Aggregation Patterns, Sampling Plan, and Economic Injury Levels for the New Citrus Pest Delottococcus aberiae (Hemiptera: Pseudococcidae)

Abstract

Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae) is the latest exotic mealybug species introduced in citrus in the Mediterranean basin. It causes severe distortion and size reduction on developing fruits. Due to its first interaction with citrus, D. aberiae economic thresholds are still unknown for this crop and the current Integrated Pest Management programs have been disrupted. The objectives of this study were to determine the aggregation patterns of D. aberiae in citrus, develop an efficient sampling plan to assess its population density, and calculate its Economic and Economic Environmental Injury Levels (EIL and EEIL, respectively). Twelve and 19 orchards were sampled in 2014 and 2015, respectively. At each orchard, population densities were monitored fortnightly in leaves, twigs, and fruit, and fruit damage was determined at harvest. Our results showed a clumped aggregation of D. aberiae in all organs with no significant differences between generations on fruit. Fruit damage at harvest was strongly correlated with fruit occupation in spring. Based on these results and using chlorpyrifos as the insecticide of reference, the EIL and EEIL were calculated as 7.1 and 12.1% of occupied fruit in spring, respectively. With all this, we recommend sampling 275 fruits using a binomial sampling method or alternatively, 140 fruits with an enumerative method bimonthly between petal fall and July.

Intrasexual Vibrational Behavior of Philaenus spumarius in Semi-Field Conditions

“…Studies of the vibrational behavior of insects, mostly focus on the mating behavior [ 12 ] and signals associated to pair formation, with bioassays that involve a pair (more often, a male and a female), sometimes in the presence of a third individual (e.g., [ 13 , 14 ]). Therefore, by targeting few individuals, behaviors that occur within groups are excluded even if for many species (especially of Hemipterans) the presence of groups on the same host plant is the rule and not the exception [ 15 , 16 , 17 , 18 , 19 ]. For this reason, the simulation of the environment in which insects live, by involving multiple individuals, could provide more reliable knowledge of their interactions that could be useful if applied to practical aspects that involve decision-making for conservation or pest control.…”

Field evaluation of Cryptolaemus montrouzieri (Mulsant) (Coleoptera: Coccinellidae) as biological control agent of the mealybug Delottococcus aberiae De Lotto (Hemiptera: Pseudococcidae)

“…Likely native to Southern Africa, it was first recorded in 2009 in eastern Spain, in the region of Les Valls, Valencia (Beltrà et al, 2012). Since then, D. aberiae has been spreading to the surrounding areas, becoming a significant citrus pest (Martínez-Blay et al, 2018a;Pérez-Rodríguez et al, 2017;Tena et al, 2017). Unlike other species of citrusinhabiting mealybug, D. aberiae causes severe fruit distortion and size reduction leading to major economic losses (Pérez-Rodríguez et al, 2017).…”

“…Since then, D. aberiae has been spreading to the surrounding areas, becoming a significant citrus pest (Martínez-Blay et al, 2018a;Pérez-Rodríguez et al, 2017;Tena et al, 2017). Unlike other species of citrusinhabiting mealybug, D. aberiae causes severe fruit distortion and size reduction leading to major economic losses (Pérez-Rodríguez et al, 2017). The damaging period ranges from April to July, during the fruit set, when D. aberiae alters fruit cell division while feeding (Martínez-Blay et al, 2018b).…”

“…The damaging period ranges from April to July, during the fruit set, when D. aberiae alters fruit cell division while feeding (Martínez-Blay et al, 2018b). Generally, D. aberiae is distributed throughout the entire tree canopy, but aggregate on fruits when they become available, resulting in direct damage (Pérez-Rodríguez et al, 2017). In the early spring, gravid D. aberiae females descend down the trunk into the soil searching for shelter in the subterranean crown (Franco et al, 2009;Martínez-Blay et al, 2018b).…”

“…Recently, the environmental economic injury level for D. aberiae has been established as 12% of fruit occupation between petal fall and July. When more than 12% of fruits are occupied by D. aberiae, a chemical treatment is recommended (Pérez-Rodríguez et al, 2017). Biological control is currently not an option because native parasitoids, the most important group of biological control agents of mealybugs, cannot develop in D. aberiae, and the role of predators is poorly known (Tena et al, 2017).…”