The twospotted spider mite, Tetranychus urticae Koch, is a worldwide pest of numerous agronomic and horticultural plants. Sulfur fungicides are known to induce outbreaks of this pest on several crops, although mechanisms associated with sulfur-induced mite outbreaks are largely unknown. Studies were conducted during 2007-2009 in Oregon and Washington hop yards to evaluate the effect of timing of sulfur applications on T. urticae and key predators. In both regions, applications of sulfur made relatively late in the growing season (mid-June to mid-July) were associated with the greatest exacerbation of spider mite outbreaks, particularly in the upper canopy of the crop. The severity of mite outbreaks was closely associated with sulfur applications made during a relatively narrow time period coincident with the early exponential phase of spider mite increase and rapid host growth. A nonlinear model relating mean cumulative mite days during the time of sulfur sprays to the percent increase in total cumulative mite days (standardized to a nontreated plot) explained 58% of the variability observed in increased spider mite severity related to sulfur spray timing. Spatial patterns of spider mites in the Oregon plots indicated similar dispersal of motile stages of spider mites among leaves treated with sulfur versus nontreated leaves; however, in two of three years, eggs were less aggregated on leaves of sulfur-treated plants, pointing to enhanced dispersal. Apart from one experiment in Washington, relatively few predatory mites were observed during the course of these studies, and sulfur-induced mite outbreaks generally occurred irrespective of predatory mite abundance. Collectively, these studies indicate sulfur induces mite outbreaks through direct or indirect effects on T. urticae, mostly independent of predatory mite abundance or toxicity to these predators. Avoidance of exacerbation of spider mite outbreaks by sulfur sprays was achieved by carefully timing applications to periods of low spider mite abundance and slower host development, which is generally early to mid-spring for hop.

The potential of using synthetic herbivore-induced plant volatiles (HIPV) (e.g., methyl salicylate, MeSA) as a cultural tool to enhance conservation biological control of mites is being researched in commercially grown hops in Washington State, USA. Compared to unbaited blocks, hop yards baited with controlled release sachet (CRS) dispensers of synthetic MeSA recruited larger (3-5x) populations of spider mite predators: Stethorus spp. (Coleoptera: Coccinellidae), Orius tristicolor (Hemiptera: Anthocoridae), Geocoris pollens (Hemiptera: Geocoridae), Deraeocoris brevis (Hemiptera: Miridae), Chrysopidae, Hemerobiidae, Nabidae, Thripidae. The enhanced community of mite predators controlled spider mite populations in MeSA-baited hops without miticide intervention. All unbaited blocks required at least one miticide for spider mite control. Direct application of natural MeSA (oil of wintergreen) to hop plants contained in canola oil or rosemary/peppermint oil pesticide formulations, resulted in greater attraction of two mite predators (O. tristicolor and Stethorus spp.) to treated than to untreated plants. MeSA-mediated stimulation of the plants to produce predator-attracting volatiles is suggested as the likely mechanism. The use of synthetic or natural versions of HIPV/plant-signaling compounds like MeSA as 'Herbivore-Induced Plant Protection Odors' (HIPPOs), has the potential to provide a novel yet practical strategy for improving the efficacy and reliability of conservation biological control of mites in a variety of agricultural ecosystems.

Hop looper moths, Hypena humuli Harris, in commercial hop yards (Humulus lupulus L.) were captured in traps baited with a combination of acetic acid plus 3-methyl-1-butanol (AAMB). The two chemicals were synergistic in attracting hop looper moths. In a comparison of the lure chemicals, most moths were trapped with AAMB as the lure, while very few moths were captured in traps baited with acetic acid alone or 3-methyl-1-butanol alone. Female and male hop looper moths were trapped with AAMB, with an overall sex ratio through the year of 44% females to 56% males. Moths were trapped in all months of the growing season, from April into October. From April through September, most females captured in traps were mated, whereas in October most females trapped had been unmated. Most of the mated females, we trapped contained one spermatophore, indicating a single mating. The numbers of moths trapped were low from April through June, and increased greatly in July, and at one site again in late August. AAMB-baited traps may be a useful tool for monitoring hop looper moths in commercial hop yards, to determine their presence, and potentially to assess the risk of damaging infestations.

Twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), and hop aphid, Phorodon humuli (Schrank) (Hemiptera: Aphididae), are the most important arthropod pests of hop (Humulus lupulus L.) in the Northern Hemisphere. A potential barrier for greater adoption of conservation biological control strategies for spider mites and hop aphid is the extensive use of fungicides for management of hop powdery mildew, Podosphaera macularis (Wallr.:Fr.) U. Braun & S. Takamatsu. Field studies conducted in experimental plots in Oregon and Washington in 2005 and 2006 quantified the effects of powdery mildew fungicide programs (i.e., sulfur, paraffinic oil, and synthetic fungicides) on arthropod pests and natural enemies on hop. Fungicide treatment significantly affected spider mite populations in all four studies. Multiple applications of sulfur fungicides applied before burr development resulted in 1.4-3.3-fold greater spider mite populations during summer. Near the cessation of the sulfur applications, or after a lag of 20-30 d, spider mite populations increased significantly faster on sulfur treated plants compared with water-treated plants in three of four experiments. The effect of paraffinic oil on spider mites was varied, leading to exacerbation of spider mites in Oregon and Washington in 2005, suppression of mites in Oregon in 2006, and no significant effect compared with water in Washington in 2006. Significant relative treatment effects for cone damage due to spider mite feeding were detected in Oregon in 2005 in plots treated with sulfur and paraffinic oil compared with water and synthetic fungicides. Mean populations of hop aphids were similar among treatments in Oregon, although sulfur treatment suppressed hop aphid populations in Washington in 2005 and 2006. Populations of individual predacious insect species and cumulative abundance of macropredators were not consistently suppressed or stimulated by treatments in all trials. However, predatory mite abundance in Washington was affected by fungicide treatments, with plots treated with sulfur consistently having 10-fold fewer phytoseiids per leaf compared with the other treatments. Based on the results of these studies, powdery mildew fungicide programs that minimize or eliminate applications of sulfur and paraffinic oil would tend to conserve predatory mites and minimize the severity of spider mite outbreaks. However, mechanisms other than direct or indirect toxicity to phytoseiid mites likely are associated with exacerbation of spider mite outbreaks on hop.

In 2001 and 2002, we monitored densities of western grape leafhopper, Erythroneura elegantula Osborn, and Virginia creeper leafhopper, Erythroneura ziczac Walsh (Homoptera: Cicadellidae), eggs front June through September in managed and nonmanaged vineyards in Washington state. Anagrus parasitoids (Hymenoptera: Mymaridae) were reared from sampled parasitized leafhopper eggs. Densities of nonparasitized and parasitized E. elegantula eggs, and nonparasitized E. ziczac eggs, were significantly higher in nonmanaged grapevines, although this pattern was not consistent for the latter two groups. Densities of parasitized E. ziczac eggs were consistently low across management regimes. Anagrus erythroneurae S. Trjapitzin & Chiappini, Anagrus daanei S. Triapitsyn, and Anagrus tretiakovae S. Triapitsyn emerged from parasitized E. elegantula eggs, whereas latter two mymarid species also parasitized E. ziczac eggs. Of these species, A. tretiakovae was the most common parasitoid of Erythroneura leafhopper eggs within sampled vineyards. From 2001-2003, we used yellow sticky traps to collect Anagrus wasps and potential leafhopper hosts from blackberry, grape, and wild rose sites, because these habitats might serve as refugia for the wasps. All three Anagrus species collected within vineyards and a fourth species, A. atomus L., were found on traps in these plant habitats. Several leafhopper taxa that could serve as potential alternative hosts for Anagrus spp. also were collected. Our collection of A. daanei, A. tretiakovae, and A. atomus in Washington represents range extensions for these species, revealing several novel candidate species for conservation. Because we consistently found Anagrus species of agricultural importance within rose and blackberry patches, cultivation of these plants close to vineyards may enhance colonization by Anagrus and thus improve grape leafhopper biocontrol.

Specialist-feeding phytoseiid mites have a well-documented role in biological control of phytophagous spider mites. However, although there is evidence for the importance of generalist-feeding phytoseiid mites in spider mite suppression, their role is less clear than that of specialists. The effectiveness of generalists as biocontrol agents and their interactions with specialists might be directly influenced by canopy structure or indirectly affected by altering plant microclimate. We manipulated densities of generalist phytoseiid mites and canopy size (large and small) in open-field experiments in an abandoned vineyard. In the first experiment, we increased generalist densities by transferring grapevine foliage housing robust generalist populations, whereas in the second experiment, we lowered generalist densities using the broad-spectrum insecticide chlorpyrifos. In both experiments, we also altered canopy size by tying grapevine shoots. Increasing densities of generalists resulted in lower spider mite densities. Generalists initially decreased densities of specialist phytoseiid mites as well, although specialist densities rebounded as spider mite densities increased later in the experiment. Lowering generalist densities appeared to slightly increase densities of both spider and specialist mites, consistent with the first experiment. However, these effects were not statistically significant, possibly because the reduction in generalist densities through chlorpyrifos application was not as dramatic as our generalist augmentation in the first experiment. Canopy size did not significantly affect pest or predatory mite densities in either experiment. These field experiments demonstrate that generalists can slow spider mite population growth in grapes. In contrast, canopy architecture appeared to have little impact on spider mite biocontrol.

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.

The influence of variable photoperiods on the feeding activity and fecundity of Galendromus occidentalis (Nesbitt) was studied on a diet of Tetranychus urticae Koch eggs. Starved G. occidentalis females were fed T. urticae eggs under ten 24-h light:dark regimes. Half of the tests started during photophase and the other half during scotophase. T. urticae eggs that were consumed and G. occidentalis eggs that were laid were counted at the end of each photophase and scotophase in a 24 h period. In general, G. occidentalis consumed more T. urticae eggs per h in the first phase of the experiment than in the second, regardless of whether the lights were on or off. In contrast to egg consumption, there were no statistical differences in the mean daily fecundity at the end of the 24-h periods. However, when the experiment was started during photophase, higher fecundity/h was encountered during scotophase than during the photophase. As a result, egg consumption rates were affected by photoperiods in both phases of the experiments. Logistic regression analysis revealed that variable photoperiods and egg consumption did not influence the fecundity of G. occidentalis.

The distribution of entomopathogenic nematodes applied by drip irrigation was evaluated by injecting small volumes of Steinernema carpocapsae (Weiser) All strain, Steinernema feltiae (Filipjev) SN strain, Steinernema glaseri Steiner, and Heterorhabditis bacteriophora HP 88 strain Poinar suspensions into drip irrigation lines. Additionally, Steinernema riobrave Cabanillas, Poinar, & Raulston, and S. carpocapsae were injected in a 10-liter volume of water with an injection pump. Overall, the nematodes were evenly distributed along the drip lines. The total number of nematodes recovered from drip emitters was variable ranging from 42 to 92%. However, drip irrigation lines have potential to deliver entomopathogenic nematodes efficiently into pest habitats.

The abundance and phenology of mites, leafhoppers, and thrips were monitored monthly (May-October) during 1999-2000 in three pairs of pesticide-treated/untreated wine grape vineyards in southcentral Washington. Spider mite populations (primarily Tetranychus urticae Koch) were generally small (0-10 mites/leaf) and showed little monthly variation. They were significantly larger in pesticide-treated (season mean: 19.2% of leaves occupied) than in untreated (1.3%) vineyards in 2000. The greatest mite density (65% of leaves occupied/14 mites per leaf) was seen after 13 applications of sulfur in an additional vineyard monitored in 2000. Six species of phytoseiid mites were recorded (Galendromus occidentalis Nesbitt, Amblyseius andersoni [Chant], Typhlodromus caudiglans [Schuster], Typhlodromus pyri Scheuten, Metaseiulus citri [Garman and McGregor], and Metaseiulus flumensis [Chant]). G. occidentalis and M. citri accounted for 80-83% of specimens identified. Phytoseiid populations were larger in untreated (season means: 7.1-9.1% of leaves occupied) than in treated (1.8-4.6%) vineyards and tended to increase in mid to late summer (up to two mites per leaf). Fungivorus tydeid mites were occasionally common in pesticide-treated and untreated vineyards in autumn (up to 73% of leaves occupied). Nymphs of the leafhoppers, Erythroneura elegantula Osborn and Erythroneura ziczac Walsh were more abundant in untreated (season means: 19.4-52.2% of leaves occupied) than treated (3.3-13.1%) vineyards with densities of up to 21 per leaf. Populations peaked in August in 1999 and July in 2000. Thrips nymphs (primarily Frankliniella occidentalis [Pergande]) were equally common in pesticide-treated and untreated vineyards (season means: 12.9-18.2% of leaves occupied) but tended to be more abundant early season in pesticide-treated vineyards. Implications of these results for improved arthropod pest management in Washington grapes are discussed.

Collections of volatiles, ovipositor extracts, and electoantennography showed the sex pheromone of female currant borer moths, Synanthedon tipuliformis (Clerck), from Washington to be a 2-component (100:3) blend of (E,Z) -2, 13-octadecadienyl acetate and (E,Z) -3, 13-octadecadienyl acetate. Pheromone-baited sticky traps (rubber septa dispensers) captured male S. tipuliformis at one abandoned and two commercial red currant sites (one treated with insecticide, one untreated) in south central Washington from 19 May to 16 August 2000. Peak catches occurred during late May and June with up to 200-300 moths/trap/wk. Lowest numbers (overall mean: 4.8 +/- 0.9 moths/trap/visit) were recorded at the insecticide-treated site and largest numbers (39.6 +/- 5.5 moths/trap/visit) occurred at the untreated, commercial site.

Binomial sequential sampling plans, based on Wald's sequential probability ratio test, were developed for adult female twospotted spider mites, Tetranychus urticae Koch, on main stem hop leaves at the 2 m elevation for early season sampling and at the 2 + 4 m heights combined for mid- to late season sampling. The 2 + Im sampling plan was tested by sampling data sets, which were generated by the Monte Carlo method. Increasing the tally threshold improved the operating characteristic curves and sampling plan robustness and caused the average sample number and percent of maximum sample termination curves to be more peaked around the critical density. Increasing the tally threshold generally reduced the magnitude of sequential sampling errors. Sequential decision errors made at means above the critical density were more serious than errors made below it. When the maximum of 100 samples was taken, the data set mean was generally above the critical density. Therefore, when 100 samples have been taken and no decision has been reached, the sampler should be aware that the field mean is near, and likely greater than, the critical density. The sampling plans were based on a nominal threshold of 5 adult female spider mites per leaf. The plans could be modified using data in this article to develop sampling plans based on an economic threshold when one is determined.

Wine grape vineyards in south central Washington were sampled to collect data to develop sampling programs for leafhoppers. Most of the vineyards had a mixture of two species: the western grape leafhopper, Erythroneura elegantula. Osborn, and the Virginia creeper leafhopper, E. ziczac Walsh. Both species had aggregated spatial distributions with E. ziczac the more aggregated of the two. Two sequential sampling programs based on Wald's sequential probability ratio test were developed for the two leafhopper generations for both, species combined. The sampling programs were validated by simulation using the Monte Carlo method. The maximum number of samples, which was limited to 50 or 100 samples, had little effect on the operating characteristic curves. Reducing the maximum number of samples reduced the average number of samples but increased the percentage of terminal decisions. Terminal decisions, made after taking the maximum number of samples had unacceptable error levels, especially at means above the critical density. However, a terminal decision indicated that leafhopper numbers were near the critical density and sampling should be repeated in a few days. Alternatively, sampling history or other information could be used to help make an informed pest control decision.

The 2 most important leafhopper pests of grapes in Washington are the Western grape leafhopper, Erythroneura elegantula Osborn, and Erythroneura ziczac Walsh. The influence of different constant temperatures on the egg and nymphal stages of E. ziczac and on the nymphal stage of E. elegantula was examined. Development times of E. ziczac eggs ranged from 33.1 d at 15 degrees C to 8.6 d at 32.5 degrees C. E. ziczac nymphal development ranged from 40.2 d at 16 degrees C to 11.1 d at 29.5 degrees C. The average number of degree-days required for development from oviposition to imaginal molt was 435.4. This was slightly higher than the previously published value of 390.5 DD for field reared E. ziczac. E. elegantula nymphal development ranged from 38.0 d at 16.0 degrees C to 11.8 d at 32.5 degrees C. The average number of degree-days required for E. elegantula development from eclosion to imaginal molt was 246.3. Constant temperature data for the egg and nymphal stages of E. ziczac and for the nymphal stage of E. elegantula was fitted to a developmental model based on enzyme reaction kinetics. The egg and nymphal stages of E. ziczac fitted the model with r(2) values of 0.9992 and 0.9990, respectively. The E. elegantula nymphal stage fitted the model with all r(2) value of 0.9996. Lethal freezing temperatures for E. ziczac adults collected on 28 January, 4 February, and 14 November, 1994 were -27.1, -26.3, and -27.2 degrees C, respectively. Freezing temperatures for E. elegantula on the same dates were -24.6, -24.1, and -25.3 degrees C, respectively.

The hop aphid, Phorodon humuli (Schrank), is a serious pest of hop, Humulus lupulus L., during the summer and overwinters on plums, Prunus spp. To determine the seasonal timing of the spring and fall hop aphid flights, hop aphids were monitored on Prunus leaves and by suction trap. The start of spring flight, indicated by the first date that fourth instar hop aphids with wing pads (alatoid IV instars) were found on Prunus, ranged from 7 May to 16 May, 1989 to 1991. The last date that alatoid TV instars were found on Prunus, marking the end of spring migration, ranged from 16 July to 7 August, 1989 to 1991. Hop aphids were found on Prunus throughout the summer in 1989, indicating that the aphids can live on Prunus throughout the year. In suction trap catches from 1984 to 1993, the average date when the first hop aphids of the autumn flight were trapped was 3 September for gynoparae (winged females) and 3 October for males. Fall flight started when daylength was about 13.5 h, but accumulated degree-days were also related to the start of flight. In the fall, the suction trap caught more gynoparae than males and more gynoparae than males were collected from hop leaves, indicating that males mate with more than one female. A suction trap in a hop growing area caught more aphids during the fall flight than in the spring flight, but a suction trap in a non-hop growing area caught more hop aphids during the spring flight.

Life tables were constructed for the asparagus aphid, Brachycorynella asparagi, caged on different ages of asparagus foliage. In trial one of the experiment, foliage age ranged from 16 to 72 d. As foliage aged, the intrinsic rate of aphid increase declined, generation time increased, projected population size decreased, prereproductive and reproductive periods lengthened, and maximum number of offspring per day declined. In trial two, foliage age ranged from 15 to 138 d. Only 3 of 10 aphids survived to reproduce on 97-d-old foliage, and none reproduced on 138-d-oldfoliage. In trial two, prereproductive period was lengthened and day of maximum reproduction was delayed by increased foliage age. The net reproductive rate was not significantly affected in either trial. It appears that the quality of asparagus as food for the asparagus aphid declined as foliage aged.

Taylor’s power law was used to develop a fixed-number sampling plan for Brachycorynella asparagi (Mordvilko) on mature asparagus, Asparagus officinalis L., foliage. For control decisions, we recommend taking 141 primary branch samples and extracting the aphids from the foliage with Berlese-Tullgren funnels. The time required to do the sampling was determined. A new method of extracting aphids in paper bags was unsatisfactory, mainly because identifying and counting aphids mixed with plant debris and dirt were difficult. Aphids had an aggregated distribution and number of aphids within fields tended to increase from west to east.