» Latania scale, Hemiberlesia lataniae – this is the most important one affecting avocado
» Fiorinia scale, Fiorinia fioriniae
Soft scale insects
» Chinese wax scale, Ceroplastes sinensis » Indian white wax scale, Ceroplastes ceriferus » Pink wax scale, Ceroplastes rubens » Soft brown scale, Coccus hesperidum » White wax scale, Ceroplastes destructor (formerly Gascardia destructor)
General comments
Scale insects typically only reach significant numbers because of excessive insecticide use, especially broad-spectrum insecticides such as pyrethroids.
These insecticides kill the natural enemies of scale insects that keep them under control.
Soft scale insects excrete honeydew on which sooty mould grows.
Scales are often spread and protected by ants, which feed on their honeydew.
Identification
Scale insects affect branches, twigs, leaves and fruit of a wide range of plants.
Many species of scale insects are only about 1 mm in diameter, so close examination is usually needed to see them.
The females lay many eggs under their scale covers. About 7 days later the eggs hatch into tiny crawlers that move around the tree or are dispersed by wind.
When crawlers eventually settle, they start to feed and grow scale covers.
Scale infestations on fruit are a cosmetic problem that leads to downgrading of fruit.
Scale are more serious in later-maturing varieties, like Hass, the longer the fruit are on the tree, the greater the opportunity for a scale population to build up.
For soft scale insects, clusters of small waxy ‘growths’ form on twigs and leaves.
Fruit infested by fiorinia scale. Fiorinia is smaller than latania.
Chinese wax scale is large (up to 7 mm across), white and dome-shaped.
Pink wax scale is pinky brown and measures 3 mm to 4 mm across.
Adult soft brown scale is light brown and about 3 mm long; young scale is yellowy green.
A white wax scale on the fruit stalk.
Treatment / Prevention
Avoid prolonged use of disruptive pesticides such as pyrethroids. Unless the scale infestation is severe, there is little effect on the tree, so check first that it is serious enough to warrant treatment.
Pay particular attention to areas of the orchard where scale was recorded in previous seasons. Monitor every 14 days when young crawlers are active (mainly during the warmer months) and monthly at other times.
A spray is justified when numbers reach four scale per fruit on rough-skinned varieties and 20 scale per fruit on smooth-skinned varieties. Higher numbers can be tolerated on smooth-skinned varieties because it is easier to brush scale off these varieties in the packing shed.
Delay sprays until eggs have hatched and young crawlers have emerged from females.
Crawlers are much easier to control than adults because they have not yet developed their protective covering.
For scale on leaves and twigs, the scale need to be obvious to justify treatment.
If spraying is necessary, it is preferable to use an appropriate and registered oil spray. Narrow range oils as these are less disruptive to beneficial insects.
Oil sprays need to be applied at high volume and achieve good coverage to be effective because the they kill the scale by suffocation.
Avoid oil sprays at flowering as they can interfere with pollination.
The risk of phytotoxicity (leaf and fruit burn) is higher if oil sprays are applied as follows:
at temperatures above 32 °C
when the relative humidity exceeds 90%
to trees in poor health
if soil moisture is low and trees are water stressed
Latania scale usually only becomes a problem as a result of excessive use of broad-spectrum insecticides such as pyrethroids. Broad-spectrum insecticides kill beneficial species that normally keep this pest under control.
The longer fruit are held on the tree, the greater the opportunity for scale to build up.
This is the most important scale on avocados because it infests the fruit.
Identification
Latania scale infest leaves (mainly along the leaf veins on the underside of leaves), twigs and fruit.
They measure 1 mm to 1.3 mm across and are shield-shaped and yellow, with hard, grey-brown to creamy-brown, semi-translucent scale covers. Latania scale can move onto the fruit in large numbers.
Latania scale on twigs.
Severe infestation (bottom) may result in tip dieback and leaf death.
Fruit infested by latania scale.
Treatment / Prevention
Regularly monitor the orchard so that action can be taken before scale insects build up to the point of infesting fruit.
If scale is obvious and numerous on leaves and twigs then infestation levels are serious enough to warrant treatment.
Avoid sprays that are disruptive to beneficial insects.
In smooth-skinned avocado varieties, scale can be brushed off in the packing shed; however, that is difficult for rough-skinned fruit like Hass.
Where required, spray with an appropriate registered oil. Oil sprays need to be applied at high volume and achieve good coverage to be effective because the oils kill the scale by suffocation.
Avoid oil sprays at flowering as they can interfere with pollination.
The risk of phytotoxicity (leaf and fruit burn) is higher if oil sprays are applied as follows:
at temperatures above 32°C
when the relative humidity exceeds 90%
to trees in poor health
if soil moisture is low and trees are water stressed
The redshoulderd leaf beetle, Monolepta australis, occurs in northern New South Wales and Queensland.
Individual beetles are common in orchards and are of little concern; however, large numbers of emerging beetles can aggregate and form swarms that invade orchards.
A ‘feeding frenzy’ develops and the leaves and fruit skin on individual trees can be completely stripped within a few hours.
Damage is often patchy through the orchard. Monolepta attacks many crops and ornamental plants and is particularly attracted to some tree species such as cadaghi (Corymbia torelliana) and Dunn’s white gum (Eucalyptus dunnii) that are often used in windbreaks.
Identification
Redshouldered leaf beetles are about 6 mm long and gold-yellow with an area of red across the top (shoulder) of each wing cover and two red spots on their backs.
The beetle larvae feed on grass and legume roots, pupate in the soil and often emerge in masses after rain. The beetles attack leaves and fruit.
The adult beetle showing the characteristic red ‘shoulders’ and two red dots on its back.
Beetles often cluster together.
Leaves – the beetles feed on the surface layers of the leaves, giving them a scorched and sometimes lacy appearance.
Mild redshouldered leaf beetle damage to leaves.
Feeding by redshouldered leaf beetles on leaves gives leaf margins a burnt and tattered appearance.
Fruit – the beetles feed on and remove the surface layers of the fruit skin. Initially, affected fruit take on a brown, suede-like appearance as the surface skin layers are removed, exposing the underlying tissues to desiccation. As the underlying tissue dries out, the surface of the fruit takes on a dark brown ‘crazed’ appearance.
If damage occurs when fruit is still small, the surface takes on a dark brown ‘crazed’ appearance as the fruit grow.
If feeding occurs when fruit are bigger the effect is not as severe.
Treatment / Prevention
If there is a history of attack by the pest, regularly monitor the orchard, especially recognised hot spots and particularly after rain in spring.
Pay special attention to trees on the edge of the orchard adjacent to windbreaks, grassy fallow and pasture, especially kikuyu.
Due to the speed at which severe damage is inflicted, sprays must be applied quickly.
Spot-spraying of swarms in infested blocks or windbreak trees may be all that is required.
Queensland fruit fly, Bactrocera tryoni, occurs in Queensland and coastal New South Wales. There are interstate regulations in place for fruit being sent from these areas to Victoria, South Australia and Western Australia.
Losses to fruit fly are generally minimal. It is not considered a major pest of Hass avocados in South East Queensland but is more serious in North Queensland.
Thin-skinned varieties such as Fuerte, Sharwil, Shepard and Wurtz are more susceptible to damage.
Identification
The adult female fly lays small, pearly-white, banana-shaped eggs in batches under the skin of fruit.
Freshly punctured green fruit exude a very small quantity of clear sap that dries to form a white, powdery deposit on the skin.
A star-shaped crack develops on the fruit surface around the puncture. On green fruit, a hard callus develops around the eggs that prevent them from hatching. However, the damaged skin means the fruit is downgraded.
Most damage occurs during December to April.
An adult fruit fly is about 6 mm long.
Typical skin damage from a fruit fly sting. The resultant crack is generally star- or T-shaped. Spotting bug stings can look similar.
Magnification of a sting cut open to reveal the white banana-shaped fruit fly eggs within
Queensland fruit fly damage can be difficult to distinguish from that caused by fruitspotting bug.
Control methods are different for these two pests so it is important to distinguish between them and this can be done by cutting through the affected tissue and examining the damage:
Fruit fly damage is superficial, penetrating no more than about 3 mm into the flesh and producing a hard, pear-shaped callus. Small banana-shaped eggs (visible with the use of a hand lens) may also be present inside the callus. Damage is more common on the lower half of the fruit.
Spotting bug damage penetrates deeply into the flesh (up to 8 mm) and is surrounded by dark, water-soaked discolouration. If there are only a few fruitspotting bug lesions, they will generally be more prevalent on the neck of the fruit.
NB fruit fly will take advantage of damage caused by spotting bugs and lay their eggs in the wound.
Treatment / Prevention
First check that the damage is serious enough to warrant treatment. Monitor fruit for damage and use male lure traps (one Amulet® bait per hectare in a Steiner trap) to assess the build-up of fly populations.
Begin monitoring after fruit set and continue until harvest is complete or mid-April.
It is better to start monitoring early so that measures can be taken to reduce the fly population before fruit becomes susceptible.
In addition to good orchard hygiene (collecting and disposing of fallen fruit), there are three treatment options available:
1. When monitoring trap catches and damage are high or increasing, apply bait sprays at 7-to-14-day intervals throughout the orchard. Bait sprays are a mixture of a fruit fly attractant (such as yeast extract or protein hydrolysate) and a pesticide registered for that purpose. Apply to foliage as a low-pressure coarse spray in a strip; bait sprays must be reapplied after rain. Bait sprays are preferred over cover sprays as they have minimal disruptive effects on beneficial insects.
2. In addition to using bait sprays, hang Amulet® Cue-Lure fruit fly stations at the rate of 10 (a grid of 33 m) to 16 (a grid of 25 m) baits per hectare. Amulet® stations should be hung in the most sheltered part of the tree about 6 to 8 weeks before fruit reaches maturity. The lures last about 3 months before needing replacement.
3. Apply a cover spray to the whole orchard. This is a last resort generally used only if Amulet® Cue-Lure stations and bait sprays have not achieved satisfactory control.
Note that regular sprays applied for fruitspotting bug, as fruit are maturing, will generally suppress fruit fly activity sufficiently to negate the need for dedicated sprays.
Nymphs (immature stages) and adults of the planthopper Siphanta galeata.
General comments
An uncommon pest of avocados, it can be problematic in Far North Queensland.
Identification
Adults have distinctive triangular wings that are folded in an inverted ‘V’ above the abdomen.
Adult colouration varies from light green to light yellow. Nymphs have long waxy-white filaments that extend from the rear of the body. Colonies of planthoppers can be detected because of the white waxy filament residues and numerous white cast skins.
Both adults and nymphs hop when disturbed or hide by moving behind stems or twigs to avoid detection.
An adult planthopper (about 10 mm long) on top of the twig and several, much smaller nymphs on the underside.
Planthopper damage to fruit and stems usually leads to the growth of sooty mould.
Treatment / Prevention
Insecticides used to control fruitspotting bug and other pests may give incidental control of planthoppers.
Avoid continuous use of insecticides that are disruptive to beneficial insects.
The insect Euwallacea fornicatus (also known as Xyleborus fornicatus and tea shot-hole borer).
General comments
There are several different species of pinhole borer in Australia, but to date, only one species has been recorded on avocado; this was in both South East and Far North Queensland. A similar species in the United States is a vector for the exotic disease laurel wilt.
Ambrosia beetles, pinhole borers and shot hole borers are all common names describing the same or similar species of tiny borers that share very similar life cycles.
Identification
Tiny beetles (about 1.5mm long) bore into the trunk and branches of trees that are usually dying or under stress. Tiny emergence holes about 0.8mm in diameter pepper the affected trunk or branch. Small amounts of fine sawdust can usually be seen around the entrances to the holes. This is an ambrosia beetle, which means that it excavates galleries in branches, inoculates them with a fungus and then feeds on the ‘gardens’ of fungus. So far it has only been recorded attacking branches up to a diameter of about 4cm, where it causes leaves to wilt then die while remaining attached to the branch. Beetles usually start feeding around the branch junctions and then move along the branch.
A pinhole borer beetle.
Damage caused by the pinhole borer, note the fine sawdust at the entrance of the holes.
Treatment/prevention
The appearance of these beetles is often (but not always) an indication that the tree is under significant stress or is dying. The cause of tree decline should be identified and addressed. This is a new and relatively unknown problem in Australia that needs further investigation. Report any detections of pinhole borers to your state department of agriculture, or the Exotic Plant Pest Hotline on 1800 084 881.
Orange fruit borer occurs along the coastal strip of eastern Australia.
It has a wide host range that includes avocado, citrus, stone fruit, strawberry, macadamia, lychee, guava and camphor laurel.
It is a minor pest on avocado that rarely requires chemical control.
Identification
The caterpillar feeds on the fruit skin, causing damage similar to that of loopers, leafrollers and light brown apple moth.
On Hass, caterpillars spin silken tunnels on the rough skin. When disturbed, the caterpillars wriggle backwards vigorously and drop off the fruit.
An orange fruit borer caterpillar is about 10 mm long.
Typical skin damage from the orange fruit borer caterpillar.
Treatment / Prevention
Monitoring for other caterpillar pests will usually detect orange fruit borer. Insecticides used to control other caterpillars may give incidental control of orange fruit borer.
Mediterranean fruit fly only occurs in Western Australia and there are interstate regulations in place for fruit being sent from Western Australia.
It is not considered a pest of Hass avocados and losses of healthy fruit to Mediterranean fruit fly do not occur.
Identification
Mediterranean fruit fly can very occasionally be found in damaged ripening fruit that has fallen. The small white larvae (maggots) are about 8 mm long when mature and have a thin, slightly tapering body.
Treatment / Prevention
Treatment is not required in avocado orchards unless they are part of a mixed farming venture with other susceptible crops, in which case any baiting program should include the avocado orchard.
Removal of fallen fruit will help stop the breeding cycle of the fruit fly.
Mediterranean fruit fly. (Photo – Scott Bauer, USDA Agricultural Research Service, Bugwood.org)
A wide range of looper species are found on native plants and on commercial crops such as avocado, apple, guava, macadamia and stone fruit.
Caterpillars exhibit the typical looping action when moving but often remain motionless, mimicking a twig, making it very difficult for predators such as birds to detect them.
Identification
» Bizarre looper
Occurs in coastal Queensland. When fully grown, it is about 40 mm long, brown in colour and has a flattened appearance due to shieldlike plates with thorn-like spines on the body. A pair of spines projects like horns from the head. The moth has transparent green wings with a creamy brown border and wingspan of 35 mm.
The bizarre looper has a distinctive appearance.
» Brown looper
Occurs throughout Queensland and northern New South Wales. Young caterpillars are velvety black with several white rings around the body.
Mature caterpillars grow to 60 mm long and are light brown in colour. The moth is brown with a wingspan of about 50 mm.
The brown looper caterpillar.
» Ectropis looper
Has only been recorded in North Queensland and the Bundaberg/Childers area of Central Queensland.
Adult moths lay green eggs in clusters of up to 750 under the old bark of the lower trunk and main limbs, or in crevices of old pruning wounds. Before eggs hatch they turn grey.
The caterpillars reach about 50 mm long and are grey-brown to dark brown or black, with velvety patches on the body. The moth has a wingspan of 30 mm to 45 mm.
Wings and body are light brown to grey with fine dark markings. During the day while it is resting, the moth spreads its wings flat against the tree trunk and branches and remains motionless. Because of its colour, it is well camouflaged against the trunk.
An Ectropis caterpillar (left) showing the typical looping action and well camouflaged Ectropis moths on an avocado trunk (right).
» Grey looper
Occurs in Queensland and coastal New South Wales. The caterpillar grows to about 40 mm in length and is light grey, speckled with yellow. The moth is grey-white.
The grey looper caterpillar reaches about 40 mm in length.
Looper caterpillars chew leaves and the skin of fruit and if present in large numbers can cause significant damage (especially the ectropis looper).
In severe infestations, trees may be completely defoliated, exposing the tree to sunburn. Damage is often more severe in trees adjacent to windbreaks.
Typical leaf damage caused by several species of loopers (left) and severe defoliation caused by ectropis looper (right).
Damage to fruit caused by looper caterpillars, unlike leaf rollers they do not web fruit together.
Treatment / Prevention
Monitor trees regularly to detect early signs of fruit damage. Check for parasitism by Apanteles wasps (white, cotton-like clusters about 5 mm long attached to caterpillars).
The Apantales wasp preys on loopers
Up to 40 Apanteles adults will emerge from one parasitised looper, so parasite numbers are able to increase rapidly if disruptive chemicals are not used in the orchard.
In unsprayed situations, several different parasitoids can be active. Spray when defoliation or fruit damage is severe and parasitism by Apanteles wasps is absent.
Spot spray heavily infested trees leaving light infestations untreated to allow the populations of Apanteles and other beneficial insects to build up.
If spraying is necessary, choose insecticides such as insect growth regulators (IGRs) that will cause the least disruption of natural enemies.
IGRs are most effective when caterpillars are small.
Damage can be caused by the caterpillar stages of two species of light brown apple moth, Epiphyas postvittana and Epiphyas pulla. The latter is known in Western Australia as the ‘western fruit moth’.
General comments
Both species occur throughout the south-west of Western Australia on a number of commercial crops including avocado, apples, stone fruit and grapes, and on a number of weeds.
Identification
The caterpillars are light green, slender and up to 15 mm long with a dark head.
The moth has buff-coloured wings with a span of about 20 mm. At rest, the moths are delta-shaped with two-tone colouring.
The light brown apple moth at rest. Photo Dr Malik Malipatil, Department of Primary Industries, Victoria.
The pest is most active in early spring, slowly tapering off into summer as the weather gets warmer.
Depending on the weather, several generations can occur each season.
Like leafrollers, caterpillars feed in sheltered positions where the fruit are bunched together and touching or where leaves rest against the fruit.
They feed on the skin of the fruit, causing irregular gouged tracks.
The caterpillars can also ringbark the fruit stalk.
Damage caused by feeding of the light brown apple moth caterpillar. (Photo – Stewart Learmonth, DPIRD)
Treatment / Prevention
Where this pest is known to be a problem, monitoring should commence in early spring and continue into mid-summer.
Pay particular attention to bunches of fruit or leaves webbed together.
Pheromone traps (synthetic lures) can help with monitoring.
Should control be necessary, it is important to act early. Formulations containing Bacillus thuringiensis are effective against this pest if applied early enough; otherwise, the use of another registered pesticide will be required.
