ABSTRACT


ROBERTO H. GONZÁLEZ R.1, HIROSHI KIDO2, ANGÉLICA MARÍN3 Y PATRICK HUGHES4
 
The biology, morphology and population dynamicsof the ground pearI of grapes, a root inhabitmg scale insect Margarodes vitis (Phil.), was studied under: laboratory and field conditions from September 1966 to March 1969. The study was condueted in the University of Chile, Agricultural Experiment Station at Maipú.Soil samples were collected periodically from three infested vineyards in the provinces of Santiago and O'Higgins. From March to October, only cyst form containing first to third nympihal stages were found feeding on the rbots or scattered throughout the soil profile. The majority of the cysts were found in the upper 10 to 60 cm uf the soil.Cysts were dissected to study viability of the encIosed nymphs and to determine the stage of development of immature females. Results showed that when the cysts were placed in water, 85 to 100% of those which sank are alive. Cysts containing dead nymphs as well as fully developed females floated on the surface.Cysts containing fully developed females are scattered throughout the soil profile but 2/3 of these cysts were found in 0-50 cm depth rather 50 to 100 cm in the soil. The percentage of adult females annually emerging from these third instar cysts was not greater than 9%. Emergence occurs from late October to late December.Reproduction occurs parthentigenetically. Average egg production is about 600 eggs per regular to large sized females. Oviposition takes place from November to early February and the larvae appear in January and February. As soon as the larva find a suitable rootlet, introduces its mouth part into the phloem tissue and starts forming the cysts. The first molt occurs in October and the next year, in November, the second molt takes place. The length of the last (third) nymphal stage is not known.
Females can be readily obtained in the Jaboratory by exposing third instar cysts totemperatures of about 30°C and 8% soil moisture.Laboratory trials with insecticides applied topically with a micro-applicator, showedthat none of the 37 organic compounds tested produced a significant reduction of t.hethird instar cysts.
Topical applications with chlorinated hydrocarbon insecticides showed that treatedadult females were able to survive and lay viable eggs. The chemicals tested were: endosulfan,DDT, lindane, methoxiclor, TOE, dieldrin, aldrin, endrin, heptachlor, chfordaneand toxaphene.
Dioxathion, Di-Syston, phorate, parathion and carbophenothion did not kili all thetreated females but eggs oviposited by the females did not hatch.Diazinon killed the treated females and prevented oviposition.Against the newly emerged larvae, Mobam, Lannate, Furadan, Baygon, diazinon aQdmethyl parathion appeared to be the most promising insecticides. A 0.125 or 0.144%(active ingredient) aqueous mixture of the comercially formulated insecticides inmobilizedthe nymphs. However when the mixtures were filtered through a 25 cm.columnof soil, the filtrates were ineffective against the larvae.Field trials directed against larvae by using 0.1% (active ingredient) aqueous mixtures of insecticides injected into the soil in Viña Carmen, Buin, showed that adecuatecontrol of larvae feeding on the roots was not obtained. The chemicals tested were:Mobam, Furadan, Baygon and Diazinon.Insect control by flooding a portien of the vineyard with water (February 1968) wasnot successful.
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1 Ingeniero Agrónomo, PhD., Profesor de la Facultad de Agronomía, Universidad de Chile, Entomólogo asesor de Instituto de Investigaciones Agropecuarias.
2 y 4 Entomólogo, PhD. y Estudiante Graduado, respectivamente, Departamento de Entomología, Universidad de California, Davis.3 Ingeniero Agrónomo, Estación Experimental Agronómica