Impact of Beauveria bassiana applications on Hypothenemus hampei infestation on organic coffee farms

The coffee berry borer (CBB), Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae), is the most important pest of coffee worldwide, inflicting economic losses up to US $500 million a year. Among its natural enemies, the fungus Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Cordycipitaceae) (Bb) has shown the best potential for biocontrol of this pest in coffee growing areas, especially in those farms adopting organic agricultural practices. The CBB has a cryptic habit, therefore the fungus must reach the female adults of this beetle when they are outside the coffee berries, making the application time of Bb very critical. We evaluated the impact of different Bb formulations (Boveril^®, strain ESALQ-PL63) applied as aqueous or dustable treatments at the same label rate (2 × 10¹² viable conidia/ha) on the percent infested berries accounting for the presence or not of CBB life stages inside the berries during a 2-year study conducted on an organic coffee farm, located in Dois Córregos, São Paulo State, Brazil. Treatments were applied twice at approximate 40 day intervals and evaluations were conducted over 160 days (1^st year) and 180 days (2^nd year). In the 1^st year-trial, the Bb treatments kept the CBB population below its action threshold (3.5% of infested berries). However, in the 2^nd year, Bb treatments were not effective in reducing CBB population under its action threshold due to the high initial infestation levels of CBB in the experimental area. Taken these results together, we concluded that the adoption of microbial control with Bb toward CBB is very effective when the initial population is low (< 3.5%) and when other strategies for integrated CBB management are also adopted, such as complete removal of remaining fruit after harvest. We also suggest the estimation of the real action threshold for this pest to take into account insect-infested berries, not simply insect-damaged berries, as counting all damaged berries over-estimates infestations in cases where the fungus or other factors have killed the insect prior to it reaching the seed.