Abstract
In 2001, the woodwasp Sirex noctilio was detected in Pinus radiata plantations in the Biobio region of southern Chile. Subsequently, an intense biological control program using the female sterilizing nematode Deladenus siricidicola was implemented in 2010. During five seasons between 2012 and 2017, we studied the parasitism of D. siricidicola nematode and its effect on woodwasp populations and infestation of P. radiata in different locations within the Biobio region. Parasitism was assessed by dissecting adult females of S. noctilio obtained from infested P. radiata logs. The total population of S. noctilio was determined by the emergence of individuals from the same logs. The level of damage caused by the S. noctilio pest was determined by establishing plots in stands of P. radiata at an intensity of 1 plot every 5 ha-1. During the study period, parasitism of S. noctilio by the nematode D. siricidicola increased from 29.6% in 2012 to 93.1% in 2016, while pest population decreased 3.4% in the same time period. Infestation increased from 0.3 to 11,6% of trees between 2012 and 2015, but subsequently decreased to 5.9% by 2017. We confirmed establishment of the nematode in the region under study and its natural dispersion to non-inoculated areas. Finally, we determined that the effect of inoculation age (antiquity) on parasitism levels reached 90% after three years of inoculation.
Highlights
The wood wasp S. noctilio Fabricius (Hymenoptera: Siricidae) drills the wood of standing trees belonging to the Pinus genus and occasionally Pseudotsuga, Abies, Larix and Picea species [1], with the most susceptible species being Pinus radiata D
Due to the significant economic burden wood wasp represents for the forest industry, coupled with the high cost of biological control of S. noctilio using D. siricidicola, we aimed to determine the level of S. noctilio parasitism by D. siricidicola over five seasons
During the first four seasons, S. noctilio adult emergence occurred between December and April
Summary
The wood wasp S. noctilio Fabricius (Hymenoptera: Siricidae) drills the wood of standing trees belonging to the Pinus genus and occasionally Pseudotsuga, Abies, Larix and Picea species [1], with the most susceptible species being Pinus radiata D. The Sirex noctilio attack begins when females oviposit in the stems of live trees and inject a phytotoxic mucus and spores of the symbiotic fungi Amylostereum areolatum [1] along with the egg and later the fungus is eaten by the wasp’s larva as food. The combined action of the mucus and basidiomycete.
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