Biological characterization and mating compatibility of Helicoverpa gelotopoeon (D.) (Lepidoptera: Noctuidae) populations from different regions in Argentina.

Helicoverpa gelotopoeon, the South American bollworm, is a polyphagous pest of the Heliothinae complex that causes damage to soybean, cotton, and chickpea crops. Some species within this complex have developed resistance to genetically modified crops and insecticides, which has led to increased interest in their genetic diversity and population structure. The objective of this study was to characterize biological and reproductive parameters of two populations of H. gelotopoeon collected in two different provinces of Argentina. Intra- and inter-population crosses revealed that H. gelotopoeon populations from both regions of Argentina did not present evidence of pre-zygotic and post-zygotic incompatibility, suggesting that Tucumán and Córdoba populations of H. gelotopoeon belong to a single wide-ranging species. Our data support the occurrence of substantial gene flow between H. gelotopoeon populations, probably due to the widely documented, long-range migratory capacity of Heliothinae species.

Impact of natural control agents of the citrus leafminer Phyllocnistis citrella on lemon trees varies among seasons.

Studies on insect natural enemies and their effects on host populations are of immense practical value in pest management. Predation and parasitism on a citrus pest, the leafminer Phyllocnistis citrella Stainton, were evaluated by sampling over 3 years in four locations within a world leading lemon producing area in Northwest Argentina. Both mortality factors showed seasonal trends consistent across locations, with predation exerting earlier and more sustained pressure than parasitism, which showed wider seasonal variations. The dominant parasitoids, native Cirrospilus neotropicus and introduced Ageniaspis citricola, showed different seasonal trends: C. neotropicus was dominant in spring whereas A. citricola superseded it in autumn and winter. Although parasitism rates were relatively low, the native C. neotropicus revealed favourable features as potential control agent, by showing density-dependence, parasitism rates comparable with those of the specific A. citricola during part of the cycle, and earlier synchronization with the host. The study provides highly relevant information for a sustainable management of this worldwide pest, for which biological control is considered the best long-term option.

Spatial and temporal variation in Chaetanaphothrips orchidii Moulton (Thysanoptera: Thripidae) population and its damage on lemon.

Chaetanaphothrips orchidii Moulton has recently been detected in lemon (Citrus limon) orchards in northwest Argentina, causing high levels of damage on fruits. Severe damage results in the rejection of fruit for export, which must then be sold in the industry. However, the restrictions imposed by the citrus industry on insecticide residues sometimes also result in fruit rejection. Here, we studied the ecology and behavior of C. orchidii in order to propose a pest management strategy that could meet both export and industry demands. Seasonal occurrence and canopy distribution of C. orchidii in lemon orchards were evaluated, and field experimental manipulations of thrips populations were performed to analyze how the length (45, 100, 130, and 200 days) and timing (January, February, or March) of C. orchidii activity related with fruit damage. Lemons harvested during summer showed lower infestation levels (∼0.64 individual per fruit) than those harvested in winter (∼1.88 individuals per fruit). Higher proportions of damaged fruits were recorded in the lower part of the tree. Changes in the population levels of C. orchidii were closely associated with fruit phenology. The longer the lemon fruits were exposed to the thrips, the higher was the damage. However, the time of infestations did not affect fruit damage. Our data provide a first step towards understanding the factors that determine the severity of fruit damage caused by C. orchidii in northwest Argentina.