Enhancing the integration of mite biological control in western United States vineyard managment programs

Final Report for GW09-008

Project Type: Graduate Student
Funds awarded in 2009: $25,000.00
Projected End Date: 12/31/2011
Region: Western
State: Oregon
Graduate Student:
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Project Information

Summary:

Vineyards throughout Oregon have recently developed Short Shoot Syndrome, which is correlated to the pest mite Calepitrimerus vitis. This vineyard-specific pest feeds on developing buds, resulting in stunted shoots and crop (cluster) loss. Typhlodromus pyri is the dominant predatory mite in western Oregon vineyards and is believed to play an integral role in managing C. vitis populations.Intense fungicide programs are maintained in vineyards throughout the growing season and are believed to be detrimental to predatory mite populations, causing increased pest mite outbreaks. Predatory mite preservation and enhancement are integral to successful biological control programs in western vineyards.

Introduction

Phytoseiid mites play an important role in providing effective control of phytophagous mites in annual and perennial cropping systems (Helle and Sabelis 1985). Beneficial phytoseiids are economically important biological control agents in vineyards, apple orchards and hopyards in the Pacific Northwest (Croft and MacRae 1992, James et al. 2002, Prischmann et al. 2002).

In the last decade, vineyards in Oregon and Washington have experienced increased symptoms of mite-related Short Shoot Syndrome (SSS) associated with the eriophyid grapevine rust mite, Calepitrimerus vitis (Perez-Moreno and Moraza 1997, Bernard et al. 2005, Walton et al. 2007). The grapevine rust mite is a host-specific pest of Vitis vinifera and occurs in many grape-growing regions throughout the world (Duso and de Lillo 1996). Economic damage occurs from C. vitis feeding on susceptible young tissues and developing buds during the early part of the season and results in stunted shoots, shortened inter-nodal growth and yield loss (Walton et al. 2010).

Typhlodromus pyri has been documented as the predominant predatory mite species in western Oregon vineyards (Prischmann et al. 2002) and is a valuable predator in several agricultural systems due to its abundance, wide geographic distribution and polyphagous feeding habits (Helle and Sabelis 1985, Hadam et al. 1986, McMurtry and Croft 1997). Suitable prey for T. pyri includes Tetranychus urticae, Panonychus ulmi, Aculus schlechtendali and C. vitis. It is believed that T. pyri plays an integral role in managing C. vitis populations in western Oregon vineyards.

The predatory mite T. pyri is highly sensitive to several pesticides, including sulfur (Candolfi et al. 1999). Sensitivity to certain pesticides, coupled with the rigorous fungicide programs, have led to concerns regarding side effects on T. pyri from compounds often employed in Pacific Northwest vineyards. Many grape growers in these regions are heavily reliant on sulfur, synthetics and horticultural oils for control of powdery mildew during the growing season.

Several field studies conducted in western U.S. vineyards have reported decreases in T. pyri and other predatory mite densities due to repeated pesticide applications (Calvert and Huffaker 1974, Hanna et al. 1997, James et al. 2002, Prischmann et al. 2005). However, it has also been reported in laboratory studies that some pesticides, including sulfur, are not toxic to T. pyri (Easterbrook 1984, Hassan et al. 1987). Based on these data, it is important to conduct laboratory bioassays and field trials to assess the impacts of commonly employed pesticides on T. pyri found in Oregon vineyards.

The life cycle of T. pyri includes four immature stages (egg, six-legged larvae, eight-legged protonymph and deutonymph) prior to reaching adulthood (Helle and Sabelis 1985). At approximately 10º C, T. pyri begins actively searching for available prey or other food resource (Mathys 1958). MacRae and Croft (1993) also suggests that T. pyri is more active compared to the phytoseiid Metaseiulus occidentalis at low temperatures (~ 15º C) representative of average spring temperatures in the Pacific Northwest. It is important to evaluate the biological parameters for T. pyri and C. vitis, such as lower and upper developmental temperature thresholds, intrinsic rate of population increase and net reproductive rate to determine suitability for biological control.

Life history parameters were recently determined for the C. vitis strain present in Oregon vineyards, enhancing our basic biological knowledge of this pest (Walton et al. 2010). Researchers in New Zealand, Europe and Canada have published developmental and reproductive data for T. pyri in relation to pest mites P. ulmi, Tetranychus urticae, Eotetranychus carpini, Colomerus vitis and Aculus schlechtendali. In these studies, developmental or population parameters were, however, either calculated for a single temperature (Herbert 1961, Overmeer 1981, Duso and Camporese 1991, Genini et al. 1991) or not estimated from developmental and reproductive data (Hayes and McArdle 1987, Hayes 1988, Hardman and Rogers 1991).

Intrinsic rate of population increase, oviposition rate and reproductive success have been examined for a German strain of T. pyri feeding on C. vitis at a constant temperature of 25ºC (Engel and Ohnesorge 1994). No data has been reported regarding the effect of temperature on these developmental parameters for T. pyri found in Oregon.

The conservation of biological control agents is a key component in developing effective management programs. Part of conservation biological control (CBC) is the ability to enhance the activity and abundance of beneficial arthropod populations through cultural practices (Khan et al. 2008). These techniques include the employment of insectary plants to provide alternative food resources, push-pull strategies and most recently the modification of insect behavior through the exploitation of semio-chemicals. In nature, many tri-trophic interactions are regulated through chemical signals that benefit either the producer (allomone), the receiver (kairomone) or both producer and receiver (synomone) of the perceived cue (Dicke and Sabelis 1988, Price 1997).

It is well established that volatile kairomones play an integral role in the relationship between phytophagous and predatory mites (Sabelis and Van de Baan 1983, Dicke 1986, 1988, Takabayashi and Dicke 1992). These chemical signals influence predatory mite foraging behaviors such as dispersal, attraction, searching and prey location. It is now understood that the infested host plant plays a key role in the release and composition of volatile kairomones (Dicke et al. 1990b). Herbivore induced plant volatiles (HIPV’s) are believed to function as indirect plant defense mechanisms capable of attracting natural enemies and increasing biological control of pest populations. HIPV’s usually contain several compounds in complex blends which vary in quality and composition based on a number of biotic and abiotic factors (Takabayashi et al. 1994). Methyl salicylate (MeSA), a phenolic compound, has been identified as one of the volatiles released from T. urticae infested lima beans (Dicke et al. 1990a, Ozawa et al. 2000). MeSA has since been identified in the volatile blend for more than 13 different crop species, including grapes, when infested with T. urticae (James 2003, Van Den Boom et al. 2004). It has also been detected in varying quantity and quality in other HIPV blends, such as cabbage fed on by caterpillars, Pieris spp (Geervliet et al. 1997), pear infested with Psyllidae (Scutareanu et al., 1997), and hops fed on by hop aphid, Phorodon humuli Schrank (Campbell et al. 1993).

Laboratory studies, conducted with an olfactometer, have reported significant attraction of the predatory mite Phytoseiulus persimilis and the generalist predator insect Anthocoris nemoralis (Fabricius) toward isolated MeSA (Dicke et al. 1999, Drukker et al. 2000, De Boer and Dicke 2004). Recently, research has begun to focus on the utilization of MeSA in field environments to attract and retain natural enemies to enhance CBC in different cropping systems. One vineyard experiment, which used sachets releasing up to 60mg/day MeSA, reported a significant increase in numbers of five beneficial species (Stethorus punctum, Chrysopa nigricornis, Orius tristicolor, Hemerobius spp and Deraeocoris brevis) along with an overall increase of natural enemy seasonal abundance (James and Price 2004).

Increased abundance and significant attraction of beneficial arthropods were also found in strawberry plots using commercially available MeSA lures (Lee 2010). Although predatory mites were not among the arthropods sampled in these studies, it is believed that MeSA lures could enhance populations of T. pyri and other principle predators of pest mites in Oregon vineyards.

Project Objectives:

1. Conduct field and laboratory bioassays to determine the effects (direct mortality, fecundity, oviposition rate and longevity) of multiple vineyard fungicides on the predatory mite T. pyri.

2. Determine the biology and foraging behaviors of T. pyri on C. vitis, particularly predation preferences and rate of predation.

2a. Adjusted objective (as explained in progress reports): Evaluate the life history and biological parameters of developing T. pyri at seven constant temperatures reared on a diet of C. vitis, T. urticae and pollen.

3. Test the ability of methyl salicylate to attract and establish T. pyri populations in vineyard systems. Field and laboratory experiments will be conducted to determine attraction rates.

Cooperators

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  • Angela Gadino

Research

Materials and methods:

Objective 1

Part 1

Field trials were conducted during the 2008 and 2009 season to evaluate the effects of fungicide spray regimes on mite populations at two commercial vineyards (Dundee and Salem vineyards) located in Willamette Valley, Oregon. Six different fungicide spray regimes were applied every 10-14 days depending on mildew pressure. Treatments were as follows:

1) Non-sulfur control (synthetics only),
2) Organic grower standard (sulfur only),
3) Sulfur early to fruit set and synthetics late,
4) Sulfur-synthetic rotation (rotated sulfur),
5) Rotation of Whey and Sulfur,
6) Sulfur late with synthetics early.

Treatments were applied to small plots (groups of 35-42 vines), replicated three times in a randomized complete block design. Treatments were applied with an ATV boom-type sprayer. Mite and beneficial populations monitoring were started before the initial treatments were applied and continued biweekly after the initial treatments in order to determine the effect of treatments on mite populations. Pest mite (including rust mite and spider mite populations) and predatory mite numbers were sampled at 14 day intervals by collecting 16 leaves (four on each of four vines in the center of each plot: two proximal and two distal). Leaves were taken to the laboratory and 15mm diameter leaf disks were investigated for mite incidence using stereo microscopes. Sampling continued until leaf senescence in autumn. All data were analyzed using repeated measures ANOVA (Using Statistica version 4 computer software).

Part 2

Pesticide mortality and reproductive effects on T. pyri were tested in laboratory bioassays by transferring 15 juvenile or adult female mites onto a single bean leaf and directly spraying them with pesticides in order to evaluate potential impacts from contact and residual exposure (Figure 1). Six pesticides were tested at three rates, the average recommended label rate (1×) and a 1.5× and 2× increase of that rate (Table 1). Control groups were also included for each tested pesticide. A Precision Potter Spray Tower (Burkard Mfg. Co Ltd, Ricksmansworth, UK) was used for all laboratory spray applications and calibrated to deposit spray quantities of 2.0 ± 0.2 mg/cm2 per 1-ml water.

To evaluate mortality, mites were observed for seven days following the initial spray treatment. All dead mites were counted and used to calculate the cumulative mite mortality. Separate bioassays were conducted for adult female and juvenile mites. The juvenile mites surviving on day 7 were counted, and male to female sex ratios determined as they had molted to adulthood by this time.

Effects on mite reproduction were evaluated for each pesticide using the same set of mites assessed for mortality effects. Observations were conducted for seven days after the initial treatment for mites exposed as adult females and from days 8 to 14 for mites exposed to the pesticides as juveniles. The number of eggs, hatched larvae and adult females present on each leaf were recorded on each observation day and used to calculate the mean number of eggs deposited per female.

Data were analyzed within each pesticide treatment using analysis of variance (ANOVA) and employing Fisher’s LSD procedure to compare treatment means (SAS Institute 2006). Data were transformed for statistical analysis using arcsine (sqrt (x + 0.375) / 100) when ANOVA assumptions (normality and/or homogeneity of variance) were not met.

Objective 2

Predatory mites were collected from northern Willamette Valley vineyards (Yamhill Co., OR) and a stock colony maintained in the laboratory. Spider mite colonies were reared on live bean plants (Phaseolus vulgaris cv. Roma) under controlled conditions at 25 ± 1º C, 75% RH and a 16:8 (L:D) photoperiod. Pinot Noir grapevine leaves (100 +) containing known infestations of C. vitis were collected from two north Willamette Valley vineyards (Yamhill Co., Oregon). Leaves were stored in cold rooms at 4 ± 1º C until offered to T. pyri during temperature experiments.

For experiments, each rearing tray was divided into 16 cells (~ 8 cm2) with a sticky barrier (Tanglefoot, USA). One gravid adult female mite was placed in each of 16 cells, provided T. urticae prey ad libitum and checked every 12 h until an egg was oviposited. Rearing trays were placed in controlled growth chambers at seven different temperatures (12.5, 15, 17.5, 20, 25, 30 and 35º C) and 60-70% RH under a 16:8 (L:D) photoperiod. Experimental units were replicated three times at each temperature.

After initial oviposition, mite development was observed every 12h. A molt to the next developmental stage was determined by the presence of exuvia and removed at each observation. Immature mites were offered ad libitum a mix of food types consisting of an estimated 50% T. urticae (all stages), 30% C. vitis (adult stage) and 20% pollen.
Adult female mites were observed every 24 h to determine pre-oviposition, oviposition and post-oviposition periods. Eggs oviposited per surviving female were recorded daily and removed at each observation. Adult female mites were fed once daily with a mix consisting of 70% T. urticae and 30% pollen. The prey C. vitis was not offered to adult females due to limited access to leaves with high population numbers and difficulties in rearing this pest mite.
Survival and fecundity data were used to estimate the intrinsic rate of population increase, rm, described as the capacity of increase in a population under optimal conditions. Development rate was modeled as a function of temperature using nonlinear (Briere et al. 1999) and linear models to calculate developmental parameters.

Objective 3

Part 1

Mites from rearing colonies used in the experiment were fed a mixed diet consisting of pollen (Tilia spp. and Typha spp.) and spider mites (T. urticae), reared on bean plants (Phaseolus vulgaris cv. Roma). Satiated adult female mites (2-5 d after final molt) were individually collected and placed into Eppendorf vials approximately two hours prior to olfactometer bioassays.

A y-tube olfactometer was employed to test the response of T. pyri in a two-way bioassay (Sabelis and Baan 1983). Compressed air was blown at 1.3 liters/minute through a glass y-tube approximately 3 cm in diameter and an inert copper wire was present as a walking platform for the mites. The predatory mite response to methyl salicylate was tested at six doses (0.002µg, 0.02µg, 0.2µg, 2.0µg, 20µg, 200µg) at a volume of 0.1 ml of diluted MeSA (99% pure, diluted in hexane) placed on filter paper. The adjacent arm of the tube held filter paper with 0.1 ml hexane representing the control. Mites were allowed five minutes to make a decision (MeSA diluted in hexane or hexane only), and once the time limit passed a ‘no decision’ was recorded for that individual.

Contingency tables (2 × N, where N = replicates) were analyzed prior to pooling the data for further analysis to establish that no significant differences occurred between tests run on different days with different cohorts of predatory mites (P > 0.05). A binomial analysis tested for within-dose differences using a 50:50 distribution. The relationship between dose and response was analyzed using logistic regression with log-dose and square log-dose as factors.

Part 2

Field experiments were conducted during 2009 and 2010 to assess the effect of MeSA lures on the seasonal population dynamics of key natural enemies and pests. Vineyards were located in Salem, OR and Dayton, OR. A randomized complete block design was used to establish experimental plots. Each plot covered an area approximately 152 m2. Treatments included MeSA lures (5 g lure) at a standard rate (4 lures/plot; 260 lures/ha), a high rate (8 lures/plot; 520 lures/ha) and an untreated control.

Samples were collected from plot center (0 m) and at 5 and 10 m laterally down the vine row every 14 days to assess arthropod density. Ten leaves were collected and transported back to the laboratory in an insulated cooler. Counts from leaf assessments were used to determine T. pyri life stages (eggs, mobiles), pest mites (Eriophyid, Tetranychid) and thrips (Thripidae) density per leaf for each treatment and distance. Yellow sticky traps (7.5 × 12.5 cm) were placed in the vine canopy approximately 1 m from the ground. The entire surface area of each sticky trap was searched using a dissecting microscope to obtain counts of key predatory arthropods for each plot and distance.

The treatment effect of MeSA lures on individual arthropod species was determined using a split-plot repeated measure analysis which included treatment, block, date and distance as factors (PROC MIXED, SAS 2006). Significant main factors and interactions (P < 0.1) were analyzed in a backward stepwise approach to further determine treatment differences. When treatment or treatment × date terms were significant, an analysis of variance (PROC GLM, SAS 2006) was conducted for individual species on that given date and means separated with Tukey’s HSD procedure (P < 0.05). Data were transformed using natural log (x + 1.0) to normalize distribution when necessary.

Research results and discussion:

Objective 1

Part 1

Fungicide field trials have been completed and all data collected and recorded from leaf samples. Results for the 2008 season show a trend of higher pest mite numbers in plots that only received synthetic fungicides in both locations. In the Dundee vineyard, mean seasonal pest mite numbers per leaf was 1.07 in plots that only received synthetic fungicides compared to 0.2 in plots that received a mix of synthetic fungicides and sulfur. The mean number of predatory mites ranged from 0.18 and 0.15 mites per leaf in each of the treatments. In the Salem vineyard, mean seasonal pest mite numbers per leaf was 8.1 in plots that only received synthetic fungicides compared to 3.44 in plots that received a mix of synthetic fungicides and sulfur. Mean seasonal predatory mites per leaf in synthetic fungicide plots were 0.48 mites per leaf compared to 0.21 mites per leaf in plots that received both synthetic fungicides and sulfur. Overall, vineyard plots with multiple sulfur applications resulted in the lowering of both pest and predatory mite populations. In cases where synthetic fungicides were the only compounds used for fungus control, both pest and predatory mite populations were higher than in plots where sulfur was used (Figure 2). In many cases, it however appeared as if pest populations were not contained by predatory mite numbers. In plots where sulfur was applied in combination with synthetic fungicides, there were lowering of pest mite numbers, and beneficial mite numbers were not affected in the same negative degree as in plots where sulfur were used as the only fungicide.

Part 2

Results (as presented in progress reports) indicate that five of the six fungicides tested did not display mortality levels greater than 50% at all rates for adult female and juvenile T. pyri. Only exposure to paraffinic oil resulted in mortality greater than 50% at all three rates and were significantly different from the control (Table 2).

Fungicide effects on adult female reproductive potential was minimal as we found no significant differences for all treatment fungicides compared to the control (Table 3). Sub-lethal effects were more pronounced in the juvenile bioassays when exposed to certain fungicides (Table 3). Significant decreases were observed in the sulfur and mancozeb treatments. Percent fecundity reduction relative to the respective control was highest in the sulfur (28%, 51.2%), myclobutanil (24.7%, 45.7%) and mancozeb (21.8%, 83.2%, 70%) treatments at different rates. Whey powder and boscalid showed no significant differences from the control and a low percent reduction in fecundity.

Overall, adult and juvenile T. pyri exposure to five of the six pesticides resulted in less than 50% mortality. Paraffinic oil treated mites displayed the most consistent significant differences from the untreated control and resulted in mortality greater than 50% for both adult and juvenile predatory mites at the three concentrations tested. The low mortality of mites exposed to the five other pesticides, especially at recommended field concentrations, suggest that other factors may be involved with decreasing populations of T. pyri observed in agricultural production. Although acute pesticide toxicity is a critical issue, additional factors such as sub-lethal effects, pesticide repellency, dispersal, repeated pesticide exposure, application timing and food availability are potential contributors to reduced field populations (Duso et al. 2007, Beers et al. 2009, Pozzebon et al. 2010).

Objective 2

Successful development of T. pyri from egg to adult occurs at temperatures ranging from 15-30ºC (Figure 3). Developmental rate of immature T. pyri increased with increasing temperature (Table 4). Adult female oviposition period and fecundity rate were highest at 25ºC and lowest at 15ºC. The function obtained by multiple linear regression using lower temperatures (15, 17.5, 20, 25) was y = 0.0089x – 0.07737 (R2 = 0.89, F = 15.55, P = 0.058, df = 1, 2) with an estimated lower developmental threshold of 8.7ºC. Upper (35.2 ºC) and optimal (26.1ºC) developmental thresholds were obtained using non-linear estimation (Briere et al. 1999) resulting in the equation y = (0.00000490) * (x-12.079) * (35.22-x) (1/0.44) (R2 = 0.95, F = 19.47, P = 0.049, df = 2, 4). The biological parameters estimated displayed in net reproductive rate (Ro) and intrinsic rate of population increase (rm) values that increased as temperature increased to 25ºC, and then decreased at 30ºC. The rate of increase was above zero in all cases, indicating positive population growth within this range of temperatures (Table 5).

The life history traits displayed in this study are comparable to findings from previous research conducted at temperatures ranging from 18 to 30ºC (Overmeer 1981, Genini et al. 1991). The development of male and female mites from egg to adult at 15ºC however occurred in approximately half the number of days (~15 d) in our study compared to the 32 d reported by Genini et al. (1991) suggesting that the T. pyri found in Oregon are biologically suited to the cool climate region. Maximum net reproduction, intrinsic rate of increase and fecundity rates occurred at 25ºC for both T. pyri and C. vitis (Walton et al. 2010). Optimal developmental temperatures were estimated at 26ºC for both mite species pointing toward similar temperature requirements. Population increase at 25ºC were rm = 0.141 for C. vitis and rm = 0.127 for T. pyri. These results signify a potential biological advantage in rust mite population growth at higher temperatures(James et al. 2002). Comparison of the intrinsic rate of increase at approximately 17ºC displayed the opposite trend where T. pyri populations have a greater capacity to increase to levels above those of C. vitis (Walton et al. 2010).

Objective 3

Part 1

Significantly higher proportions of T. pyri preferred MeSA at doses 0.02, 0.2, and 20 µg (Table 6). No differences were detected at the highest (200 µg), lowest (0.002 µg) and intermediate (2.0 µg) doses (Figure 4). Approximately 70% of predatory mites responded positively to the 0.2 µg and 20 µg dose of MeSA. A response to dose was observed but not significant (P = 0.057; P = 0.739), suggesting there is a weak relationship between dose quantity and T. pyri response.

These results are comparable to those of De Boer and Dicke (2004) in MeSA olfactometer experiments with the predatory mite Phytoseiulus persimilis. The 0.2 µg dose was attractive to both of these predatory mite species. In our bioassays, T. pyri did not respond significantly to 2 µg doses, which was unexpected with no clear explanation. T. pyri was also not attracted to, nor repelled by, the lowest (0.002 µg) and highest (200 µg) dose, whereas P. persimilis displayed a significant repellent response to the highest MeSA dose (200 µg) (De Boer and Dicke 2004). The response of phytoseiids to HIPV’s is known to vary a great deal between species (Dicke et al. 1998) and is the most obvious explanation for differences found between T. pyri and P. persimilis. Overall, we found that T. pyri is attracted to synthetic MeSA in olfactometer bioassays. The use of synthetic MeSA lures in vineyards may have the potential to attract and increase populations of T. pyri, thereby enhancing pest mite biological control.

Part 2

During 2009 at Salem, the mean seasonal density of T. pyri was higher in control plots compared to plots baited with MeSA lures (Table 7). Mean seasonal abundance of pest thrips was higher in control versus both rates of MeSA baited plots during 2009. A significant decrease of pest thrips (Thripidae) occurred later in the season during berry ripening in low rate MeSA treatments compared to control plots (Table 9). Temporal analysis of macro predators displayed greater natural enemy populations in high rate MeSA plots during the berry ripening period (Table 9). Significantly lower numbers of macro predators however were found in MeSA treated plots earlier in the season during bloom. Seasonal abundance of T. pyri in Salem was approximately 4× lower in 2010 compared to 2009 densities in all plots (Table 7). There were no significant differences in T. pyri density between control and MeSA treated plots, although counts in the control plots were numerically higher. During 2010, Coccinellid and total macro predators displayed a pattern of increased mean seasonal abundance in MeSA-baited compared to control treatments, but differences were not significant (Table 7). No C. vitis mite populations were recorded at this location in 2009 or 2010.

During 2009 at Dayton, the mean seasonal abundance of T. pyri was numerically higher, but not significantly, in MeSA baited plots compared to control plots (Table 8). Pest mites (C. vitis and Tetranychids) and pest thrips (Thripidae) were present in all treatment plots, but no significant differences were found between treatments in this season. During 2010, a numerically higher mean seasonal abundance of T. pyri was displayed in the high rate MeSA treatments (Table 8), but significant differences between treatments were not displayed. No significant differences in pest density however occurred between MeSA-baited and control treatments. Tetranychid pest mites were present in all treatment plots during 2010, but densities were too low for statistical analysis.

Higher mean seasonal abundance of Coccinellidae were recorded during 2009 (P = 0.029) and 2010 (P = 0.040) with the highest counts recorded in high rate MeSA treatments (Table 8). Peak captures of coccinellids occurred in early June (> 4.5 per trap) and late July (> 2.0 per trap) in 2009. During 2010, peak captures of coccinellids occurred during bloom (> 2.0 per trap) and again during fruit development (> 1.5 per trap) in low and high rate MeSA treatments. Total macro predator mean seasonal abundance was significantly greater (P = 0.029) in MeSA-baited plots (Table 8).
Our data did not show consistent trends in T. pyri population response to synthetic MeSA in two field sites and seasons. These inconclusive results were unexpected as T. pyri displayed significant attraction to MeSA in laboratory bioassays. It may be that the relative presence or absence of the prey resource, C. vitis, at the two vineyard locations affected the response of T. pyri to synthetic MeSA lures. Research has documented that predatory arthropods display learning behaviors that enable them to discriminate between prey by using chemical cues (Drukker et al. 2000, De Boer et al. 2005, De Boer and Dicke 2006). Higher mean seasonal abundance of Coccinellidae was found in the MeSA baited treatments in both locations during both years. These findings support other field experiments where coccinellids, such as Stethorus spp., were shown to be significantly attracted to synthetic MeSA (James and Price 2004, Lee 2010). The responses of all other natural enemy groups to MeSA showed no clear patterns in our study.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

1) V. Walton, A. Gadino and A. Dreves. 2009. Vineyard Pest Management News, OSU Extension Service, February 22, Winter Publication.
2) A. Gadino, VM Walton, AJ Dreves. Impacts of vineyard pesticides on Typhlodromus pyri in laboratory bioassays. Accepted: Journal of Economic Entomolgy, March 2011.
3) A. Gadino, VM Walton, JC Lee. Olfactory response of a predatory mite, Typhlodromus pyri (Acari: Phytoseiidae) to methyl salicylate in laboratory bioassays. Submitted: Journal of Applied Entomology, October 2010; currently in revision.
4) A. Gadino and VM Walton. Temperature-related development and population parameters for Typhlodromus pyri (Acari: Phytoseiidae) found in Oregon vineyards.

Submitted: Experimental and Applied Acarology, May 2011
1. April 2009, Pacific Branch Entomology Society of America annual meeting (San Diego, CA), Impacts of six fungicides on the lethal and sub-lethal effects on Typhlodromus pyri, poster presentation.
2. July 2009, OSU Extension Vineyard Workshop (Vineyard, Willamette Valley, OR), oral presentation on initial results of fungicide bioassays on T. pyri and the implications of this information for vineyard spray programs.
3. January 2010, 69th Annual Pacific Northwest Insect Management Conference (Portland, OR), Effects of six vineyard fungicides on the juvenile predatory mite Typhlodromus pyri, presentation and printed abstract.
4. February 2010, Graduate Student Symposium, Oregon State University, The effect of six vineyard fungicides on the predatory mite Typhlodromus pyri, poster presentation.
5. March 2010. OSU Viticulture and Enology Research Colloquium presented for Oregon Wine Industry members (OSU campus), Behavioral response of the predatory mite, Typhlodromus pyri to methyl salicylate, oral presentation
6. April 2010. Pacific Branch ESA annual meeting (Boise, ID), The behavioral response of a predatory mite Typhlodromus pyri to methyl salicylate, oral presentation
7. September 2010. OSU/LIVE Sustainable Vineyards Field day (Ann Amie Vineyards, Dundee OR), Impact of six vineyard fungicides on the predatory mite, Typhlodromus pyri, presentation and handouts
8. January 2011. 70th Annual Pacific Northwest Insect Management Conference (Portland, OR), Evaluation of methyl salicylate lures on populations of Typhlodromus pyri and other key natural enemies in vineyards, oral presentation (abstract online)
9. January 2011. Association of Applied IPM Ecologist 46th Annual meeting (Monterey, CA), Impact of six vineyard fungicides on a predatory mite Typhlodromus pyri, oral presentation
10. February 2011. OSU/OWRI Viticulture and Research Colloquium (OSU campus), Enhancing pest mite biological control by Typhlodromus pyri, in Pacific Northwest Vineyards, oral presentation
11. March 2011. Pacific Branch ESA Annual meeting, Effect of methyl salicylate lures on Typhlodromus pyri and other natural enemies in vineyards, oral presentation

Project Outcomes

Project outcomes:

This research provides benefits to Oregon wine grape growers through promotion of sustainable management practices based on increased education regarding fungicide spray regimes, predatory mite biology and novel tools which may attract and/or retain predatory mites in areas of pest infestation. Producers are gaining the knowledge to develop spray regimes which are beneficial to predatory mite populations through reduced-risk material choices and application timing. Additionally, by understanding the biological parameters and temperature related development, we are better able to assess the suitability of T. pyri as a biological control agent through different times in the growing season. This information will assist growers in understanding the dynamics of the predator-prey system in Western vineyards and aid in management decisions. Producers are also gaining an understanding of the efficacy and optimal use of the commercially available MeSA lures (Predalure®™) as potential management tools in an IPM program for control of the grapevine rust mite, C. vitis.

Economic Analysis

A detailed analysis was not part of the research project, but a summary of economic costs, returns and risks is provided. The overall goal of our three research objects was to enhance the biological control of pest mites by T. pyri in Oregon vineyards. The results from this research aid in the conservation of T. pyri populations via improved knowledge of the impacts of commonly applied vineyard pesticides and increased understanding of the developmental and biological parameters of this organism. Based on this knowledge, growers can optimize vineyard management programs to include reduced-risk pesticides. Through the conservation of predatory mite populations, successful pest mite suppression is achievable without the use of chemicals (i.e. miticides or pesticides). There is potential for growers to reduce chemical sprays by two-three applications during the spring season (wooly bud stage) and/or one-two applications in mid- to late- part of the growing season (reduction of overwintering pest population) for C. vitis control.

Possible risks for adoption of these practices are minimal. Growers will still maintain active and effective powdery mildew programs. Synthetic materials can be more costly compared to sulfur, however they can also be applied less frequently and their addition to management programs will likely be cost neutral. The adoption of the use of MeSA lures to potentially attract T. pyri populations is estimated to cost approximately $100-200/acre, depending on the rate that is applied. PredaLure wholesale costs for a 90 d (5g weight) lure, as used in our project, is approximately $1.95 per lure when purchasing a pack of 25 lures. Application rates will vary between 35 to 100 lures per acre. It is recommended, however, since our research was inconclusive regarding the efficacy of this product to attract T. pyri that the use of MeSA lures may be most effective in pest hot spots and not over entire vineyard blocks, and this would reduce the per acre cost. Potential risks involved with the adoption of this practice include an expectation for increased biological control of C. vitis through increased predatory mite populations, however since the efficacy and optimal rate for use of MeSA lures is not clear, the money spent on lures may not provide the expected returns.

Farmer Adoption

The results and information learned from our research projects have been presented to growers throughout the Willamette Valley at multiple events and in several formats, including grower field days, OSU research colloquium and newsletters. The extension of information is estimated to have reached approximately 100 vineyard managers and owners. Over 50% of Oregon states vineyard acreage is planted in the Willamette Valley, and the adoption of information gained through our research has the potential to impact approximately 11,000 acres of wine grapes. Currently, about 10-20% of the 11,000 acres in this region are controlling for pest mites, while increases in infested vineyard acreage is reported yearly. We believe a number of Willamette Valley growers have adopted powdery mildew spray programs that reduce the amount of sulfur applied over the season based on our recommendations to limit sulfur use. Additionally, we would recommend that pre-bloom sprays with horticultural oils be avoided if trying to conserve predatory mite populations. From our research, we found that T. pyri has the potential to rapidly increase population levels when temperatures are cooler (15-20ºC) in the spring season. Based on this information, we also suggest limiting the use of sulfur during the early part of the growing season to conserve T. pyri populations.

Recommendations:

Areas needing additional study

Based on our findings from the current research projects, we believe that future research should include:

1) evaluating additional sub-lethal impacts, such as pesticide repellency, of commonly applied vineyard pesticides on predatory mites;

2) conducting augmentative predatory mite releases in vineyards with known pest issues to determine if this technique will increase pest control;

3) evaluating other species of native predatory mites known to be more active in warmer temperatures and that may compliment the control provided by T. pyri in the early part of the season; and

4) Test additional HIPV’s in conjunction with MeSA to determine if combinations of volatiles can increase attraction or retention rates of predatory mites.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.