UsIng this guide Beneficial Insects

Beneficial Insects

Using this Guide Beneficial Insects Beneficial insects have many roles in the environment, including in agricultural systems. Those we are most familiar with are pollinators, nutrient cyclers and natural enemies. Natural enemies play an important role in suppressing populations of many of the key pest species common in grain crops. Being aware of, and familiar with, the suite of natural enemies that are active in your crops is the first step in recognising them as an integral part of the crop fauna. The preservation of natural enemies, through the judicious and selective use of insecticides, is central to harnessing the contribution that these important insects make to suppressing pest populations, and consequently minimising crop loss. This guide provides a snapshot of key natural enemies of pests commonly encountered in grain crops in the northern region. The photographs and information on identification are designed to assist growers to include natural enemies in their day to day crop monitoring.

Caterpillar parasitoids wasps Several small to medium-sized (3 to 20mm) wasps contribute to the biocontrol of pest larvae, including armyworm and Helicoverpa. Caterpillar parasitoids tend to be slender, the most common species are black, orange or black, orange and white. Adult wasps are commonly observed flying in crops, or attracted to lights at night. The black eggs of Netelia wasps are visible attached to the head of parasitised larva. Most species attack larvae, but do not kill the larva until it pupates. Microplitis another wasp species do kill mid-sized larvae, and their cocoons adhere to larvae. Some Microplitis transmit ascovirus which kills the caterpillar. Netelia adult Photo: J Hopkinson DEEDI Microplitis cocoon and larva Photo: N Parker DEEDI

Caterpillar parasitoids flies Tachinid flies are stout-bodied and bristly and usually grey-brown in colour. They range in size from 5 to 10mm in length. There are many species of tachinids parasitising caterpillars, bugs and beetles. Tachinid activity is most evident from the presence of white eggs adhering to the head and neck of caterpillars. Tachinid larvae develop in the host, but do not kill them until they pupate. They play a role in reducing pest populations over time. In grain crops, noctuid caterpillars (armyworm, Helicoverpa, loopers) are commonly attacked. Tachinid adult Noctuid larva with tachinid egg attached

Bug parasitoids flies The green vegetable bug parasitoid (Trichopoda giacomellii) has been introduced to some areas of the northern region. Adult flies are about 8mm long, female flies are black, males orange. Off-white eggs adhering to adult and final nymph instar are the most obvious sign of Trichopoda activity. Parasitised bugs stop feeding soon after being attacked, but do not die for up to two weeks. Green vegetable bug with Trichopoda eggs adhering to thorax Trichopoda female

Helicoverpa egg parasitoids Trichogramma and Telenomus egg parasitoids are tiny wasps that lay their eggs into caterpillar eggs, killing the developing larvae. Trichogramma are yellow-brown with red eyes, Telenomus is black with black eyes. Egg parasitoids are about 0.5mm in length. Seeing these tiny wasps and the black, parasitised eggs in the field is difficult. To determine if they are active, collect the eggs of the caterpillar pest and store them for 10 days. If parasitised, the eggs will turn black and an adult wasp will emerge. If unparasitised, a caterpillar larva will emerge. Egg parasitoids can limit crop damage as they kill the caterpillar before it emerges from the egg. They attack all major caterpillar pests of grain crops. Trichogramma adult inspecting egg Photo: B Scholz DEEDI Unparasitised white egg, left, and parasitised black egg Photo: B Scholz DEEDI

Whitefly parasitoids Eretmocerus sp. and Encarsia sp. are small (0.5mm) parasitoid wasps that attack whitefly nymphs. These wasps are active throughout the year in crops and non-crop vegetation that host whitefly. Nymphs parasitised by Encarsia turn black, and this change is visible in the field with a hand lens. Parasitism by Eretmocerus is more difficult to determine as there is no obvious colour change. Parasitised nymphs do not emerge as adult whitefly, so the activity of these parasitoids which attack whitefly nymphs can have a significant impact on the rate of population build-up in the crop. Encarsia adult Photo: Z Ludgate DEEDI Parasitised whitefly nymphs (blackened) Photo: Z Ludgate DEEDI

Predatory bugs Small to medium predatory bugs are common in grain crops. The damsel bug, Nabis kingbergii, is 8mm in length, pale-coloured and slender, with long antennae. Nymphs are similar in appearance to adults but lack wings. Predatory bugs are active in the canopy. These small, slender bugs are often overlooked in scouting, but are readily dislodged with beatsheet sampling. These bugs attack a wide range of soft-bodied prey including aphids, whitefly nymphs, small caterpillars, leafhoppers, mites, immature bugs and beetles. Damsel bug adult Photo: K Power DEEDI Damsel bug nymph

Predatory bugs Small to medium predatory bugs are common in grain crops. The adult brown smudge bug, Deraeocoris signatus, is small (4.5mm) and mottled brown. Nymphs are maroon, and often mistaken for aphids. Predatory bugs are active in the canopy. These small, slender bugs are often overlooked in scouting, but are readily dislodged with beatsheet sampling. These bugs attack a wide range of soft-bodied prey including aphids, whitefly nymphs, small caterpillars, leafhoppers, mites, immature bugs and beetles. Brown smudge bug adult Brown smudge bug nymph

Bug egg parasitoid Trissolcus basalis are small, shiny black wasps (0.5mm). Trissolcus does not distinguish between the eggs of pests and beneficial species, and will parasitise eggs of the predatory shield bugs as well as the green vegetable bug. Parasitised eggs turn black as the wasp larva develops inside them. Parasitised eggs of the green vegetable bug (GVB) can be distinguished from the naturally dark eggs of the predatory shield bugs, which have a fringe of spines around the top. Parasitised eggs are killed as the wasp larva develops inside them, and an adult wasp rather than a bug nymph emerges. Trissolcus adult on GVB egg mass Photo: H Brier DEEDI

Predatory beetles Labybirds are probably the most recognisable beneficial insect in grain crops. There are a number of species, most are brightly coloured yellow or red with black and white spots or lines. Adults are shiny, round to oval (3 to 7mm). Larvae tend to be grey-black and elongated with yellow markings. Eggs are bright yellow, elongated and laid in clusters. The bright colours of adults make them highly visible in the crop. Larvae can be more difficult to observe, but easily seen in colonies of aphids, mites and other pests. Both larvae and adults are predacious. Across the species, ladybirds have a wide range of prey including aphids, mites, whitefly, thrip, small caterpillars, moth eggs and scale. Transverse ladybird adults and larva Photo: D Ironside DEEDI Ladybird eggs

Predatory shield bug The spined predatory bug, Oechalia schellenbergii, has distinctive spines on its shoulders. These bugs are large (11mm), and prey on caterpillars, bug pests and other soft-bodied insects. Nymphs do not have spines, but have a distinctive red-orange ring on their backs. Adult bugs are often seen in the field and can be easily dislodged when sampling with a beatsheet. Eggs are laid in rafts and are distinctive with their fringe of long spines around the top. Early instar nymphs tend to aggregate. Adults and nymphs are predatory, feeding on and killing a wide range of soft-bodied prey. These large bugs are capable of killing medium-to-large caterpillar larvae. Oechalia adult feeding on GVB nymph Photo: K Knight DEEDI Oechalia eggs Photo: J. Wessels DEEDI

Predatory shield bug The glossy shield bug, Cermatulus nasalis, is a large (12mm) predatory shield bug. These bugs prey on caterpillars, bug nymphs and other soft-bodied insects. Nymphs are dark with four red-orange spots on their back. Adult bugs are often seen in the field and can be easily dislodged when sampling with a beatsheet. Eggs are laid in rafts and are distinctive with their fringe of long spines around the top. Early instar nymphs tend to aggregate. Adults and nymphs are predatory, feeding on and killing a wide range of soft-bodied prey. These large bugs are capable of killing medium-to-large caterpillar larvae. Glossy shield bug adult Glossy shield bug nymph Photo: H Brier

Lacewings Adult lacewings hold their tent-like, clear wings over their back, have long antennae and prominent eyes. The brown lacewing (8mm) is mottled brown and the green lacewing is larger (15mm) and pale to bright green. Larvae have forward-protruding, sickleshaped jaws. Green lacewing larvae are stout and camouflage themselves with the bodies of their prey. Brown lacewing larvae are elongated, and do not camouflage themselves. Clusters of green lacewing eggs are distinctive due to their long stalks, and indicate lacewing activity. Adults of the green lacewing are not predatory. Brown adults and larvae of both species feed on soft-bodied insects, mites and eggs. Brown lacewing adult Green lacewing eggs (left) and green lacewing larva (right) PhotoS: J Wessels DEEDI

Hoverfly Adult hoverflies are small (4 to 7mm), slender flies with dark and yellow markings on the body. They are often mistaken for wasps. Characteristically, adults hover in the crop. Small, white, oval eggs are laid close to aphid colonies. Larvae are green (up to 8mm) and maggot-like. Adults are easily observed flying and hovering in the crop. To find larvae, look carefully in colonies of aphids, although they can be difficult to see without close inspection. Tear-shaped pupae may be found adhering to leaves. Adults are not predatory. Larvae are voracious predators and kill aphids by piercing them and sucking them dry. Hoverfly adult Hoverfly larva

Spiders A large variety of spiders occur in grain crops, including active hunters like the wolf, lynx and nightstalkers, or web spinners like the tangle web and orbweaver. While considered relatively sedentary, juvenile spiders can travel large distances on the wind and colonise fields. Most spiders are well-camouflaged, and many are active at night either hiding in nests in the soil or in the canopy. Spiders are often dislodged onto beatsheets when sampling. Spiders have a broad range of prey. Active hunters prey on slowmoving targets including caterpillars, bug nymphs and eggs. Webspinners can catch flying prey. Jumping spider

Aphid parasitoids Several species of wasp parasitise aphids and it is difficult to distinguish between the species in the field. Generally they are small (2 to 3mm) and dark with clear wings and long antennae. Adult wasps can be difficult to see because of their small size. The presence of parasitised aphid mummies is evidence of parasitoid activity. When fully developed the wasps emerge from a circular hole in the mummy. Female wasps insert eggs into live aphids, and the wasp larva grows within the aphid. Aphid parasitoids can have a major impact on aphid populations. Adult parasitoid Photo: M Miles DEEDI Aphid mummy showing wasp emergence hole Photo: M Miles DEEDI

Disclaimer: Any recommendations, suggestions or opinions contained in this publication do not necessarily represent the policy or views of the Grains Research and Development Corporation (GRDC) and Agri-Science Queensland, Department of Employment, Economic Development and Innovation (DEEDI). No person should act on the basis of the contents of this publication without first obtaining specific, independent professional advice. The GRDC and Agri-Science Queensland, DEEDI will not be liable for any loss, damage, cost or expense incurred or arising by reason of any person using or relying on the information in this publication. Copyright: All material published in The Back Pocket Guide is copyright protected and may not be reproduced in any form without written permission from the Grains Research and Development Corporation and Agri-Science Queensland, DEEDI. September 2010 Dr Melina Miles, Agri-Science Queensland, Department of Employment, Economic Development and Innovation T: 07 4688 1369 E: melina.miles@deedi.qld.gov.au www.deedi.qld.gov.au Maureen Cribb, GRDC Publications Manager T: 02 6166 4500 E: m.cribb@grdc.com.au Useful resources GRDC Pest Links www.grdc.com.au/pestlinks GRDC Integrated Pest Management Fact Sheet www.grdc.com.au/factsheets deedi Insect Pest management website www.dpi.qld.gov.au/26_3510.htm Tthe Beatsheet Blog www.thebeatsheet.com.au Crop Insects: The Ute Guide (Northern Region Grain Belt edition), copies available at Ground Cover Direct Ground Cover Direct How to order Free phone 1800 11 00 44 Free fax 1800 00 99 88 Email ground-cover-direct@canprint.com.au Post Ground Cover Direct, PO Box 7456, Canberra MC ACT 2610 For a complete listing of all GRDC publications, go to www.grdc.com.au/bookshop Production and design by Coretext T: 03 9670 1168 www.coretext.com.au