Predatory Bugs

Bugs are a large group of insects which includes many pests of plants. There are however many bugs that are important natural enemies. They range in size from the minute Orius to the ferocious Assassin bug. They undergo a gradual metamorphosis usually through five instars in which they shed their skins in a series of molts until adulthood when they develop wings. Unlike beetles there is no pupal stage.

Minute Pirate Bugs, Orius spp.

Primary Hosts: moth eggs and thrips

Key identifying characteristics:

The tiny predatory bugs (about 2.5 mm long) predominately black with light wing patches, are found in most crops in SE Qld. Their tiny eggs are rarely seen as they are laid singly into plant tissue.

Nymphs are yellow-orange or brown tear shaped (top right). Orius feed on Heliothis eggs, thrips and may feed on Dried Fruit Beetle eggs and larvae. They are first encountered in the tassels and then in the silks.

Significance:

These are major predator in the Lockyer District and also common in the Western Sydney area. What constitutes a significant number is unclear but current studies indicate that two per silk will have a significant impact on a moderate egg lay.

Big Eyed Bugs, Geocoris spp. and Germalus spp.

Primary Hosts: Soft bodied insects and mites

Key identifying characteristics: They are slightly larger than Orius at about 3 mm long and distinguished by their very large eyes.

Significance: These bugs are not nearly as abundant as Orius in the Lockyer Valley but are found in most crops.

Damsel Bugs, Nabis kinbergii

Primary Host: Soft bodied insects, moth eggs, small larvae and mites

Key identifying characteristics: adults slender, about 8 mm long, pale brown, narrow head with large eyes and long antennae.

They are a fast moving general predator which feeds on moth eggs and small larvae. In the pre tassel stage often seen in the whorl, then the tassel and latter around the cob and silk area.

Damsel bugs move quickly when disturbed.  

Significance: varies from season to season. Can be very significant in Lockyer Valley with up to one per plant in sweet corn observed.

Assassin Bugs, various species

Primary Host: small to large larvae

Key identifying characteristics:

12 to 18 mm long, curved beak is held beneath the narrow head. Long front legs for grasping its prey.

Significance: Sometimes seen in corn crops but not as common as the other predatory bugs mentioned above.