Relative susceptibility of cashew types to infestation by the tea mosquito Helopoltis antonii Signoret (Hemiptera:Miridae)

Abstract

The relative susceptibility of fourteen cashew accessions (Anacardium occidentale L.) to infestation by the tea mosquito bug Helopeltis antonii signoret (miridae: HEmiptera ) was evaluated in the field experiments conducted at the Cashew Research Station , Madakathara during September 1979-March1980. The field damage Intensites and the extent of damage Inflicted by the insect consequent on confinement on shoots and panicles were recored on a 0-5 scale and it was found that the accessions 22,1112, 1430 and 1097 were least susceptible with regard to the intensity of natural field infestation of the vegetative shoots. Regarding the intensity of field infestation on floral branches, the accessions, 22, 1112,1352,1469 and 1097 were significantly less susceptible than the other types . With reference to the intensity of damage to vegetative shoots under confinement none of the accessions was found to be promising . The accession numbers 1219 , 1469 and 1431 were found to be least susceptible to H. antonii infestation under confinement on floral branches . Since the damage to the floral branches, particularly under confinement , Is relatively more important factor responsible for yield reduction these trees can be identified to be relatively more promising . The influence of certain biochemical factors (total nitrogen , soluable sugar and tannins ) on pest infestation in shoots and floral branches was ascertained by working out simple correlation coefficients. The only significant association detected was between the tannin content in the vegetative shoots on the one hand and the pest infestation intensities under confinement , on the other. The shade intensities within the canopies had no the extent of susceptibility to the pest. The tree architecture patterns were found to be of two basic types, namely, extensively branching (spreading ) and intensively branching (bushy ). Variations in the canopy configuration did not influence the susceptibility trends. The inconsistencies in the relative susceptibility of different accession with reference to shoot and panicle damage intensities have been discussed.