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The twospotted spider mite, Tetranychus urticae Koch, is a serious pest of many nursery crops. Regular acaricide applications are required to maintain acceptable population levels of this pest. Phytoseiulus persimilis Athias-Henriot is a commercially available predator used to control T. urticae populations. The effects of acaricide residues were tested on P. persimilis and T. urticae using a leaf disk system. Both species were exposed to residues for 24 hours 1, 3, 7, and 14 days after acaricide application. Abamectin, Gowan 1725, hexythiazox, horticultural oil, neem oil, pyridaben, and spionosyn residues caused no mortality to P. persimilis 1, 3, 7, or 14 days after application. Chlorfenapyr was harmful to both species at all times after application. Bifenthrin residue was toxic to P. persimilis at all times after application, but was only harmful to T. urticae up to one week after application. Tetranychus urticae mortality from Gowan 1725, horticultural oil, and neem oil residues was significantly greater than the control 24 hours after application, but not thereafter. Tetranychus urticae mortality from hexythiazox and spinosad residues was not significantly greater than the control. Proper pesticide selection may create favorable conditions for release of P. persimilis and reduce acaricide dependency.

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In this study, we report on the compatibility of two commercially available predatory mites, Neoseiulus californicus and Phytoseiulus persimilis, with three miticides used in greenhouse production systems to control the twospotted spider mite, Tetranychus urticae. We determined the lethal effects of the miticides chlorfenapyr, spiromesifen, and bifenazate to both predatory mite species 24 hours after exposure to spray applications in petri dishes. Two rates of chlorfenapyr (0.40 and 0.81 mL/2-L) and spiromesifen (0.15 and 0.31 mL·L–1), and one rate of bifenazate (0.62 mL·L–1) were used. All rates were based on the manufacturer label recommendations for twospotted spider mite. Both rates of chlorfenapyr and spiromesifen, and the single rate of bifenazate were not harmful to N. californicus with percent live mite values ≥85% for chlorfenapyr and ≥95% for spiromesifen, and 93% for bifenazate. However, these same miticides were substantially toxic to P. persimilis with percent live mite values of ≤63% for all the miticides tested. Based on the results of this study, the miticides chlorfenapyr, spiromesifen, and bifenazate are compatible with N. californicus whereas these miticides are toxic to P. persimilis indicating a difference in susceptibility based on predatory mite species.

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Biological control agents were ordered from three U.S. suppliers three times during 1994 and were evaluated (total of nine orders evaluated). Biological control agents evaluated were a whitefly parasitoid [Encarsia formosa Gahan (Hymenoptera: Aphelinidae)], mealybug destroyer [Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae)], insidious flower bug [Orius insidiosus (Say) (Heteroptera: Anthocoridae)], and a predatory mite [Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae)]. Arrival time, packaging methods, cost, quality, and quantity for each shipment were recorded. Six of the nine orders evaluated did not arrive by the date promised by the supplier. Most biological control agents were shipped in styrofoam boxes; the method by which they were packed in the box differed among suppliers. The cost of each biological control agent order ranged from $260.64 to $327.03 and varied with the same supplier. The number of viable E. formosa emerging ranged from 745 to 4901; two of the nine orders met the quota of 2000 live wasps. The total number of live C. montrouzieri received ranged from 234 to 288; five orders contained the expected number of 250 live beetles. For the expected order of 1000 O. insidiosus, quantities of live insects ranged from 423 to 1333; three orders contained at least the expected amount. The number of live P. persimilis ranged from 199 to 4447. Three orders contained the targeted amount of 2000. Our findings indicate that there are problems with the quantity of viable biological control agents being shipped. To build consumer confidence in the potential effectiveness of biological control, suppliers and producers of biological control agents must address ways to ensure that the consumer receives a high-quality product, in quantity and viability.

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In three experiments, damage caused by twospotted spider mite (TSSM; Tetranychus urticae Koch) was correlated with the quality of ivy geranium [Pelargonium peltatum (L.) L'Her ex Aiton], and the action threshold for TSSM on ivy geranium was developed. Ivy geranium quality was measured as overall plant quality—plant size and form, and leaf greenness and glossiness—leaf browning, and leaf distortion. Young plants with high initial TSSM numbers (30 TSSM/plant) exhibited the greatest damage, suggesting that monitoring for TSSM early in the plant production cycle is necessary to prevent extensive damage. The leaf distortion index and overall plant quality were correlated with cumulative TSSM density and marketability in 4-week-old plants infested with 30 TSSM, whereas leaf browning was not correlated with either. Thus, either leaf distortion or overall plant quality can be used to measure economic damage resulting from TSSM. The action threshold for TSSM on ivy geranium was determined using overall plant quality. When the predatory mite, Phytoseiulus persimilis Athias-Henriot, is used to control TSSM, the action threshold was found to be 2 TSSM/leaf. Results also showed that fertilizer combinations of 8 or 24 mm nitrogen and 0.32, 0.64, or 1.28 mm phosphorus had no effect on cumulative TSSM density. When P. persimilis was released at predator: prey ratios of 1:60, 1:20, and 1:4, TSSM damage, measured as both leaf distortion and overall plant quality, was significantly reduced at 1:4 and 1:20, but not at 1:60. A 1:4 rate resulted in the most marketable plants. These results suggest that P. persimilis should be released at a rate of 1:4 when the TSSM action threshold is reached.

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managing TSM. The most frequently used biological agent for TSM is the predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae) ( Gillespie and Raworth, 2004 ). A primary advantage of using predatory mites is that the predators are mass-produced in

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In recent years, the tomato russet mite (TRM) [Aculops lycopersici (Acarina: Eriophyidae)] has become one of the more important pests of greenhouse tomatoes in northeastern North America. As a first step toward developing a biological control strategy for the TRM, our objective has been to test the potential of already commercialized mite predators. In laboratory experiments, voracity of Chrysopa carnea (Neuroptera: Chrysopidae), Phytoseiulus persimilis (Acarina: Phytoseiidae), and Amblyseius cucumeris (Acarina: Phytoseiidae) was determined for egg, immature, and adult stages of the TRM. The first two predator species did not prey on TRM, whereas A. cucumeris fed on each of the life stages of the eriophyid mite. Further experiments showed that A. cucumeris was able to develop and reproduce when feeding on TRM. Implication of these results for controlling TRM in greenhouses is discussed with respect to predator specificity and prey suitability.

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The effects of overhead and drip tube irrigation on twospotted spider mite (TSMs) (Tetranychus urticae Koch) and predatory mite (PMs) (Phytoseiulus persimilis Athias-Henriot) populations, as well as the biological control of TSMs by PMs, were investigated on Impatiens wallerana Hook. f. `Impulse Orange'. To determine the effects of the two irrigation methods on TSM populations, plants were inoculated with female TSMs 6 weeks after seeding. Plants were then irrigated twice every three days, and TSM counts were taken 3 weeks later. To assess the effects of irrigation method on PMs, plants were inoculated with TSMs 6 weeks after seeding, PMs were released 10 days later, plants were irrigated about once per day, and the number of predatory mites on plants was counted 3 weeks after release. To assess the effects of irrigation method on the biological control of TSMs by PMs, plants were inoculated with TSMs and PMs were released as before, but then plants were irrigated either three times every 2 days or three times every 4 days using either drip or overhead irrigation. The number of TSMs on plants and the number of leaves showing TSM feeding injury were measured 3 weeks after predator release. Overhead watering significantly reduced TSM and PM populations as much as 68- and 1538-fold, respectively, compared to drip irrigation with microtubes. Perhaps more important, overhead watering with or without predators significantly reduced the number of leaves sustaining TSM feeding injury as much as 4-fold compared to drip irrigation. These results confirm the common observation that TSM infestations and injury may be reduced by irrigation systems that wet plant foliage. However, predators still reduced TSMs even though overhead irrigation had a suppressive effect on predatory mites. Predators are particularly useful for reducing TSM injury when plants are watered infrequently. Overhead watering could be used in tandem with biological control as a component of an integrated crop management program for TSMs in ornamental greenhouses by rapidly lowering TSM population levels in hot spots before PMs are released.

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, like the predatory mite Phytoseiulus persimilis , are thought to be less effective and more costly to use than chemical controls. Holt et al. (p. 322) showed that using a sampling plan to determine the appropriate number of the predatory mites to

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. 2016 Plant spatial distribution and predator-prey ratio affect biological control of the twospotted spider mite Tetranychus urticae (Acari: Tetranychidae) by the predatory mite Phytoseiulus persimilis (Acari: Phytoseiidae) Biocontrol Sci. Technol

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conducted to date in nursery production has been performed by biological control companies consulting with private nursery owners to address specific pests. A large-scale evaluation of persimilis mite ( Phytoseiulus persimilis ) for control of two

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