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2001 - 2002 CUIPM Grants -
Final Reports
Management of Pests on Medicinal Plants and Influence of Pest Damage on Active Principle
Project Leader/Cooperators:
B. Merle Shepard
Principal Investigator
Professor of Entomology and Director
Coastal REC
Clemson University
James Rushing
Associate Professor of Horticulture
Coastal REC
Clemson University
Robert Dufault
Professor of Horticulture
Coastal REC
Clemson University
Richard Hassell
Assistant Professor of Horticulture
Coastal REC
Clemson University
Anthony Keinath
Associate Professor of Plant Pathology
Coastal REC
Clemson University
Mr. Russell Duncan
County Agent -Clarendon
Mr. Harry Durant
Double D Farms
Gable, SC
Dr. Gloria McCutcheon
Associate Professor
Coastal REC
The major objectives of this project were to:
- Determine the major species and seasonal abundance of insect pests and beneficial insect species associated with 5 medicinal plant species grown on bare ground and with "living mulch".
- Identify major plant diseases and their severity throughout the season.
- Develop and test alternatives to chemical pesticides, eg., botanicals, microbial agents, oils or soaps, etc., for control of pest species that are identified as economically important.
- Determine the influence of insect damage on active principle.
- Assess the growth and production of medicinal plants under grower conditions.
Results (2000-2001)
Cultural Systems
A key component of IPM is "growing a healthy crop". A large part of this year's work focused on developing cultural systems for the 5 species of medicinal plants. Insects and plant diseases also were monitored and selected samples were dried and the active principle determined.
Three cultural systems were evaluated for feasibility of producing the five medicinal crops including feverfew, Echinacea purpurea and E. pallida, St. Johnswort, and Valerian. The cultural systems included bareground with minimal fertility, bareground with high fertility, and black plastic mulch with high fertility. All plots were drip irrigated, periodically fertigated, and hand-hoed. All plots were sampled at 3 week intervals with a back-pack suction sampler for insects.
Feverfew: Two seed sources of green feverfew were obtained, one from Richter's Seed (Ontario) and the other from Johnny's Seed (Maine). Another type of feverfew referred to as golden feverfew from Richter's was also field transplanted in spring, 2001. Green feverfew were harvested at the following growth stages: 1.) foliar stage, 2.) pre-bud stage, and 3.) full flower stage. Golden feverfew was harvested in the foliar stage on the first and second harvest periods. The plants were separated into leaf, stem and flower parts in the second and third harvest stages and parthenolide (marker compound of commercial interest) determined for all stages. In the first harvest, both Richter's green and golden feverfew had over 5 times the marker compound than Johnny's green feverfew. Fresh weights of all feverfew were enhanced on plastic mulch, but marker compound was unaffected by fertility differences with any of the three feverfew. Marker compound in golden feverfew, however, increased with the mulch system due to a "mulch effect", not fertility effect. In the second harvest at bud stage, Richter's green feverfew had high marker compound in all three plant parts with flower buds having the highest marker compound, followed by leaf material and stems. Johnny's feverfew, on the other hand, was very low in marker compound in all plant parts to the point that it was not useable for dietary supplements no matter what cultural system used.
A low infestation of the leafminer, Liriomyza trifolii, was observed attacking the leaves but populations did not develop to levels that were considered economically important. There were rich communities of beneficial insects and spiders and no pesticide applications were necessary.
Echinacea: E. purpurea and E. pallida species require at least one full year of growth before root harvest. Growth of E. purpurea has excelled on the plastic mulch system. Less foliage was produced, even at the same fertility, level on bare ground. Apparently, E. purpurea responds to a "mulch" effect similar to feverfew. E. pallida grew slowly during the first season with root disease problems induced by a long dry spell followed by 3 to 4 inch rainfalls. E. pallida may respond better to summer planting versus spring planting to take advantage of maturing in cooler climates of fall. Root harvests will occur in December, 2001.
St. John's wort: This crop grew well through the early season and flowered in the first year within 4 months after planting, which is very unusual. Plant growth appeared to excel on the mulch system, however, by late July, the entire collection of plants in all systems died due to southern blight. Clearly, this species has no tolerance to this disease. Other potentially important varieties of Saint John's Wort need to be evaluated to find one that thrives in our environment and tolerates southern blight. Similar to E. pallida, Saint John's Wort may respond better to summer planting versus spring planting to take advantage of maturing in cooler climates of fall and avoidance of the conditions that exacerbate southern blight. As with feverfew and Echinacea spp., no damaging insects were present.
Valerian: Valerian struggled in growth in all three cultural systems showing a tremendous diversity between individual plants within each system. By mid-August, all mulched valerian had died, but valerian grown at high fertility on bare ground was struggling, but still alive. Valerian succumbed to disease that is exacerbated by moisture and mulch retains too much water. Similar to E. pallida and feverfew, valerian may respond better to summer planting versus spring planting to take advantage of maturing in cooler climates of fall and avoidance of the conditions that enhance disease. Surviving valerian will be harvested in August, the roots air dried and replanted in mid-fall into fresh beds for continued growth into the fall and winter. Expected harvest will be in late spring, 2002. Again, natural enemies probably took care of any potential problems by plant feeding insects and mites so no outside interventions were necessary.
Results (2001-2002)
Feverfew:
Grower participation: Mr. Harry Durant, Double D Farms in Manning, SC, successfully grew feverfew and valerian on black plastic mulch in a production system that was essentially like that used for vegetable production. Mr. Russell Duncan, County Agent for Clarendon County led this effort. Periodic sampling by vacuum suction device and whole plant inspection revealed that plant-feeding insect did not reach economically-important levels. Rich communities of predators were found in feverfew after the crop canopy begun to develop. The major pest complex encountered was weeds. Clearly, a system is needed for weed control that does not rely on chemical herbicides. Cultural techniques (frequent cultivation) may be one option.
Postharvest: Infestations by the cigarette beetle (see photo 1) was a major postharvest/storage problem that rendered the harvested feverfew from growers' fields unmarketable. Prevention of infestation by the beetle is probably the simplest and most practical approach. It is advisable to keep the stored product out of the tobacco warehouse after curing, packing in clean boxes, taping the boxes closed, and holding them in low-humidity temperature-controlled storage. Implementation of these Good Agricultural Practices (GAPs) effectively resolved the infestation problem that had previously rendered the crop unmarketable. Handling feverfew in a tobacco handling system that involves baling the product in a warehouse where tobacco is present is not an acceptable method for preparing the crop for storage. In addition to the beetles, the presence of mold, sand, and weeds also precluded sale of the baled product, but this was also resolved with the implementation of GAPs.
Photo 1: Cigarette Beetle (Lasioderma serricorne)
Future work with feverfew must either include storage and handling protocols that preclude infestation or must include a treatment that either repels or kills the pests when they try to enter the product.
Production practices/Variety Selection: A major part of IPM is based on the principle of "growing a healthy crop". Thus, identification of the most efficient elements that go into production practices is essential. This includes varietal selection, fertility, and the use of mulch compared to bare ground. Production practices also may influence levels of active principle.
Yield and quality of two varieties of green feverfew (Richter's Green and Johnny's Green) and one variety of golden feverfew (Richter's Golden) were compared. The first determinant of success is the production of biomass. Figure 1 illustrates that highest biomass production was with Richter's Green and Johnny's Green varieties grown with high fertility and mulch.
Figure 1
Foliage yield of Golden feverfew was unaffected by production system. This data negates the idea that a mulch effect reduces yield as originally hypothesized and, in fact, this mulch effect is very beneficial to increase yield. Additionally, Golden feverfew has been recommended as the best variety to grow for marker compound (parthenolide), but the biomass production of this dwarf variety renders it a very unsuitable biomass producer.
The second critical need with feverfew is a high concentration of parthenolide. Figure 2 illustrates the differences among varieties and cultural systems.
Figure 2
Johnny's variety was found to contain very little parthenolide and even though this variety produced the highest biomass, the concentration was so low in the foliage that the quality of the yield would be considered unacceptable and very poor. Richter's Green, on the other hand, was adequately fortified with marker compound and when grown with mulch and high fertility, the yield of parthenolide per plant greatly exceeded all other systems. The "ingredient" in the mulch/high fertility system that enhanced yield the most was the mulch since high fertility in bare ground plots did not boost parthenolide content to the same extent as the mulch/high fertility systems. In order to further increase both biomass and marker compound content to higher levels the bare ground culture, and Golden and Johnny's Green varieties will be abandoned in favor of Richter's Green variety. This experiment verifies that the mulch/high fertility system and Richter's Green variety are the best systems evaluated in this study for yield.
Insects: This medicinal plant has a well-developed canopy and the diversity of insect that occupy it is usually high (figure 3).
Figure 3
In general, a rich community of predators (see major ones in photograph 2) and parasitoids keep pest populations in check but this year (2002) there were two arthropod pest outbreaks. One involved Thrips nigropilosus that attacked the crop in massive numbers and killed many of the plants (see photograph 3).
Photo 2: Major predators of insect pests
Photo 3: Feverfew damaged by Thrips nigropilosus
Although many of the plants died, those that survived recovered and it is likely that major predator species had a major impact on populations of T. nigropilosus. Treatments including Neem, Spintor, Trilogy and control were applied, but in all treatments, the population of the thrips declined rapidly over a 5-week period (Figure 4). Populations decline more rapidly, however, in the Spintor treatment. The presence of T. nigropilosus is a new record for the Charleston area.
Figure 4
Leaves with feeding damage by the thrips were assayed to determine if thrips feeding influence the level of active principle (parthenolide). Leaves were dried, suspended in a solvent and parthenolide analyzed using HPLC. The active principle was reduced in leaves that were damaged by thrips compared to leaves with no thrips feeding.
The second major pest outbreak on feverfew involved an unknown noctuid that we keyed in our laboratory as Agrotis sp. (see photograph 4 and 5) (currently awaiting verification by experts). Interestingly, some varieties of feverfew were not attacked but Richter's Golden variety was completely defoliated by this pest (see photograph 6).
Photo 4 and 5: Agrotis sp.
Photo 6: Feverfew plants damaged by Agrotis(?) larvae
Feverfew supported the most abundant and diverse group of predators (Figure 5). This was likely due to the well-developed canopy. Spiders, fire ants, and geocorids were particularly abundant. Geocorids were an abundant predator on all 4 species of medicinal plants that were monitored.
Figure 5:
Echinacea spp.
Plant Pathogens:Southern blight was observed on Echinacea spp. in Charleston in late August 2002. This medicinal plant may be more susceptible to this disease than previously thought. Plans are being made to screen different Echinacea spp. to see if any are more tolerant to the pathogen than others.
Insects: As in the previous year, whiteflies (see photograph 7) (Bemisia argentifolia) attacked a late planting of Echinacea. In addition, for the first time, the sunflower moth infested the dried seed heads. In a random count, the sunflower moth (Homeosoma electellum) larvae (see photograph 8) infested 49 out of 50 seed heads. While not important on the growing crop, strategies for controlling this pest should be developed for protecting the drying seed heads. Later studies will evaluate microbial and botanical materials for control of this pest.
Photo 7: White Flies
Photo 8: Sunflower Moth
St. John's wort
This medicinal plant appears not to be well adapted to the area. Although we did not find major insect pests at population densities that were affecting the crop, it is very susceptible to southern blight. In addition, the growth habits suggest that it is not adapted to our soil and/or weather conditions.
Valerian
This plant is slow growing and did not form a lush canopy. Arthropods associated with it are shown in figures 3 and 5. Except for one date where populations of the false chinch bug were exceptionally high, most other arthropod species (both pest and beneficial) remained low throughout the season.
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Questions or comments:
Amy Nichols
Associate Coordinator
IPM and
Sustainable Agriculture
Programs
Contact
Dr. Geoffrey Zehnder
Professor of Entomology, Soils & Plant Sciences
IPM and
Sustainable Agriculture
Programs
114 Long Hall, Box 340315
Clemson, SC 29634-0315
864 - 656 - 6644
Contact
Last revised:
8/4/2006 |
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