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SPECIFIC PESTS

SPECIFIC PESTS OF Crops

CODLING MOTH

Palaearctic origin - dependant upon pome fruit.

Introduced into Australia 1850s --> Tasmania and spread north

Larvae enter fruit feeding mainly near the core. More damage when they leave to pupate. Cocoons spun in shelter in tree or in debris

Larvae diapause over winter and autumn. Multiple generations in warmer districts.

Normal infestation of 50-100% in unprotected crop.

Control

Light brown apple moth

Species Name: Ephiphyas postvittanna

Australian native leaf roller - polyphagous

Originally in cooler areas of Australia, now extended range to Qld.

Damage includes stunting and deformation of young trees and superficial injury to fruit.

Larvae shelter in leaf roll and so protected against direst sprays.

High resistance ability

Control

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Specific Pests of Livestock

Sheep blow fly

Species Name: Lucilia cuprina

Introduced from South Africa late 1800s

American strain mostly dark-coloured (map of distribution)

Flies oviposit in wounds or fleece rot and some in carrion

Evidence that in Australia L. cuprina is evolving towards obligate parasitism

Exacerbated by skin folds of sheep and diarrhoea caused by helminth (worm) infestation.

Control problems:

Control

SCREW WORM

Species Name: Cochliomyia hominivorax

Distribution:

Old World --> Africa, India, SE Asia, PNG
New World --> USA, South America

Damage:

Similar to sheep blowfly strike on cattle, sheep, goats
$750 million annual losses

Control:

Wound treatment, insecticide spray or dip

Eradication:

Achieved first in USA then Mexico and finally Central America by mass release of irradiated sterile males. USA declared free in 1966.

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Specific Pests of stored products

Warehouse beetle

Species Name: Trogoderma variabile Ballion

This beetle is related to, but is not as big a pest problem as the dreaded khapra beetle, T granaries. The beetle was first found in Australia in rice mills at Griffith, Leeton, Coleambally and Deniliquin: in March 1977 an eradication campaign was started.

Southwest NSW, including the MIA, was declared a quarantine area in December and a survey undertaken during April 1978. Infestations were found in Dubbo and Sydney during 1979 and by November 1979 doubts starting that eradication was not possible. Major infestations were found in northern centres, based on Gunnedah in August 1981 and a major control program started in December 1981. The control program was terminated in December 1982 after 33 farms were found to be infested in the Gunnedah area, as well as infestations found in several Grain Handling Authority premises.

A further survey conducted in NSW during 1993/94 indicated most of the northern infestations had been eliminated, but there were infestations within the MIA (Yenda, Griffith mainly). Rice mills were still the main site of infestations. An Australia-wide survey during 2003 indicted this beetle was widely distributed throughout the mainland states.

Control

T variabile does not disperse well on its own, with most new infestations starting from infested material brought into the premises. Overall hygiene is very important as infestations were usually associated with spilled material, especially old rat or snail bait. The same range of stored product protectants and fumigants are used to control existing infestations. Infested bagged grain is fumigated. It is important to clean up the premises as thoroughly as possible before applying any chemical treatment.

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Other PESTS

Bush fly

Species Name: Musca vetustissima

Native, favoured by European settlement. Distributed over most of Australia, particularly in warmer months and in open areas.

Die out over winter in the south but spread from he north with winds in spring.

Feed on sweat, tears, saliva and blood of large animals + faecal material

Mostly nuisance value but can be vectors of eye infections.

Breeds in fresh, moist dung, pupates in soil beneath.

Control by introduction of African dung beetles - many species - increase mortality of eggs and larvae by disturbing and burying dung.

Thrips vectors of Tospoviruses

At present there are three different plant tospoviruses and four known vectors present in Australia. The tospoviruses are Tomato Spotted Wilt Virus, (TSWV), Capsicum Chlorosis Virus, (CaCV) and Iris Yellow Spot Tospovirus (IYSV). The vector thrips are Onion Thrips, Thrips tabaci, Melon Thrips, T. palmi, Tomato Thrips, Frankliniella schultzei and Western Flower Thrips, F. occidentalis.

TSWV is vectored by T. tabaci, F. schultzei and F. occidentalis: CaCV appears to be vectored by T. palmi and IYSV is only vectored by T. tabaci. T. tabaci is cosmopolitan and may have been in Australia for some time. F. schultzei arrived in the early 1800's, and has spread throughout mainland Australia. T. palmi arrived in the late 1980's and at present is confined to tropical Australia. F. occidentalis arrived in separate introductions to Western Australia and New South Wales during 1993; it is slowly spreading in areas of intensive horticulture, but is not establishing in native vegetation.

TSWV has always been of importance in Australia - the disease was first described from Australia in 1915 and the role of T. tabaci and F. schultzei as vectors was also determined in Australia. It was after the arrival of F. occidentalis that TSWV became more frequent and of greater intensity. This is because vector thrips can only acquire the virus as first instar larvae, so the thrips have to reproduce on infected plants. Of the vector thrips, only F. occidentalis does not migrate very much, with populations turning over in the same area; if there are any infected hosts, the chances of a thrips acquiring the virus is much higher.

There are two components of disease transmission by vectors:

  1. the inherent ability of a thrips species to become infected and to pass on that infection,
  2. the probability a thrips will acquire the virus.

Most work is done on component 1 and component 2 can only be assessed from detailed field studies. It is because Australia has had at least two vectors that TSWV has flourished here, despite the absence of F. occidentalis, which is regarded internationally as the main vector. Once it arrived in Australia, TSWV became a larger and more regular problem, but not to the same extent as in Europe and eastern North America.

CaCV originated in Queensland in the late 1980's and appears to be associated with T. palmi, although both species of Frankliniella are usually present as well. This tospovirus is noteworthy in that it infects TSWV-resistant cultivars of capsicum and chilli. At present the virus is mainly in the Childers/Bundaberg area, where considerable intensive horticulture is conducted.

IYSV has been recently found and probably came in as infected planting material. The only known vector, T. tabaci is abundant, so it is a matter of waiting to see what develops. Main hosts are Allium crops and irises.

Control

All thrips need to be managed, rather than controlled. This is best done by farm hygiene including suppressing flowering non-crop hosts. This latter group includes clovers and medics, which in the Sydney basin are the main non-crop thrips hosts. Also, known tospovirus non-crop hosts should be eliminated - all thistles are good hosts. F. occidentalis is the only thrips to have developed major insecticide resistance problems, to the extent many chemicals are no longer effective.

There is a Resistance Management Strategy, which involves applying three sprays 3-5 days apart using one chemical. The next spray cycle uses a chemical from a different group, with a different mode of action and a different resistance mechanism. At present, using all available insecticides, there are five groups that can be used. Unfortunately, some of these groups rely heavily on the newer insecticides (so called New Chemistry), so there is a single chemical in the group.

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Resistant Varieties

Insect Resistant Lucerne Cultivars

There are presently three species of exotic lucerne aphids present in Australia: Therioaphis trifolii (Monell) f maculata, spotted alfalfa aphid (SAA), Acyrthosiphon kondoi Shinji, bluegreen aphid (BGA) and Acyrthosiphon pisum (Harris), pea aphid (PA). SAA and BGA were first recorded in Australia in 1977 and PA in 1980.

Prior to the arrival of these aphids, the Australian lucerne industry was reliant on one cultivar of lucerne - Hunter River, which although highly adapted to Australian growing conditions, was highly susceptible to aphid attack. In response, aphid resistant cultivars were imported from the USA and set in a major plant breeding initiative by State Departments of Agriculture, CSIRO and commercial seed companies. Starting in 1978, by 1988 there were over 30 locally produced lucerne cultivars available, all showing various levels of resistance to each of the aphids. A rating system was developed, usually based on field studies, to classify the plant response to aphid attack: these classes ranged from susceptible to highly resistant for SAA and susceptible to Moderately resistant for BGA and PA.

Considering the aphid response, this was most dramatic for SAA, with marked reduction in fecundity for even low level resistance, whereas for BGA and PA, the reductions were much less. This also reflects the effects aphid feeding has on the lucerne plants. SAA produce a toxic saliva that directly harms the plant, BGA produces a plant hormone mimic that reduces the internode length and PA shows direct feeding effects.

There was a range of native and established parasites and predators that helped reduce aphid numbers. In addition, several parasites were introduced, mainly Trioxys complanatus for SAA, Ephedrus plagiator and Aphidius ervi for BGA.

Overall, lucerne aphids are now commercially controlled by a combination of parasites, predators and resistant varieties. Considering the total devastation of lucerne that was occurring in 1997 and 1978, this is a remarkable illustration of interdisciplinary research and adaptation.

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