Biological Pest Control

PESTS AND DISEASES

Biological pest control

Vera Sergeeva often coincide with climatic changes in association with black scale in School of such as irregular rainfall, increased Australia. These wasps lay their eggs Natural Sciences, humidity or drought. Pest outbreaks inside scale insects. The wasp larva University of may have a devastating impact hatches and feeds on the host as it Western Sydney in a given year, but cause only grows. Beneficial parasitic wasps marginal losses in other years. and predators (e.g., lacewings and Scale lady beetles) that control scale are iological and non-chemical available from commercial sources. plant protection is important Ants worldwide as an alternative Ants play a role in soil development Bto the use of conventional through their underground nesting chemical pesticides. Biological activity. Ants are general predators pest control is the use of natural of insects and a few species can organisms as an alternative to, or interfere with the biological control in conjunction with, pesticides. of scale and other olive pests. It has become well established Orchards with a history of sooty within protected crops and some mould and considerable ant activity field crops around the world. may require specific ant control The biological control of pests relies measures. Honeydew attracts ants on predation, parasitism or other onto olive trees, and while they natural mechanisms. It can be an forage for honeydew they disturb and important component of integrated attack beneficial insects, disrupting pest management (IPM) programs. the biological control. High levels of The use of biological control methods ant activity on trees often indicate can reduce spraying costs and lead significant populations of honeydew- to a reduction in the potential for producing insects. Ant activity can pesticide resistance. Many pesticides Black scale on olives (above) and therefore be a useful indicator of oleander scale (inset) kill beneficial insects as well as pests. which trees to check more closely for There is an enormous number of these and other pests. An exception The main pest of commercial olives beneficial insects, including hover is that ant activity may be high is black scale (Saissetia oleae). Black flies, lacewings, parasitic wasps, during flowering when the ants scale infestations can result in yield predatory wasps, ladybirds, predatory are attracted to nectar. Ants can be loss, increased fruit washing and mites, spiders and ground beetles. deterred from climbing the trees higher spraying costs. The scale is Flowers are a source of food for with the use of a sticky band traps. actually a hard shell which protects many pest controlling insects, the female insect and eggs. The Olive Lace Bug particularly in their adult form. insects themselves are soft-bodied Plants in the daisy, mint and carrot Olive Lace Bug (Frogattia olivinia) and feed by sucking sap from the families are particularly attractive is the second most common pest plant. Adults do not move around to these beneficial insects. of olives and is found in most olive the plant once they are established growing areas in Australia. This Fungi that infect insects have and form the scale covering. Young simple sucking insect can reduce the received considerable attention scale insects, or “crawlers”, lack the vigour of olive trees. Female lace bugs from scientists for their potential hardened shell and are more mobile. can lay three to four generations of for biological control of pests. Excessive nitrogen fertiliser can eggs per year which are laid along Much research has focused on the make plants more susceptible to the leaf mid-vein, then protected selection of virulent strains for damage from insects such as scale by a cover of black excreta. Trees target pests and their development that feed with piercing-sucking suffering from stress will be more as biological control agents. mouthparts, because nitrogen is affected by lace bug. Natural enemies Pests and diseases are almost always a critical nutrient for them. By are important in controlling some the result of plant stress. These fertilising too frequently, you may species of lace bugs. Predators of lace include: nutrient deficiency, water actually be creating a situation that bugs include lacewing larvae, lady stress, temperature extremes and favours the scale. At least 15 species beetles, jumping spiders, predatory chemical damage. Pest infestations of parasitoid wasp have been recorded thrips, and predaceous mites.

32 THE OLIVE PRESS April 2011 PESTS AND DISEASES

Entomopathogenic fungus Green Vegetable Bug (GVB) Entomopathogenic fungi are The Green Vegetable Bug Nezara( widespread in agroecosystems. viridula) or stink bug, is widespread Beauveria bassiana is a fungus across Australia and can cause which causes a disease known as the trouble for olive growers. It generally white muscadine disease in insects. pierces the fruiting parts of plants When spores of this fungus come and sucks out the juices. Stink bug in contact with the cuticle (skin) of populations can be suppressed by susceptible insects, they germinate predators and parasitic wasps. and grow directly through the cuticle A parasitoid wasp Trissolcus basalis to the inner body of their host. The has proved an effective parasite of Green vegetable bug nymph on an olive fungus then proliferates throughout GVB. This tiny wasp (1–1.3mm the insect, eventually killing it. in length) also attacks the eggs Unlike bacterial and viral pathogens, of other species of stink bugs. control will completely replace Beauveria infects the insect via T. basalis females parasitise stink bug chemical pesticides in the foreseeable contact, and does not need to be eggs by inserting one of their own ingested. Once the fungus has killed future, the use of biological eggs inside the host’s egg. They grow it’s host, it grows back out through the control agents could be used as and pupate inside the egg where the softer portions of the cuticle, covering one component of an integrated adults emerge 9 to 12 days later. the insect with a layer of white mould. management program to achieve This downy mould then produces T. basalis is also known to parasitise the best possible results. Biological adult stink bugs, laying its eggs millions of new infective spores that control is the key for up-to-date directly on the stink bug. Once the are released to the environment. and environmentally respectful Commercial development of this young exit the egg, they bore a hole integrated crop protection. fungus for biological control has inside the adult stink bug and feed primarily been targeted against foliar on them until they are completely You can view images and read more about feeding pests as soil borne pests developed, killing the bug. beneficial insects at Vera’s website, www. tend to be tolerant to the fungus. While it is unlikely that biological olivediseases.com

April 2011 THE OLIVE PRESS 33