Evaluation of tolerance and susceptibility to conventional and biorational insecticides in Chrysoperla externa and C. asoralis (Neuroptera: Chrysopidae)

HARAMBOURE, MARINA

UGent

Lugar: Gante; Año: 2016 p. 165

978-90-5989-874-5

Integrated pest management (IPM) is a decision-making system for selecting suitable strategies for the control of phytophagous pests. This management is based on theanalysis of cost-benefit, taking into account the interest and impact on farmers, societyand the environment. Since the beginning of its definition, IPM has come a long wayadding the concept of ?plant protection methods? instead of ?pest control techniques? and the notion of ?ecological justification? instead of economic justification. Among the different strategies implemented by IPM, some of them are: cultural control (mechanical tillage methods, soil management, crop rotation, etc.), genetically modified cropping systems (use of pest-resistant crops and plant breeding), ethological control (autocidal control, sex pheromones, repellents, etc.), chemical control and biological control. Chemical control has been promoted worldwide during decades until negative impacts of this strategy came to light, and within the framework of IPM this type of control is used only when other strategies do not yield satisfactory results and with selective pesticides. Biological control is accomplished through the use oforganisms to maintain the population of phytophagous pests below the Economic Injury Level. The control is based on the relationships between different organisms in agroecosystems (predator-prey, host-parasitoid, and host-entomopathogen). Pest control in Argentina is mainly based on the use of broad-spectrum pesticides, especially organophosphates, carbamates and pyrethroids. Extensive use and often disregard and/or irresponsible use of these pesticides has led to the emergence ofresistance in many pest populations. As a result, control fails and this lead to bad practices, such as increasing the dose or frequency of pesticide applications. Pesticide resistance by pests has been extensively studied because of its importance in economical terms, since it reduces the effectiveness of control of a chemical treatment. Other consequences of these activities are the negative effects onpopulations of natural enemies. But it is also known that natural enemies can develop resistance, which would mean an opportunity to integrate the biological and chemicalcontrol in agro-ecosystems where pests have to be controlled with this type of insecticides.The Horticultural Belt of La Plata (i.e., Cinturón Hortícola Platense [CHP]) is a veryimportant productive region which has been developed in an economical, technological and commercial way, in a constant manner since its origin around the capital of Buenos Aires Province. In the last 24 years, this development adds aqualitative distinction to the quantitative one, with a high quality product and an extension in the supply period. On the other hand, the use of greenhouse production starts in the ?80s with an important increase in the ?90s, boosting the value of this area not only in a regional level (with a 90% of greenhouses in the province), but also in a national level (50% of greenhouses in the country).The genus Chrysoperla Steinmann (Neuroptera: Chrysopidae) is the most abundant within the family, and it is used as a biological control agent in IPM programs. Chrysoperla carnea Stephens, widely distributed in the Holarctic region, is the most commercialized species as a biological control agent. In Argentina, there are fourspecies of Chrysoperla: C. externa Hagen, C. asoralis Banks, C. argentina González Olazo & Reguilón, and C. defreitasi Brooks. In this work, C. externa was evaluated as it is present in the studying area. It presents a high adaptability to different environmental conditions, high reproductive potential, efficient search capability, and it is associated with various agricultural crops. The larvae of this species are effective natural enemies of aphids, whiteflies, thrips, mites and moths. These features make C.externa a good candidate for biological control and in recent years, it has promoted the mass rearing and subsequent release in the field of this species, in several South American countries. Previous studies have shown tolerance to insecticides in this species so it could be combined in programs in which both chemical and biologicalcontrol are required.C. externa proved to be a promising natural enemy that can be used in IPM programs. The species C. externa presents natural tolerance to the insecticide cypermethrin, probably because of a high detoxifying action by P450 enzymes and esterases. This self-tolerance of the species is present in laboratory strains without previous exposure to insecticides.However, acetamiprid which was considered a biorational insecticide, proved to be toxic to C. externa. Azadirachtin did not cause mortality to treated larvae but the 100% of pupae did not reach the adult stage. The insect growth regulator (IGR) pyriproxyfen on the contrary was harmless to the species.As another goal in this work, the distribution of the species C. argentina and C. asoralisin the country, has been expanded, citing them in the CHP, and in association with sweet pepper crops, for the first time. For that reason, C. asoralis ?the most abundant of the two new species was evaluated as well. Bioassays with insecticides on the species C. asoralis compared with C. externa, showed a greater susceptibility to insecticides in the first one, and regarding cypermethrin the mortality reached a 100%. These results reinforce the hypothesis of a natural tolerance to pyrethroids in C.externa, exclusively of that species.