Biocontrol of Pests of Apples and Pears in Northern and Central Europe - 3. Predators

Predators of apple and pear pests in northern and central Europe and their use as biological control agents are reviewed. Many natural enemy species are specialized feeders and are able to respond to the population dynamics of particular pest species. The most oustandingly successful example of this is the use of phytoseiid mites, particularly Typhlodromus pyri , against phytophagous pest mites in apple. This mite management strategy is now widespread throughout European apple growing regions. Another example is the use of Anthocoris nemoralis against pear psyllids, Cacopsylla pyricola and C. pyri . Several groups of naturally occurring polyphagous predators, such as chrysopids, coccinellids, syrphids and spiders, also prey on a number of pest species in orchards, contributing generally to the reduction in pest populations. However, they are unlikely alone to prevent pest damage fully and reliably. In seeking biological control opportunities for a particular pest, these polyphagous natural enemies are unlikely to be a high priority. An exception, due to its abundance in orchards, is the common earwig, Forficula auricularia , although this predator may also cause some fruit injury. Another option to consider when reviewing possibilities for biological control in orchards is the introduction of biological control agents. The success rate of this approach, using arthropod predators to control pests of field crops, has been generally poor. Furthermore, mass production methods for predators are likely to be difficult and very costly. The biological supplies industry is constantly seeking culture techniques, largely for arthropod biological control agents of pests of protected crops. It is possible that some future advance may be relevant to orchards, though currently available predators do not appear promising. A careful economic appraisal of the feasibility of use of any potential biological control agent would be prudent before embarking on research.     

Juvenile Survival and Development in Euseius Finlandicus, Typhlodromus Pyri and Kampimodromus Aberrans (Acari: Phytoseiidae) Feeding on Con- and Heterospecific Immatures

Juvenile survival and development in Euseius finlandicus (Oudemans), Typhlodromus pyri Scheuten and Kampimodromus aberrans (Oudemans) feeding on con- and heterospecific phytoseiid immatures were investigated in the laboratory at 25 ± 1 °C and 65 ± 5% RH. More than 50% of T. pyri protonymphs preying on larvae of K. aberrans or E. finlandicus reached the adult stage. The mean developmental time of T. pyri from the protonymphal stage to adulthood was 6.3 days when feeding on K. aberrans and 7.5 days when feeding on E. finlandicus. The majority (approximately 90%) of K. aberrans protonymphs feeding on larvae of T. pyri or E. finlandicus died before reaching the deutonymphal stage; in both cases only one individual completed juvenile development. Euseius finlandicus larvae require food to reach the subsequent life stage, in contrast to larvae of T. pyri and K. aberrans, which usually do not feed at all: 10% of E. finlandicus immatures feeding on larvae of K. aberrans or T. pyri completed juvenile development (mean developmental time from larva to adult 7.0 and 6.7 days, respectively). Cannibalizing immatures of T. pyri and K. aberrans were able to reach adulthood, whereas those of E. finlandicus were not. Unfed immatures of T. pyri lived longer than the corresponding stages of E. finlandicus and K. aberrans. The present study indicates that phytoseiid immatures are suitable prey for developing stages of polyphagous phytoseiids. Since E. finlandicus, T. pyri and K. aberrans partly inhabit the same plant species, their immatures can be regarded as potential prey for competitive phytoseiids in times of food scarcity.     

Directional substitution and evolution of nucleotide content in the cytochrome oxidase II gene in earwigs (dermapteran insects)

The cytochrome oxidase subunit II (COII) gene was sequenced for six dermapteran species. The nucleotide composition of this gene is biased in most animals. While the CG content of other insect orders is low (mean, 27.6%; range, 19.5%-33.1%), species from the Forficula genus showed unusually high values (mean, 42.4%; range, 37.3%-44.1%), mostly due to high CG frequencies at third codon positions: the mean CG content at these positions was around 45% (range, 43.9%-46.9%) for Forficula, compared with only 13.3% for other insects. This effect was so strong that in one species, Forficula lesnei, there was no significant difference between the frequencies of the four bases. During evolution, this loss of bias has involved a significant increase in the synonymous substitution rate and an increase of transitions over transversions compared with other insects. A strong directionality of substitutions has favored T-->C and A-->G changes. This phenomenon was also observed between two conspecific populations of Forficula auricularia. A species from a closely related genus, Anechura bipunctata, was intermediate between Forficula and other insects for these parameters, while two remotely related dermapteran species, Labidura riparia and Euborellia moesta, were similar to other insects. These results suggest that the evolution of Forficula DNA content has been both rapid and recent.     

Intra- and interspecific predation by adult female Metaseiulus occidentalis and Typhlodromus pyri (Acari: Phytoseiidae) when provisioned with varying densities and ratios of Tetranychus urticae (Acari: Tetranychidae) and phytoseiid larvae

The phytoseiid mites Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Schueten are used together and alone as biological control agents against tetranychid pest mites of apple. Their effectiveness as control agents may be impacted by intraguild predation. The effects of prey species and prey density on the rates of inter- and intraspecific predation and oviposition by these two predators were investigated through a series of experiments. Adult female predators were given prey as mixed populations of phytoseiid larvae and larvae of a more preferred species, the spider mite, Tetranychus urticae Koch, at different densities and ratios. Typhlodromus pyri, more of a generalist predator, showed higher rates of predation and cannibalism on phytoseiid immatures at most prey densities and ratios. Manly preference indices indicated that T. pyri switched to feed on phytoseiid larvae at higher prey levels and ratios of T. urticae than M. occidentalis. This greater ability to use phytoseiid larvae as prey may help stabilize T. pyri populations when more preferred prey is unavailable. This may, in part, explain the observed persistence of T. pyri populations when M. occidentalis populations were decreasing in orchard test plots.     

Performance of a pyrethroid-resistant strain of the predator mite Typhlodromus pyri (Acari: Phytoseiidae) under different insecticide regimes

An organophosphate pyrethroid-resistant strain of Typhlodromus pyri Scheuten imported from New Zealand was reared on potted apple trees in an outdoor insectary. From 1988 to 1995, the population was selected one to three times per year with a dilute solution (1.7 ppm) of the pyrethroid cypermethrin. Petri dish bioassays with cypermethrin in 1995 indicated that the insectary-reared T. pyri had an LC50 of 81 ppm versus 0.006 ppm for native T. pyri taken from a research orchard. The bioassays suggested that recommended orchard rates of cypermethrin would cause heavy mortality in native populations of T. pyri but only moderate losses in the imported New Zealand strain. Bioassays in 1996 with the organophosphate insecticide dimethoate indicated both New Zealand and native T. pyri were susceptible and that recommended orchard rates of dimethoate likely would cause high mortality of T. pyri in apple orchards. These findings from bioassays were supported by data from orchard trials. In June and July 1993, insectary-reared New Zealand T. pyri were placed on five apple trees in each of eight 38-tree plots in the research orchard. In late August 1994, New Zealand T. pyri from orchard trees that had been sprayed twice by airblast sprayer with the full recommended rate of 50 g (AI)/ha (83 ppm) cypermethrin were placed on the other 33 trees in each of six plots. In the summers of 1994-1996, plots were treated with one of the following insecticide regimes: (1) conventional integrated pest management (IPM) (registered neurotoxic insecticides considered harmless or slightly toxic to T. pyri); (2) advanced IPM (use of newer, more selective insecticides); (3) pyrethroid (at least one full-rate application of cypermethrin); (4) dimethoate; and (5) dimethoate plus pyrethroid. Densities of European red mite, Panonychus ulmi (Koch), were highest in all plots treated with dimethoate and in pyrethroid plots not yet inoculated with New Zealand T. pyri. Densities of apple rust mite, Aculus schlechtendali (Nalepa), and of the stigmaeid predator Zetzellia mali (Ewing) were highest in plots treated with dimethoate and were nearly absent in the IPM plots. Densities of T. pyri were high enough for effective biocontrol in the IPM plots and in the pyrethroid plots 1-2 yr after release of the New Zealand strain, provided pyrethroid was applied just before the resistant strain was released in the orchard. A recurring theme of this study was the generally negative association between densities of phytophagous mites and those of T. pyri, suggesting the ability of this predator to suppress their prey. In contrast, the positive association between phytophagous mites and Z. mali suggests the inability of this predator to regulate their prey at least under the conditions of this study.     

Processed kaolin as an alternative insecticide against the European pear sucker, Cacopsylla pyri (L.)

Abstract:  Application of processed kaolin particle film (Surround^® WP; Engelhard Corporation, Iselin, NJ, USA) repels insects without lethal effects; hence side effects on beneficial arthropods are low. Processed kaolin may be an alternative to broad-spectrum insecticides used against European pear sucker, Cacopsylla pyri (L.), in organic and conventional pear production. A small-plot field trial was conducted in spring 2003 to assess this hypothesis. Multiple applications of processed kaolin during the first flying period of C. pyri significantly reduced the number of nymphs compared to the untreated control. Processed kaolin protected pear trees at least as good as the standard organic insecticide rotenone. Since the effects on the summer population could not be assessed in this small-plot trial due to the high mobility of the adult C. pyri , a large-plot trial was conducted in 2004. Thereby, the processed kaolin showed a very high efficacy and the population of C. pyri was kept under a damaging level over the whole season. At the end of June the population density of C. pyri in the processed kaolin treated area was lower than in the IPM treated plot. In conclusion, kaolin shows promise as an alternative control for C. pyri in organic and IPM orchards.     

Powdery mildew (Ascomycotina: Erysiphales) — an alternative food for the predatory mite Typhlodromus pyri Scheuten (Acari: Phytoseiidae)

The ability of Typhlodromus pyri Scheuten to feed on powdery mildew was investigated. Adult females of T. pyri which had previously been fed on the pollen of Pinus sylvestris L. were offered three powdery mildew species and their feeding behaviour was observed. The females fed readily on the conidia of Erysiphe orontii Cast. from tobacco and Oidium fragariae Harz. from strawberry while no feeding was observed on Erysiphe polygoni DC. from red clover, even after the mites were starved for 2 days. Erysiphe orontii was tested for its effect on the survival, oviposition and development of T. pyri. The results showed that the conidia of E. orontii can supply mites with the water and nutrients necessary for their normal development. Mature females successfully mated and reproduced, although their oviposition rate was low. This revised version was published online in November 2006 with corrections to the Cover Date.     

Sampling of Cacopsylla pyri (Hemiptera: Psyllidae) and Pilophorus gallicus (Hemiptera: Miridae) in pear orchards

The psyllid Cacopsylla pyri L. (Hemiptera: Psyllidae), is one of the principal pests of pear (Pyrus spp.) orchards and, along with its natural enemies, needs to be carefully monitored for correct integrate pest management and biological pest control decision making. We compare sampling techniques and develop sampling methods for C. pyri and Pilophorus gallicus Remane (Heteroptera: Miridae). Four pear orchards were sampled periodically from 2007 to 2010 in southern Spain by beating branches into funnels or 45-cm-diameter nets and taking shoot samples. Different sampling techniques were compared, and several sampling methods were assayed for adults and nymphs of C. pyri and P. gallicus. Psylla adult and P. gallicus counts in the nets and funnels were similar and closely correlated. Counts of C. pyri adults in the funnels and nets were higher than on shoots, but all measures were closely correlated. The number of nymphs on shoots and leaves was correlated, as were the counts on leaves within shoots. A guide for choosing the sampling unit in cost/precision terms is given. C. pyri nymphs and adults showed an aggregated distribution, whereas P. gallicus had a less-crowded spatial distribution. Enumerative sequential sampling was evaluated for both insects by using the different sampling techniques by resampling experimental data. The negative binomial distribution fitted the experimental data gathered using the different sampling techniques for C. pyri adults and P. gallicus. The use of binomial sampling is discussed for the two insects and the costs involved are compared with those implied in the sequential enumerative method.     

Mite Population Dynamics on Different Grape Varieties With or Without Phytoseiids Released (Acari: Phytoseiidae)

In a three-year study, mite populations were monitored in two vineyards, each having two grape varieties with different leaf hair density. In both vineyards native phytoseiids were present: Amblyseius andersoni in one vineyard, and Phytoseius finitimus in the other. The economically important predators Kampimodromus aberrans and Typhlodromus pyri were released in both vineyards in order to study their efficacy in controlling tetranychids and eriophyids and their persistence during periods of prey scarcity. In both vineyards, relative abundances of the mite species, especially phytoseiids, were found to differ on different varieties in the same vineyard. In the first experiment, A. andersoni reached higher densities and was more persistent on the variety with slightly pubescent leaf under-surface (Merlot). Typhlodromus pyri and K. aberrans releases were successful and the mites became more abundant on the variety with pubescent leaf under-surface (Verduzzo). In the second experiment, P. finitimus was more abundant on a variety with pubescent leaf under-surface (Prosecco) than with glabrous leaf under-surface (Riesling). The most interesting results of the present study concerned the interactions between native and released predators. In the first vineyard, different results were obtained when releasing T. pyri on the two varieties. On the variety with pubescent leaves, A. andersoni was rapidly displaced by T. pyri, whereas the former species persisted on the other variety throughout the three-year study, apparently becoming dominant during the last season. In contrast to T. pyri, interactions between K. aberrans and A. andersoni in this vineyard did not depend on variety. The results of the experiments carried out in the second vineyard stressed the importance of interspecific competition for phytoseiid releases. Typhlodromus pyri colonization failed on both varieties. Kampimodromus aberrans releases appeared to be more successful on Riesling than on Prosecco, where P. finitimus was more abundant. At the end of the experiments, K. aberrans displaced P. finitimus on both varieties.     

Temperature-related development and population parameters for Typhlodromus pyri (Acari: Phytoseiidae) found in Oregon vineyards

The beneficial mite Typhlodromus pyri is a key predator of grapevine rust mite Calepitrimerus vitis in Pacific coastal vineyards. Rust mite feeding has been associated with damage such as stunted, deformed shoot growth and reductions in fruit yield. The life history traits of T. pyri were assessed at seven constant temperatures (12.5, 15, 17.5, 20, 25, 30 and 35 °C) to determine population parameters providing data to better predict biological control of C. vitis populations by T. pyri in vineyards. Successful development from the egg to adult stage was observed at temperatures ranging from 15 to 30 °C. Constant exposure to 12.5 and 35 °C resulted in 100 % mortality in immature T. pyri. Developmental times, fecundity and longevity were highest at 25 °C. The estimated minimum and maximum developmental thresholds were 7.24 and 42.56 °C, respectively. Intrinsic rate of increase (r ( m )) was positive from 15 to 30 °C indicating population growth within this range of temperatures. Net reproductive rate and intrinsic rate of increase were greatest at 25 °C. These developmental parameters can be used to estimate population growth, determine seasonal phenology and aid in conservation management of T. pyri. Results presented in this study will aid in evaluating the effectiveness of T. pyri as a key biological control agent of C. vitis during different periods of the growing season in Pacific Northwest vineyards.     

Dimorphisms and fluctuating asymmetry in the forceps of male earwigs

Male dimorphisms are particularly conspicuous examples of the alternative reproductive strategies employed within some species. Such dimorphisms are thought to exist as genetic polymorphisms under ESS conditions, or to be conditional strategies where exogenous conditions determine the adult body plan. Fluctuating asymmetry (FA) is currently considered to be a fitness correlate of significant use in interpreting the functional significance of secondary sexual characteristics. In particular, negative slopes of FA on trait size are thought to arise in traits whose expression is dependent on condition. We measured forceps lengths and asymmetries in 2 island populations of the European earwig Forficula auricularia and Museum specimens of 5 other earwig (Dermaptera, Forficulidae) species from different genera, that appeared to be dimorphic. In a detailed study of Forficula auricularia we found a significant fit to a statistical model for the identification of dimorphisms and, for all species examined, morphs differed in the slope and/or elevation of the allometric relationship between body size and forcep length. Possible determinates of male dimorphisms are suggested from the data. Contrary to expectation, FA was not found to be greater in the minor morphs. Negative relationships between FA and forceps length were absent in both morphs of species examined from museum collections. Of the two island populations of Forficula auricularia, the smaller and more isolated population had higher FA and a negative relationship between FA and forceps length in the major morph. We discuss these patterns in the light of recent theories of FA and honest signalling.     

Influence of leaf trichomes on predatory mite (Typhlodromus pyri) abundance in grape varieties

Non-glandular leaf trichomes positively influence the abundance of many phytoseiid mites. We characterized the influence of grape leaf trichomes (domatia, hairs, and bristles) on Typhlodromus pyri Scheuten abundance over two years in a common garden planting of many grape varieties and 2 years of sampling in a commercial vineyard. In general, a lack of trichomes was associated with much lower predator numbers and in the case of Dechaunac, a cultivar with almost no trichomes, very few T. pyri were found. Phytoseiid abundance was best predicted by a model where domatia and hair had an additive effect (r (2) = 0.815). Over two years of sampling at a commercial vineyard there were T. pyri present on all of the 5 cultivars except Dechaunac. At the same time, European red mite prey were present on Dechaunac alone. These results suggest that on grape cultivars lacking leaf trichomes, T. pyri likely will not attain sufficient densities to provide biological control of European red mite, despite presence of the mite food source. The relationship between leaf trichomes and phytoseiid abundance that is observed at the scale of single vines in a garden planting appears to also be manifest at the scale of a commercial vineyard. Because persistence of predatory mites in or nearby the habitats of prey mites is important for effective mite biological control, leaf trichomes, through their influence on phytoseiid persistence, may be critical for successful mite biological control in some systems.     

Population growth and persistence when prey is diminishing in single-species and two-species systems of the predatory mites Euseius finlandicus, Typhlodromus pyri and Kampimodromus aberrans

Population growth and persistence of Euseius finlandicus (Oudemans), Typhlodromus pyri Scheuten and Kampimodromus aberrans (Oudemans) (Acari: Phytoseiidae) were studied in single-species and two-species systems on apple seedlings primarily infested by Panonychus ulmi Koch (Acari: Tetranychidae) in an environmentally controlled greenhouse. During the experiment, the seedlings developed natural infestations by Tetranychus urticae Koch (Acari: Tetranychidae), Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), and powdery mildew. Several weeks after the start of the experiment a condition of diminishing prey availability was created by use of hexythiazox treatments. Without heterospecific competitors, T. pyri attained a higher population level than E. finlandicus or K. aberrans when similar amounts of food (spider mites) were available to each. Population growth of T. pyri was decisively favoured by the presence of T. urticae. In the single-species systems each predatory species persisted to the end of the experiment in spite of diminishing prey. In two-species systems with T. pyri/E. finlandicus and T. pyri/K. aberrans that were started with the same number of individuals of each species, only T. pyri was left at the end of the experiment. Typhlodromus pyri became more numerous than the other species when prey was abundant (which was in accordance with the results of the single-species groups) and finally displaced E. finlandicus and K. aberrans towards the end of the experiment. The following factors may have contributed to the dominance of T. pyri: (1) the ability of adult females to survive longer without food than those of E. finlandicus and K. aberrans, (2) the ability to complete juvenile development and to sustain reproduction with phytoseiid prey and (3) an advantage in foraging behaviour over K. aberrans and E. finlandicus at low spider mite levels. Euseius finlandicus predominated in the two-species system E. finlandicus/K. aberrans, but both species persisted to the end of the experiment.     

Inter- and intraspecific predation on immatures by adult females in Euseius finlandicus, Typhlodromus pyri and Kampimo dromus aberrans (Acari: Phytoseiidae)

In a series of experiments, the interspecific predation and cannibalism on immatures by the adult females of Euseius finlandicus, Kampimodromus aberrans and Typhlodromus pyri were examined under laboratory conditions. The three species showed differing tendencies to prey on each other's motile immature stages. Euseius finlandicus females consumed more larvae and protonymphs than the females of T. pyri and K. aberrans. In cages without free water E. finlandicus ate a range of 6.51 larvae or 5.31 protonymphs of T. pyri and 5.27 larvae or 5.95 protonymphs of K. aberrans per female per day. Kampimodromus aberrans and T. pyri females exhibited a greater tendency to prey on heterospecifics than on conspecifics. When feeding on phytoseiid immatures and without free water, T. pyri females survived longer and laid more eggs than the females of E. finlandicus and K. aberrans. Adult females of E. finlandicus and T. pyri having free water and preying on heterospecific protonymphs were able to maintain egg laying during the whole experimental period of 12 days. The females of all three species had difficulties in piercing phytoseiid eggs, and the number of sucked eggs per female per day was low. Kampimodromus aberrans females ate 0.48 eggs of T. pyri daily, which was the highest recorded number. The great tendency to interspecific predation on motile immature phytoseiids by the females of E. finlandicus is discussed with regard to the dominance of this species on deciduous trees and bushes in Austria.     

Effects of potential food sources on biological and demographic parameters of the predatory mites Kampimodromus aberrans, Typhlodromus pyri and Amblyseius andersoni

Kampimodromus aberrans, Typhlodromus pyri and Amblyseius andersoni are generalist predatory mites important in controlling tetranychid and eriophyoid mites in European vineyards. They can persist by exploiting various non-prey foods when their main prey is absent or scarce. A comparative analysis of the effects of various prey and non-prey foods on the life history of these predators is lacking. In the laboratory, predatory mites were reared on herbivorous mites (Panonychus ulmi, Eotetranychus carpini and Colomerus vitis), a potential alternative prey (Tydeus caudatus) and two non-prey foods, i.e. the pollen of Typha latifolia and the mycelium of Grape downy mildew (GDM) Plasmopara viticola. Developmental times, survival, sex ratio and fecundity as well as life table parameters were estimated. Kampimodromus aberrans developed faster on E. carpini, C. vitis or pollen than on P. ulmi and laid more eggs on pollen than on prey. Low numbers of this predator developed on GDM infected leaves. Tydeus caudatus was not suitable as prey for any of the three predatory mites. Kampimodromus aberrans showed the highest intrinsic rate of population increase when fed on pollen. Developmental times of T. pyri on prey or pollen were similar but fecundity was higher on pollen than on P. ulmi. Typhlodromus pyri had higher intrinsic rates of population increase on C. vitis and pollen than on P. ulmi; E. carpini showed intermediate values whereas GDM resulted in the lowest r ( m ) values. Development of A. andersoni females was faster on pollen and C. vitis than on P. ulmi and GDM. Fecundity was higher on pollen and mites compared to GDM. Life table parameters of A. andersoni did not differ when predators were fed with prey or pollen while GDM led to a lower r ( m ) value. On a specific diet A. andersoni exhibited faster development and higher fecundity than T. pyri and K. aberrans. These findings improve knowledge on factors affecting the potential of predatory mites in controlling phytophagous mites in European vineyards.     

The use of image analysis to study the effects of residues of esfenvalerate on the locomotory behaviour of Panonychus ulmi and Typhlodromus pyri (Acari: Tetranychidae, Phytoseiidae)

The influences of esfenvalerate on mite behaviour were investigated by image analysis. Video recordings of the locomotory behaviour of two mite species were converted into a series of x,y coordinates that, when joined, closely resembled their paths. These coordinates were used to calculate walking speed, direction of travel, turning frequency, turn bias and tortuosity. Two experimental arenas were used: (1) a leaf disc arena for the European red mite, Panonychus ulmi and (2) a glass coverslip arena for Typhlodromus pyri. The behavioural responses of P. ulmi and T. pyri to esfenvalerate (field rate) indicated that these mites did not show a preference for the unsprayed halves of the arenas during the first 48 min. However, significant differences between most of the behavioural parameters to esfenvalerate residues were found with P. ulmi when whole arenas were compared. © Rapid Science Ltd. 1998     

Side effects of mancozeb on Typhlodromus pyri (Acari: Phytoseiidae) in vineyards: results of multi-year field trials and a laboratory study

The side effects of mancozeb on the predatory mite Typhlodromus pyri were studied in 4-year field trials on grapevine and in the laboratory. In the field, the effect of mancozeb varied according to previous mancozeb use. In vineyards where mancozeb had commonly been used over years, this fungicide is generally slightly toxic, in some cases moderately toxic and rarely toxic. In plots were mancozeb has never been used, its effect on T. pyri was more pronounced and varied from moderately toxic to toxic. Despite the toxicity of mancozeb, T. pyri populations have never been eradicated. Laboratory results obtained with the French CEB guideline no. 167 confirmed those of the 4-year field study: mancozeb was significantly more toxic to T. pyri populations collected in plots where it had rarely been used before the field experiment. In plots where mancozeb had been used for a long time, the susceptibility of T. pyri populations to this fungicide was reduced and female survival, fecundity but also viability of female progeny were less affected by mancozeb. Even though toxicity of mancozeb increased in controlled conditions, a significant correlation was established between field and laboratory results.     

Insecticidal activity of proteinous venom from tentacle of jellyfish Rhopilema esculentum Kishinouye

Insecticidal activity of proteinous venom from tentacle of jellyfish Rhopilema esculentum Kishinouye was determined against three pest species, Stephanitis pyri Fabriciusa, Aphis medicaginis Koch, and Myzus persicae Sulzer. R. esculentum full proteinous venom had different insecticidal activity against S. pyri Fabriciusa, A. medicaginis Koch, and M. persicae Sulzer. The 48 h LC50 values were 123.1, 581.6, and 716.3 microg/mL, respectively. Of the three pests, R. esculentum full proteinous venom had the most potent toxicity against S. pyri Fabriciusa, and the corrected mortality recorded at 48 h was 97.86%. So, S. pyri Fabriciusa could be a potential target pest of R. esculentum full proteinous venom.     

Biological control of the two-spotted spider mite Tetranychus urticae on strawberries by the predatory phytoseiid mite Typhlodromus pyri (Acari, Tetranychidae, Phytoseiidae)

The ‘Mikulov’ strain of the predatory mite Typhlodromus pyri Scheuten from south Moravian vineyards was released on cultivated strawberries infested with the two-spotted spider mite, Tetranychus urticae Koch. The strawberries were grown in field plantations and under glass. Typhlodromus pyri on vine shoots were successfully introduced into the field strawberry plantation but they produced no demonstrable control of the spider mites and they eventually declined in density with their prey. In contrast, T. pyri gave good control of spider mites in the glasshouse despite the occurrence of low humidity and water stress of the plants.     

The predatory mite Typhlodromus pyri (Acari: Phytoseiidae) causes feeding scars on leaves and fruits of apple

Typhlodromus pyri Scheuten (Acari: Phytoseiidae) is the most important predator of Panonychus ulmi (Koch) (Acari: Tetranychidae) in orchards and vineyards. It was recently found that adult T. pyri females cause microscopic scars on apple leaves. The present laboratory experiments were carried out to confirm the production of scars on apple leaves and to assess if females cause scars on fruits as well. Scar production on apple leaves and/or fruits was investigated under various nutritional conditions: no food, pollen of Scots pine (Pinus sylvsestris L.) only, nymphs of P. ulmi only, and pollen + prey. Both on leaves and fruits, either offered alone or in combination, feeding scars were produced under all nutritional conditions, but mostly in the 'no food' treatment. The predators consumed significantly more P. ulmi nymphs when offered alone than when offered in combination with pollen. T. pyri laid eggs under all nutritional conditions, but mostly in the 'pollen + prey' treatment and least when no food was offered. T. pyri females caused scars on both leaves and fruits when offered simultaneously, but more on leaves than on fruits. The scars were also bigger on leaves than on fruits in all experiments. T. pyri survived and reproduced on plant material in the absence of other food sources. Whether the scars produced on leaves and fruits harm the quality of fruits or the yield of apple cannot be concluded from the present experiments.