RIRDC - Research Compendium 1993

Rural Industries
Research & Development Corporation

Research Compendium 1993 - 1994

Research Project

EVALUATION OF EGG PARASITOIDS FOR HELIOTHIS MANAGEMENT IN SORGHUM

Objectives

To collect egg parasitoids of Heliothis from field plantings of sorghum and monitor natural levels of egg parasitism.
To establish laboratory cultures of these parasitoids and develop mass rearing facilities.
To investigate the oviposition of Heliothis on different sorghum hybrids.
To evaluate inundative releases of parasitoids for managing Heliothis.

Background

The development of midge resistant sorghums has elevated the status of Heliothis as a pest of this crop. Currently, the use of insecticides provides the only means for controlling the pest. The development of resistance, environmental contamination, and the high cost of developing new insecticides make it imperative that the dependence on insecticides is reduced. Other forms of pest management, including biological control therefore warrant investigation.

Research

In this project, naturally occurring egg parasitoids of Heliothis were collected from sorghum in the field. Methods of laboratory rearing and mass production were evaluated, and the effectiveness of inundative releases of the parasitoids were tested in the field on crops of sorghum at different stages of crop growth. The potential for commercially managing Heliothis using the egg parasitoids Trichogramma and its relatives was then determined.

Outcome

Egg parasitoids of Heliothis were successfully recovered from the field, laboratory culturing and mass rearing methods developed, and inundative releases made in sorghum crops at different stages of maturity.

The parasitoids were shown to parasitise eggs of Heliothis, but the populations of parasitoids which subsequently developed, were not able to reduce numbers of Heliothis sufficiently to prevent crop damage to acceptable levels in all cases.

Implications

The use of egg parasitoids alone will not provide an economically acceptable level of control of Heliothis on sorghum. Their use, together with minimal application of insecticides in IPM programs, probably warrants further investigation. The rapid increase in the level of resistance to insecticides developing in Heliothis, will provide the impetus for this to occur.

RIRDC Project No: DAQ-130A

RESEARCHER: Mr Brad Stoltz

ORGANISATION: QLD Dept of Primary Industries

Plant Industry

Entomology Branch

PO Box 102

TOOWOOMBA QLD 4350

PHONE: 076 31 4200

FAX: 076 34 7421