Olfactory response of the predator <Emphasis Type="Italic">Zetzellia mali</Emphasis> to a prey patch occupied by a conspecific predator

While searching for food, predators may use volatiles associated with their prey, but also with their competitors for prey. This was tested for the case of Zetzellia mali (Ewing) (Acari: Stigmaeidae), an important predator of the hawthorn spider mite, Amphitetranychus viennensis (Zacher) (Acari: Tetranychidae), in black-cherry orchards in Baraghan, Iran. Using a Y-tube olfactometer, the response of this predatory mite was tested to odour from black-cherry leaves with a conspecific female predatory mite, either with or without a female of the hawthorn spider mite when the alternative odour came from black-cherry leaves with the hawthorn spider mite only. Female predators avoided odours from leaves with both a hawthorn spider mite and a conspecific predator, as well as leaves with a conspecific predator only. We discuss whether avoidance emerges in response to cues from the competitor/predator, the herbivore/prey or the herbivore-damaged plant.     

Influence of diet on life table parameters of <Emphasis Type="Italic">Iphiseius degenerans</Emphasis> (Acari: Phytoseiidae)

Studies on the reproduction, longevity and life table parameters of Iphiseius degenerans (Berlese) were carried out under laboratory conditions of 25 ± 1 °C, 75 ± 5% RH and 16L:8D h. As food sources for the predatory mite, Ricinus communis L. pollen, all stages of the spider mite Tetranychus urticae Koch, Frankliniella occidentalis (Pergande) larvae, and Ephestia kuehniella Zeller eggs were selected. All diets were accepted as food by the adult mites. Female longevity ranged from 29.5 to 42.4 days, the highest value was recorded on a diet of Ephestia eggs. The highest percentage of females escaping the experimental arena was observed on the diet consisting of thrips larvae. The highest oviposition rate (1.9 eggs/female.day) was recorded when the predator was fed on spider mites on an artificial substrate. For other diets, oviposition rates ranged from 1.0 to 1.3 eggs/female.day. The intrinsic rate of natural increase (r _m) of I. degenerans varied between 0.015 and 0.142 females/female.day. The diet consisting of castor bean pollen resulted in the highest population growth whereas the diet on spider mites brushed off onto a bean leaf arena resulted in the slowest population growth. This can be explained by the inability of the predator to cope with the webbing of T. urticae, and the high escape rate of the progeny when reared on spider mites. The percentage of females in the offspring ranged from 40 to 73%.This revised version was published online in May 2005 with a corrected cover date.     

The influence of sublethal deposits of agricultural mineral oil on the functional and numerical responses of <Emphasis Type="Italic">Phytoseiulus persimilis</Emphasis> (Acari: Phytoseiidae) to its prey, <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Tetranychidae)

Occasional pesticide application in integrated pest management to at least part of a crop requires that any biological control agents must re-invade previously sprayed areas in order that resurgent pests can be constrained. The ability of the phytoseiid predatory mite Phytoseiulus persimilis to feed on adult two-spotted spider mite (TSSM) Tetranychus urticae on excised leaf discs in both control conditions and in a treatment with a sub lethal residue of agricultural mineral oil (AMO) was assessed. The predator exhibited a Type II functional response with the asymptote significantly higher in the AMO conditions due to the fact that the prey grew slower and reached a smaller size in this treatment. In terms of prey volume eaten, the satiation level of the predator was unchanged by the AMO deposits. The numbers of eggs produced by adult P. persimilis females at densities of 4, 8 and 16 TSSM adult females/disc in the control were significantly higher than those in the AMO treatment, but were similar for the higher density levels, 32 and 64 prey per disc. Thus the functional response in terms of volume of prey eaten explained the numerical response in terms of predator eggs produced. The presence of AMO deposits when the prey were at high density had no effect on predator efficiency (volume eaten) but resulted in a lower intake than that in control conditions when there was a greater distance between prey.     

Life history of the predatory mites <Emphasis Type="Italic">Neoseiulus paspalivorus</Emphasis> and <Emphasis Type="Italic">Proctolaelaps bickleyi</Emphasis>, candidates for biological control of <Emphasis Type="Italic">Aceria guerreronis</Emphasis>

The eriophyoid mite Aceria guerreronis Keifer (Eriophyidae), commonly called the coconut mite, is a key pest of coconut fruits. Surveys conducted on coconut palms in Brazil revealed the predatory mites Neoseiulus paspalivorus DeLeon (Phytoseiidae) and Proctolaelaps bickleyi Bram (Ascidae) as the most commonly associated natural enemies of A. guerreronis on coconut fruits. However, virtually nothing is known about the life history of these two predators. We conducted laboratory experiments at 25 ± 0.1°C, 70–90% RH and 12:12 h L:D photoperiod to determine the life history characteristics of the two predatory mites when feeding on A. guerreronis and other potential food sources present on coconut fruits such as Steneotarsonemus furcatus DeLeon (Tarsonemidae), coconut pollen and the fungus Rhizopus cf. stolonifer Lind (Mucoraceae). In addition, the two-spotted spider mite Tetranychus urticae Koch (Tetranychidae) was tested for its suitability as prey. Both predators, N. paspalivorus and P. bickleyi, thrived on A. guerreronis as primary food source resulting in shorter developmental time (5.6 and 4.4 days, respectively), higher oviposition rate (1.7 and 7.0 eggs/female/day, respectively) and higher intrinsic rate of increase (0.232 and 0.489 per female/day, respectively) than on any other diet but were unable to develop or lay eggs when fed T. urticae. Coconut pollen and S. furcatus were adequate alternative food sources for N. paspalivorus and Rhizopus for P. bickleyi. We discuss the relevance of our findings for natural and biological control of the coconut mite A. guerreronis.     

Effects of pesticides on the functional response of predatory thrips, Scolothrips takahashii to Tetranychus viennensis

Abstract: It is of importance to integrate the biological control of hawthorn spider mite, Tetranychus viennensis, by predatory thrips in commercial orchards in north China. In this study, a leaf disc bioassay was employed to investigate the effects of two insecticides, i.e. abamectin and fenpropathrin, and two fungicides, i.e. mancozeb and carbendazim, on the functional response of an acarophagous thrips, Scolothrips takahashii Priesner, to eggs of the mite at the conditions of 25 ± 1°C, 60 ± 10% relative humidity, and a 16 : 8 h (L : D) photoperiod. Results indicated that the type of functional response in predatory thrips differed depending on the types and doses of the pesticides exposed. Holling‐II type responses were exhibited by all predatory thrips but females that were exposed to labelled dose of abamectin and half‐labelled dose of fenpropathrin exhibited the Holling‐III type responses. Parameters of random predator equation for both exposed and unexposed predators were estimated and compared with an equation with indicator variables. Both doses of both fungicide treatments did not have any impact on the attack rates of the thrips. Handling time (T_h) estimates for males exposed to both doses of both fungicides were similar to that of the control, but there seemed to be a trend towards prolonged handling times for females in these exposures with a significantly prolonged T_h found in labelled dose of mancozeb. Exposures of both doses of fenpropathrin and labelled dose of abamectin produced significantly lower attack rates and significantly prolonged handling times in both males and females, whereas an exposure of half‐labelled dose of abamectin had no obvious influence on the attack rates of the predator, but the handling time in females prolonged significantly. The theoretical maximum number of prey attacked by the thrips were 59.81 eggs per day per female and 23.21 eggs per day per male in the control, but it reduced by 57.03–71.41% and 6.03–36.75% for females and males in the insecticide exposures and 23.91–44.26% and ?5.13–11.55% in the fungicide exposures, respectively. The finding implies that the natural control effects of S. takahashii would be weakened by the application of the pesticides such as fenpropathrin, abamectin and mancozeb, which are often used to control insect pests and fungal diseases in apple orchards.     

Life history of the predatory mite <Emphasis Type="Italic">Phytoseiulus fragariae</Emphasis> on <Emphasis Type="Italic">Tetranychus evansi</Emphasis> and <Emphasis Type="Italic">Tetranychus urticae</Emphasis> (Acari: Phytoseiidae,Tetranychidae) at five temperatures

Tetranychus evansi Baker and Pritchard and Tetranychus urticae Koch (Acari: Tetranychidae) are important pests of Solanaceae in many countries. Several studies have demonstrated that T. urticae is an acceptable prey to many predatory mites, although the suitability of this prey depends on the host plant. T. evansi, has been shown to be an unfavorable prey to most predatory mites that have been tested against it. The predator Phytoseiulus fragariae Denmark and Schicha (Acari: Phytoseiidae) has been found in association with the two species in Brazil. The objective of this work was to compare biological parameters of P. fragariae on T. evansi and on T. urticae as prey. The study was conducted under laboratory conditions at 10, 15, 20, 25 and 30°C. At all temperatures, survivorship was lower on T. evansi than on T. urticae. No predator reached adulthood at 10°C on the former species; even on the latter species, only about 36% of the predators reached adulthood at 10°C. For both prey, in general, duration of each life stage was shorter, total fecundity was lower and intrinsic rate of population increase (r _m ) was higher with increasing temperatures. The slower rate of development of P. fragariae on T. evansi resulted in a slightly higher thermal requirement (103.9 degree-days) on that prey than on T. urticae (97.1 degree-days). The values of net reproduction rate (R ₀), intrinsic rate of increase (r _m ) and finite rate of increase (λ) were significantly higher on T. urticae, indicating faster population increase of the predator on this prey species. The highest value of r _m of the predator was 0.154 and 0.337 female per female per day on T. evansi and on T. urticae, respectively. The results suggested that P. fragariae cannot be considered a good predator of T. evansi.     

Predation and reproductive output of the ladybird beetle <Emphasis Type="Italic">Stethorus tridens</Emphasis> preying on tomato red spider mite <Emphasis Type="Italic">Tetranychus evansi</Emphasis>

Predatory behaviour and reproductive output of the ladybird beetle Stethorus tridens Gordon as function of the tomato red spider mite (TRSM), Tetranychus evansi Baker & Pritchard, densities was investigated in the laboratory. Adult female of S. tridens were isolated in cylindrical plastic arenas, containing a leaf disc of Solanum americanum Mill. with 5, 20, 40, 60, 80 or 100 T. evansi nymphs. The number of prey consumed and eggs laid were evaluated daily for ten consecutive days, starting at the oviposition. Oviposition of S. tridens was positively correlated with prey consumption and lower threshold prey consumption for S. tridens laying eggs was 16.3 mites per day. The instantaneous rate of attack (ca. discovery area) and the handling time were 0.0062 h⁻¹ and 0.83 h, and 0.00254 h⁻¹ and 0.78 h, respectively, for predators at the 1st- and 10th-oviposition day. The predator exhibited a type II functional response at 1st- and 10th-oviposition day with a maximum consumption per predator of 33 T. evansi nymphs per day at the highest prey density. The ladybird beetle S. tridens is often collected associated with red spider mite colonies on solanaceous wild plants and the results suggest the potential of this ladybird beetle to control T. evansi in tomatoes crops. Handling editor: Eric Lucas.     

Function of the web box as an anti-predator barrier in the spider mite,<Emphasis Type="Italic"> Schizotetranychus recki</Emphasis>

Spider mites inhabiting Sasa bamboo show considerable variation in traits believed to be the result of coevolution between predator and prey. In Schizotetranychus recki Ehara inhabiting the hairy leaves of a dwarf bamboo, Sasa senanensis, all quiescent stages, including eggs, appear within web boxes in the leaf hairs of their host plant, and this habit is thought to be a trait involved in predator avoidance. To test this hypothesis, the survival rates of S. recki eggs inside a web box and those freed of a web box were assessed in relation to six predator species that co-occur with the spider mite in the field. The results clearly show that the webbing behavior (web box) of S. recki has a function in avoiding five predator species. However, one predator species, Agistemus summersi Ehara, preyed more on eggs protected by a web box. This suggests that this predator species has a special trait to overcome the nest barriers.     

Influence of selected fruit tree pollen on life history of <Emphasis Type="Italic">Euseius stipulatus</Emphasis> (Acari: Phytoseiidae)

Euseius stipulatus (Athias-Henriot) is a predatory mite widespread in the Mediterranean region considered to be important for the biological control of spider mites in citrus orchards. Development, survival and reproduction of this phytoseiid mite feeding on seven commercially obtained pollen were studied under constant laboratory conditions (20 ± 1°C, RH 65 ± 5%, photoperiod 16L: 8D h). Mites were kept individually at rearing units with ample quantity of almond (Prunus amygdalus Batch), apple (Malus domestica Borkh), apricot (Prunus armeniaca L.), cherry (Prunus avium L.), pear (Pyrus communis L.), plum (Prunus domestica L.) and walnut (Juglans regia L.) pollen as food source. Developmental time from egg to adult varied between the several pollen tested from 8.38 ± 0.08 to 9.58 ± 0.11 days for females and from 8.23 ± 0.12 and 9.07 ± 0.12 days for males. Female longevity varied from 11.53 ± 1.22 to 51.38 ± 2.45 days, while fecundity ranged from 22.84 ± 2.30 to 43.61 ± 3.78 eggs/female. The predator was unable to reproduce when feeding on walnut pollen. Data were submitted to life table analysis and values of the intrinsic rate of increase were derived, ranging from 0.079 to 0.146 (day⁻¹). The cumulative Weibull function that was used to describe the age specific survival of females produced excellent fits to the survival data. Results show that almond, plum, cherry and apricot pollen possess higher nutritional value for E. stipulatus than pear and apple pollen and thus may contribute in sustaining and increasing the predator population in field conditions. Walnut pollen can be utilized by the predator only to survive during short periods of time when principal or alternative food sources are scarce.     

Biological control of the citrus red mite <Emphasis Type="Italic">Panonychus</Emphasis><Emphasis Type="Italic">citri</Emphasis> by the predator mite <Emphasis Type="Italic">Typhlodromus athiasae</Emphasis> on two citrus cultivars under greenhouse conditions

This study examined the efficacy of the predatory mite Typhlodromus athiasae Porath and Swirski (Acari: Phytoseiidae) as a biological control agent of the citrus red mite Panonychus citri (McGregor) (Acari: Tetranychidae) on seedlings of Washington and Valencia citrus cultivars at 1:10, 1:20 and 1:40 predator:prey release ratios under greenhouse conditions. At predator:prey ratios of 1:10, significant reductions on P. citri populations were observed one week after release of T. athiasae, and populations remained at low levels thereafter. The highest mean numbers of P. citri were found in the third week on the Washington cultivar and in the fourth week on Valencia, in a control group with no predators. This study demonstrates the potential of T. athiasae to effectively control P. citri on Washington and Valencia cultivars under greenhouse conditions at predator:prey ratios of 1:10. However, T. athiasae was unable to control the citrus red mite populations when the predator:prey ratio was reduced to 1:40. We therefore recommend a release ratio of 1:10 for effective control of P. citri in greenhouses on seedlings of Washington and Valencia citrus.     

Limitations of <Emphasis Type="Italic">Neoseiulus baraki</Emphasis> and <Emphasis Type="Italic">Proctolaelaps bickleyi</Emphasis> as control agents of <Emphasis Type="Italic">Aceria guerreronis</Emphasis>

Several predatory mites have been found in association with the coconut mite, Aceria guerreronis Keifer, in northeast Brazil. However, the latter still causes damage to coconut in that region. The objectives of this work were to compare the frequencies of occurrence of Neoseiulus (Phytoseiidae) and Proctolaelaps (Melicharidae) species on standing and aborted coconuts in coastal Pernambuco State, northeast Brazil and to analyze their possible limitations as control agents of the coconut mite, based on evaluations of the restrictions they may have to access the microhabitat inhabited by the pest and their functional and reproductive responses to increasing densities of the latter. Neoseiulus baraki (Athias-Henriot) was found mostly on standing coconuts whereas Proctolaelaps bickleyi (Bram) was found mostly on aborted coconuts. Measurements of the entrance to the microhabitat occupied by the coconut mite, between the bracts and the subjacent fruit surface, showed that this different pattern of predator prevalence could be related to predator sizes, although other environmental factors could not be disregarded. Progressively higher predation rate of N. baraki was observed up to an experimental density that corresponded to 1,200 coconut mites per fruit, which is close to the average number determined in northeast Brazil, reducing slightly afterwards. Predation rate of P. bickleyi reduced consistently but slightly with increasing prey densities, but in absolute values, rates were always much higher than determined for N. baraki. The excessively high killing capacity of P. bickleyi, probably related to its high feeding requirement, may be detrimental in terms of stability. In fact, such high requirement for food suggests that P. bickleyi might not have a strong relation with the coconut mite and that the latter may not be its main food source under natural conditions. It is concluded that body sizes of both predators and the exceedingly high feeding requirement of P. bickleyi may limit their performance as control agents of the coconut mite.     

Gene silencing in the spider mite <Emphasis Type="Italic">Tetranychus urticae</Emphasis>: dsRNA and siRNA parental silencing of the <Emphasis Type="Italic">Distal-less</Emphasis> gene

A major prerequisite to understanding the evolution of developmental programs includes an appreciation of gene function in a comparative context. RNA interference (RNAi) represents a powerful method for reverse genetics analysis of gene function. However, RNAi protocols exist for only a handful of arthropod species. To extend functional analysis in basal arthropods, we developed a RNAi protocol for the two-spotted spider mite Tetranychus urticae focusing on Distal-less (Dll), a conserved gene involved in appendage specification in metazoans. First, we describe limb morphogenesis in T. urticae using confocal and scanning electron microscopy. Second, we examine T. urticae Dll (Tu-Dll) mRNA expression patterns and correlate its expression with appendage development. We then show that fluorescently labeled double-stranded RNA (dsRNA) and short interfering RNA (siRNA) molecules injected into the abdomen of adult females are incorporated into the oviposited eggs, suggesting that dsRNA reagents can be systemically distributed in spider mites. Injection of longer dsRNA as well as siRNA induced canonical limb truncation phenotypes as well as the fusion of leg segments. Our data suggest that Dll plays a conserved role in appendage formation in arthropods and that such conserved genes can serve as reliable starting points for the development of functional protocols in nonmodel organisms.     

Testing for non-target effects of spiromesifen on <Emphasis Type="Italic">Eretmocerus mundus</Emphasis> and <Emphasis Type="Italic">Orius laevigatus</Emphasis> under greenhouse conditions

Spiromesifen is a novel insecticide/acaricide belonging to the new chemical class of spirocyclic phenyl-substituted tetronic acids, and it is especially active against whiteflies and tetranychid spider mite species. In the biologically based integrated pest management (IPM) programs in vegetable crops in southeastern Spain, the key natural enemies include the parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) for sweetpotato whitefly control, and the minute pirate bug, Orius laevigatus (Fieber) (Hemiptera: Anthocoridae) for western flower thrips control. Side effects of spiromesifen on E. mundus and O. laevigatus, were evaluated by laboratory studies and field trials in commercial greenhouses under IPM programs. Results indicate that spiromesifen had favourable selectivity to O. laevigatus and E. mundus and would complement biological control of Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) by E. mundus. Handling editor: Patrick De Clercq     

Incidence of the endosymbionts <Emphasis Type="Italic">Wolbachia</Emphasis>, <Emphasis Type="Italic">Cardinium</Emphasis> and <Emphasis Type="Italic">Spiroplasma</Emphasis> in phytoseiid mites and associated prey

Endosymbiotic bacteria that potentially influence reproduction and other fitness-related traits of their hosts are widespread in insects and mites and their appeal to researchers’ interest is still increasing. We screened 20 strains of 12 agriculturally relevant herbivorous and predatory mite species for infection with Wolbachia, Cardinium and Spiroplasma by the use of PCR. The majority of specimens originated from Austria and were field collected or mass-reared. Eight out of 20 strains (40%) tested, representing seven of 12 mite species (58%), carried at least one of the three bacteria. We found Wolbachia in the herbivorous spider mites Tetranychus urticae and Bryobia rubrioculus, with the former also carrying Spiroplasma and the latter also carrying Cardinium. Cardinium was furthermore found in two populations of the predatory mite Euseius finlandicus and the spider mite Eotetranychus uncatus. Spiroplasma was detected in the predatory mite Neoseiulus californicus. All bacteria positive PCR products were sequenced, submitted to GenBank and analyzed in BLAST queries. We found high similarities to complete identity with bacteria found in the same and different mite species but also with bacteria found in insect species like ladybirds, butterflies and minute pirate bugs, Orius. We discuss the significance of potential (multiple) infections with the investigated bacteria for biological control.     

Effect of mating frequency on fecundity and longevity of the predatory mite <Emphasis Type="Italic">Kampimodromus aberrans</Emphasis> (Acari: Phytoseiidae)

The effect of single versus multiple mating on longevity and fecundity as well as the number of matings required to maximize a female’s reproductive success of the predatory mite Kampimodromus aberrans Oudemans were studied under laboratory conditions. Newly emerged adult females of the stock colony of K. aberrans were placed individually on a bean leaf disc, and maintained at 25°C and 16:8 LD. A young male remained with a female for limited periods or continuously. Mating was a requisite for oocyte maturation and oviposition. Females which mated three to four times during their life and females in continuous presence of males, laid significantly and considerably more eggs than single-mated females. Virgin females lived the longest, and those in continuous presence of males the shortest. In all cases and irrespective of the number of matings, the sex ratio of the offspring was male-biased in the first three to four days of oviposition period, and female-biased in later days.     

Development and reproductive capacity of the predatory mite <Emphasis Type="Italic">Parasitus consanguineus</Emphasis> (Acari: Parasitidae) reared on the larval stages of <Emphasis Type="Italic">Megaselia halterata</Emphasis> and <Emphasis Type="Italic">Lycoriella ingenua</Emphasis>

Development and reproduction of the predatory mite Parasitus consanguineus Oudemans et Voigts (Acari: Parasitidae) reared on a diet of first and second instars of Megaselia halterata (Diptera: Phoridae) or Lycoriella ingenua (Diptera: Sciaridae) were studied. Mites were allowed to feed on these diets until death. The developmental time of immature stages of P. consanguineus was significantly longer when reared on L. ingenua than on M. halterata larvae (8.3 vs. 7.9 days, respectively). Survival to adulthood of P. consanguineus reared on L. ingenua or M. halterata larvae was 63 and 49%, and mite fecundity was 17.8 and 12.3 eggs/female, respectively. Adult females reared on L. ingenua lived on average 6.9 days, whereas those reared on M. halterata lived for 5.7 days. Mite survival, female longevity and fecundity were significantly different among the two diet types.     

Consumption rate and functional response of the predaceous mite<Emphasis Type="Italic"> Kampimodromus aberrans</Emphasis> to two-spotted spider mite <Emphasis Type="Italic">Tetranychus urticae</Emphasis> in the laboratory

Prey stage preference of female Kampimodromus aberrans (Oudemans) (Phytoseiidae) at constant densities of different stages of Tetranychus urticae Koch (Tetranychidae), functional response types and parameters of the predator females to the varying densities of eggs, larvae, protonymphs and deutonymps of T. urticae were determined in order to establish its potential for the mite biological control. Experiments were conducted at 25 ± 1°C, 65 ± 10% RH and 16:8 (L:D) photoperiod. Our results indicated that the predator consumed significantly more prey larvae than other prey stages. Functional response type of predator was determined by a logistic regression model. The predator exhibited a Type II response on all prey stages. The attack rate (α) and handling time (T _h ) coefficients of a Type II response were estimated by fitting a “random-predator” equation to the data. The lowest estimated value α and the highest value of T _h (including digestion) were obtanined for the predator feeding on deutonmph. The lowest value of T _h were obtained for the predator feeding on prey larvae, but the attack rate value obtained on larva wasn’t different than that obtained on egg and protonymph. According to our results, K. aberrans could be an efficient biological control agent of T. urticae at least at low prey densities. However, further field based studies are needed to draw firm conclusions.     

Reproductive tables of predatory phytoseiid mites (<Emphasis Type="Italic">Phytoseiulus persimilis,Galendromus occidentalis</Emphasis>, and <Emphasis Type="Italic">Neoseiulus cucumeris</Emphasis>)

Feeding of predatory mites (Phytoseiulus persimilis, Galendromus occidentalis, and Neoseiulus cucumeris) on different life stages of Tetranychus atlanticus under optimal conditions was studied. Daily and total consumption of prey by predators and selection of prey of different life stages were studied for 5 days and for the entire feeding period. Average daily food consumption [number of individuals] for the entire life period of mature mite females constituted 0.43 females + 5.0 [nymphs and males] + 3.4 eggs of Tetranychus atlanticus in P. persimilis; 0.12 females + 3.70 [nymphs and males] + 3.10 eggs in G. occidentalis; and 0.19 females + 4.10 [nymphs and males] + 3.50 eggs in N. cucumeris. During the entire period of feeding, P. persimilis preferred large individuals and at the postembryonic stages selected prey to a greater extent than G. occidentalis and N. cucumeris (61.8 and 55.1%, respectively). The use of a 5-day express-method is possible for estimation of some biological characteristics of phytoseiids that previously consumed the same food for a long period. In other cases, analysis of characteristics for the entire life period is necessary.     

Impact of habitat manipulation on mycopathogen, <Emphasis Type="Italic">Fusarium semitectum</Emphasis> to control <Emphasis Type="Italic">Scirtothrips dorsalis</Emphasis> and <Emphasis Type="Italic">Polyphagotarsonemus latus</Emphasis> of chilli

Environmental manipulation or conservation is one among several approaches evolved for harnessing the potentiality of entomopathogens in an integrated pest management. Cultural manipulation can permit the pathogen to reproduce more than usual or can preserve or enhance those already present. Among the key pest of chilli thrips, Scirtothrips dorsalis Hood (Thripidae: Thysanoptera) and broad mite, Polyphagotarsonemus latus [Banks] (Tarsonemoidea: Acari) are reported to cause the leaf curl in the leaves of chilli. Fusarium semitectum has infected the thrips and mites. The effectiveness of the mycopathogen, F. semitectum is chiefly influenced by the environmental conditions. Enhancing the microclimate the mycopathogen can be able to develop and buildup further. Chilli has been grown as sole crop, however companion crops such as sorghum, cotton, red gram, castor and maize were grown to understand the cropping system effect. Chilli-sorghum, chilli-cotton-chilli and chilli-red gram were the best cropping systems in terms of total chilli yield. The chilli-cotton-chilli cropping system ranked second with respect to benefit-cost ratio of 1:1 where as chilli-sorghum cropping system claimed the highest as 1.125:1. Interestingly, sorghum is not grown as a companion crop with chilli in Karnataka under rain fed conditions, where as chilli-cotton combination is a practice in many places of the state.     

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.