Stages Of Mite Research Articles

Settlement decisions by the two-spotted spider mite Tetranychus urticae

In silk-spinning arthropods, silk can be used for web building, protection, and communication. Silk is an informative material about the presence of conspecifics. It can therefore inform on habitat suitability and hence assist in habitat choice. In this context, we investigated the influence of silk on microhabitat choice by the two-spotted spider mite, Tetranychus urticae. Three factors that could potentially influence habitat choice were manipulated: the strain, number, and the stage of mites. Our study showed that these factors all influence the choice of microhabitat. The tendency of whether to settle on a silk-covered area was influenced by the origin of mites (strain effect). Adult females showed a higher tendency to settle on an area covered with the silk laid by numerous congeners (number effect). Moreover, larvae seemed to be more responsive to the presence of silk than adults (stage effect). This suggests that individuals use silk as a social cue in selecting their microhabitat and that the spatial organization and group behaviour seem to be shaped by the individuals’ response to social cues, such as the amount of silk already present.

Ontogenetic stages of Gymnodamaeus irregularis, with remarks on morphology of the juveniles of Gymnodamaeidae (Acari: Oribatida: Plateremaeoidea)

The juvenile stages of oribatid mites of the family Gymnodamaeidae are insufficiently known, and little information is available on the morphology of ontogenetic stages. Comparative characteristics of juvenile stages of species belonging to family Gymnodamaeidae are given based on our own data and available literature sources. Herein, the morphology of ontogenetic instars of Gymnodamaeus irregularis Bayartogtokh & Schatz, 2009 is investigated. The larva and nymphs are generally similar in their habitus. Basic characteristics in juveniles are the less sclerotized and unpigmented body with granulate surface of gastronotum, larva with 11 pairs of gastronotal setae (h3 absent) and nymphs with 10 pairs of gastronotal setae (setae la, lm and d-series absent, but setae lp and p-series present). Nymphs with ridge-like structure on prodorsum, and large excrescence on posterior end of gastronotum, bearing one pair of long (h1 ) and another pair of medium-long (p1 ) setae. All prodorsal, notogastral and adanal setae of larva and nymphs are densely barbed throughout. Conspicuous characters in the larval stage are the very long interlamellar setae, which are reduced in nymphs and adults to minute setae and the subequal lengths of gastronotal setae. All stages of nymphs carry gastronotic exuviae with reticulate granular sculpture of the previous instars. Adults are coated with thick cerotegument on the idiosoma, legs and most body setae. The sensillus is dilated in its distal part and covered with cerotegument. The notogaster has two pairs of irregular longitudinal ridge-like structures (procuticle); five pairs of notogastral setae; and a pair of strongly developed tubercles Sp on epimeral region III. Gymnodamaeus irregularis is a Western Palaearctic species, currently known from Central (East Tyrol, Austria) and Eastern Europe (Nizhny Novgorod region, Russia) and appears to be primarily an inhabitant of mosses and litter, and it prefers the xeric habitats.

Toxicity of insecticides and acaricides to the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae)

This study determined the side effects of a selection of pesticides on the eggs, nymphs and adults of the predatory mite Neoseiulus californicus. It assessed the acaricides spirodiclofen, cyhexatin, hexythiazox and clofentezine; the insecticides indoxacarb, chlorantraniliprole, diflubenzuron and pyriproxyfen; and the insecticide/acaricides abamectin and spiromesifen. A spray tower-leaf disk method was used to determine the side effects of pesticides on N. californicus. Three doses of each pesticide were applied: a field application dose (T), half of the field application dose (T/2) and double the field application dose (2T). Dead–live counts were made at days 1, 3, 5 and 7 after application. Daily observations were made during egg applications to observe whether the eggs were hatching. None of the pesticides, except for hexythiazox, showed any effect on the eggs of predatory mites. At the 2T dose, chlorantraniliprole and hexythiazox were harmless, and cyhexatin and pyriproxyfen were found to be slightly harmful to N. californicus nymphs and adults. At T and T/2 doses, all of the pesticides except abamectin were found to be harmless to nymphs. Abamectin was harmful at all doses to nymphs. At the T and T/2 doses in adults, chlorantraniliprole, indoxacarb and diflubenzuron were harmless; clofentezine, cyhexatin, spiromesifen, spirodiclofen and pyriproxyfen were slightly harmful; and abamectin was harmful and moderately harmful, respectively. The effect of pesticides varies with predatory mite stages.

Gene pyramiding of peptidase inhibitors enhances plant resistance to the spider mite Tetranychus urticae.

The two-spotted spider mite Tetranychus urticae is a damaging pest worldwide with a wide range of host plants and an extreme record of pesticide resistance. Recently, the complete T. urticae genome has been published and showed a proliferation of gene families associated with digestion and detoxification of plant secondary compounds which supports its polyphagous behaviour. To overcome spider mite adaptability a gene pyramiding approach has been developed by co-expressing two barley proteases inhibitors, the cystatin Icy6 and the trypsin inhibitor Itr1 genes in Arabidopsis plants by Agrobacterium-mediated transformation. The presence and expression of both transgenes was studied by conventional and quantitative real time RT-PCR assays and by indirect ELISA assays. The inhibitory activity of cystatin and trypsin inhibitor was in vitro analysed using specific substrates. Single and double transformants were used to assess the effects of spider mite infestation. Double transformed lines showed the lowest damaged leaf area in comparison to single transformants and non-transformed controls and different accumulation of H2O2 as defence response in the leaf feeding site, detected by diaminobenzidine staining. Additionally, an impact on endogenous mite cathepsin B- and L-like activities was observed after feeding on Arabidopsis lines, which correlates with a significant increase in the mortality of mites fed on transformed plants. These effects were analysed in view of the expression levels of the target mite protease genes, C1A cysteine peptidase and S1 serine peptidase, identified in the four developmental mite stages (embryo, larvae, nymphs and adults) performed using the RNA-seq information available at the BOGAS T. urticae database. The potential of pyramiding different classes of plant protease inhibitors to prevent plant damage caused by mites as a new tool to prevent pest resistance and to improve pest control is discussed.

Suitability of webworm Loxostege sticticalis L. (Lepidoptera: Crambidae) eggs for consumption by immature and adults of the predatory mite Neoseiulus pseudolongispinosus (Xin, Liang and Ke) (Acarina: Phytoseiidae)

The genus Loxostege has a worldwide distribution and includes an economically important group of insect pests of different crops. The effectiveness of predator Neoseiulus pseudolongispinosus (Xin, Liang and Ke) as a potential bio-control agent of webworm Loxostege sticticalis L., was investigated by measuring rates of prey consumption and destruction by the different life stages of mite, duration and viability of immature, pre-oviposition and oviposition periods, total oviposition capacity, and longevity of adults. When eggs food was offered in similar amounts, there were variations in consumption tendency among the different life stages of predator. Mean development period was shortest for egg-fed larvae, whereas, longest in deutonymph followed by egg and protonymph, and total life cycle was completed in a mean of 12.75 days for male or female. A mean pre-oviposition period of 4.28 days was recorded in female and period of oviposition lasted for 8.71 days. The mean number of eggs recorded was 1.42 day-1 female-1. Mortality was recorded in all life stages and percent viability was best in egg stage, adult females and males, and slightly less in larvae, protonymphs and deutonymphs. Further, predatory activity of mites, such as their feeding habits, number of eggs damaged, how they were damaged and oviposition were observed. It is concluded that N. pseudolongispinosus can be successfully reared on L. sticticalis eggs, which proved a good food for adults and nymphs. Laboratory data indicated that this predatory mite has the potential to act as a biological control agent of L. sticticalis in crops.

Cysteine peptidases and their inhibitors in Tetranychus urticae: a comparative genomic approach

BackgroundCysteine peptidases in the two-spotted spider mite Tetranychus urticae are involved in essential physiological processes, including proteolytic digestion. Cystatins and thyropins are inhibitors of cysteine peptidases that modulate their activity, although their function in this species has yet to be investigated. Comparative genomic analyses are powerful tools to obtain advanced knowledge into the presence and evolution of both, peptidases and their inhibitors, and could aid to elucidate issues concerning the function of these proteins.ResultsWe have performed a genomic comparative analysis of cysteine peptidases and their inhibitors in T. urticae and representative species of different arthropod taxonomic groups. The results indicate: i) clade-specific proliferations are common to C1A papain-like peptidases and for the I25B cystatin family of inhibitors, whereas the C1A inhibitors thyropins are evolutionarily more conserved among arthropod clades; ii) an unprecedented extensive expansion for C13 legumain-like peptidases is found in T. urticae; iii) a sequence-structure analysis of the spider mite cystatins suggests that diversification may be related to an expansion of their inhibitory range; and iv) an in silico transcriptomic analysis shows that most cathepsin B and L cysteine peptidases, legumains and several members of the cystatin family are expressed at a higher rate in T. urticae feeding stages than in embryos.ConclusionComparative genomics has provided valuable insights on the spider mite cysteine peptidases and their inhibitors. Mite-specific proliferations of C1A and C13 peptidase and I25 cystatin families and their over-expression in feeding stages of mites fit with a putative role in mite’s feeding and could have a key role in its broad host feeding range.

Population Density and Phenology ofTetranychus urticae(Acari: Tetranychidae) in Hop is Linked to the Timing of Sulfur Applications

The twospotted spider mite, Tetranychus urticae Koch, is a worldwide pest of numerous agronomic and horticultural plants. Sulfur fungicides are known to induce outbreaks of this pest on several crops, although mechanisms associated with sulfur-induced mite outbreaks are largely unknown. Studies were conducted during 2007-2009 in Oregon and Washington hop yards to evaluate the effect of timing of sulfur applications on T. urticae and key predators. In both regions, applications of sulfur made relatively late in the growing season (mid-June to mid-July) were associated with the greatest exacerbation of spider mite outbreaks, particularly in the upper canopy of the crop. The severity of mite outbreaks was closely associated with sulfur applications made during a relatively narrow time period coincident with the early exponential phase of spider mite increase and rapid host growth. A nonlinear model relating mean cumulative mite days during the time of sulfur sprays to the percent increase in total cumulative mite days (standardized to a nontreated plot) explained 58% of the variability observed in increased spider mite severity related to sulfur spray timing. Spatial patterns of spider mites in the Oregon plots indicated similar dispersal of motile stages of spider mites among leaves treated with sulfur versus nontreated leaves; however, in two of three years, eggs were less aggregated on leaves of sulfur-treated plants, pointing to enhanced dispersal. Apart from one experiment in Washington, relatively few predatory mites were observed during the course of these studies, and sulfur-induced mite outbreaks generally occurred irrespective of predatory mite abundance. Collectively, these studies indicate sulfur induces mite outbreaks through direct or indirect effects on T. urticae, mostly independent of predatory mite abundance or toxicity to these predators. Avoidance of exacerbation of spider mite outbreaks by sulfur sprays was achieved by carefully timing applications to periods of low spider mite abundance and slower host development, which is generally early to mid-spring for hop.

Eradication of Elephant Ear Mites (Loxoanoetus bassoni) in Two African Elephants (Loxodonta africana)

Elephant ear mites, not previously described in North America, were eradicated in two African elephants (Loxodonta africana) after six otic instillations of ivermectin at 2-wk intervals. The microscopic examination of a clear, mucoid discharge collected from the external ear canals of two wild-born African elephants housed in a New York State zoo for 25 yr revealed live mites (Loxoaneotus bassoni). The cytologic examination demonstrated no evidence of inflammation or infection. Both elephants were asymptomatic with normal hemograms and serum chemistry panels. A diagnosis of otoacariasis was made. Each elephant was treated six times with 5 ml of 1% ivermectin syrup instilled in each ear canal once every 2 wk. Microscopic examinations of clear mucus collected from each elephant's ear canals 9 days after the first instillation of ivermectin were negative for any life stages of ear mites. Microscopic examinations of mucus collected from both elephants' ear canals at 6, 11, and 16 wk, as well as annually post-treatment for 7 yr, confirmed eradication of the ear mites. The L. bassoni ear mite was first identified in the external ear canals of wild, asymptomatic, lesion-free, African elephants culled in Kruger National Park in South Africa. However, a new species in the same genus of mites (Loxoanoetus lenae) was identified at the necropsy of an 86-yr-old Asian elephant (Elephas maximus) living in a circus in Australia. The autopsy revealed a marked, ballooning distension of bone around the left external acoustic meatus, suggestive of mite-induced otitis externa, as seen in cattle infested with ear mites (Raillieta auris). Elephant health care providers should identify the prevalence of, and consider treatment of, elephants in their care infested with ear mites, given the possible risk for adverse health effects.

Feeding biology of Tetranychus ludeni Zacher (Acari: Tetranychidae) on velvet bean.

Feeding characteristics and damage induced by the spider mite, Tetranychus ludeni Zacher on the detached leaves of the velvet bean Mucuna deeringiana were evaluated in the laboratory at 30 + 2 o C and 70 + 5% RH. Cultivation of mite-infested (M + ) and mite-free (M - ) host plants was done by constructing block design plots and replicated. Live cultures of different stages of mites were also maintained in the laboratory using leaf flotation technique. The results showed that T. ludeni could infest almost all age groups of leaves though the middle aged ones showed high population densities. Further, the upper leaf lamina was the preferable feeding site of the mite. Concomitant with feeding, deposition of two types of faecal pellets (black & white) were a notable feature. These pellets exhibited hygroscopic property in accordance with the ambient RH on the leaf surface. The results further reflected on the highly complex colony structure of T. ludeni through silken webbing of the individuals. Analysis of damage symptoms revealed extensive bleaching and chlorosis of the leaves. Chlorophyll loss was significant at 1% levels. Per cent loss in chlorophyll 'a' and 'b' recorded 79.26 + 4.3 % and 74.09 + 4.07 % respectively

Asynchronous Development of Honey Bee Host and Varroa destructor (Mesostigmata: Varroidae) Influences Reproductive Potential of Mites

A high proportion of nonreproductive (NR) Varroa destructor Anderson & Trueman (Mesostigmata: Varroidae), is commonly observed in honey bee colonies displaying the varroa sensitive hygienic trait (VSH). This study was conducted to determine the influence of brood removal and subsequent host reinvasion of varroa mites on mite reproduction. We collected foundress mites from stages of brood (newly sealed larvae, prepupae, white-eyed pupae, and pink-eyed pupae) and phoretic mites from adult bees. We then inoculated these mites into cells containing newly sealed larvae. Successful reproduction (foundress laid both a mature male and female) was low (13%) but most common in mites coming from sealed larvae. Unsuccessful reproductive attempts (foundress failed to produce both a mature male and female) were most common in mites from sealed larvae (22%) and prepupae (61%). Lack of any progeny was most common for mites from white-eyed (83%) and pink-eyed pupae (92%). We also collected foundress mites from sealed larvae and transferred them to cells containing newly sealed larvae, prepupae, white-eyed pupae, or pink-eyed pupae. Successful reproduction only occurred in the transfers to sealed larvae (26%). Unsuccessful reproductive attempts were most common in transfers to newly sealed larvae (40%) and to prepupae (25%). Unsuccessful attempts involved the production of immature progeny (60%), the production of only mature daughters (26%) or the production of only a mature male (14%). Generally, lack of progeny was not associated with mites having a lack of stored sperm. Our results suggest that mites exposed to the removal of prepupae or older brood due to hygiene are unlikely to produce viable mites if they invade new hosts soon after brood removal. Asynchrony between the reproductive status of reinvading mites and the developmental stage of their reinvasion hosts may be a primary cause of NR mites in hygienic colonies. Even if reinvading mites use hosts having the proper age for infestation, only a minority of them will reproduce.

Freeze Mortality Characteristics of the Mold Mite Tyrophagus putrescentiae, a Significant Pest of Stored Products

The mold mite Tyrophagus putrescentiae (Shrank) is a common pest of stored food products. Until recently, commodity and facility treatments have relied on acaricides and fumigants to control this mite. However, T. putrescentiae will cause infestations in areas where acaricide or fumigant use may be restricted, prohibited, or highly impractical. Because temperature is an essential factor that limits the survival of arthropod species, extreme temperatures can be exploited as an effective method of control. Making low-temperature treatments reliable requires better temperature-time mortality estimates for different stages of this mite. This was accomplished by exposing a representative culture (eggs, nymphs, and adults) of noncold-acclimated T. putrescentiae to subfreezing temperatures to determine their supercooling points (SCPs), lower lethal temperatures (LLTs) and lethal times (LTimes) at set temperatures. The results indicate that the adult and nymphal stages of T. putrescentiae are freeze intolerant; based on 95% CIs, the adult LLT90 of -22.5 degrees C is not significantly different from the SCP of -24.2 degrees C and the nymphal LLT90 of -28.7 degrees C is not significantly different from the SCP of -26.5 degrees C. The egg stage seems to be freeze tolerant, with an LLT90 of -48.1 degrees C, significantly colder by approximately 13.5 degrees C than its SCP of -35.6 degrees C. The LTime demonstrates that 90% of all mite stages of T. putrescentiae can be controlled within commodity or packaged product by freezing to -18 degrees C for 5 h. By achieving the recommended time and temperature exposures, freezing conditions can be an effective way of controlling mites and reducing chronic infestations.

ESTUDOS PRELIMINARES PARA A AVALIAÇÃO DA CAPACIDADE DE SOBREVIVÊNCIA DO ÁCARO Lynxacarus radovskyi (TENORIO, 1974) FORA DO HOSPEDEIRO

This study aimed to evaluate the survival possibility of the Lynxacarus radovskyi life cycle stages out of the host under laboratory conditions. Eggs, immature and adult forms of L. radovskyi were collected from cats naturally parasitized. The collected specimens were separated and put into plastic containers and into Durhan pipes, being submitted to room temperature and humidity, in the Parasitic Diseases of Domestic Animals Laboratory – DMV – UFRPE, and in climatic chamber at temperature of 27 ºC ± 1ºC and relative humidity > 70%, in scotophase, with and without cat hair supply as substrate to evaluate the survival capacity of the stages out of the host. There was a 100% hatch of the collected eggs, with larval survival within one to four days; the survival for the collected larvae was from one to five days. For all the experiment phases the nymphs presented bigger survival average than the other ones. In general, females survived more than males. The addition of hair provided a bigger survival to all the mite stages. KEYWORDS: Astigmata, cats, longevity, stages.

Prey Preference of the Predatory Mite,Amblyseius swirskiibetween First Instar Western Flower ThripsFrankliniella occidentalisand Nymphs of the Twospotted Spider MiteTetranychus urticae

The prey preference of polyphagous predators plays an important role in suppressing different species of pest insects. In this study the prey preference of the predatory mite, Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) was examined between nymphs of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and first instar larvae of the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), as well as between active and chrysalis spider mite protonymphs and active and chrysalis spider mite deutonymphs. The study was done in the laboratory on bean leaf discs at 25 ± 1° C and 70 ± 5% RH. Amblyseius swirskii had a clear preference for thrips compared to both spider mite protonymphs and deutonymphs. About twice as many thrips as spider mites were consumed. Amblyseius swirskii did not show a preference between active and chrysalis stages of spider mites.

In vitro and field studies on the contact and fumigant toxicity of a neem-product (Mite-Stop®) against the developmental stages of the poultry red mite Dermanyssus gallinae

The acaricidal activity of the neem product MiteStop was investigated for its potential use as a botanical acaricide for the control of the poultry red mite Dermanyssus gallinae. This neem product is a special formulation of an extract of the seeds of the neem tree Azadirachta indica A. Juss. The efficacy was tested under laboratory conditions as well as in poultry houses. Four different methods of application were used in a filter paper bioassay to evaluate contact and vapour phase toxicity tests. The neem product proved to be already active in very small doses. In order to investigate the efficacy under field conditions, a poultry house was sprayed twice within a 7-day period using 1:33 and 1:50 diluted MiteStop. Cardboard traps were used to assess the mite population before, during and after the treatment. The mite population could be reduced by 89%. In a second poultry house, the spraying of defined areas with a 1:30, 1:33 or 1:50 dilution of the acaricide proved to be highly efficacious against all mite stages. Three other field trials proved that MiteStop is highly active against the red poultry mite. The most efficient dilution is 1:33 with tap water and spraying two or three times at intervals of 7 days.

Effect of different eriophyid and tetranychid mango mite species on development, longevity, fecundity and predation of Typhlodromus mangiferus Zaher and El-Brolossy (Acari: Phytoseiidae)

Effects on development, longevity, fecundity and predation of the predatory phytoseiid mite Typhlodromus mangiferus Zaher and El-Brolossy were studied in the laboratory at different temperatures and relative humidities using four prey mite species: the motile stages of the eriophyid mango bud mite Aceria mangiferae Sayed, the eriophyid leaf coating and webbing mite Cisaberoptus kenyae Keifer, the eriophyid mango rust mite Metaculus mangiferae (Attiah) and nymphs of the tetranychid mango red mite Oligonychus mangiferus (Rahman and Sabra). The increase of different temperatures and decrease of relative humidities from 25°C and 60% to 30°C and 55% and 35°C and 50% shortened development and increased reproduction and prey consumption. The developmental durations were almost similar when the predator was fed on eriophyids compared to that on tetranychid. The maximum reproduction (2.70, 2.08, 1.97 and 1.66 eggs/ ♀ /day) was recorded at the highest temperature and the lowest relative humidity, while the minimum reproduction (1.7, 1.54, 1.53, and 1.06 eggs/ ♀ /day) was noted at the lowest temperature and highest relative humidity with all mango prey species. Life table parameters indicated that feeding of T. mangiferus on A. mangiferae led to the highest reproduction rate (rm = 0.204 and 0.139 females/female/day), while feeding on O. mangiferus gave the lowest reproduction rate (rm = 0.137 and 0.116) at 35°C and 50% relative humidity and 25°C and 60% relative humidity, respectively. T. mangiferus seems to be a voracious predator of both mango eriophyid and tetranychid mites. The adult female daily consumed about 127 A. mangiferae, 97 C. kenyae, 86 M. mangiferae, and 18 O. mangiferus at 35°C and 50% relative humidity, while it devoured only 99.81, 86, 81, and 15 individuals, respectively at 25°C and 60% relative humidity. The present study revealed that each injurious mite is thought to be profitable prey species to T. mangiferus as a facultative predator.

Development and reproduction of Sancassania polyphyllae (Acari: Acaridae) feeding on entomopathogenic nematodes and tissues of insect larvae

Abstract We studied the effect of different food sources, infective juveniles of the entomopathogenic nematodes, Steinernema feltiae and Heterorhabditis bacteriophora (Rhabditida: Steinernematidae, Heterorhabditidae), and tissues from the insect larva, Polyphylla fullo (Coleoptera: Scarabaeidae) or Galleria mellonella (Lepidoptera: Pyralidae), on the development, reproduction and longevity of Sancassania polyphyllae (Acari: Acaridae). We showed that the immature mite stages – protonymph and tritonymph – could develop to the next developmental stage on living or sonicated (i.e., ruptured) S. feltiae or H. bacteriophora. However, the mite larval stage could only develop to the next developmental stage on sonicated infective juveniles of the nematodes. Subsequently, we demonstrated that S. polyphyllae completed development from protonymph to adult on live S. feltiae or H. bacteriophora, whereas all immature stages of S. polyphyllae completed their development from larva to adult on insect tissues. The total developmental period of S. polyphyllae that fed on insect tissues was significantly shorter than those that fed on live infective juveniles. The pre-oviposition, oviposition, and post-oviposition periods and female longevity were not significantly different among the food sources. The total and daily fecundity of S. polyphyllae feeding on P. fullo and G. mellonella was significantly higher than those feeding on S. feltiae and H. bacteriophora, although there was no significant difference observed between P. fullo and G. mellonella or between S. feltiae and H. bacteriophora. The net reproductive rate (R0) was highest (588.3♀/♀) when S. polyphyllae fed on P. fullo. The longest mean generation time (T0) occurred on H. bacteriophora (12.6 days) and the shortest occurred on P. fullo (10.5 days). S. polyphyllae, which fed on P. fullo (rm=0.61) and G. mellonella (rm=0.55) had the highest intrinsic rate of increase (rm) compared to mites that fed on S .feltiae (rm=0.45) and H. bacteriophora (rm=0.41).

Food preference and some biological aspects of the predator Stethorus gilvifrons (Muls) (Coccinellidae: Coleoptera) on deferent stages of Tetranychus urticae Knock- on cotton

A laboratory experiment was undertaken to evaluate the food preference of Stethorus gilvifrons (Muls.) on deferent stages of the spider mite Tetranychus urticae Kock.The influence of prey stages on the biological performance of predator was also evaluated .Results showed that the predator larvae preferred the egg of over others stages, while adult mite were the least preferred host .Females of the predator preferred mite larvae in the first place followed by egg and then other stages subsequently. Males preferred mite eggs followed by other subsequent stages. The prey consumption time by predator larvae increased with the increasing size of prey and decreased with increase of the predator developmental stages. First and fourth instars larvae needed an average of 2.1 and 0.5 minutes to consume an egg of mite. The same predator stage needed an average of 11.8 and5.4 minutes respectively to consume adult mite. Results also indicated that the shortest developmental period and the highest survival rate were 10.2 days and 94.1% respectively obtained when the predator fed on mixed stages of mites. The longest period and lowest survival rate were 18.9day and 85.6% recorded for larvae fed on mixed stages of egg and adult mites. The biological performance of the predator adults was also improved when fed on diet containing mixed stages of mites.

Predation efficacy of Stethorus gilvifrons (Muls) (Coleoptera: Coccinellidae) against the two spotted spider mite Tetranychus urticae Koch on cotton

Several experiments were conducted to evaluate the efficacy of the predator, Stethorus gilvifrons (Muls) against deferant stages of the two spotted spider mite Teranychus urticae Koch. Results indicated that both larvae and adults of the predator were highly efficient in their feeding on all mite stages. Larvae consumed an average of 1045.76 egg, 647.79 larva, 588.80 nymph and 715.03 adult mites when fed on each stage separately during the whole larval duration. The female consumed an average of 7488.17, 8100.25, 6889.4 and 4811.46 individuals of mite stages respectively when fed on each separately during the whole life span, While the male consumed an average of 1826.90, 1977.82, 1759.70 and 810.52 individuals of mite stages respectively. Females consumption of mite stages was higher during the oviposition period followed by pre oviposition and then post oviposition periods. The number of prey decreased with their size increase. The feasibility of including this predator in the management programs of mite was discussed.

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.

Relative toxicity ofnC24 agricultural mineral oil toTetranychus urticaeKoch (Acari: Tetranychidae) andPhytoseiulus persimilisAthias-Henriot (Acari: Phytoseiidae) and its possible relationship to egg ultrastructure

The relative toxicity (LC50 values based on µg oil/cm2) is evaluated of aqueous nC24 agricultural mineral oil (AMO) emulsions to the egg, six-legged nymph (larva), eight-legged protonymph and adult stages of two-spotted mite (Tetranychus urticae) and its predator, Phytoseiulus persimilis, on French bean leaf discs, using a Potter spray tower to apply of the oil. The egg of P. persimilis was the least susceptible stage (LC50 444.84) and its LC50 was significantly higher than all other stages tested of either P. persimilis or T. urticae. The LC50 for adult female T. urticae (LC50 63.89) was significantly lower than the larva (LC50 93.86); however, there was no significant difference in response between the protonymph (LC50 70.44) and the larva, which were both higher than T. urticae eggs (LC50 17.55). LC50s for P. persimilis larva (LC50 43.87), protonymph (LC50 41.55) and adult female (LC50 53.34) were similar. Scanning electron microscopy showed that the egg surface of T. urticae is usually well covered with fine silk that may trap more oil and increase AMO efficacy. Other possible differences in AMO efficacy between T. urticae and P. persimilis may be due to differences in egg size, egg incubation period, egg surface structure and the presence of vulnerable respiratory cones in T. urticae eggs. Dose of 0.2–0.3% (w/w) is considered to be the most appropriate for nC24 AMOs use against T. urticae in combination with P. persimilis in integrated pest management programs.