Reducing the impact of pesticides on biological control in Australian vineyards: pesticide mortality and fecundity effects on an indicator species, the predatory mite Euseius victoriensis (Acari: Phytoseiidae)

Laboratory bioassays on detached soybean, Glycine max (L.) Merr., leaves were used to test 23 fungicides, five insecticides, two acaricides, one herbicide, and two adjuvants on a key Australian predatory mite species Euseius victoriensis (Womersley) in "worst-case scenario" direct overspray assays. Zero- to 48-h-old juveniles, their initial food, and water supply were sprayed to runoff with a Potter tower; spinosad and wettable sulfur residues also were tested. Tests were standardized to deliver a pesticide dose comparable with commercial application of highest label rates at 1,000 liter/ha. Cumulative mortality was assessed 48 h, 4 d, and 7 d after spraying. Fecundity was assessed for 7 d from start of oviposition. No significant mortality or fecundity effects were detected for the following compounds at single-use application at 1,000 liter/ha: azoxystrobin, Bacillus thuringiensis (Bt) subsp. kurstaki, captan, chlorothalonil, copper hydroxide, fenarimol, glyphosate, hexaconazole, indoxacarb, metalaxyl/copper hydroxide, myclobutanil, nonyl phenol ethylene oxide, phosphorous acid, potassium bicarbonate, pyraclostrobin, quinoxyfen, spiroxamine, synthetic latex, tebufenozide, triadimenol, and trifloxystrobin. Iprodione and penconazole had some detrimental effect on fecundity. Canola oil as acaricide (2 liter/100 liter) and wettable sulfur (200 g/100 liter) had some detrimental effect on survival and fecundity and cyprodinil/fludioxonil on survivor. The following compounds were highly toxic (high 48-h mortality): benomyl, carbendazim, emamectin benzoate, mancozeb, spinosad (direct overspray and residue), wettable sulfur (> or = 400 g/100 liter), and pyrimethanil; pyrimethanil had no significant effect on fecundity of surviving females. Indoxacarb safety to E. victoriensis contrasts with its toxicity to key parasitoids and chrysopid predators. Potential impact of findings is discussed.     

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.     

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.     

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.     

Effects of fungicide residues on the survival, fecundity, and predation of the mites Tetranychus urticae (Acari: Tetranychidae) and Galendromus occidentalis (Acari: Phytoseiidae)

Representative fungicides from three or four families used for management of powdery mildew and other diseases in tree fruits were evaluated for their effects on a common spider mite and predator mite species, respectively. A modified Munger cell technique was effective in measuring the response of phytophagous and predaceous mites to fungicide residues on detached leaves in the laboratory. Demethylation-inhibiting (DMI) (imidazole [triflumazole] and triazole [myclobutanil]) and strobilurin (trifloxystrobin) fungicides were not toxic to female Tetranychus urticae Koch and Galendromus occidentalis (Nesbitt), and no sublethal effects were found on fecundity and predation rate after 3-5-d exposure to residues. Benomyl, a benzimidazole fungicide, increased adult mortality and reduced fecundity for both mite species; however, it did not alter the predation rate of G. occidentalis females on T. urticae eggs and larvae. Female G. occidentalis that survived the lethal effects of benomyl and the comparison acaricide pyridaben were unimpaired in predation. Our results for benomyl substantiate those of earlier studies and provide evidence for nontoxic effects of DMI and strobilurin fungicides on mites. We propose that DMI and strobilurin fungicides are a good fit for integrated mite management programs due to conservation of phytoseiid predatory mites.     

Life tables of Neoseiulus cucumeris exclusively fed with seven different pollens

The juvenile development and survival, and demographic parameters of the predatory mite Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) fed on pollen of castor bean, tulip, apple, Christmas cactus, horse-chestnut, maize, and birch were assessed under laboratory conditions. Deprivation of food and pollen of castor bean plants resulted in 100 % juvenile mite mortality. Feeding mites with tulip and horse-chestnut pollen resulted in the shortest development and the highest total fecundity. Adult mites fed on birch, tulip, maize, and apple pollen lived significantly longer compared with those fed on pollen of horse-chestnut and Christmas cactus. The intrinsic rate of natural increase ranged between 0.1013 ♀♀/♀/day for maize and 0.1806 ♀♀/♀/day for horse-chestnut pollen as food. Net reproductive rate was the lowest when fed with maize pollen and highest when fed with horse-chestnut pollen. Population doubling time was highest on maize pollen and shortest on horse-chestnut pollen. Our study revealed that birch, tulip, horse-chestnut, apple, and maize pollen can be used by N. cucumeris from early spring to late summer as a suitable alternative food in periods when prey in the field are scarce or absent.     

Studies of the growth, development and reproductive performance of the aphid shape Myzus persicae on artificial diets containing potato glycoalkaloids

Using data sets of phytophagous and predaceous mites, we introduce a method for estimating standard error bands for the proportion of habitat occupied by a species as a function of mean density, by transforming error bands from the variance-mean power law. Error bands produced by this method were more conservative than bands produced by bootstrapping and repeated subsampling methods applied to the same data. Though conservative, the binomial model showed potential to be an easily interpreted, powerful method for detecting differences in the proportion of habitat occupied among data sets (interpreted as differences in species aggregation) on one spatial scale. This was demonstrated in three specific cases: between years for the predaceous mite Typhlodromus pyri Scheuten (Acari: Phytoseiidae) on Red Delicious apple trees (Malus pumila Miller), for the phytophagous mite Tetranychus urticae (Koch) (Acari: Tetranychidae), whether or not it was preyed upon by the predaceous mite Neoseiulus fallacis (Garman) (Acari: Phytoseiidae) on hops (Humulus lupulus L.), and among individual life stages of the predaceous mite Metaseiulus occidentalis (Nesbitt) (Acari: Phytoseiidae) on apple.     

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.     

Predicting the population dynamics of the house dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) in response to a constant hygrothermal environment using a model of the mite life cycle

A generalised model of the life cycle of a house dust mite, which can be tailored to any particular species of domestic mite, is presented. The model takes into account the effects of hygrothermal conditions on each life cycle phase. It is used in a computer simulation program, called POPMITE, which, by incorporating a population age structure, is able to predict population dynamics. The POPMITE simulation is adapted to the Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) (DP) mite using published data on the egg development period, total development period, adult longevity, mortality during egg development, mortality during juvenile development, and fecundity of individual DP mites held at a range of constant hygrothermal conditions. An example is given which illustrates how the model functions under constant hygrothermal conditions. A preliminary validation of POPMITE is made by a comparison of the POPMITE predictions with published measurements of population growth of DP mites held at a range constant hygrothermal conditions for 21 days. The POPMITE simulation is used to provide predictions of population growth or decline for a wide range of constant relative humidity and temperature combinations for 30 and 60 days. The adaptation of the model to correctly take account of fluctuating hygrothermal conditions is discussed.     

Biological control of spider mites on grape by phytoseiid mites (Acari: Tetranychidae,Phytoseiidae): emphasis on regional aspects

Leaf samples were taken from 34 (1998) and 10 (1999) vineyards in five valleys in western Oregon to assess spider mite pests and biological control by predaceous phytoseiid mites. A leaf at a coordinate of every 10 m of border, 5 m into a vineyard, was taken to minimize edge effects; 20 leaves were taken at regular intervals from vineyard centers. Variables recorded at each site included grape variety and plant age, chemicals used, and vegetation next to vineyards. Sites were rated as occurring in agricultural versus riparian settings based on surrounding vegetation types. Multiple linear regressions and a computer genetic algorithm with an information content criterion were used to assess variables that may explain mite abundances. Typhlodromus pyri Scheuten was the dominant phytoseiid mite species and Tetranychus urticae Koch the dominant tetranychid mite species. High levels of T. urticae occurred when phytoseiid levels were low, and low levels of T. urticae were present when phytoseiid levels were high to moderate. T. urticae densities were higher in vineyards surrounded by agriculture, but phytoseiid levels did not differ between agricultural and riparian sites. Phytoseiids had higher densities on vineyard edges; T. urticae densities were higher in centers. Biological control success of pest mites was rated excellent in 11 of 44 vineyards, good in 27, and poor in only six sites. Predaceous mites appeared to be the principal agents regulating spider mites at low levels in sites where pesticides nontoxic to predators were used. Effects of surrounding vegetation, grape variety, growing region, and other factors on mites are discussed.     

Effects of chlorpyrifos and sulfur on spider mites (Acari: Tetranychidae) and their natural enemies

In many agricultural systems spider mites are believed to be induced pests, only reaching damaging densities after pesticides decimate predator populations. Wine grapes typically receive two types of pesticides, insecticides and fungicides. Chemicals in either class could impact spider mite densities both directly through spider mite mortality, and indirectly by negatively affecting natural enemies. The impact of a broad-spectrum insecticide (chlorpyrifos) and an inorganic fungicide (sulfur) on mites and their natural enemies was monitored in replicate open-field experiments conducted in an abandoned vineyard in Washington State. In both experiments, chemicals were applied within a 2 × 2 factorial design, allowing assessment of both main and interactive effects of the two chemicals. Following typical management practices on wine grapes in Washington State, we made a single insecticide application early in the season, but repeatedly applied sulfur throughout the season. In the absence of sulfur, chlorpyrifos application led to higher spider mite densities. The main effect of chlorpyrifos appeared to be indirect, perhaps mediated through mortality of generalist phytoseiid mites; generalists appeared to be unable to recover following even a single insecticide application, while there was no evidence for harmful effects of chlorpyrifos on specialist phytoseiid mites. Sulfur had direct suppressive effects on both pest and predatory mites, although in the second experiment the suppressive effect of sulfur on spider mites was weaker when chlorpyrifos was also applied. These field experiments suggest that a complex mix of direct and indirect effects of the two chemicals impacted spider mite population dynamics in our system.     

Efficacy and persistence of rosemary oil as an acaricide against twospotted spider mite (Acari: Tetranychidae) on greenhouse tomato

Efficacy of rosemary, Rosmarinus officinalis L., essential oil was assessed against twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), as well as effects on the tomato, Lycopersicum esculatum Mill., host plant and biocontrol agents. Laboratory bioassay results indicated that pure rosemary oil and EcoTrol (a rosemary oil-based pesticide) caused complete mortality of spider mites at concentrations that are not phytotoxic to the host plant. The predatory mite Phytoseiulus persimilis Athias-Henriot is less susceptible to rosemary oil and EcoTrol than twospotted spider mite both in the laboratory and the greenhouse. Rosemary oil repels spider mites and can affect oviposition behavior. Moreover, rosemary oil and rosemary oil-based pesticides are nonpersistent in the environment, and their lethal and sublethal effects fade within 1 or 2 d. EcoTrol is safe to tomato foliage, flowers, and fruit even at double the recommended label rate. A greenhouse trial indicated that a single application of EcoTrol at its recommended label rate could reduce a twospotted spider mite population by 52%. At that rate, EcoTrol did not cause any mortality in P. persimilis nor did it affect their eggs. In general, EcoTrol was found to be a suitable option for small-scale integrated pest management programs for controlling twospotted spider mites on greenhouse tomato plants.     

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.     

Control of the straw itch mite (Acari: Pyemotidae) with sulfur in an insect rearing facility.

The ectoparasitic mite Pyemotes tritici (Lagrèze-Fossat & Montané) (Acari: Pyemotidae) caused paralysis and reduced longevity in eucalyptus longhorned borer, Phoracantha semipunctata F., under laboratory rearing conditions. Application of dusting sulfur to logs that contained pupating borers greatly reduced densities of mites on emerging adult beetles and increased beetle survivorship. Uniform application to all logs in a glasshouse effectively eradicated the mite infestation. A bioassay showed that sulfur may physically impede the dispersal of immature mites by adhering to the cuticle, but sulfur vapor did not act as a toxin.     

Changes in intraspecific aggregation and the coexistence of predaceous apple mites

The leaves of an apple tree are a patchy environment for leaf-inhabiting predaceous and phytophagous mites, consisting of discrete patches of leaf resources connected by relatively inhospitable petioles and branches. We investigated four species of predaceous mites ( Amblyseius andersoni , Galendromus occidentalis , Typhlodromus pyri (Acari: Phytoseiidae), and Zetzellia mali (Acari: Stigmaeidae)) inhabiting 'Red Delicious' apple trees ( Malus pumila ). These mites experience intra-guild predation (IGP), and we hypothesized that the vulnerable species would show increased aggregation when they are in plots with other predators. We also hypothesized that the increase in aggregation will be proportional to the vulnerability of the predator to IGP. We measured intraspecific aggregation with a binomial model that measures P(I), the amount of space a species occupies at a given average density, and compares this statistic among species at a common average density: samples that exhibit lower values of P(I) at a particular average density are considered to be more aggregated. We measured P(I) for the predaceous mites over four years, combining counts of all life stages. Data were segregated into groups with plots containing each predator alone, and each predator together with combinations of other predators. G. occidentalis and Z. mali showed significant increases in aggregation when other predators were present, with G. occidentalis showing the greatest change. T. pyri showed significant change only in the presence of Z. mali . A. andersoni , the largest mite studied here, showed no change in aggregation in the presence of other predators. We discuss possible causes of these changes in intraspecific aggregation and how they may promote long-term coexistence of predaceous mites.     

Acaricidal properties of a Chenopodium-based botanical

The emulsifiable concentrate UDA-245 [25% EC (vol:vol)], based on an essential oil extract from Chenopodium ambrosioides variety ambrosioides, a North American herbaceous plant, was compared with commercially available pesticides for their effectiveness to control the adult stage and egg hatch of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) and the European red mite, Panonychus ulmi (Koch) (Acari: Tetranychidae). After a laboratory bioassay with adult twospotted spider mites, a 0.5% concentration of UDA-245 was more effective than 0.7% (AI) of neem oil (Neem Rose Defense). After a similar bioassay with the European red mite, a 0.5% concentration UDA-245 was as effective as 0.006% (AI) of abamectin (Avid). UDA-245 at 0.5% significantly reduced egg hatch of the twospotted spider mite, 5 and 9 d after treatment and of the European red mite 6 d after treatment. Egg hatch was significantly lower using 0.006% (AI) of abamectin, 0.7% of neem oil, and 1.0% insecticidal soap than UDA-245. Residual tests indicated that UDA-245 may be persistent in the environment only for a few hours. Only 23% mortality was noted when mites were introduced on bean leaves 1 h after treatment with a 2% concentration of UDA-245. At the recommended dose of 0.5%, UDA-245 was not considered phytotoxic for most plants tested, i.e., lettuce, roses, and tomatoes. Results suggest that a greenhouse integrated pest management program using UDA-245 could effectively and selectively control mite infestations by treating "hot spots" with negligible effect on biological control agents when treating before introduction or when natural enemies are absent.     

Effects of the fungicides mancozed and dithianon on mortality and reproduction of the predatory miteAmblyseius andersoni

Laboratory studies using commercial formulations of mancozeb and dithianon at concentrations equivalent to recommended field rates of 200 and 80 g/hl, respectively, were conducted to evaluate toxic effects of these fungicides on the predatory miteAmblyseius andersoni Chant. In short-term tests where females were placed on apple-leaf disks and sprayed with mancozeb, no mortality of adults was observed; however, there was a 34% decrease in fecundity, a 7.1% decrease in egg hatch, and mortality of larvae and protonymphs was 6.7%. In long-term tests, a significant reduction in fecundity was also observed. A decrease in hatch that was dependent on age at time of treatment was found when eggs were treated directly with mancozeb. No effects on mite mortality or reproduction were observed in short-term tests with dithianon. These results suggest that dithianon might be considered as a potential alternative to mancozeb for scab control.     

Pest response in packed table grapes to low temperature storage combined with slow-release sulfur dioxide pads in basic and large-scale tests

The effect of low temperature storage combined with slow release sulfur dioxide pads was determined in basic laboratory and large-scale commercial tests on western flower thrips, Frankliniella occidentalis Pergande; grape mealybug, Pseudococcus maritimus (Ehrhorn); Pacific spider mite, Tetranychus pacificus McGregor; twospotted spider mite, Tetranychus urticae Koch; and omnivorous leafroller, Platynota stultana Walshingham. Temperatures within the foam containers among the packed clusters decreased from ambient to 2 degrees C within approximately 1 d and ranged from 0.4 to 1.7 degrees C in all tests. Sulfur dioxide concentrations in the foam containers ranged between 0.2 and 1.6 ppm during the 1- to 6-wk storage period in basic tests and 0.5-1.1 ppm during the 1- to 8-wk storage period in the large-scale test. Western flower thrips was completely controlled by a > or =1-wk exposure. Grape mealybug mortality was > or =93% after 2-5 wk exposures and 100% after a 6-wk exposure in basic tests. Pacific spider mite and twospotted spider mite mortality was 98.0 and 99.6%, respectively, after a 6-wk exposure. Mortality of grape mealybug and twospotted spider mite increased significantly at > or =3-wk exposures and Pacific spider mite mortality increased significantly at > or =4-wk exposures. Mortality of the spider mites in general was directly related to the duration of exposure. An 8-wk exposure to low temperature storage combined with slow release sulfur dioxide pads in the large-scale test resulted in 100% mortality of western flower thrips, twospotted spider mite, and omnivorous leafroller. The treatment resulted in <8% survival of grape mealybug and <1% survival of Pacific spider mite in the large-scale test. The combination treatment offers an economical method to attain quarantine control of certain insects and mites.     

Overwintering survival and postdiapause fecundity in a population of the Kanzawa spider mite <Emphasis Type="Italic">Tetranychus kanzawai</Emphasis> (Acari: Tetranychidae) on <Emphasis Type="Italic">Orixa japonica</Emphasis> (Rutaceae)

In several adult-diapausing insects and mites, long duration of diapause decreases egg production after diapause termination. However, such nonlethal effects are much less studied than overwintering survival. In this study, lethal and nonlethal effects of different periods of diapause were investigated in an adult-diapausing spider mite, Tetranychus kanzawai Kishida (Acari: Tetranychidae), through field experiments. Diapausing females produced in the laboratory were kept in their natural habitat from October or November to the next April, and survival rate and postdiapause fecundity were compared between the months. The survival rate was lower, but not significantly, in the October treatment. Postdiapause fecundity was also not significantly different between the months. These results suggest that the effects of diapause on survival and reproduction are quite small after October, when diapausing mites are increasing in their natural habitat.     

Life table characteristics of Macrolophus caliginosus preying upon Tetranychus urticae

The life table characteristics of the polyphagous mirid Macrolophus caliginosus Wagner (Heteroptera: Miridae) preying on various stages of Tetranychus urticae Koch (Acari: Tetranychidae) with tomato as host plant were described at 22 °C. The following average parameters were obtained: Female longevity: 28.7 days; fecundity: 0.7 eggs/female/day; egg mortality: 2.6%; pre-oviposition period: 5.5 days; oviposition period: 18.1 days; post-oviposition period: 3.2 days; juvenile development time: 26.8 days; juvenile mortality: 34.9%; and sex ratio (/(+): 0.46. Life table parameters were estimated as net reproduction rate (R ₀): 6.15; intrinsic rate of increase (r _m): 0.031 day^–1; finite rate of increase (): 1.032; mean generation time (T _c): 58.17 days; and doubling time (T ₂) 22.2 days. The parameters obtained were in accordance with those reported for M. caliginosus fed on another mite species (T. turkestani Ugarov & Nikolski (Acari: Tetranychidae)). However, compared to the performance of M. caliginosus fed on common glasshouse insect pests, a diet consisting of only mites appeared to be inferior. However, being a voracious predator, M. caliginosus may be a valuable addition to existing methods of mite control.