The coffee berry borer Hypothenemus hampei is the most important pest of coffee worldwide causing immense economic losses in the main production areas of Central and South America, Indonesia, South East Asia, Hawaii, and Puerto Rico where infestation levels are variable but can reach up to 95%. Like many ambrosia beetles that form galleries for the development of progeny, mated adult CBB females bore into coffee berries to form galleries. CBB is not effectively controlled by the action of parasitoids, the establishment of which in new world coffee has proven difficulty. An early multitrophic study of the coffee agroecosystem using the mechanistic physiologically based demographic modeling approach demonstrated that CBB parasitoids alone were not efficient in controlling CBB. Those findings were confirmed in subsequent restudy of the coffee system using PBDMs that introduced extensive new data from Colombia on the dynamics of coffee growth and development, the effects of solar radiation on foral bud initiation; effects of leaf water potential on breaking dormancy in flower buds; effects of low temperature on photosynthesis and defoliation; enhanced CBB biology and population dynamics including the effects of intraspecifc competition, planting gutter temperature and rainfall on CBB adult emergence; the impact of baited traps for CBB control; and refinements of parasitoid biology and interactions .

These PBDMs provided excellent fits to the field data on coffee growth and development, on CBB dynamics, and provide a solid base for evaluating the efficacy of the four parasitoids singly and in combinations in mitigating the impact of CBB . In this paper, we add to the PBDM system the following factors: Conventional cultural practices using intensive harvesting, cleanup of abscised berries, and insecticides, and biopesticides based on two entomopathogenic fungal species , and two entomopathogenic nematodes , and the interaction of all control components. The scope of the coffee system components included in the analysis are depicted in Fig. 1. Field data are time consuming and prohibitively expensive to collect and are unlikely to yield global conclusion across time and geographic space. Realistic mechanistic weather driven PBDMs used as the objective function in our bio-economic analysis are not constrained by such limitations. There are two main periods of fruit ripening in the Colombian coffee region, April–June, and September–November, but occasional dry periods occur in between that induce the presence of ripe fruits on the plant and abscised fruit on the ground.

Common cultural practices for CBB control are periodic harvesting of overripe and dry fruits on the tree and cleanup of abscised fruit on the ground. Insecticides are commonly used for CBB control, causing mortality of free-flying adult females before they bore into berries. The action of insecticides decreases over 15 days from the time of application. Benavides and Arévalo and Benavides et al. recommended, that chemical control should start 90 days after flowering, when berries have a dry matter content of approximately 20%, and that it should be continued if infestation levels are higher than 2%. However, because berries are often present year around in Colombia, it is difficult to apply this criterion for initiating chemical control. A further drawback is that the chemicals are hazardous to farm workers and adversely affect biodiversity conservation, particularly natural enemies resulting in outbreaks of new pests and contamination of water and soils, but also pollinators potentially resulting in decreased fruit set. Due to these drawbacks, it has been suggested that farmers should increase resources for field sanitation.Sprays infused with the fungus B. bassiana have been reported as an effective control agent of CBB adults. Using B. bassiana as a stand-alone method of control was questioned by Hollings worth et al. The infection rates in the field depend on climatic conditions and strain of the pathogen, with mortality rates ranging from 17.7% at a concentration of 106 conidia/ml to 40.6% at a concentration of 109 conidia per plant, though Bustillo reported mortality as high as 75%.

The spores must come in contact with the beetles, and hence are most infective on new adults emerging from host berries or during the initial phases of fruit penetration. Infection by Metarhizium anisopliae has a similar etiology, with reported infection rates ranging between 22.1% and 43.1%.Nematodes are not widely employed in commercial crops due to their high cost of production. Experimental evidence in laboratory suggests that they could be useful against CBB stages. A field evaluation confirmed that both species can be effective in controlling CBB in abscised fruits in the soil with mortalities of as high as 80% sixty days after the application of 250,000 infective Steinernema sp. juveniles per tree. Similarly, applications of 125,000 infective Heterorhabditis sp. juveniles per tree can cause 75% mortality after 75 days.Several studies have reported the use of parasitoids for control of CBB, and their biology were well documented and modeled by Gutierrez et al. and Rodríguez et al.. The bethylids Cephalonomia stephanoderis, C. hyalinipennis and Prorops nasuta enter the CBB gallery to attack the immature stages. In contrast, the eulophid Phymastichus cofea parasitize female CBB adults as they are burrowing into the coffee berry. Results of Rodríguez et al. show that C. hyalinipennis, interacts negatively with the other betilids and provides poor control of CBB, and this argues against its introduction, and hence was not considered here. The present work explores only the performance of C. stephanoderis, P. nasuta and P. cofea.Geographical coordinates of the localities and weather data used in these simulation studies are listed in Table 1. The field studies for the plant and CBB were conducted for Colombia during 1990–1995and 2009–2010, and during 1982–1986 for Londrina, PR, Brazil . Daily maximum and minimum temperatures , relative humidity , precipitation , and hours of sunshine for Colombia were obtained from data published in the Anuario Meterológico Cafetero. Daily solar radiation was estimated from recorded hours of sunshine using the relationship developed by Prescott. Weather data for Londrina, Brazil were obtained from the Instituto Agronômico do Paraná.Bioeconomics is the study of the economics of renewable resource acquisition and allocation applicable to all trophic levels. In human economies, harvesting of renewable resources occur via the economic system. Econometric marginal analysis is best done with extensive field data, but such data may be difficult to collect and is prohibitively expensive . However, simulation data generated by a well parameterized, field validated mechanistic models can provide a highly suitable alternative because the results can be compared to limited field data. Our PBDM system developed to simulate the growth and development of coffee, the dynamics and infestation levels of coffee berry borer and the action of four parasitoids of CBB is based on extensive data and provide a very suitable platform for including the effects of cultural practices such as harvest , cleanup of abscised berries and the time intervals between these activities, and the effects of sprays of insecticide and of biopesticides of two fungal pathogens and two nematode parasites. Intensive international efforts to achieve biological control of CBB have failed. Our simulation results for Colombia explain the average reduction of<15% by parasitoids, entomopathogens, and chemical control. Additionally, antagonistic effects among these control tactics were found. For example, harvesting and cleanup affected the action of CBB parasitoids, P. nasuta and P. cofea increasing CBB infestation levels. Specifically, positive coefficients for the interactions PnˑH, PcˑH and PcˑCU indicate detrimental effects to parasitoid efficacy of harvesting and cleanup because parasitoid life stages are also removed from the system, gutter berries resulting in lower future CBB parasitization rates.

The incompatibility between cultural control and parasitoids was also found by Gutiérrez et al. and Aristizábal et al.. Similar antagonistic effects were found for harvests and cleanup with sprays of pathogenic fungi and cultural practices as indicated by the positive sign interactions of BbˑH and BbˑCU. Bustillo reports that sustained efcacy of the pathogen B. bassiana in the field is strongly associated with the production of spores from field infected CBB, but harvest and cleanup remove these inoculum sources. Another significant antagonistic effect identified for Colombia was the interaction of the eulophid parasitoid P. cofea and B. bassiana . In laboratory studies, Castillo et al. found that exposure to B. bassiana caused mortality rates of 100% in P. cofea immature stages and a reduction of 22% in adult longevity which reduces parasitoid efcacy. Chemical control also affects the efficacy of P. cofea as indicated by the positive interaction PcˑC. This occurs because unlike the bethylid parasitoids that enter the berry, P. cofea female are entirely free living and attacks CBB females initiating penetration of coffee berries making them susceptible to insecticides. Despite some detrimental effects on biological control agents, periodic harvest of fruit and clean up were found to be the major control practice reducing CBB infestation levels in both Colombia and Brazil, with the efficacy of the practice decreasing as the time between harvests and cleanup increased from 15 to 60 days. The analysis for Colombia suggests that cleanup is the second most important control strategy for reducing the level of infestations. These simulation result agrees with Johnson et al., who found that ground and tree raisins left after harvest, could be the main CBB reservoir in the inter-crop season in Hawaii. The results for these cultural practices also agree with field studies of Duque and Cháves who found that>94% of Colombian farmers participating in a survey considered cultural control to be the most important method for reducing CBB populations. Bustillo et al. found that periodic harvesting reduced CBB populations up to 80%, with Benavides et al. and Aristizábal et al. in Colombia and Aristizábal in Hawaii, reporting that periodic harvests at 15 day was the main method for reducing CBB populations, and for generating higher yield and income. Unfortunately, producers have a checkered record of implementation cultural control tactics, as Aristizábal et al.found that only 45% were applying periodic harvest according to the criteria proposed by Bustillo et al.. Gutierrez et al. found for Brazil that harvesting and cleanup had little impact on control because at harvest most berries were infested, the females inside fruits were near the end of their reproductive life, and most adult progeny had emerged. However, as in Colombia, harvesting was the most important factor reducing CBB infestation. In summary, harvesting and cleanup at 15-day intervals is the only control tactic that significantly reduces CBB infestation level in Colombia and Brazil. Aristizabal et al. analyzing the cost of harvesting and cleanups in Hawaii, remarked that while initially the cost appears to be high, in the final analysis, sanitation pays the cost of labor and processing, while reducing the source of the pest. That study for Hawaii and the study of Benavides et al. for Colombia, shows that harvesting and cleanup can be economically feasible. However, it may not be economic in Londrina, Brazil which is at the southern climatic limits of coffee production, with short dry periods followed by short periods of rain throughout the year, resulting in the production of susceptible berries over a longer period than in Colombia. This fruiting phenology has a strong impact on the dynamics of the system and on CBB control as shown by our PBDM results. The socio-economic conditions differ in various coffee growing regions, the fuctuation of prices in the international market can vary widely , and infestation levels have an important impact on coffee yield and price. Hence, in economic analyses, control tactics must enter not only as cost, but also as price enhancing attributes. For example, effective CBB control based on sustainable periodic harvesting could be an important element in promoting and positioning select coffees on the international markets as unique, organic, and highest quality. To this end, an in-farm mixture of shade grown, and sun grown coffees using organic cultural practices to control CBB has been proposed as a sustainable option for coffee production on small to medium properties. In conclusion, our model is a realistic virtual crop system that provides a very useful general tool for investigating aspects not readily amenable to field experimentation and has the capacity to integrate more layers such as a socio-economic one. This tool can also be used to examine new technological opportunities prior to their wide adoption. For example, CBB control may be affected by disrupting the symbiotic bacteria in CBB’smicrobiome responsible for cafeine breakdown. Another tactic is the development of attractants that are more competitive with the activeness of coffee berries; a tactic that could be especially important because coffee flowering phenology varies widely throughout the world in response to regional climate patterns that influences the phenology and dynamics of CBB infestation and the success of progeny development.