Effect of conventional and biorational insecticides on larvae of Chrysoperla extena

RIMOLDI, FEDERICO; SCHNEIDER, MARCELA INÉS; PINEDA, SAMUEL; RONCO, ALICIA

Belgica

Simposio; 59th International Symposium on Crop Protection; 2007

Effect of conventional and biorational insecticides on larvae of Chrysoperla extena Rimoldi1 F., Schneider2, M.I., Pineda3, S.  and Ronco1 A.E. 1CIMA, Facultad de Ciencias Exactas, 2CEPAVE, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 47 y 115, (1900) – La Plata, Argentina, CONICET. 3Instituto de Investigaciones Agropecuarias y Forestales, Universidad Michoacana de San  Nicolás de Hidalgo, Km. 9.5 Carr. Morelia-Zinapécuaro, 58880 Tarímbaro, Michoacán, Mexico.  frimoldi@quimica.unlp.edu.ar Poster presentation Abstract Crysopids are generalist predators frequently used in the biological control of pests affecting extensive agriculture like soybean, corn, wheat, alfalfa, between other crops. In particular, Chrysoperla externa is widely distributed species, from the south-east of the United States, through the Antilles, down to South America. Its wide distribution makes a suitable organism to be used as an agent for biological control of pests. Several South American countries still make use of conventional insecticides like cypermethrin and endosulfan, and very recently, although indicated by control agencies the introduction of biorational ones like spinosad or methoxyfenozide, the use by the productive sector is still very incipient. The objective of the present communication is to study short term effects under laboratory conditions of the above mentioned conventional and biorational insecticides on the larvae (third instar) of C. externa to assess potential damage on this natural enemy of relevant pests from agroecosystems of the Pampas plains of Argentina. Standardized toxicity test conditions were: 25ºC, 16 h light period, 75% relative humidity, in a conditioned chamber. Tests were carried using 9 cm Petri dishes, exposing L3 C. externa larvae per concentration (in individual compartments within the dish) via ingestion of 50 eggs of Sitrotoga cerealella, previously dipped in the insecticide solutions with the addition of a tensoactive. End-point assessment included mortality, phase duration, fecundity and fertility. Results indicate that neither the two conventional insecticides nor the two biorational ones affected C. externa at the maxima recommended field concentrations when exposed in the L3 instar stage. These results are in opposite behavior respect to previous experiences with C. externa eggs, where conventional insecticides exhibited 100 % mortality on exposed organisms via immersion. Literature reports on the same organism observed no effects by other growth regulators like methoxyfenozide carried for larvae and adult stages. The lack of observed effects in the L3 instar of C. externa, together with those producing an effect observed for other stages or exposure routes enforce the necessity of a wide range of assessments that should be taken into account in the risk assessment evaluation pesticides in integrated pest management.