Annual Report 2018-2019

FUENTES CORONA, MALENA ; VARONE, LAURA; LOGARZO, GUILLERMO ALEJANDRO; POVEDA MARTÍNEZ, DANIEL

2019-04-01/2021-03-31

29-33

Biológica

Sanidad vegetal-Prevencion

The cactus moth Cactoblastis cactorum, is native to South America and has entered North America accidentally some years ago, and is spreading across the United States, with high risk of reaching Mexico. This constitutes a threat to native cactus biodiversity and the prickly pear industry. Current research on cactus moth control includes mass rearing of the potential biocontrol agent Apanteles opuntiarum, a parasitoid exported to quarantine facilities at Gainesville (FL). Fluctuations in parasitism rates of A. opuntiarum were evaluated in the field, as well as the effect of the cactus moth on fruit production in its native range, where the introduced O. ficus-indica has become an increasingly important crop. Finally, we have undertaken genetic analyses to understand population structure of the cactus moth, and related species, in relation with their host plants. Field parasitism rates of A. opuntiarum was evaluated on an O. ficus-indica plantation in the province of Santiago del Estero, Argentina. Three different size categories of larvae (L1-2, L3-4 and L5-6) were collected and transported to the laboratory to determine A. opuntiarum parasitism rates. Sampling procedure was repeated in each of the three yearly moth generations to evaluate changes in parasitism rates. Effect of C. cactorum on fruit production of O. ficus-indica was evaluated for two consecutive years in the same plantation. Attack rates were related to egg stick density per plant for 25 plants (4-8-12-16-20 egg sticks/plant, with five replicates. Five additional plants without eggs sticks were evaluated as controls. After four consecutive generations of the cactus moth feeding on the plants, fruit production per terminal cladode were accounted, as was fruit quality in terms of sugar content (Brix °) per fruit. To evaluate Phylogenetic relationships of the cactus moth and related species, surveys were carried out throughout Argentina to collect fresh material to conduct genetics analyses using the mitochondrial gene COI. A total of 83 samples of C. cactorum larvae were collected in three areas of Argentina (Northwest = 20, Northeast = 45, and Center = 18) in a variety of native and exotic Opuntia species. Ten 10 samples of Cactoblastis doddi were collected from O. sulphurea (Northwest), and 15 samples of Cactoblastis bucyrus were collected from Trichocereus atacamensis (Northwest) and Cleistocactus baumannii (Center).