2016 Virginia Tech 3104-1579 (ENTO-201NP)

FungusGnats

EricDay,DepartmentofEntomology,VirginiaTech

Description:Fungus gnats are flies that are greenhouse pests aswell as commonhousehold pests. Theadultsareslender,mosquito-like,anddelicatewith long legsandonepairofclearwings.Theyareaboutbout1/8inch(3-4mm)longandgrayishtoblack.Thelarvaeareslenderpalewormlikemaggotsinthesoilwith a dark head. They can be up to ½ inch long. Fungus gnats are in the order Diptera and familySciaridae.

Habitat:Theyarenoticedingreenhousesasplantsaremovedandlargenumbersofthemflyoutfromunder leaves and from the surface of the pottingmedium. Inhouses theyareusually seen flyingatwindows and around houseplants. Homeownersmaynotice thesesmall flieswhenwateringpottedplants. Thealsooccur incommercialgreenhouseswhere they candamage the rootsof containerizedplants.Fungusgnatsalsoliveoutsideinmulchandcomeindoorviawindowsanddoors.

LifeCycle:Thelarvaeoffungusgnatsliveinmoistsoilandfeedondecayingorganicmatterwithin½inchof thesurface.Theseconditionsareabundantoutside inthefallseasonandnearlyyearroundinpottedplants.

TypeofDamage:Althoughthelarvaerarelyattackhealthyplantroots,theymaynibbleatafewrootsandreducethevitalityofhouseplants.

Chemical Control: For severe cases, consider using a soil drench of an insecticide labeled for use onhouseplantsorgreenhouses. Chemicalcontrolneedstobecombinedwithpropermoisturemanagementthataddressesoverwateringtosuccessfullyobtaincontrol.

CulturalControl:Controloffungusgnatsinthehouseisrelativelysimple.Adultfungusgnatsareattractedtomoist,organicallyrichsoil.Examineallhouseplantsfor"over-wateredsoil."Allowingthesoiltodryoutforseveraldays,oruntilthetop½inchofsoildries,isprobablythebestcontrolofthesepests.Thelarvaeliveinthetoplayerofsoil. Ifthetoplayerofsoilbecomesdry,thelarvaewilldieandtheadultswillnothaveaplacetolaytheireggs.

InterestingFacts:Larvaefeedonhighlyorganicsoilsandcandamagetherootsofbeddingplants,Africanviolets,carnations,poinsettiasandfoliageplants.

Replaces:3104-1579