- Fruits: general small fruits
- Pest Management: general pest management
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.
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.
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.