<0.05) reduced scarring on Palmer Navel oranges,Citrus sinensis (L.) Osbeck, caused by the citrus thrips,Scirtothrips aurantii Faure (Thysanoptera: Thripidae). A chemical exclusion method employing dicofol was used to determine the effect of the predator and numbers ofS. aurantii were monitored on sticky yellow traps. At two sites where numbers of citrus thrips and predacious mites were high, the percentage fruit culled from export quality due to damage byS. aurantii was reduced from 25.5 to 15.5% and from 32.7 to 18.7% by predacious mite activity.Euseius a. addoensis sometimes prevented damage from exceeding 1% cull and was most effective when mean numbers exceeded one mite per inside leaf at petal fall. The best correlation between numbers of mites and the percentage fruit culled at harvest was –0.96 at the location with the highest number of citrus thrips. Tartar emetic (0.398% a.i.) plus sugar (0.4% a.i.) treatments for citrus thrips were slightly detrimental toE. a. addoensis populations but their numbers soon recovered. An alternative treatment, methiocarb 0.016% a.i. plus sugar (0.4% a.i.), almost eliminated the predacious mites and resulted in more citrus thrips damage (10.7% cull) than in the adjacent untreated control (0.2% cull) which contained predacious mites.     

Sub-lethal effects of fenbutatin oxide on prey location by the predatory mite <Emphasis Type="Italic">Iphiseiodes zuluagai</Emphasis> (Acari: Phytoseiidae)

We used a Y-tube olfactometer to assess the sub-lethal effects of the acaricide fenbutatin oxide on the olfactory response of the predatory mite Iphiseiodes zuluagai towards odours from: (1) air or undamaged coffee plants; (2) undamaged or red spider mite Oligonychus ilicis-infested coffee plants; (3) undamaged or false spider mite Brevipalpus phoenicis-infested coffee plants. Predatory mite adult females were exposed to residues of fenbutatin oxide or distilled water on leaf discs during a period of 72 h prior experiments. When exposed to distilled water (control treatments), predatory mites significantly preferred undamaged plants over air, O. ilicis-infested plants over undamaged plants, and they did not prefer B. phoenicis-infested plants over undamaged plants. However, predatory mites that had been exposed to residues of fenbutatin oxide were neither attracted towards undamaged plants nor to O. ilicis-infested plants. Thus, fenbutatin oxide affected negatively the olfactory response of I. zuluagai. We conclude that sub-lethal-effect studies should be considered in pesticide selectivity programs since the ability of predatory mites to locate their prey may be negatively affected by non-lethal concentrations of pesticides.     

Egg-harvesting allows large scale rearing ofAmblyseius finlandicus (Acari: Phytoseiidae) in the laboratory

An improved method to rearAmblyseius finlandicus (Oudemans) in the laboratory is described that allows large numbers to be produced. Mites developed faster and had a higher ovipositional rate when fed on pollen and reared on a bean (Phaseolus vulgaris L.) leaf substrate than when fed on pollen on an artificial arena. Two-spotted spider mites (Tetranychus urticae Koch) were an inferior food source forA. finlandicus mainly because of their profuse webbing.A. finlandicus was able to develop and reproduce on all 11 types of pollen tested although immature mortality was high on cedar (Cedrus sp.) pollen. Total number of mites increased almost 100-fold in three weeks on bean leaf substrate when eggs were collected and transferred (=egg-harvesting) in cotton tufts from the base colonies every two or three days to initiate new colonies. Only about a 13-fold population increase occurred when egg-harvesting was not employed, probably due to a combination of cannibalism and reduced fecundity. Egg-harvesting using cotton tufts is especially suitable for large scale rearing of species likeA. finlandicus that are cannibalistic and/or lay fewer eggs with increasing population density. In addition, the phytoseiidsAmblyseius reductus Wainstein andAnthoseius rhenanus (Oudemans) were reared successfully on pollen and spider mites using either leaf or artificial arenas. This is the first record of successful rearing ofA. rhenanus in the laboratory and ofA. reductus in the laboratory on pollen.     

Residual Effects of Carbaryl and Dicofol on Aphytis holoxanthus Debach (Hymenoptera: Aphelinidae)

Aphytis holoxanthus Debach is an important biological control agent of Florida red scale, Chrysomphalus aonidum (L.). Laboratory tests quantified the mortality of this hymenopteran parasite caused by field residues of carbaryl and dicofol. Behavior and mortality of adult A. holoxanthus on carbaryl-treated “Hamlin” orange leaves were related to quantities of dislodgeable pesticide residues over time as field residues weathered. After 24 h, mortality of A. holoxanthus by dicofol was not observed through day 31 when the experiment was terminated. Our data showed that field-weathered carbaryl residues killed A. holoxanthus for a period of up to 22 days posttreatment under spring conditions in Florida.