EFECTO DE DIVERSOS INSECTICIDAS SISTEMICOS EN EL COMBATE DEL PULGON VERDE PALIDO (METOPOLOPHIUM DIRHODUM) (WALKER) EN CEBADA (HORDEUM VULGARE L)

Abstract

The effect of different systemic insecticides of current usage in Chile on regulation of aphid population in barley was studied in Chillan fort two years (1969-1970).
The predominant species of aphids was Metopolophium dirhodum (Walker), which included about the 99% of the population.
The following systemic insecticides were evaluated: Bidrin, Azodrin, Ekatin, Metasystox R, Dimethoate and Anthio. All of these insecticides significantly reduced the aphid populations during fifteen days in relation to those without treatment.
Bidrin, Azodrin, Ekatin, Metasystox I and Metasystox R treatments proved to be more effective in reducing the aphid number than Anthio and Dimethoate, even though, the differences related to performance were statistically significant during three days only. In later counts, even though the population levels of these treatments were lower the differences among treatments significant.
Counts made twenty four days after the insecticides spray in 1970, proved that the insecticide treated populations were 215% superior to those without pesticides. This result can be deduced from the complete destruction caused by the insecticide treatments to the population of syrphid larva Allograpta pulchra (Shan), as 20% was detected in the control. Another possible explanation could be derived from a minor effect of the fungi parasite of aphids, due to a lower density of population in the plots treated.
The differencesh in yield concerning the insecticide treated plots were not statistically significatant although there was a difference to the ones without pesticides. The productiveness of the plots treated with insecticides was superior in a 24,1% and 25,3% during the two years of research.
Only the number of grains per ear showed differences among the check treatment an the rest of them. Other factors such as one thousand grain weight, hectoliter weight, yield of straw and number of shoots per surface did not show statistically significant differences.