Chilo Partellus in Maize: Neonate Behaviour, Field Dispersal and Infestation

Dispersal behaviour of early instars of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) was investigated in maize under screen house and field conditions. Observations on ballooning, larval settling in leaf sheaths/central whorl were made 10, 30, 60 min and 4 h after larval infestation. Larval distribution in the field was assessed by sampling maize plants 2 and 7 days after infestation. The plants were either infested with neonate larvae or egg batches to examine the effect of mode of infestation on larval dispersal and infestation levels were compared for their effect on plant damage. C. partellus larvae showed ballooning immediately after infestation, however, all ballooned larvae did not reach ground. The larval settling in leaf sheaths increased with time, the maximum (42%) being 4 h after infestation. None of the C. partellus larvae reached central whorl within 30 min, but 15% of them climbed after 4 h. About 24% and 10% of the larvae successfully dispersed in the field, when sampling was done 2 and 7 days after infestation, respectively. Majority of the larvae (71%) were lost within first 7 days of infestation. The larvae dispersed within the rows (up to 45 cm), while the dispersal between rows was insignificant. The mode of infestation had no effect on interplant larval dispersal and leaf injury rating was lower (4.0) at infestation level of 15 larvae/plant.