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Funded Project |
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Funding Program:
Regional IPM Competitive Grants - Northeastern |
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Project Title:
Parasitoid Evaluations: A New Paradigm |
Project Directors (PDs):
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Lead State: RI Lead Organization: University of Rhode Island |
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Cooperating State(s):
Connecticut, Massachusetts |
| Research Funding: $100,000 |
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Start Date: Jul-01-2000 End Date: Jun-30-2003 |
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Pests Involved: lily leaf beetles |
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Site/Commodity: lily, lilies, flowers, nursery, greenhouse |
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Area of Emphasis: biocontrol, biological control |
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Summary:
The lily leaf beetle, Lilioceris lilii, first officially reported in the U.S. in 1992, has become a serious pest of native and cultivated lilies throughout its New England distribution. It is now present in every state in New England and is spreading rapidly. With no effective North American natural enemies, this exotic insect is eliminating native lilies from its range and causing growers to use insecticides or remove lilies from landscapes. It is capable of spreading throughout North America. Based upon the severity of the problem and the probability of solving it through biological control, the USDA in 1999 ranked the lily leaf beetle 7th among national biological control priorities.
In four seasons of research in Europe, we have determined that this insect is under natural control there and we have identified 6 European parasitoids. Several of these may have potential for introduction into North America. We propose to continue researching biological control of this pest. We have already released Tetrastichus setifer, a host-specific parasitic wasp that is widely distributed throughout Europe. This parasitoid shares many characteristics with T. julis which was so successful in solving the cereal leaf beetle problem in the in the Midwest in the 1970's. We plan to follow T. setifer establishment and measure its spread and impact from the initial release site near Boston. We also plan two additional releases of this parasitoid to determine its effectiveness over a larger geographic area. While we assess the impact of the already-released parasitoid, we will conduct studies in our quarantine lab and direct field and laboratory studies in Europe to allow ranking of the additional parasitoids for their potential as biological control agents in North America. Studies on host specificity, fecundity, synchrony, European distribution, and competitive interactions will allow us to develop a profile on each species and its potential to interact with the host and other parasitoids. This will allow an orderly introduction of additional parasitoid species, if they are needed. It may also serve as a prototype for future evaluations of potential biological control agents and may provide some insight into the selection of additional European parasitoids against some closely related criocerine pests, including the two species of asparagus beetles. We believe that studies of chemical ecology of pests, plants, and parasitoids can be very useful in predicting parasitoid behavior and that they can be an important supplement to host specificity studies. We propose to continue preliminary research showing that some of our parasitoids are highly attracted to lily leaf beetle-damaged plants and that they lay their eggs in response to the fecal shields which lily leaf beetle larvae carry on their backs. A parasitoid that is so intimately related to its insect host and its host plant, is highly unlikely to attack some other host in a new environment. We expect that T. setifer will result in a high level of parasitism, eventually reducing populations of L. Iilii and the damage they cause in the Northeast. We plan to distribute parasitoids throughout the region through cooperation with the Massachusetts Horticultural Society, the North American Lily Society, and bulb distributors. THE PROBLEM, BACKGROUND, AND JUSTIFICATION The Pest. The lily leaf beetle, Lilioceris lilii, has one generation per year in New England, overwintering as an adult before emerging in April/May when it begins feeding. Adults cause minor feeding damage and oviposit primarily during May. Larvae feed extensively from late May to mid July. The 5/8 inch long larvae carry their excrement on their back (referred to as a fecal shield). This behavior is effective in repelling many predators, but makes them highly repulsive to gardeners. Without suppression efforts lilies are totally defoliated by larvae and most growers respond by using insecticides or eliminating their lilies. Adult beetles emerge and feed in late summer before overwintering. Host Plants. Lilioceris lilii defoliates all species of Lilium in its host range, including L. giganteum, L. martagon, L. tigrinum, L. candidum as well as Asiatic and Oriental hybrids. It extensively damages Fritillaria sp. and causes minor damage to several Solanum species, including S. tuberosum, potato). In addition to damaging cultivated lilies, L. Lilii impacts native plant communities. There are 21 species of lilies that are native to North America including 8 that are found east of the Rocky Mountains). Three of these species lie within the current range of L. Lilii ( Lilium canadense, Lilium philadelphicum, and Lilium superbum). Wild populations of these native plants will be severely impacted by L. Lilii throughout their range as they have near Boston. As the lily leaf beetle continues to spread throughout North America, pesticide use against this pest will increase and fewer gardeners will grow lilies. The use of insecticides against L. Lilii can expose applicators, generally untrained gardeners, to organic phosphate and carbamate insecticides. (Most Boston gardeners use diazinon or carbaryl against this pest.) This presents some risk to these individuals and their families, particularly if the insecticides are improperly applied or stored. Natural Enemies. To date, no insect natural enemies have been reported on L. Lilii in North America. We have seen no evidence of parasitism in 6 years of examining L. Lilii life stages from the Boston area. In Europe, where L. Lilii is native, it is not considered a problem. We have found it to be under good natural control there from the actions of 6 species of parasites: 5 wasps and a parasitic fly. Our plan is to evaluate these parasitoids and determine which would work best, either singly or in combination to control L. Lilii in North America. We will then work through appropriate USDA procedures for securing release permits, make releases and follow-up studies, and make further releases as necessary. Research Goals and Obiectives. The long-term goal of our research on L. lilii is to bring this pest under biological control in North America and in the process, to advance the science supporting classical biological control. Lioceris lilii is a serious problem, but not an emergency. It affords us the opportunity to carefully evaluate European natural enemies and to make important advances in this process. Our research program has progressed to a point where we have released one parasitoid in New England and we have 5 other European parasitoids to consider. We have 3 objectives for which we seek support in this proposal. Objectives: 1. To evaluate the parasitoid Tetrastichus setifer in field releases against the lily leaf beetle in New England, determining if it is adequate to control this pest. Our goal for 2000 is to check for establishment of a French strain of T. setifer we released in 1999 at the Massachusetts Horticultural Society's Elm Bank facility and to release additional French parasitoids there, comparing their performance with Swiss populations which we will release at two other sites (one in MA and one in RI). In 2001 we will monitor parasitoid performance at all sites, comparing parasitoid populations for synchrony, distribution, and impact on the larval population of L. Iilii. While this objective is clearly directed toward solving this particular problem, it also sets a standard for careful evaluation of field releases and testing of multiple parasitoid strains. This approach (in conjunction with objective 2) may allow biocontrol specialists to revisit some of the programs against other criocerine pests that have been less than completely successful in North America. These pests include the asparagus beetles (Crioceris asparagi, and C duodecimpunctata, and the cereal leaf beetle (Oulema melanopus). All three pests have many natural enemies in Europe, some of which may be more effective than already-released material in parts of their North American ranges. 2. To evaluate additional European parasitoids of L. lilii, determining which (if any) would be the next candidate for release into New England if T. setifer does not provide adequate control. While we assess the impact of the already-released parasitoid, we will conduct laboratory studies in quarantine and direct field and laboratory studies in Europe to allow ranking of the additional parasitoids for their potential as biological control agents in North America. Studies on host specificity, fecundity, synchrony, European distribution, and competitive interactions will allow us to develop a profile on each species and its potential to interact with the host and other parasitoids. This will allow an orderly introduction of additional parasitoid species, if they are needed. It may also serve as a prototype for future evaluations of potential biological control agents. 3. To investigate the chemical ecology of European parasitoids of L. lilii in relation to their host insects and host plants, as a means of understanding and perhaps validating results of host specificity studies. We propose to continue research on the chemical cues involved in host finding and acceptance by our biocontrol candidates. Preliminary studies show that at least two of the parasitoids under consideration are highly attracted to lily leaf beetle-damaged plants and that all candidate species oviposit in response to lily leaf beetle fecal shields. |
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