Spider Mite Eggs Research Articles

Predation and Life Table of Feltiella acarisuga (Diptera: Cecidomyiidae) Preying on Eggs of Tetranychus urticae (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common gall midge that feeds on many species of spider mites. Predation and all major biological and life table parameters of F. acarisuga were determined using eggs of the twospotted spider mite, Tetranychus urticae (Koch), as prey under laboratory conditions (26.7°C, 85% RH, and 14:10 [L:D] h). First-, second-, and third-instar F. acarisuga larvae consumed an average of 37.8, 60.4, and 87.2 T. urticae eggs per day, respectively. Larvae consumed a total of 185.4 eggs each from first to third instars, and female larvae consumed 201.2 spider mite eggs, 18.6% more than male larvae. Developmental time of F. acarisuga was 2.6, 7.8, and 7.0 d for eggs, larvae, and pupae, respectively, with an average of 17.4 d from oviposition to adult emergence. Female immatures developed slightly slower (≈1 d) than males. Adult longevities of F. acarisuga averaged 13.0 d. After an average of 1.1-d preoviposition period, each female laid an average of 33.3 eggs during her lifespan. The intrinsic rate of natural population increase (r), net reproductive rates (Ro), gross reproductive rate (Σmx), generation time (T), doubling time (DT), and the finite rate of increase (&lgr;) of F. acarisuga were estimated by life table analysis at 0.1155/d, 15.25 eggs per female, 21.69 eggs per female, 23.6 d, 6.0 d, and 1.1225/d, respectively. Because the r value of F. acarisuga is relatively lower than that of T. urticae, frequent release of F. acarisuga may be necessary to suppress populations of T. urticae.

Predation and Life Table of <I>Feltiella acarisuga</I> (Diptera: Cecidomyiidae) Preying on Eggs of <I>Tetranychus urticae</I> (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common gall midge that feeds on many species of spider mites. Predation and all major biological and life table parameters of F. acarisuga were determined using eggs of the twospotted spider mite, Tetranychus urticae (Koch), as prey under laboratory conditions (26.7 degrees C, 85% RH, and 14:10 [L:D] h). First-, second-, and third-instar F. acarisuga larvae consumed an average of 37.8, 60.4, and 87.2 T. urticae eggs per day, respectively. Larvae consumed a total of 185.4 eggs each from first to third instars, and female larvae consumed 201.2 spider mite eggs, 18.6% more than male larvae. Developmental time of F. acarisuga was 2.6, 7.8, and 7.0 d for eggs, larvae, and pupae, respectively, with an average of 17.4 d from oviposition to adult emergence. Female immatures developed slightly slower ( approximately 1 d) than males. Adult longevities of F. acarisuga averaged 13.0 d. After an average of 1.1-d preoviposition period, each female laid an average of 33.3 eggs during her lifespan. The intrinsic rate of natural population increase (r), net reproductive rates (R(o)), gross reproductive rate (Sigmam(x)), generation time (T), doubling time (DT), and the finite rate of increase (lambda) of F. acarisuga were estimated by life table analysis at 0.1155/d, 15.25 eggs per female, 21.69 eggs per female, 23.6 d, 6.0 d, and 1.1225/d, respectively. Because the r value of F. acarisuga is relatively lower than that of T. urticae, frequent release of F. acarisuga may be necessary to suppress populations of T. urticae.

Biology, life table and predation of Feltiella acarisuga (Diptera: Cecidomyiidae) feeding on Tetranychus cinnabarinus eggs (Acari: Tetranychidae)

Abstract Feltiella acarisuga (Vallot) is a common predatory gall midge, which feeds on many species of spider mites. All major life history and life table parameters of F. acarisuga were determined using the carmine spider mite, Tetranychus cinnabarinus (Boisduval) eggs as prey under laboratory conditions [26.7 ± 2 °C, 75 ± 5% RH, and a photoperiod of l4:10 (L:D) h]. Developmental times of F. acarisuga were 2.6, 7.1, and 6.7 d for eggs, larvae, and pupae, respectively, with an average of 16.4 d from egg to adult emergence. Female immatures development took ≈1 d longer than male immatures did. Adult F. acarisuga lived an average of 12.8 d, and the female adults (13.3 d) lived significantly longer than male adults did (11.9 d). After an average of 1.5 d preoviposition period, each female laid an average of 27.3 eggs in its life span with an average of 2.1 eggs per day and an average of 2.8 eggs on each of its oviposition day. The raw data were analyzed using an age-stage, two-sex life table method that takes into consideration of the variable developmental rates among individuals and between sexes. The intrinsic rate of natural population increase (r), net reproductive rates (Ro), gross reproductive rate ( ∑ m x ) , generation time (T), and doubling time (DT), and the finite rate of increase (λ) of F. acarisuga were estimated using the age-stage, two-sex (male and female) life table analysis as 0.122 d−1, 16.19 eggs per female, 20.81 eggs per female, 22.81 d, 1.1298 d, and 5.7 d−1, respectively. Each of the first, second, and third instar larvae of F. acarisuga consumed an average of 35.5, 54.0 and 86.9 T. cinnabarinus eggs per day, respectively. Larvae of F. acarisuga could consume an average of 175.4, T. cinnabarinus eggs, and female larvae consumed 14% more spider mite eggs (187.6 eggs) than male larvae (165.1 eggs). The significance of other life table parameters related to the population and the potential of using F. acarisuga as a biological control agent are discussed.

Host plant preference of aphids, thrips and spider mites on GNA-expressing and control potatoes

The effect of snowdrop lectin (Galanthus nivalis agglutinin: GNA) expression on host-plant preference was examined with a two-choice disc test. Discrimination between a transgenic potato [Solanum tuberosum (Solanaceae)] capable of synthesizing GNA, and an isogenic cultivar, was studied under laboratory conditions using the glasshouse potato aphidAulacorthum solani (Hemiptera: Aphididae), the onion thripThrips tabaci (Thysanoptera: Thripidae), and the two-spotted spider miteTetranychus urticae (Acari: Tetranychidae). Adults of these species were placed individually on leaf discs (one half transgenic and one half control) and observed 1, 24, 48, 72 and 96 h after release, at which times also the distributions ofA. solani nymphs andT. urticae eggs on the discs were recorded. Aphids were found more frequently on control leaves at all observation periods, with the highest bias observed at 72 h (only 35.9% of all aphids were found on the GNA halves). Similarly, more aphid nymphs (57.6% of the total) were found on isogenic half-discs. The percentage of thrips found on GNA halves ranged from 36.8% to 48.4%, with significant control-potato bias at the first three observations. Contrary to this, the proportion ofT. urticae females found on GNA halves was significantly lower than the expected proportion (0.5) at 72 and 96 h, with a minimum of 34.0% on GNA. The distribution of spider mite eggs reflected the observed biased distribution of females (only 34.1% of all eggs were laid on GNA half-discs). These results indicate that potatoes expressing GNA for resistance against aphids are less preferred than an isogenic cultivar by all three tested species under a choice test condition using excised leaves.

Host‐plant species modifies the diet of an omnivore feeding on three trophic levels

The diet choice of omnivores feeding on two adjacent trophic levels (either plants and herbivores or herbivores and predators) has been studied extensively. However, omnivores usually feed on more than two trophic levels, and this diet choice and its consequences for population dynamics have hardly been studied. We report how host‐plant quality affects the diet choice of western flower thrips feeding on three trophic levels: plants (cucumber or sweet pepper), eggs of spider mites and eggs of a predatory mite that attacks spider mites. Spider mites feed on the same host plants as thrips and produce a web that hampers predator mobility. To assess the indirect effects of spider mites on predation by thrips, the thrips were offered spider‐mite eggs and predatory‐mite eggs on cucumber or sweet pepper leaf discs that were either clean, damaged by spider mites but without spider‐mite web, or damaged and webbed. We show that, overall, thrips consumed more eggs on sweet pepper, a plant of low quality, than on cucumber, a high quality host plant. On damaged and webbed leaf discs (mimicking the natural situation), thrips killed more predator eggs than spider‐mite eggs on sweet pepper, but they killed equal numbers of eggs of each species on cucumber. This is because web hampered predation on spider‐mite eggs by thrips on sweet pepper, but not on cucumber, whereas it did not affect predation on predatory‐mite eggs. We used the data obtained to parameterize a model of the local dynamics of this system. The model predicts that total predation by the omnivore has little effects on population dynamics, whereas differential attack of predator eggs and spider‐mite eggs by the omnivore has large effects on the dynamics of both mite species on the two host plants.

Prey preference of the predatory mite Neoseiulus womersleyi Schicha is determined by spider mite webs

Abstract: We experimentally verified a proximate cause for the preference of prey species by the predatory mite Neoseiulus womersleyi, which prefers the eggs of Amphitetranychus viennensis Zacher to those of Tetranychus urticae Koch. To separate the effects of spider mite eggs and spider mite webs on the prey preference of the predatory mite, we manipulated combinations of eggs and webs of the two prey species. The number of eggs consumed by adult female N. womersleyi was compared with respect to two factors: eggs of the same species under webs of the different species and eggs of different species under webs of the same species. The results revealed that the prey preference of N. womersleyi was determined by the webs, and not by the eggs.

Life-history traits of the acarophagous lady beetle,Stethorus japonicus at three constant temperatures

Stethorus japonicusKamiya (Coleoptera: Coccinellidae) is an indigenous ladybird beetle in Japan, which feeds on many spider mite species. We evaluated the development, survivorship and life-history parameters of this lady beetle on a diet of eggs of the two-spotted spider mite, Tetranychus urticae Koch (red form) (Acari: Tetranychidae). In addition, the effect of short photoperiod on its reproduction was assessed. Survival rates from egg to adult were more than 71% at temperatures between 17.5 and 30 °C. The highest immature mortality was 100% at 35 °C followed by 76% at 15 °C and 52% at 32.5 °C. The lower threshold temperature for development from egg to egg-laying adult was 13.0 °C and the thermal constant was calculated as 238.7° days. Based on these data, the maximum number of generations that could complete development in a year under field conditions in Ibaraki, central Japan, would be between five and seven. The intrinsic rates of natural increase (rm) were 0.093 at 20 °C, 0.156 at 25 °C and 0.241 at 30 °C. Reproductive diapause was induced at photoperiods with light phases shorter than 13 h at 18 °C.

Why does the predatory mite Neoseiulus womersleyi Schicha (Acari: Phytoseiidae) prefer spider mite eggs to adults?

Adult female Neoseiulus womersleyi feed on all stages of tetranychid mites, although they show a strong preference for eggs over adult females when both are available. We found that the oviposition rate of N. womersleyi females supplied with eggs of Tetranychus kanzawai or T. urticae was significantly higher than that of N. womersleyi females supplied with adult females of the respective prey species. The results suggested that the preference of N. womersleyi females for spider mite eggs simply reflected the optimal foraging of the females.

A new monitoring approach for the two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) in hop culture

The two-spotted spider mite, Tetranychus urticae Koch, is a major pest in hops with world-wide economic importance. According to official guidelines, the monitoring of the infestation level of T. Urticae is done in Germany as well as the rest of Europe by exact counts of living spider mites per hop leaf, while numbers above 50 or 100 mites per leaf, respectively, are estimated roughly. This monitoring approach is very time-consuming, requires good diagnostic knowledge to identify younger developmental stages, may overestimate the true infestation level if mean values include high outliers, and, most important, spider mite eggs on the leaves are not considered at all. Therefore, a six-stage pest index was developed during the years 1998–2000 in order to facilitate field monitoring of T. Urticae, in particular for hop growers. With this new monitoring method, numbers of living mites are assigned to different abundance classes, and deposited eggs on the leaves are considered additionally. This approach proved to be easy to handle, and was reliable during a further three-years’ testing period.

Nest-size variation reflecting anti-predator strategies in social spider mites of Stigmaeopsis (Acari: Tetranychidae)

The social spider mites (Acari: Tetranychidae) of Stigmaeopsis weave dense nests on the underside of host leaves. Four species occur on the leaves of bamboo in Japan: Stigmaeopsis longus, S. celarius, S. takahashii and S. saharai. We initially reconfirmed the occurrence of distinct variation in nest size among the species. Based on the hypothesis that this variation plays a role in protecting the spider mites from predators, we looked at the behavior of the natural enemies that occur on the host plants along with members of Stigmaeopsis. We found considerable variation in the ability of nests to protect the spider-mite eggs. The smallest nests protected the eggs against three predators, whereas the largest nests protected the eggs against only one predator species. So, decreases in nest size increased egg defense. Thus we concluded that nest-size variation reflects a strategy for reducing predation.

Lethal effect of Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces fumosoroseus on the eggs of Tetranychus cinnabarinus (Acari: Tetranychidae) with a description of a mite egg bioassay system

Fungal biocontrol agents, including 10 isolates of Beauveria bassiana, Metarhizium anisopliae, and Paecilomyces fumosoroseus were bioassayed for their lethal effects on the eggs of the carmine spider mite, Tetranychus cinnabarinus. The eggs were naturally laid on detached fava bean leaves on agar in petri dishes at 25 °C under a photophase of 12:12 L:D. Suspensions of aerial conidia produced on rice were sprayed onto the leaves, yielding three conidial concentrations (No. conidia/mm2) from low to high for each of the fungal isolates with 3 or 4 replicates (30–65 eggs/leaf or replicate) at each concentration. During a 12-day observation period after spray, the infected eggs shrunk in shape, then turned orange-brown for B. bassiana and P. fumosoroseus or dark-gray for M. anisopliae, and eventually had outgrowths of the sprayed fungus when maintained under moist conditions. Egg mortalities caused by fungal infection varied over time but had no change from day 8 or 9 onward. Differences of the mortalities on day 9 were significant among the fungal species or isolates tested. Based on the LC50 estimates determined by the concentration–mortality relationships of all isolates from probit analysis, B. bassiana Bb2860 with an LC50 of 548 conidia/mm2 was highly infectious to T. cinnabarinus eggs, followed by P. fumosoroseus Pfr116 (848 conidia/mm2) and Pfr153 (913 conidia/mm2). Two M. anisopliae isolates with LC50s of 1717 and 1985 conidia/mm2 were inferior to the three isolates. The other isolates were poor or very poor in ovicidal activity. Our results confirmed the ovicidal activity of the three fungal species and suggested the feasibility to search for more ovicidal isolates from fungal species that may serve as biocontrol agents against spider mites such as T. cinnabarinus. The mite egg bioassay system developed in this study will be useful towards this goal.

Prey consumption and functional response of three acarophagous species to eggs of the two-spotted spider mite in the laboratory

Comparative investigation of the characteristics related to prey consumption, reproductive rate and searching capacity among predators, which remain largely unexplored, could yield important information for selection of novel control agents. In this paper, the daily prey consumption rate of the immature stages and adult females until 20 days after eclosion of three predators, Stethorus japonicus (lady bug), Scolothrips takahashii (predatory thrips) and Amblyseius californicus (predatory mite), on eggs of Tetranychus urticae (red form) was determined, as well as the functional response of adult females to T. urticae eggs, on lima bean leaf discs in the laboratory at three constant temperatures (18–20, 25 and 30°C) and 16L : 8D. Female and male immatures of S. japonicus consumed the same number of spider-mite eggs, whereas more eggs were eaten by female immatures of S. takahashii and A. californicus than by male immatures at each of the temperatures tested. The total number of eggs consumed during the immature stages did not differ significantly among temperatures for any of the three predators. Consumption of T. urticae eggs by S. japonicus was fastest, followed by S. takahashii. Average daily consumption rates of adult females during the first 20 days after emergence at 25°C were 13.4 eggs for A. californicus, 23.0 eggs for S. takahashii and 294.4 eggs for S. japonicus. Adult females of the three predator species showed a type II functional response to prey density, regardless of the temperatures tested.

USE OF RADIATION TO STERILIZE TWO-SPOTTED SPIDER MITE (ACARI: TETRANYCHIDAE) EGGS USED AS A FOOD SOURCE FOR PREDATORY MITES

One-, 2- and 3-day-old two-spotted spider mite eggs were treated with increasing doses of gamma radiation ranging from 0-280 Gy. Percent egg hatch decreased as radiation increased for each age group; however, older eggs required higher doses of radiation to prevent egg hatch than did younger eggs. Based on the regression lines for 1-, 2- and 3-day-old eggs, the best estimates of the doses of radiation that would prevent 100% of the eggs from hatching were 43.6 Gy, 55.1 Gy and in excess of 280 Gy, respectively. In general, irradiating spider mite eggs had no significant effect on their acceptability as prey by females of the predatory mite Neoseiulus californicus McGregor, except for 1-day-old eggs treated at 240 Gy. Female N. californicus consumed 50-75% fewer of these eggs than they did eggs of other treatments, in both no-choice and choice experiments.

Biocontrol of Two-spotted Spider Mite Tetranychus urticae on Dwarf Hops by the Phytoseiid Mites Phytoseiulus persimilis and Neoseiulus californicus

Two female Phytoseiulus persimilis and their offspring eliminated two-spotted spider mite Tetranychus urticae from hop leaf discs faster than two female Neoseiulus californicus and their offspring at 25°C. A combination of one female of each species and their offspring eliminated spider mites faster than the N. californicus alone, but slower than P. persimilis alone. Air relative humidities of 55% and 93% had no effect on predation. Both predator species cannibalised eggs and juveniles when spider mite numbers were low. In field experiments in 1996, fewer spider mites were recorded where P. persimilis was released, irrespective of the presence of N. californicus. Pest numbers on cv. 'First Gold' were lower than on cv. 'Herald'. No differences were recorded between the numbers of spider mite eggs in predator release treatments on 'First Gold', but fewer active stages of spider mites were recorded on plots with P. persimilis than controls soon after the time of peak pest population densities. On 'Herald', fewer spider mite active stages and eggs were recorded where predators were released than on untreated controls.

Poor host plant quality causes omnivore to consume predator eggs

Summary Omnivorous arthropods are known to change their diet when host plant quality is low. Consequently, it has been suggested that decreased plant quality has a twofold negative effect on herbivore populations: (1) a decrease in growth rate of herbivores; (2) omnivores include more herbivores in their diet. We hypothesized that decreased host plant quality may also cause omnivores to feed on predators, including their own enemies. We tested this hypothesis, using the omnivorous western flower thrips. This species is known to feed on many plant species, but also on the eggs of another herbivore, the two‐spotted spider mite. Previous research has shown that a decrease in plant quality leads to increased feeding on spider mite eggs by western flower thrips. Western flower thrips also kill the eggs of various predatory mites, including those of the specialist predator of spider mites and those of a predatory mite that attacks western flower thrips itself. In this paper we investigate whether thrips larvae kill predator eggs to feed on them and whether this predation depends on host plant quality. Larval survival as well as developmental rate increased when plant tissue of low quality (sweet pepper) was supplemented with eggs of two predatory mite species or when it was supplemented with pollen, a high‐quality food type. Supplementing high quality leaf tissue (cucumber) with predator eggs did not lead to increased survival and developmental rate. Thrips larvae fed significantly less on predatory mite eggs when pollen was available. Thus, thrips larvae indeed feed on predator eggs, including those of their predator, and they feed more on predator eggs when host plants are of low quality.

Efficacy of Silwet L-77 Against Several Arthropod Pests of Table Grape

Silwet L-77, an organosilicone surfactant, was applied to several arthropod pests of California table grapes. Eggs of grape mealybug, Pseudococcus maritimus (Ehrhorn), and omnivorous leafroller, Platynota stultana Walsingham, were tolerant to 0.1, 0.25, and 0.5% treatment solutions; however, eggs of Pacific spider mite, Tetranychus pacificus McGregor, were highly susceptible with mortality >99.4% (0.1% Silwet L-77). Mortality of immature and adult stages of cotton aphid (Aphis gossypii Glover), Western flower thrips (Frankliniella occidentalis Pergande), and Pacific spider mite (Tetranychus pacificus McGregor) was ≥93.8, ≥98.5, and ≥99.4% for 0.1, 0.25, and 0.5% Silwet L-77, respectively. Grape mealybug crawlers had 100% mortality when treated with 0.5 and 1.0% Silwet L-77 solutions; however, mortality was only 6.7% when 0.1% Silwet L-77 was applied. ‘Thompson Seedless’ table grapes were not damaged when treated with up to 1% Silwet L-77; however, grapes treated with the 0.5 and 1.0% solutions appeared wet after removal from cold storage because of the effect of the surfactant spreading the water condensation. Grapes dried with the normal bloom on the berries when they reached room temperature.

Efficacy of Silwet L-77 against several arthropod pests of table grape.

Silwet L-77, an organosilicone surfactant, was applied to several arthropod pests of California table grapes. Eggs of grape mealybug, Pseudococcus maritimus (Ehrhorn), and omnivorous leafroller, Platynota stultana Walsingham, were tolerant to 0.1, 0.25, and 0.5% treatment solutions; however, eggs of Pacific spider mite, Tetranychus pacificus McGregor, were highly susceptible with mortality >99.4% (0.1% Silwet L-77). Mortality of immature and adult stages of cotton aphid (Aphis gossypii Glover), Western flower thrips (Frankliniella occidentalis Pergande), and Pacific spider mite (Tetranychus pacificus McGregor) was > or = 93.8, > or = 98.5, and > or = 99.4% for 0.1, 0.25, and 0.5% Silwet L-77, respectively. Grape mealybug crawlers had 100% mortality when treated with 0.5 and 1.0% Silwet L-77 solutions; however, mortality was only 6.7% when 0.1% Silwet L-77 was applied. 'Thompson Seedless' table grapes were not damaged when treated with up to 1% Silwet L-77; however, grapes treated with the 0.5 and 1.0% solutions appeared wet after removal from cold storage because of the effect of the surfactant spreading the water condensation. Grapes dried with the normal bloom on the berries when they reached room temperature.

Prey-Stage Preference in Generalist and Specialist Phytoseiid Mites (Acari: Phytoseiidae) When OfferedTetranychus urticae(Acari: Tetranychidae) Eggs and Larvae

We tested 13 species of phytoseiid mites for prey preferences between eggs and larvae of twospotted spider mite, Tetranychus urticae Koch. In general, oligophagous, specialized spider mite predators preferred eggs whereas more polyphagous, generalist predators showed no prey-stage preference or preferred larvae: Phytoseiulus macropilis (Banks), P. persimilis Athias-Henriot, Neoseiulus longispinosus (Evans), and Neoseiulus fallacis (Garman) preferred eggs; Kampimodromus aberrans (Oudemans), Galendromus occidentalis (Nesbitt), N. barkeri Hughes, N. californicus (McGregor), N. cucumeris (Oudemans), and Typhlodromus pyri Scheuten showed no prey-stage preference; and Amblyseius andersoni Chant, Euseius finlandicus (Oudemans) and E. hibisci (Chant) preferred larvae. When the ratio of spider mite eggs to larvae was altered, adult females of E. finlandicus, G. occidentalis, N. fallacis, and P. persimilis maintained relatively constant feeding ratios, resulting in slight negative prey-stage switching due mostly to the changes in prey-stage ratios offered. However, when offered a prey-stage ratio that was biased toward eggs, adult females of T. pyri exhibited positive switching, feeding disproportionately more on eggs than would be expected given the change in the ratio offered. There was no clear trend in the effect of starvation time on prey-stage preference for N. fallacis adult females. The egg preference of N. fallacis was also not affected when individuals were reared solely on eggs or larvae of T. urticae and subsequently tested as adult females. Individuals of field-collected strains of N. fallacis and P. persimilis showed no differences in prey-stage preferences when compared with individuals from long-term reared laboratory strains of the same species. However, individuals of one field-collected strain of G. occidentalis showed a stronger preference for eggs than individuals from three other strains (one laboratory and two field-collected) of the same species.

Quality Control of the Mass-Reared Predatory Mite, Amblyseius cucumeris (Acarina: Phytoseiidae)

Quantity, sex ratio, survival, fecundity, mobility, predation and feeding preference were investigated to assess the post-shipment quality of commercially available strains of Amblyseius cucumeris from 3 different companies supplying this product to growers in Canada. The quantity of live mites promised on the labelz was close to the number estimated from subsampling for companies A and C; whereas company B had provided only 66% of the number of mites on the label. The sex ratio of mites from company A was close to 1:1, whereas companies B and C had a greater proportion of females. All 3 products failed to meet the IOBC guideline of 7 eggs per female over 7 days at 22°C, although companies B and C were close to this standard. Survival of mites over 9 days was quite variable among companies. Only products B and C reached the IOBC standard of 80% survival over 5 days. Product A with only 58% survival on day 5 is unacceptable. Mobility of mites was good and similar for products B and C; whereas mites from product A were the least mobile. Predation tests indicated similar consumption of grain mite nymph in 24 hours for A. cucumeris from products B and C, whereas mites from product A consumed approximately 25% less nymphs in 24 hours. Feeding preference tests of adult predator mites from companies B and C indicated a preference for spider mite eggs rather than grain mite eggs.

Macrolophus caliginosus: Functional response to whiteflies and preference and switching capacity between whiteflies and spider mites

AbstractLaboratory experiments were performed with adult female Macrolophus caliginosus Wagner (Heteroptera: Miridae) at 22°C on bean plants to determine the functional response towards whiteflies, as well as the preference and switching capacity between the two prey species: whiteflies and spider mites. Predation of females presented with first instars of Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae) was of a Type III functional response. The observed maximum predation was approximately 75 first instars at high prey densities within a 24‐h period. The preference of M. caliginosus females between eggs of T. vaporariorum and Tetranychus urticae Koch (Acarina: Tetranychidae) changed with the ratio of offered prey. The preference for T. vaporariorum eggs increased non‐linearly with increasing proportions of this prey type. The average maximum predation of whitefly and spider mite eggs were approximately 166 and 111 eggs per day, respectively, at the highest ratio of the two preys. The proportion of M. caliginosus females found on the test plants at the end of the experiment increased with prey density suggesting that this mirid spends more time in areas with high prey density. Macrolophus caliginosus females are voracious predators of eggs and first instars of T. vaporariorum as well as of spider mite eggs and may thus be a valuable addition to existing methods of biological control of T. vaporariorum and T. urticae.