Grantee Research Project Results
Final Report: Low-cost Pheromone Traps and Insect-Resistant Varieties of Tomatillos: Sustainable Tools to Achieve Reduction in Pesticide Use and Diminish Damage by the Fruit-Feeding Caterpillar, Heliothis subflexa Guenee (Noctuidae) in the State of Jalisco, Mexico
EPA Grant Number: SU831862Title: Low-cost Pheromone Traps and Insect-Resistant Varieties of Tomatillos: Sustainable Tools to Achieve Reduction in Pesticide Use and Diminish Damage by the Fruit-Feeding Caterpillar, Heliothis subflexa Guenee (Noctuidae) in the State of Jalisco, Mexico
Investigators: Gould, Fred , Lopez, Guillermo Gonzalez , Groot, Astrid , Schulze, Birgit , Schiers, Jan , Bateman, Melanie , Benda, Nicole
Institution: North Carolina State University
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 15, 2004 through September 14, 2005
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2004) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Sustainable and Healthy Communities , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities
Objective:
In West-central Mexico, the tomatillo (Physalis philadelphica Lam.) is a fundamental feature of people's day-to-day diets, and, as such, it is an important crop. Within Mexico, cultivation of this plant is shifting from small, intercropped farms to larger monocultures. Thus far, sustainable control measures have not been developed to respond to changes in scale and concomitant increases in herbivore pressure. Caterpillars of the species Heliothis subflexa Guen�e (Noctuidae) are the primary agents of damage to tomatillo fruits, and, at present, broad spectrum pesticides are used to control H. subflexa. Our major objective with our P3 project is to research, develop, and deploy tools that farmers can use to sustainably manage this herbivore. To achieve this goal, we are pursuing two strategies. As an immediate means of pesticide and damage reduction, low- cost pheromone-baited traps can be used to detect early stages of H. subflexa infestation and limit the application of control measures to "hot spots" where they are needed. A more direct means by which pesticide applications and H. subflexa damage may be reduced is the development of H. subflexa resistant varieties of the tomatillo. In phase I, we are identifying compounds present in Physalis plants that confer resistance to H. subflexa.
Summary/Accomplishments (Outputs/Outcomes):
Our team has evaluated several avenues by which the herbivore H. subflexa may be managed sustainably. Our results to date indicate that some traditional integrated pest management methods can not be applied successfully to this system. Scouting for eggs of this insect is impractical, and parasitoid releases would be ineffectual because this insect behaviorally escapes its natural enemies. Given the biology of H. subflexa aid the tomatillo, we feel that an indirect method of population monitoring (rather than scouting for eggs) would enable farmers to detect early stages of infestation by this herbivore. In phase I, we compared moth capture using inexpensive P3 traps and commercial traps. Tn August and September of 2004, we followed H. subflexa damage and moth capture in the two trap types at eight sites distributed throughout the state of Jalisco. We checked traps every three weeks, and found the moth capture was a positive indicator of H. subflexa damage. Within this long time frame, it was impossible to evaluate the relationship between moth capture and subsequent infestations. Often the moths in the traps had been partially destroyed by ants and spiders. In October and November, we took data every three days on moth capture and H. subflexa damage at four tomatillo farms. We found no statistical difference in the effectiveness of two trap types. In the second study, male moth capture was positively correlated to subsequent damage by H. subflexa. In a third study, we analyzed the composition of pheromone blends of H. subflexa females collected in three different regions (Florida, North Carolina, and Texas). We found that composition of pheromone blends varied regionally and that this variation lead to differences in attraction of males.
A direct method to both reduce pesticide use and H. subflexa damage would be the development of H. subflexa resistant varieties of the tomatillo. Through interviews with tomatillo growers, we have found that farmers across the board are receptive to trying new seeds. To move towards the goal of H. subflexa-resistant tomatillos, we are identifying plant compounds associated with resistance to feeding by H. subflexa. Previous studies have found that fatty acid and alkaloid content of some Physalis plants affect insect feeding, growth, and survival. Thus far, the secondary chemistry of the majority Physalis species has not been studied nor is its impact on H. subflexa known. With partners at the Max Planck Institute of Chemical Ecology, we are investigating these plant compounds and how they affect H. subflexa. We are growing the tomatillo and 12 other Physalis species. We are evaluating the fatty acids and alkaloids (specifically calystegins) content of our greenhouse plants. To assess how they H. subflexa survivorship, we are carrying out feeding assays using Physalis fruits.
Conclusions:
At present, within the same basic geographic area of Mexico, horticultural practices differ widely. Of the farms that we have visited, some were no-till and intercropped with several plant species whereas others were weed-free and exclusively planted with tomatillos. The number of tomatillo plants ranged from four or five squeezed into a small kitchen garden to 80 hectare farms. Some farmers use chemicals whereas others do not. With regards to culture, education, and socio-economics, the communities can be worlds apart. For instance, some farmers have little or no formal education whereas other farmers have university degrees in agronomy. We visited farms in indigenous communities in Guerrero where Spanish was spoken as a second language. Given that our inexpensive P3 trap was as effective as the commercial trap, we feel that this tool could be made available to farmers across a wide range of socioeconomic circumstances. Another variable that was strongly related to H. subflexa damage was fruit abscission. Taken together, the two variables may enable farmers to evaluate when and where control measures are needed. Benefits of this approach will be greater if it is taken in conjunction with the use of biocontrol agents like pathenogenic fungi. The development of hybrid-tomatillos may still be a long term goal, but the identification of intrinsically resistant strains of wild tomatillos is immediately achievable. This is a laudable aim in that reduction in pesticide use will be "built-in". Farmers will be able to reap immediate and tangible rewards.
Proposed Phase II objectives and strategies:
In phase II, we will begin by developing region-specific pheromone lures. We will fine tune the population monitoring protocol, and we will assess whether incorporating other variables like fruit abscission improves pest prediction. We will also establish spray/no spray guidelines for farmers. In field studies conducted throughout West-Central Mexico (2002-2004), we have observed differences in infestation by H. subflexa to wild tomatillo populations. This may indicate that tomatillo landraces vary in terms of resistance to H. subflexa. In phase II, we will collect tomatillos from landrace populations with both high and low infestations of H. subflexa. We will grow these tomatillo plants under controlled conditions in the greenhouse, and we will use their fruits in bioassays in the laboratory. We will screen larval performance on the fruits of the plants from the different accessions. This way, we will be able to gauge whether differences in infestation are due to environmental effects or differences in resistance to H. subflexa. Beginning with the compounds that we measured in Phase I (fatty acid and alkaloid content), we will investigate the underlying plant compounds to which the differences in resistance are attributable.
Finally, during the summer of 2006, we will conduct field trials. We will sow fields with H. subflexa-resistant landrace tomatillos and the commercial tomatillo cultivar "Rendidora" as a control. To monitor H. subflexa populations, we will set up traps baited with region-specific pheromone lures. Biocontrol agents are available both commercially and through the biocontrol program of the University of Guadalajara. To extend the potential for reductions in pesticide applications, we will pair population monitoring via the pheromone baited traps with microbial agents like pathenogenic fungi, and we will assess whether H. subflexa outbreaks can be prevented. For experimental farms that employ the "P3 plan" and control farms where growers manage tomatillo pests independently, we will compare chemical applications, economic inversion, damage by H. subflexa, and yields.
Supplemental Keywords:
integrated pest management, population monitoring, biocontrol, plant chemistry, landrace,, RFA, Scientific Discipline, Sustainable Industry/Business, Sustainable Environment, Environmental Chemistry, Technology for Sustainable Environment, Ecology and Ecosystems, alternative products, environmental sustainability, insect resistant tomatillos, pheromone traps, pesticide alternative, fruit feeding catepillars, agriculture, pollution preventionRelevant Websites:
www.cals.ncsu.edu/entomology/gould/ Exit
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.