«Robert Spooner-Hart, Len Tesoriero, Barbara Hall 1 © 2007 Rural Industries Research and Development Corporation. All rights reserved. ISBN 1 74151 ...»
In larger groves, driving slowly down rows makes it possible to detect only high populations of pests and diseases that have already caused a signiﬁcant level of damage or, in the case of black scale, produced a signiﬁcant amount of honeydew. (Remember, though, that even when sooty mould is highly visible, it does not necessarily indicate active scale infestations.) Monitoring from a vehicle will also detect only advanced symptoms associated with severe root or limb disease, pesticide injury or nutrient imbalance.
Assessing individual trees is important for early detection of pests and diseases. Within the monitored rows, examine at least one tree in detail. Choose trees in a structured way so that, for example, you check a tree in the ﬁrst third of the ﬁrst checked row, then one in the middle third of the second checked row, and one in the last third of the third checked row. The position of the checked tree within the row in each sub-block should change with each visit. For example, the next time, check a tree in the second third of the ﬁrst checked row, then one in the last third of the second row and so on.
Carefully examine individual trees from all sides and at all heights using a systematic approach. Inspect samples of twigs, ﬂowers and fruit for the presence of pests, 12 diseases or damage using a 10 hand lens (if you ﬁnd hand lenses difﬁcult, you can use a magnifying glass, but be aware that their magniﬁcation and therefore the quality of the observations are inferior). Inspect trees for abnormal ﬂower buds, and check for the presence of thrips by beating ﬂower clusters onto a white background such as cardboard. Inspect fruit for the presence of fruit ﬂy or other damage, as well as for symptoms of disease or deformity.
If scale or lace bug is detected, the life stage(s) should be assessed. Examine scale infestations carefully under magniﬁcation to determine the stage of scale development and the level of parasitism. Turn over adult scales to check for developing eggs or crawlers.
If a pest or disease is detected, check surrounding trees in the row and in adjacent rows to establish the extent of the infestation. Make note of the pattern of infection,
which is the association of the disease or pest with:
terrain (e.g. sheltered or exposed locations, lowlying areas) weather and aspect (e.g. prevailing wind direction, orientation to sun) tree characteristics (e.g. cultivar, tree age, part of tree affected) cultural practices (e.g. irrigation, fertilizers, pesticides, pruning, mulching).
Identiﬁcation of disease pathogens is often more difﬁcult, and if the symptoms are unclear, send specimens to a qualiﬁed plant pathologist for diagnosis.
13 Recording data Record date, tree identiﬁcation and position, pest or disease name, extent of damage, pattern of infection, life stage and any parasitism. Records of pesticide applications, cultural practices and weather greatly help in interpreting monitoring data.
Action thresholds Action thresholds are the levels of pests, diseases or damage at which a decision is made about the action to be taken; they normally take into account natural enemy activity. The decision also needs to take into account previous experience, predicted weather, projected yield and market prices, and grower preference.
Unfortunately, no detailed action thresholds (requiring detailed research) have been determined for major olive pests in Australia, although they have been made for some of the same pests or diseases in different crops, or for olives grown overseas.
Once action is taken, follow up on its results by further monitoring, and by postharvest assessment of fruit and oil yield and quality.
15 Beneﬁcial species In this guide, we have used the term beneﬁcial species to describe the natural enemies of olive pests that may be observed in olive groves, and that give some level of biological control of the pests. These beneﬁcial species may be either native or exotic, and a number occur naturally in groves. In such situations, they can be conserved and encouraged by environmental modiﬁcations, such as the planting of nectar- and pollen-producing cover crops (which can bring negative beneﬁts: see Thrips, p 35) and the reduction in use of broad-spectrum pesticides. Several beneﬁcial species are mass-reared in Australia and are available for purchase (see Australasian Biological Control, www.goodbugs.
Host-speciﬁc natural enemies are discussed and illustrated along with their host pests. Many of these natural enemies are small (2 mm) parasitic wasps (known as micro-Hymenoptera) in the superfamily Chalcidoidea, particularly in the families Aphelinidae, Chalcididae, Encyrtidae and Pteromalidae. Most members of these diverse families parasitise small arthropods, including scales, aphids and insect eggs.
Larger wasps found in groves belong primarily to the families Braconidae, Ichneumonidae and Sphecidae, which prey on larger insects and spiders.
A number of species of ladybirds (family Coccinellidae) are also found in olive groves. Both immature (larval) 16 and adult ladybirds eat soft-bodied insects. Two of the most common species are Cryptolaemus montrouzieri
and Hippodamia variegata:
Cryptolaemus montrouzieri, known as the mealy-bug destroyer, is a native species commonly found on trees infested with scale insects and honeydew.
Hippodamia variegata, known as the white collared or spotted amber ladybird, is a European species. It was ﬁrst recorded in Australia in 2000, and is now common and widespread. H. variegata feeds on aphids, thrips and insect eggs.
Other common predators are spiders, lacewings (see Olive Lace Bug, p 30) and larvae (maggots) of hover ﬂies (family Syrphidae). While these species eat a range of arthropods, their role and impact in olive ecosystems is yet to be fully determined.
L: Adult syrphid hover ﬂy R: Larva of the syrphid hover ﬂy Leafcurling spider Phonognatha graeffei in olive tree © UWS 18 Invertebrate pests Ants (Hymenoptera: Formicidae) Many species Size 3–12 mm Biology and damage Ants do not cause any direct damage to olives, but disrupt biological control of black scale (p 19). Ants enter the tree canopy searching for honeydew secreted by the scale and interfere with predators and parasites, thereby favouring the development of black scale infestations. In some cases, larger species of ants in foliage can be a source of annoyance for grove workers.
Natural enemies None signiﬁcant.
Comments Baiting has been successful in other orchard crops.
Ants attending scales
© Qld DPIF
Armoured scales (Hemiptera:
Diaspididae) Red scale, Aonidiella aurantii (most common) Oleander scale, Aspidiotus nerii Ross’s black scale, Lindingaspis rossi Circular black scale, Chrysomphalus aonidum Parlatoria scale, Parlatoria oleae Size 2 mm Biology and damage Armoured scales are most common in Queensland and WA. There are two to six generations per year. First-generation crawlers normally emerge in late spring. Hot, dry weather reduces the survival of crawlers.
Scales infest leaves and twigs and, sometimes, fruit. No honeydew or associated ants (p 19) or sooty mould (p
51) occur. Can cause fruit marking or pitting and scaleencrusted fruit. Leaf fall and twig dieback can occur in severe infestations.
Major natural enemies Small parasitic wasps, including Aphytis melinus and A. lingnanensis, both of which are mass-reared and commonly released into citrus orchards; wasps Comperiella bifasciata and Encarsia spp.; ladybirds, lacewings and predatory mites.
Comments Sprays need to be targeted at crawlers and young nymphal stages.
20 © UWS L: Red scale infestation on mid-vein of olive leaf R: Red scale infestation on leaves and fruit of ‘Jumbo Kalamata’
L: Armoured scale parasite Comperiella bifasciata with red scale. Note wasp emergence hole R: Red scale parasite Aphytis melinus with red scale 21 Black scale, Saissetia oleae (Hemiptera: Coccidae) Size 3–5 mm Biology and damage Two or three generations occur per year. Widely distributed in Australia. Firstgeneration crawlers normally emerge in late spring.
Hot, dry weather reduces the survival of crawlers.
Scales attack leaves and twigs, resulting in leaf drop, reduced tree vigour and twig dieback in heavy infestations. Ants (p 19) and sooty mould (p 52) are commonly associated with the production of honeydew by adults and nymphs of black scale.
Major natural enemies Small parasitic wasps such as Metaphycus spp. and Scutellista caerulea;
ladybirds (Coleoptera: Coccinellidae), lacewing larvae (Neuroptera) and the scale-eating caterpillar Catoblemma dubia.
Comments Sprays need to be targeted at crawlers and young nymphal stages.
L: Young adult female scales. Note H-shaped ridge on back R: Adult scale on leaves
L: Adult Scutellista caerulea (parasite and egg predator) near black scale adult R: Cocoon of the scale-eating caterpillar Catoblemma dubia.
Note black scale cases on the cocoon © Qld DPIF Parasite Metaphycus helvolus 23 Cicadas (Hemiptera: Cicadidae) Various species, particularly bladder cicada, Cytosoma schmeltzi Size 30–40 mm Biology and damage Cicadas have been recorded in central Queensland laying large numbers of eggs into olive twigs, causing severe damage. The females slit the twigs and insert rows of eggs. The emerging nymphs cause further damage before moving to the soil, where they feed on plant roots for several years. Adults emerge in spring to summer.
Cicada oviposition damage to woody twig
© Qld DPIF
24 Fruit ﬂies (Diptera: Tephritidae) Queensland fruit ﬂy (QFF), Bactrocera tryoni, in NSW and Queensland Mediterranean fruit ﬂy (medﬂy), Ceratitis capitata, in WA Size Adults: QFF, 6–7 mm ; medﬂy, 4–5 mm Biology and damage Female ﬂies lay eggs in ripening fruit, causing small piercing marks. Larvae may develop in fruit. Damaged fruits may prematurely ripen or fall, and are predisposed to fungal fruit rots.
Natural enemies Braconid parasites (Hymenoptera:
Braconidae), the assassin bug Pristhesancus plagipennis and birds, although these rarely achieve economic control. Sterile insect release is used against QFF in south-western NSW, Victoria and SA.
Comments Commercial lures are available for both QFF and medﬂy. However, these target males and are not effective for direct control.
25 Grasshoppers (Orthoptera: Acrididae) Plague locust, Chortoicetes terminifera Spur-throated locust, Austracris guttulosa Migratory locust, Locusta migratoria Wingless grasshopper, Phaulacridium vittatum Biology and damage Plague locust is the most devastating of the locusts, although wingless grasshopper can be a serious olive pest in southern and western Australia. In the non-swarming phase, grasshoppers feed primarily on terminal leaf margins, but the locust phase devours most green plant material, stripping trees rapidly.
Comments During plagues, immediate action is essential. Permits for pesticide use are normally issued in locust plague outbreak years.
Plague locust Wingless grasshoppers © WA DAF 26 Green vegetable bug, Nezara viridula (Hemiptera: Pentatomidae) Size 15 mm Biology and damage This large stink bug damages fruit by piercing with its mouth parts. Immature nymphs are commonly gregarious (found in groups), and are darkcoloured with lighter white, yellow and orange spots.
Natural enemies A small egg parasite wasp, Trissolcus basalis, has been introduced and is well established in many districts.
© Qld DPIF 27 Lightbrown apple moth, Epiphyas postvittana (Lepidoptera: Tortricidae) Size Adult wingspan 18 mm Biology and damage Lightbrown apple moth (LBAM), Epiphyas postvittana, is a native species of leafroller with a wide plant host range. It damages growing tips or inﬂorescences of olives, tying them together with silken threads to form a protected area within which it feeds.
Natural enemies Various parasitic wasps, including the minute egg parasites Trichogramma spp. LBAM is susceptible to the bacterial pathogen Bacillus thuringiensis.
Comments Trichogramma carverae and Bacillus thuringiensis are commercially available.
Above: LBAM larvae © NSW DPI L: Trichogramma wasp 28 Olive bud mite, Oxycenus maxwelli (Acari: Eriophyidae) Size 0.1–0.2 mm Biology and damage Bud mite was ﬁrst detected in NSW in 2000. The mites feed on developing buds, shoots and leaves, causing malformations and shortening of internodes between young leaves (‘witch’s broom’ effect). Most severe in young trees under conditions of warm temperature and high humidity.
Natural enemies Likely to be attacked by predatory mites (family Phytoseiidae) and small ladybirds (e.g.
L: Olive bud mite damage on tree. Note witch’s broom effect R: Olive bud mites on young leaf (magniﬁcation 40) L: Euseius elinae mite, predator of eriophyid mites R: Bud mite damage on young olive leaves
29 Olive lace bug, Froggattia olivinia (Hemiptera: Tingidae) Size Adults 3 mm Biology and damage An Australian native species recorded in NSW, Queensland, Victoria and SA. Adults are mottled brown. There are two to four generations per year. Spiny nymphs occur in clusters on undersides of leaves; the ﬁrst generation commonly emerge from leaves in spring. All stages attack leaves with piercing mouthparts, causing yellow spotting. Black tar spots occur on undersides of leaves. Leaf drop and twig dieback may occur in severe infestations.
Natural enemies Few have been recorded; green lacewings have been observed predating on lace bug nymphs, and birds may also be predators.
Comment The native green lacewing Mallada signata is commercially available.
L: Olive lace bug damage to leaves R: Female olive lace bug and feeding and oviposition marks