THE BIOLOGICAL CONTROL OF WEEDS BOOK

INSECTS COMMONLY MISTAKEN FOR BIOCONTROL AGENTS

Before biological control agents are introduced into New Zealand great care is taken to ensure that they will only damage their target weed (see How safe are biocontrol agents for weeds?). Sometimes there are other species present in New Zealand that look a lot like these biological control agents, or damage other plant species in a similar way. Often only people with a specialised knowledge of are able to tell them apart. Also some people are Ragwort flea beetle not aware that New Zealand native plants have natural enemies of their own and become alarmed if they notice any damage. All these native trees and shrubs and have also become a factors can lead to false reports that biological well-known pest of orchards, gardens, and even control agents are damaging non-target plants. pine trees. Although they are normally harmless, Below we describe some species that can easily bronze beetles can sometimes completely be mistaken in this way. defoliate plants and seriously damage fruit crops (especially apples, stone fruit, and berry fruit). You are most likely to see bronze beetles from Bronze beetle October to January. Ragwort flea beetles can The common native bronze beetle (Eucolapsis often be seen all year round now that they are brunneus) is sometimes mistaken for the ragwort completing more than one generation per year flea beetle (Longitarsus jacobaeae). However, in New Zealand. Bronze beetles are larger (about unlike the ragwort flea beetle, which has a limited 6 mm long) than ragwort flea beetles (about host-range, the bronze beetle has a wide host- 2.5–3.8 mm long) and darker in colour, being range. Bronze beetles feed on the foliage of many bronze to black as opposed to golden-brown. When disturbed bronze beetles leap around like ragwort flea beetles do and they make similar ‘shot-holes’ in foliage.

See also Ragwort flea beetle

Flower thrips

New Zealand flower thrips (Thrips obscuratus) can be found on the flowers of a wide range of native and introduced plants, such as flax, kiwifruit, pipfruit, stonefruit, citrus, and Bronze beetle commercially grown cut flowers. They may also

TE WHAKAPAU TARU - ISBN 0-478-09306-3 BASICS March 2007 BASICS ( are checkingforgorsethrips one specieswillbepresent. Ifyou Zealand, andsometimesmore than species ofthripsfoundinNew The adults look similar to many other fruits. be foundonthesurfaceofvarious ( The caterpillarsofanativeinsect,themagpie Magpie moth See also except gorse. gorse thripsare unlikelytodamageanything wings. Host specificity tests have indicated that underway. Flower thrips always have full-length widespread releases ofthisstrainare now more commoninthePortuguesestrain,and seldom haswings,onlywingbuds.Wings are commonly walk.TheUKstrainofgorsethrips tend tojump,whileflowerthripsmore thirds thelengthofflowerthrips.Gorsethrips as ageneralrule gorsethripsare abouttwo- squat while flower thrips are longer and thinner; two speciesapart.Gorsethripsare shortand need a hand lens to be able to tell the encounter flowerthrips. You may at floweringtime,youare likelyto mistaken for the ( Sericothrips staphylinus annulata Gorse thrips. ), particularly Woolly bearcaterpillar ), are sometimes Tyria jacobaeae ). See also has onlyone. two generations per year, whereas cinnabar moth ragwort oroccasionallyonothercloselyrelated host range.Itwillonlybeseenfeedingon preferred. Cinnabar moth has a much narrower where ornamental cineraria are grown, these are weeds (suchasragwortandgroundsel), but a widehostrange,includingmanycomposite tend tobepaleryellow. Themagpiemothhas tell their eggs apart, although magpie moth eggs red markings. You wouldnoteasily beableto cinnabar are brownish-black with striking are brownish-black with white markings whereas size, are also easy to distinguish. Magpie moths bodies. Theadultmoths,althoughsimilarin yellow- andblack-coloured ringsalongtheir caterpillars have smooth bodies and alternating and have long black bristles. By contrast cinnabar stripes running alongthelengthoftheirbodies predominantly blackwithyellowish-orange hatched, theyare notdifficult totellapart.The You may find both on ragwort, but unless newly species.Themagpiemothhasatleast Cinnabar moth. Cinnabar mothcaterpillar Spider mites on Coprosma

Large colonies of reddish spider mites can be found on Coprosma. These mites and their webbing bear an uncanny resemblance to gorse spider mites (Tetranychus lintearius). However, the mites on Coprosma are in fact a closely related related species (Tetranychus sp. near pacificus). Host specificity tests have indicated that gorse spider mites are unlikely to damage anything except gorse. You may see gorse spider mites on other plants from time to time. They will be Closely related mites on Coprosma crawling over these plants seeking out new gorse bushes to attack but they will not be feeding on them. New Zealand. All have patterned wings and you may see them on native daisies (Asteraceae) See also Gorse spider mite. such as Celmisia, Helichrysum, Brachyglottis and Senecio. Host specificity tests have indicated Seed-feeding fly on Celmisia that the two nodding thistle seed feeders are Larvae can be found feeding on the developing unlikely to feed on anything except Carduus seeds inside New Zealand native cotton and Cirsium thistles. plant (Celmisia spectabilis) flower heads. These See also Nodding thistle receptacle weevil, Nodding larvae are similar to nodding thistle gall fly thistle gall fly. (Urophora solstitialis) larvae, but have also been mistaken for nodding thistle receptacle weevil (Rhinocyllus conicus) grubs. However, the fly that lives on cotton plant has been identified as Trypanea sp. This native seed-feeding fly and the introduced nodding thistle gall fly belong to the same family (Tephritidae). We have several other native tephritid flies in

Gorse spider mites BASICS BASICS man’s beard leafminer( ( most commonlymadebythenativeleafminer Clematis Mines maybefoundontheleavesofnative Leaf mineronnative Clematis occasionally beenrecorded attackingnative Nevertheless, the old man’s beard leaf miner has See also attack nativeplants. attack introduced plantsandnativeleafminers wasps. As a general rule introduced leaf miners New Zealand, including flies, moths, beetles and There are manykindsofleaf-mininginsectsin man’s beard. cannot layfertileeggsunlessithasfedonold Thisisbecausetheoldman’sbeard leafminer are grown closeto from theintroduced leafminer, butonlyifthey Some ornamental not leavingadistinctivesemi-circular exitslit. their mines whereas the introduced species does can be identified: the native species pupate inside adult fliesare hard totellapartbutoldmines also occasionallyattacksoldman’sbeard. The forsteri Phytomyza clematadi Fax (03)3219998 Ph (03)3219694 email: [email protected] NEW ZEALAND PO Box 40, Lincoln 7640 Landcare Research Lynley Hayes informationFor contact: further ononeoccasion).Thenativeleafminer (e.g. plants(mainlyC. Old man’sbeardleafminer. Clematis forsteri Native leafmineron Clematis old man’sbeard infestations. ); acloserelative oftheold Clematis Phytomyza vitalbae species may be at risk foetida ). Theseminesare , butalsoC. Clematis forsteri ). like gorseseedweevil( ( inside the pods of native Larvae can be found feeding on developing seeds Weevils on investigate allclaimsofnon-target attack. We takesafetyextremely seriouslyand a non-target plant,pleasefeelfree tocontactus. our introduced biological control agents attacking you are concernedthatyouhavefoundoneof insect youfindononeofourtarget weeds,or If youare uncertainabouttheidentityofan Identifying See also legumes andfoundnosignofattack. studies havecheckedfordamagetoother attack anythingotherthangorse.Recentfield that itisunlikelythegorsepodmothwill on them.Hostspecificitytestshaveindicated sitting on other plants but they will not be feeding than gorse. You mayfindtheadultweevils never beenrecorded attackinganythingother and hasbeenhere formor the gorse seed weevil is common in New Zealand kowhai podsas Peristoreus sudus inside are nativespecies.Theweevillarvaefeeding pod moth( Sophora Carmichaelia ) species. Athough theymaylookabit Gorse seedweevil,podmoth. Cydia succedana Carmichaelia Old man’sbeard leafmineron Stathmopoda aposema andthecaterpillarsinside pods have been identified as Exapion ulicis Carmichaelia e than60years,ithas ) larvae,theseinsects and Sophora and kowhai ) orgorse . Although March 2007 spp. Clematis vitalba