Easily sustainable rose/strawberry gardens near orchards provide an alternate host (Ancylis comptana) for a parasitoid (Colpoclypeus florus) of pest leafrollers that can dramatically stimulate parasitism in adjacent orchards. Parasitism of the pest leafroller OBLR by C. florus in apple orchards near rose gardens was high in the spring and summer larval generations at several study sites during 2004-2006. In gardens, strawberries better foster the Ancylis leafroller, but Ancylis is more reliably parasitized on roses. Seven presentations to grower and pest manager groups were made since 2004 and a grower-targeted paper was published and web page on gardens was created.
1. Evaluate the impact of large gardens of Rosa woodsii and wild strawberry harboring the strawberry leafroller, Ancylis comptana (SLR), which supports C. florus overwintering and enhances parasitism of OBLR and PLR in adjacent orchards.
2. Disseminate information on how to establish, maintain and benefit from these alternate habitats through traditional presentations, grower magazines, a web site and consultation.
3. Develop greater understanding of the ecology of this system, particularly how far into orchards parasitoids disperse from gardens and the stability of the beneficial community in gardens with rose alone versus strawberry alone and rose plus strawberry.
Pest leafrollers in Washington and Oregon apple, pear and cherry orchards account for 15-25% of insecticide use in these commodities. Leafrollers have become important pests in many orchards using mating disruption (MD) for codling moth control (Brunner et al. 2001) and multiple applications of Lorsban or Bacillus thuringiensis can be used against leafrollers. These solutions are imperfect: Lorsban and more recently the neonicotinyl replacements (Assail) conflict with the biological control advantages provided by MD and Bt can be unreliable, expensive, and more and more difficult to purchase. Newer insect growth regulators (IGRs) for leafroller control may offer important relief from neurotoxin sprays but are candidates for resistance development. Similar problems occur in Europe (including resistance to IGRs) but with a different leafroller complex and a different toolbox of insecticides. Mating disruption does not appear to be a viable solution to leafroller control despite several commercial formulations that were developed for its implementation.
Biological control stands out as a valuable part of leafroller management but it too is plagued by problems. The spring leafroller larval generation typically shows very low levels of parasitism, both in the US and in Europe (Pfannenstiel and Unruh 2003). However, our observations that parasitism of pest leafrollers was higher adjacent to naturally occurring rose patches led us to the idea that roses could be intentionally planted near orchards to enhance leafroller parasitism. Experimental rose hedges with strawberry understory infested with the strawberry leafroller (SLR), Ancylis comptana, planted near to orchards was shown to dramatically increased parasitism of our key leafroller pests (Pandemis pyrusana [PLR] and Choristoneura roscaceana [OBLR]) (Brunner and Beers 1996) in adjacent orchards (Pfannenstiel and Unruh 2003). Specifically in three of four gardens, spring parasitism in adjacent orchards increased from <10% to greater than 90% in the edges of orchards near the experimental plantings. The experimental garden not associated with the upswing was found to harbor no SLR. This SARE project was designed to provide the pome-fruit producer community the knowledge and skills required to enhance biological control of leafrollers in the orchards of the Northwest by these rose/strawberry habitats, ultimately to significantly reduce pesticides use for leafroller control.
The use of refuge plantings to supplement natural enemy abundance and biological control is well known in tree fruits (Bugg and Pickett 1998). In France, hawthorn hedges support alternate psylla species, which act as hosts to parasitoids of Cacopsylla pyri (Nguyen et al, 1984, Delvare 1984). Prune trees harboring a non-pest leafhopper supported the parasite, Anagrysus epos, leading to a doubling of adult A. epos density in adjacent grape vineyards which can then parasitize the grape leafhopper (Murphy et al. 1996). The key landscape element in the tree fruit leafroller story is rose plants hosting Ancylis comptana, the strawberry leafroller (SLR), which provides an overwintering host for Colpoclypeus florus and other parasitoids. SLR is also thought to enhance parasitism of Oriental Fruit Moth in peaches when strawberries are interplanted (Letourneau and Altieri 1999), in that case acting as a host for the wasp, Macrocentrus ancylivorus. The parasitic wasp, Colpoclypeus florus, is an important leafroller control agent in many countries in Europe (Dijkstra 1986, Gruys and Vaal 1984). However, it requires a large host caterpillar on which to overwinter while our two main leafroller pests, as well as other leafrollers in our orchards, overwinter as small larvae or eggs, unsuitable for the wasp. SLR overwinters in diapause as a mature larvae and provides a highly suitable overwintering host for C. florus. SLR is a native of Eastern N.A. but apparently has naturalized onto wild multifloral roses, Rosa woodsii and R. nutkana, and strawberry found in some low altitude riparian zones of central Washington and Oregon. Colpoclypeus florus, was discovered in Washington in 1992 (Brunner 1996), some 25 years after it was released in Ontario Canada for control of the Red-banded leafroller.
Our project will demonstrate how this alternate host habitat is a missing link in the biology of an important beneficial wasp which will enhance producer awareness of these otherwise esoteric ecological relationships. Growers will learn how to position, plant, and maintain gardens, how to infest gardens with non-pest leafrollers, and how to maximize benefits of the key natural enemies by careful stewardship of the adjacent habitat and minimum pesticide use in nearby orchards. We have seen a remarkable desire by producers to understand all aspects of the ecology of their trees and the pests that attack them and to make their product as natural and pesticide-free as possible. Parasitic wasps, including the main wasp involved here, are very susceptible to most insecticides (Brunner et al. 2001). It has been our experience since studying experimental gardens in close collaboration with growers, that once growers understand the ecological phenomena involved, they become much more active participants and promote the idea to their peers.
Brunner, J. F. 1996. Discovery of Colpoclypeus florus (Walker) (Hymenoptera: Eulophidae) in apple orchards of Washington. Pan-Pacific Entomologist. 72: 5-12.
Brunner, J. F. and E. H. Beers. 1996. Pandemis and obliquebanded leafrollers. Washington State University Extension Bulletin 1582. WSU, Pullman, WA.
Brunner, J., S. Welter, C. Calkins, R. Hilton, E. Beers, J. Dunley, T. Unruh, A . Knight, R. Van Steenwyk and P. Van Buskirk. 2001. Mating disruption of codling moth: a perspective from the western United States. Bulletin of the International Organization for Biological and Integrated Control. IOBC/WPRS. 25:207-215.
Bugg, R. L. and C. H. Pickett. 1998. Introduction: Enhancing biological control – habitat management to promote natural enemies of agricultural pests, pp. 1-23. In Bugg, R. L. and Pickett (eds.). Enhancing Biological Control – Habitat Management to Promote Natural Enemies of Agricultural Pests. University of California Press, Los Angeles, United States.
Delvare, G. 1984. Cycle biologique et reproduction de Prionmitus mitratus Dalman, un important parasite des psylles du poirier et de l’aubepine. Bull SROP 7(5): 184-190.
Dijkstra, L. 1986. Optimal selection and exploitation of hosts in the parasitic wasp Colpoclypeus florus (Hymenoptera: Eulophidae). Netherlands Journal of Zoology. 36: 177-301.
Gruys, P. and F. Vaal. 1984. Colpoclypeus florus, an eulophid parasite of tortricids in orchards: Rearing, biology and use in biological control. Entomologia experimentalis et applicata. 36: 31-35.
Letourneau, D. K. and Altieri M. A. 1999. Environmental Management to Enhance Biological Control in Agroecosystems, pp. 319-354 In: Handbook of Biological Control (T Bellows and T. Fisher, eds), Academic, San Diego.
Murphy B. C., J. A. Rosenheim and J. Granett J. 1996. Habitat diversification for improving biological control : Abundance of Anagrus epos (Hymenoptera: Mymaridae) in grape vineyards. Env. Entomol.25: 495-504.
Nguyen, T.X., Delvare, G., and Bouyjou, B., 1984. Biocenose de psylles du poirier dans la region Toulousaine, France, Bull. SROP 7 (5) : 191-197.
Pfannenstiel, R. and T.Unruh. 2003. Conservation of leafroller parasitoids through provision of alternate hosts in near-orchard habitats. Pp 256-262. In: Proceeding 1st International Symposium on the Biological Control of Arthropods. USDA Forest Service Publ. FHTET -03-05.
Pfannenstiel,R. S., T. R. Unruh and J. F. Brunner. 2000. Biological Control of Leafrollers: Prospects using habitat manipulation. WA Horticultural Association, 95: 145-149.
Parasitism was assessed by deployment of sentinel 4th instar OBLR directly onto the leaves of apple or cherry trees and exposure of these to parasitism for 2 weeks. Larvae are then collected and reared to adults using clean apple leaves as food as needed. Parasitism is calculated from the proportion of parasitized hosts where parasitoids emerged divided by the total number of moths emerged plus parasitized hosts. To initially infest gardens, leafroller-infested foliage is placed on to growing strawberry and rose foliage in the early fall following planting and again during the following summer. In most cases this approach has led to establishment of this leafroller. In some instances the infestation procedure was repeated during a second summer. Parasitism of Ancylis in gardens was based on collection of Ancylis from a fixed number of leaves of strawberry or terminal shoot of rose plants.
1. Demonstrated spatial patterns of parasitism by C. florus in spring were associated with the nearby gardens on the orchard perimeter (2005).
2. Demonstrated that 78% of gardens (31 of 40) harbor the beneficial leafroller Ancylis comptana and of the 8 orchards showing no parasitism by C. florus, 7 were adjacent to a garden with no SLR.
3. Parasitism of Ancylis in gardens by C. florus was higher for Ancylis found high up in the foliage, with parasitism much higher in experimentally elevated strawberry foliage compared to strawberry foliage on the ground or Ancylis in leaf rolls of low-hanging rose foliage.
4. Virtually 100% parasitism of Ancylis in roses was seen by October while only 50% of Ancylis were parasitized in strawberries at the same time, supporting the idea that strawberries help maintain this 2 species trophic system in the gardens
5. A website was created to describe planting, placement, and maintenance of gardens with links to articles, essays and websites on why do this habitat manipulation and the biology of the pests and beneficial insects. Seven formal presentations were made and multiple site consultations were provided prior to and during new garden establishment by growers.
Accomplishments under objective 1:
Success in enhancing biological control of leafrollers through habitat manipulation first requires the presence of a stable population of the alternative/overwintering host, Ancylis comptana. Ultimately 78% of gardens were successfully infested with Ancylis (Table 1) and there was a trend that the chances of success increased when a healthy understory planting of strawberries persisted (strawberries are the preferred host of Ancylis comptana). Ninety percent of gardens with Ancylis showed parasitism by C. florus in adjacent orchard.
Our traditional season-long studies of parasitism were restricted to 11 orchards in 2005 and in general we found lower than normal parasitism rates. However, the seasonal pattern observed from sentinel deployments of OBLR in orchards demonstrated high spring and summer parasitism due to C. florus at some sites while later in the season parasitism was almost uniformly high. (Figure 1). A seasonal long monitoring adjacent to four gardens is depicted in Figure 2.
In 2006 we focused on patterns of parasitism early in the season when parasites are just entering orchards from adjacent garden overwintering sites. This contrasts with the work in the preceding five years when parasitism through the season in orchards was monitored. In early spring of 2006 sentinel leafrollers were deployed around the periphery and internally in a 100 acre IPM orchard which has 4 gardens planted also on its periphery. Parasitism around the perimeter was associated with garden sites (red dots) and surprisingly all interior sites show spring parasitism (Figure 3).
The presence of C. florus attacking sentinel larvae in the interior early in spring suggests at least 3 nonexclusive hypotheses that merit future research: H1) larger than exptected pest leafroller larvae are present in the orchard in fall and are attacked by C. florus late enough in the season that the wasps diapause and overwinter. This may arise from some segment of the normal overwintering generation of OBLR larvae attaining 4th instar in the fall (or larger), or the presence of laggard larvae from the first generation. These effects may also be induced by insecticides which delay insect development. H2) There is an alternative host other than OBLR, or Pandemis in the orchard interior. H3) C. florus readily flies deeper into the orchard, but not around its periphery, to search for hosts.
Accomplishments under Objective 2.
To date we have presented our results of the first year of this WSARE project at the third National Organic Tree Fruit Symposium held in Chelan WA in June 2005 and at the Washington Horticultural Association Convention held in Wenatchee in December 2005 and 2006. We also provided written, oral, and poster reports to the Washington Tree Fruit Research Commission in February 2006 and oral presentation to the 79th annual Western Orchard Pest Management and Disease Workshop in Portland Oregon in January 2006. See Publications and outreach below.
Accomplishments under objective 3.
Studies of the phenology of Ancylis and C. florus in the gardens were conducted in 2006 and 2007. Data from 2006 demonstrate the preference of C. florus in attacking Ancylis higher in the foliage both experimentally (strawberries exposed at different heights; Figure 4, left panel) and in comparisons of strawberry and the taller rose foliage (Figure 4, right panel). Also, parasitism of SLR increases tremendously in late summer into fall with parasitism of roses approaching 100% while that on strawberries ending up just over 50%. This demonstrates that strawberries can complement roses by providing a refuge from parasitism for the SLR. This refuge prevents the wasp from completely decimating the host leafroller in fall-winter (Fig. 4b below right).
In 2007 a mixed garden of roses and strawberries was studies intensively, sampling strawberries weekly to biweekly depending on weather. Roses were sampled for fewer dates because they are leafless for a longer period than are strawberries. The counted number of Ancylis in each life stage on both plants suggests two generations each year but shows striking differences between the two plants. Two well developed generations of Ancylis is evident in the strawberries with a partial third generation suggested (Figure 5). In contrast barely two generations are completed on the roses, with the first generation of eggs not visible in the roses at all, suggesting eggs are laid someplace other that the shoot terminals that we sampled (Figure 6). Taken together Figures 5 and 6 validate the 2006 season observations and suggest strongly that the ideal garden would be a combination of rose and strawberry. We propose that this is best arranged by planting rose and strawberry in clearly separated plots that are near one another. Physical seperation enforced by absence of irrigation should prevent the highly aggressive roses from overgrowing the strawberries.
Finally, we have collaborated with Dr. Vince Jones (Washington State University, Tree Fruit Research and Extension Center, Wenatchee WA) in developing a method to mark C. florus at gardens and capture them in orchards in order to determine the best placement and number of gardens in orchard landscapes. The preliminary work has resulted in a method to mark the wasp as it naturally emerged from the rose gardens and to capture it on host-baited traps. To date, the largest distance from a garden we have captured marked C. florus (in an orchard) is 128m.
There are two measurable impacts that may stem from this work. The first is an increase in parasitism of leafrollers in orchards adjacent to gardens infested with SLR. We have documented increased parasitism in several cases at the outset of this study but most orchards have not been monitored since 2005. Second is a reduction in pesticide use (and concomitant improved biological control for other pests). We have not closely monitored pesticide use practices with some 25 orchards (40 gardens, 60 plus adjacent orchard blocks). In the most recent statewide grower survey (2001) more than 80% (160,000 acres) of the pome fruits in Washington were treated with Lorsban for leafrollers, and more than 50% used Success, Intrepid, Esteem or Bt. Subsequently, Lorsban is being largely replaced by the neonicotinyl insecticides, which also have broad spectrum activity. Reductions in pesticide sprays are intimately tied to grower adoption of the gardens. There is no information on how much of this pesticide use is prophylactic and the industry does not maintain consistent records of leafroller damage on these commodities. Wherever we sample orchards intensively we find leafrollers, suggesting that if growers want prophylactic insecticidal control, they will find leafrollers in their orchards or traps that supports this desire. We have seen that familiarity with the rose gardens changes the producer’s mindset. They begin to think of the effect the sprays have on beneficials and become reticent to spray unless they have high levels of leafrollers in the spring generation.
Educational & Outreach Activities
Presentations to grower groups or pest managers:
Unruh, T. 2004. Leafroller Biocontrol Enhanced Near Rose and Strawberry Gardens: An Update. 78th Western Orchard Pest and Disease Management Conference, January, Portland, OR
Unruh, T., C. Peters and F. De LaRosa. 2004. Leafroller biocontrol enhanced by rose gardens: a continuing saga. 99th Ann. Meeting, Washington Horticultural Assoc. December (poster)
Unruh, R. Gardens of multifloral rose enhance biological control of pest leafrollers
in pome fruits in the Northwest. Pacific Branch of the Entomological Society. 2005
Unruh, T. J. Brunner, C. Peters and F. De LaRosa. 2005 Rose and strawberry plantings adjacent to orchard to enhance leafroller biological control. 3rd International Organic Tree Fruit Research Symposium, Chelan Washington. (poster)
Peters, C. and T. Unruh. 2005. Gardens for leafroller biological control: A five year summary. 100th Ann. Meeting, Washington Horticultural Assoc. December (poster)
Unruh, Tom and Cathy Peters. 2006. Rose-Strawberry Gardens to Enhance Parasitism of Leafrollers: A 5th Year Update. 80th Western Orchard Pest and Disease Management Conference, January, Portland, OR
Peters, C. and T. Unruh. 2006. How does your garden grow? Design, placement and managmement of rose and strawberry plantings to enhance leafroller parasitism in orchards. 101st Ann. Meeting, Washington Horticultural Association. December (poster).
Unruh, T. 2007. Multi-floral rose: A Great Basin riparian habitat element that enhances sustainability of commercial pome fruits. Join meeting, Society for Ecological Restoration International/Society of Wetland Ecologists, NW chapters. Yakima WA
Unruh, Tom and Jay Brunner. 2005. Rose and Strawberry Plantings Adjacent to Orchard to Enhance Leafroller Biological Control. Proc.3rd National Organic Tree Fruit Research Symposium. June 2005, Chelan, WA.. Pp. 41-42.
Jones, V., T. Unruh D. Horton and J. Brunner. 2006. Improving apple IPM by maximizing opportunities for Biological Control. GoodFruit Grower, December 2006.
Pfannenstiel1 R. S., T. R. Unruh and J. F. Brunner. 2008. Overwintering hosts for the exotic leafroller parasitoid Colpoclypeus florus (Hymenoptera: Eulophidae): implications for habitat manipulation to augment biological control of leafrollers in pome fruits. J. Insect. Sci. (in press).
Pfannenstiel, R.S. and T. R, Unruh. (in manuscript). Landscape patterns of parasitism of leafrollers in pome fruit orchards in the Yakima Valley of Washington.
Pfannenstiel, R.S. and T. R, Unruh. (in manuscript). An alternative leafroller host found in wild rose patches enhances parasitism of pest leafrollers in pome fruit orchards.
Unruh, T. R. and R.S. Pfannenstiel. (in manuscript). Planting of rose and strawberry habitats adjacent to pome fruit orchards to increase parasitism of pest leafrollers.
We have created a website (http://www.ars.usda.gov/Research/docs.htm?docid=14646) describing how to implement gardens including how and where to plant and maintain the roses and strawberries, where to find infested roses for transferring Ancylis to a new garden, and overviews of our results for the last 5 seasons. The website also provides links on insect biology and to articles and reports related to this work. While we will continue to provide information to growers on how to create gardens through direct contacts, the new website represents a decentralized approach for growers to get this information
No economic analysis was possible. See impact statement.
Seven new gardens were added during the course of these studies, affecting some 2,000 acres of tree fruit. We also have been contacted about a fairly large implementation that will occur in 2008.
Areas needing additional study
Long-term behavior of the gardens and impact assessments of parasitism are clearly needed. We are currently planning on evaluating the behavior of 1 or two gardens each year with the assistance of growers or field IPM personnel. The size of gardens required influencing a fixed acreage of orchard and the distance which C. florus can move is closely related and require additional studies.