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

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

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.

Objectives/Performance Targets

1. Conduct field and laboratory bioassays to determine the effects (direct mortality, fecundity, oviposition rate and longevity) of six 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.
Adjusted objective (see 2010 progress report): Evaluate temperature-related development of T. pyri and determine biological parameters to assess predatory suitability to provide effective biological control.

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.

Accomplishments/Milestones

Part 1

To determine the effects of fungicide spray regimes in the field, experiments were conducted during the 2008 and 2009 season at two commercial vineyards (Dundee and Salem vineyards), located in Oregon’s Willamette Valley. 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.

Leaf samples (basal and terminal) were collected every other week (n=16) until September and brought to the laboratory to count both predator and pest mite density.

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.

In 2009, the Dundee vineyard, mean seasonal pest mite numbers per leaf was 0.49 in plots that only received synthetic fungicides compared to 0.036 in plots that received a mix of synthetic fungicides and sulfur. No differences could be found for mean predatory mites in different treatments. In the Salem vineyard, mean seasonal pest mite numbers per leaf were 0.0036 in plots that only received synthetic fungicides compared to 0.003 in plots that received a mix of synthetic fungicides and sulfur. No differences could be found for mean predatory mites in different treatments. It appears as if a synthetic fungicide-only spray protocol may result in excessively high pest numbers in the following spring in all of our trial sites during both years.

The fungicide field trials have been completed. The work remaining includes paper review and publication, extension bulletin publication and presentation of results and conclusions at professional meetings and vineyard field day workshops (spring-summer 2011).

Part 2

Laboratory bioassays were conducted using a precision Potter Spray tower to test the direct toxicity and sub-lethal effects of six vineyard fungicides on T. pyri adult females and juveniles (0-4 d old). Fungicide treatments were micronized sulfur (92%), whey powder (milk bi-product), manganese ethylenebisdithiocarbamate (75%, mancozeb), boscalid (plus pyraclostrobin, 38%), myclobutanil (40%) and paraffinic oil (97.1%) at three different rates (recommended label rate (1×), 1.5× increase and 2× increase), a water spray and check (no spray) were also included.

Results (as presented in the 2010 progress report) indicate that five of the six fungicides tested can be classified as non-toxic to both adult female and juvenile T. pyri as levels of mortality were less than 50% for all rates at 7 d after treatment. Paraffinic oil was the single fungicide which showed direct mortality greater than 50% at 1 d after treatment for all three rates and was significantly different from the check (Table 1 & 2). Fungicide effects on adult female reproductive potential appeared to be minimal as there were no significant differences detected for all tested fungicides compared to the check (Table 3). However, sub-lethal effects were more pronounced among the fungicides tested in the juvenile bioassays (figures presented in 2010 progress report). Significant decreases were seen in the sulfur (1.5× rate) and mancozeb (1.5×, 2× rate) treatments compared to the check. The percent fecundity reduction relative to the check was highest in the sulfur (28%, 51.2%), myclobutanil (24.7%, 45.7%) and mancozeb (21.8%, 83.2%, 70%) treatments at label rate, 1.5× rate and 2× rate, respectively. Whey powder and boscalid showed no significant differences, at all three rates, from the check and a low percent reduction in fecundity relative to the check. Fecundity comparisons between fungicides of similar rates, did show treatment differences at the 1.5× rate (P ? 0.001) and 2× rate (P ? 0.05).

The laboratory bioassay experiments and data analysis have been completed. The paper has been submitted to the Journal of Economic Entomology and is currently undergoing edits from reviewer comments. The paper will be resubmitted by March 8, 2011. Information gained from the experiment results has been presented at both professional meetings and vineyard field day workshops. An extension publication is planned for spring 2011 that will highlight findings from both field and laboratory experiments.

Life table experiments were conducted to determine longevity, developmental rate, oviposition length and population rate of increase for T. pyri. Experiments were conducted at seven constant temperatures (12.5, 15, 17.5, 20, 25, 30, and 35ºC; 16:8 L:D photoperiod, 60 – 70% RH) and fed a mixed diet including C. vitis. The diet consisted of 50% spider mites (reared in laboratory), 30% C. vitis (collected from commercial vineyard infested leaves) and 20% pollen (collected from Willamette Valley). Eggs (0-12 hours old) were placed in one of sixteen cells on a divided tray. Mite cells were checked twice daily (approximately every 12 hours) and hours from egg to adult stage were recorded to attain developmental rates. Adult females had one male mite added to ensure copulation. Pre-oviposition length, oviposition length, oviposition rate and adult female longevity were assessed and recorded.

Results show that successful development of T. pyri from egg to adult occurs at temperatures ranging from 15-30ºC (Figure 1). Adult female oviposition period and fecundity rate were highest at 25ºC and lowest at 15ºC. 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 over this range of temperatures (Table 4).

Trials and data analysis have been completed. The paper will be submitted to the Journal of Experimental and Applied Acarology in March-April 2011. Results and conclusions will be presented in February 2011 at a professional meeting.

Part 1.

Y-tube olfactometer assays were conducted to test the behavioral response of Typhlodromus pyri toward methyl salicylate (MeSA) under controlled laboratory conditions. Six MeSA doses were tested (0.002µg, 0.02µg, 0.2µg, 2.0µg, 20µg, 200µg) on 18 individual predator mites and replicated five times over different days with different adult females. Each female mite choice (MeSA, control) was recorded upon reaching a decision, and if no decision was made after a five minute interval then a no choice was recorded. Experiments have been completed and data has been analyzed.

Significantly higher proportions of T. pyri preferred MeSA at doses 0.02, 0.2 and 20 µg (P < 0.05). No differences were detected at the highest (200 µg) and lowest (0.002 µg) doses (Figure 2). The response to dose was not significant (P = 0.057; P = 0.739), suggesting there is no relationship between dose quantity and T. pyri response. Subsequent analysis confirmed no correlation between dose level and mite response, however, an overall positive attraction (62%, P < 0.0001) of T. pyri to MeSA was found.

The paper has been submitted to the Journal of Applied Entomology and is currently undergoing edits to address reviewer comments. The revised manuscript will be re-submitted by February 16, 2011. Results from this work have been presented at professional meetings within the past year.

Part 2.

Methyl salicylate field trials were carried out in two commercial vineyards (Salem and Dayton,) located in the Northern Willamette Valley starting in 2009 season. Lures were placed in the center of each baited block (four/block or eight/block) and no lures were placed in the control block. Leaf samples (30/block) were collected to determine predatory mite and pest mite density in each block at a distance of 0, 5 and 10 meters from block center every two weeks until mid-October. Leaf samples were brushed and counted in the laboratory; to date all samples have been processed.

Field trials have been completed and the data entered for analysis. The majority of data analysis has been completed and results interpreted. Identification and curation of mite specimens collected in 2010 from the field is in progress (specimens from 2009 have been completed). Higher mean seasonal T. pyri abundance was found in the MeSA plots compared to control plots at the Dayton vineyard in 2009 and 2010. The opposite trend, however, was found at the Salem vineyard, with higher mean seasonal predatory mite abundance in the control plots. MeSA-treated plots did not show significantly higher or lower C. vitis populations.

The manuscript for this paper is in progress and will be submitted for publication by April 2011. The results and conclusions from this work have been and will continue to be presented at professional meetings and grower workshop events in 2011.

• Tables 1,2 and 3
• Table 4 and Figure 1
• Figure 2

Impacts and Contributions/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 predatory mites towards 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 have been better able to assess the suitability of T. pyri as a biological control agent during different seasons. 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 employment of the commercially available MeSA lures (Predalure®™) as potential management tools in an IPM program for control of grape rust mite, C. vitis.

Outreach and professional presentations to date include:

• 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.

• 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.

• 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.

• February 2010, Graduate Student Symposium, Oregon State University, The effect of six vineyard fungicides on the predatory mite Typhlodromus pyri, poster presentation.

• 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.

• April 2010, Pacific Branch ESA annual meeting (Boise, ID), The behavioral response of a predatory mite Typhlodromus pyri to methyl salicylate, oral presentation.

• 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.

• 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).

• 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.

Outreach/education and professional presentations for spring 2011 will include:

• February 2011, OSU/OWRI Viticulture and Research Colloquium (OSU campus), Enhancing pest mite biological control by Typhlodromus pyri, in Pacific Northwest Vineyards, oral presentation.

• March 2011, Pacific Branch ESA Annual meeting, Effect of methyl salicylate lures on Typhlodromus pyri and other natural enemies in vineyards, oral presentation.

Collaborators: