Optimizing the releasing strategy used for the biological control of the sugarcane borer Diatraea saccharalis by Trichogramma galloi with computer modeling and simulation.

One of the challenges in augmentative biological control programs is the definition of releasing strategy for natural enemies, especially when macro-organisms are involved. Important information about the density of insects to be released and frequency of releases usually requires a great number of experiments, which implies time and space that are not always readily available. In order to provide science-based responses for these questions, computational models offer an in silico option to simulate different biocontrol agent releasing scenarios. This allows decision-makers to focus their efforts to more feasible options. The major insect pest in sugarcane crops is the sugarcane borer Diatraea saccharalis, which can be managed using the egg parasitoid Trichogramma galloi. The current strategy consists in releasing 50,000 insects per hectare for each release, in three weekly releases. Here, we present a simulation model to check whether this releasing strategy is optimal against the sugarcane borer. A sensitive analysis revealed that the population of the pest is more affected by the number of releases rather than by the density of parasitoids released. Only the number of releases demonstrated an ability to drive the population curve of the pest towards a negative growth. For example, releasing a total of 600,000 insects per hectare in three releases led to a lower pest control efficacy that releasing only 250,000 insects per hectare in five releases. A higher number of releases covers a wider range of time, increasing the likelihood of releasing parasitoids at the correct time given that the egg stage is short. Based on these results, it is suggested that, if modifications to the releasing strategy are desired, increasing the number of releases from 3 to 5 at weekly intervals is most likely preferable.

Biology at Different Temperatures, Thermal Requirements, and Ecological Zoning of Opogona sacchari (Lepidoptera: Tineidae).

The banana moth, Opogona sacchari (Bojer, 1856), is a polyphagous pest that causes serious damage to different crops around the world, particularly to bananas in southern Brazil. The insect is designated a quarantine pest in several countries including Argentina, the main consumer market for bananas produced in southern Brazil. To provide support for the management of O. sacchari, the present study investigated the biology and thermal requirements at eight temperatures (18, 22, 25, 28, 30, 32, 33, and 34 ± 1°C) and constructed a fertility life table at five temperatures (18, 22, 25, 28, and 30 ± 1°C). Above 30°C, the mortality of all life stages was 100%; the best temperature for development was 25°C. Based on this information, an ecological zoning of the pest was developed for Brazil. The lower temperature threshold was 8.6°C. The zoning indicated that the pest does not occur in regions with warmer climates, corresponding to the actual distribution of this pest in Brazil.