Orange wheat blossom Summer 2016 midge · Orange wheat blossom midge survive in the soil, as larvae...

Cocoons Cocoons

Adults

Orange wheat blossommidge survive in the soil,as larvae inside cocoons,for ten years or more.They pose a major threatfor up to four years.

Larvae emergeand move to thesoil surface.

If soil is warm (over 13°C) andmoist – usually after heavyrainfall – larvae pupate. Ifconditions are unsuitable,larvae return to cocoon stage.

Larvae feed on developing grain forabout two weeks before dropping to theground. When conditions are suitable,usually after rain has moistened the soilsurface, they burrow into soil andhibernate as larvae within cocoons.

PupaeLarvae

layer of the grain (pericarp) allowswater to enter, resulting in sproutingin the ear and facilitating secondaryattack by fungi causing fusarium andseptoria. This affects both the yieldand quality of grain harvested.

Always read product labels, consider yourlocal conditions and consult a professionalagronomist, if necessary.

ImportanceTwo wheat blossom midge speciesoccur in the UK: orange wheatblossom midge (Sitodiplosismosellana) and yellow wheatblossom midge (Contarinia tritici).Orange wheat blossom midge(OWBM) is usually the most

significant and economicallyimportant species.

Wheat blossom midge larvae feedon the developing seeds, causingsmall, shrivelled grains with poorgermination. Damage to the outer

After hatching, larvae crawl down tothe developing grain and begin tofeed. They exude enzymes that breakdown cell walls and convert starchback to sugar. Larvae hatching afterflowering do not develop properly andcause little damage.

Life cycleMidges usually fly when airtemperature exceeds 15°C but flighthas been observed down to 10°C,especially within crop canopies.

Male midges fly to seek a mate onthe first evening after hatching.Mated females then fly on the nextfive suitable evenings. They lay mosteggs on their first evening of flight.

Females fly in low light conditions,so, on sunny days, they fly later in theevening than on dull, overcast days.Only female midges fly betweenfields and only when conditions arestill. On windy days, they lay eggs onears sheltered within crops.

Eggs are laid inside the florets ofemerging wheat ears. Crops atGS53–59 are vulnerable. Dependingon temperature, larvae hatch within4–10 days.

Latest information– There are a number of winter wheatvarieties resistant to OWBM.

– Natural enemies provide a usefullevel of control.

– Pheromone traps provide theearliest warning of midge activity.

– There are three active substancesapproved to reduce damage causedby OWBM.

– The effective window for treatmentis narrow.

Action– Grow resistant varieties wheresuitable.

– Use pheromone traps to monitoractivity.

– If thresholds are exceeded, treatcrops as quickly as possible.

– When control is necessary,prioritise seed crops and premiumcrops, ie milling.

Orange wheat blossommidge

©Jon Oakley

Information Sheet 53Summer 2016

Orange wheat blossom midges

Risk factors– Growing a susceptible wheatvariety: OWBM can be found in anyfield where susceptible wheatvarieties have been grown in thepast four years

– Rye-grass is also a very good hostplant for orange wheat blossommidge

– Larvae will pupate in warm, moistsoil, usually after heavy rainfall

– Midges usually fly when airtemperatures exceed 15°C

– Ears are most at risk from when aquarter of ears have emergedabove flag leaf ligules until earshave completely emerged aboveflag leaf ligules (GS53–59)

Monitoring Pheromone trapping– Place traps within fields damagedby OWBM in the past two years,regardless of whether the currentcrop is cereals, any other crop orfallow

– Attach traps to stakes at cropheight when the flag leaf sheath is

swollen (GS45), a week before thefirst ears emerge

– A minimum of two traps should beplaced in each field and should coverdiscrete blocks of cerealsrepresenting different soil types,rotations, rainfall or soil temperature

– Leave the traps in position until anycrop in the immediate area hasreached flowering (GS61)

Place pheromone traps at heightof crop ears

Visual crop inspection– Inspect susceptible crops at earemergence (GS53–59)

– Inspection is best conducted frommid-evening as light levels fallwhen midges are spread evenly

– Walk about 30 metres into thefield, examining up to 100 ears, toassess if infestations exist andexceed threshold levels

Resistant

Susceptible feed crops

Susceptible millingand seed crops

Not applicable

One midge for every three ears through GS53–59or if a cloud of midges is seen when parting thecrop

One midge for every six ears through GS53–59 orif a cloud of midges is seen when parting the crop

Variety status Treatment threshold

Place yellow sticky traps level withemerging ears

30 or more

Over 120

General risk to crops in following week when fertilisedfemales lay eggs. Monitor crops for female midges usingthe visual crop inspection method

Very high risk. Treat susceptible wheat crops insurrounding fields at GS53–59 as soon as possible.

Pheromone trap catchesMidges/trap/day

Yellow sticky traps– Yellow sticky traps are used toassess risk and monitor movementin current wheat fields

– Give priority to milling or seedcrops and to more sheltered feedcrops

– Use at least two yellow stickytraps, hung at ear height in eachfield at ear emergence

– Both sexes are caught, as well asmany other insects, so correctidentification is essential

A catch of around ten midges/trapduring ear emergence indicatesan increased risk and the visualinspection method should beused.

The highest crop risk is on thethree nights following a rise inpheromone trap catches.

Adult orange wheat blossommidge

©ADAS

©Jon Oakley

Assess risk and monitormovement

Cultural controlRotation has little effect on overallrisk of OWBM. Where crops aregrown in blocks, this may helpmonitoring and control in currentcrops. It may also reduce future risk.

Cultivation methods that are moreaggressive can cause the greatestreductions in OWBM numbers butmay also have a negative effect onnatural enemies that also overwinterin the soil. The presence of strawresidues can reduce the incidence ofOWBM but may encourage slugs.

Resistant varieties do not requiremonitoring or insecticide treatment.Wound plugs form on attacked grainsand prevent larvae from feeding.Varieties that are resistance toOWBM are listed on the AHDBRecommended List. Resistantvarieties are, however, susceptible toyellow wheat blossom midge,although this species is lesscommon.

Growth Stage (GS)*

GS41

GS43

GS45

GS47

GS51

GS53

GS55

GS59

Flowering

Pheromone trapping

Set up traps

Check traps daily andrefer to treatment

thresholdsInspect ears daily in theevening and refer totreatment thresholds

Visual inspection Yellow sticky trap

Risk assessmentThresholds

Monitoring timings

*Refer to the AHDB Cereal growth stages guide for information on growth stages

Orange wheat blossom midgelarvae

Orange wheat blossom midgedamage

Booting

Ear emergence

©ADAS ©ADAS

Orange wheat blossom midgelaying eggs

©Jon Oakley

Growth stagesFor more information, see Cerealgrowth stages – a guide for croptreatmentscereals.ahdb.org.uk/publications

Biological control Natural enemies

Dance flies (Platypalpus spp.) feedon adult midges during flight.Occasionally, large numbers in Junecan significantly reduce midgepopulations.

All of these natural enemies are vulnerable to insecticides. Only use insecticides when orange wheat blossom midgeinfestations above the thresholds are observed and only treat at susceptible stages.

Further informationCaroline Nicholls, AHDBcaroline.nicholls@ahdb.org.uk

AHDB Recommended Lists forcereals and oilseeds (annual)

cereals.ahdb.org.uk/pests

Encyclopaedia of pests andnatural enemies in field crops(AHDB, 2014)

Cereal growth stages – a guidefor crop treatments (AHDB, 2009)

AHDB Recommended Lists forcereals and oilseeds(cereals.ahdb.org.uk/varieties)

Project Report 451: Integratedmanagement strategies forvarieties tolerant and susceptibleto wheat blossom midge (AHDB,2009)

Project Report 363: Integratedcontrol of wheat blossom midge:variety choice, use of pheromonetraps and treatment thresholds(AHDB, 2005)

Publication orders0845 245 0009cereals.publications@ahdb.org.uk

Chemical controlThree active substances areapproved for OWBM control:lambda-cyhalothrin (eg HallmarkZeon) and beta-cyfluthrin (Gandalf)are both pyrethroid insecticides,thiacloprid (Biscaya) is aneonicotinoid.

An insecticide should be applied ifthe threshold is reached during earemergence, to reduce damage fromOWBM larvae. Larvae cannot becontrolled once they have moveddown into the ear, emphasising theneed to use monitoring to timespraying effectively.

Warning:Correct insecticide timingis critical.

Always read product labels and checkfor buffer zone reductions.

Information Sheet 53Summer 2016

AHDB Cereals & Oilseeds publications are free to levy payers

Electronic version can be downloaded at cereals.ahdb.org.uk

To join the mailing list, contact:cereals.subscriptions@ahdb.org.uk © Agriculture and Horticulture Development Board 2016. All rights reserved.

While the Agriculture and Horticulture Development Board seeks to ensure that the informationcontained within this document is accurate at the time of printing, no warranty is given in respectthereof and, to the maximum extent permitted by law, the Agriculture and Horticulture DevelopmentBoard accepts no liability for loss, damage or injury howsoever caused (including that caused bynegligence) or suffered directly or indirectly in relation to information and opinions contained in oromitted from this document.

Reference herein to trade names and proprietary products without stating that they are protected doesnot imply that they may be regarded as unprotected and thus free for general use. No endorsement ofnamed products is intended, nor is any criticism implied of other alternative but unnamed products.

AHDB Cereals & Oilseeds is a part of the Agriculture and Horticulture Development Board (AHDB).

Parasitic wasps Macroglenspenetrans and Platygaster tuberosulalay their eggs within midge eggs.Wasp larvae attack midge larvae asthey hatch the following year andprevent pupation.

Spiders' webs can trap many wheatblossom midges.

Ground beetles (Carabidae) eatmidge larvae. Numbers eatenincrease if soil is dry, preventinglarvae burrowing into it.

©Jon Oakley

©Jon Oakley

©Jon Oakley