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Honeydew from aphidsStem Pests:(some Homoptera)Before we move on to stem pests, there are still some basic entomological topics to discuss.In particular, the digestive system. Why?In order to better understand yourfavorite aphid and other homopteransRemember Aphid FeedingMouthForegutMidgutHindgutMalpighiantubulesRectalareaGeneralized insect digestivesystemForegutMidgutHindgutMalpighian tubuleMidgutFilter chamberof aphids andother homopteransHoney dewHoneydew from aphidsNow we can move on to the stempests, starting with the balsamwoolly adelgid11 Really belong to the family Phylloxeridae0.5mmThe Balsam Woolly Adelgid1,Adelges piceae.1 PhylloxeridGallsGalls1905 in a small coastal town in Maine, a Quarantine Inspector.These European fir trees have only femaleAdelges piceae -- I’ll let them pass.“Males? We don’t need males; we’reparthenogenic.”Unfettered population growth by the BWA began and in a few decades; they killed fir trees in the Canadian Maritime Provinces and today are into the Appalachian Mtns. destroying Fraser fir across thousands of acres.Dead Fraser-firBWAAdelgidThe BalsamWoolly AdelgidComes West in1950The BWA infest and kill: No. 1 subalpine fir, No. 2 grand fir, No.3 silver fir & noble fir, and No. 4 Shasta-red fir is barely attacked.(1) The BWA overwinter as a diapausing1stinstar, the winter form.(2) In early spring, the 1stinstar swells andbegins to produce honey dew as the treesap starts flowing.(3) The immature female molts several timesand becomes an adult in ± 3 weeks.(4) Each female then lays ± 100 eggs.BWA layingeggsLife Cycle of the BWA(5) Eggs hatch in about a week and eachmotile nymph crawl rapidly around thenew foliage, twigs and branches.BWA crawlers(6) These motile nymphs then thread theirstylets through the bark and tap a vascularbundle -- they are stuck for life, a life of sucking sap, the summer form.(7) This summer generation, then aestivatesfor 1 - 2 months. (8) In July they “wake up” and quicklymolt to adults. These summer-generationadults lay ± 50 eggs apiece.(9) Dependingon the climate,elevation, site,aspect etc., theremaybe 2 - 3generations/yr.EggAdultMotile nymphNymph stuckin the phloemOne mmThe BWA in action!Bark surfaceAs BWA feed they inject a toxin intothe actively growing tissues, whichcauses hyperactive growth & gallsA fewBWAMillionsBWAThe BWA DisasterSubalpinefir nearthe town ofConcreteMore BWA DamageIn order to understand why its so difficult to control the BWA, let’sdiscuss the Mortality Quotient.The Mq asks: “how many individuals of an insect population must be killed to prevent the population from increasing.”Mq depends on: (1) fecunditynumber of eggs a female will lay, & (2) sex ratio.Mq = (F)(SR) - 1(F)(SR)Mq = Mortality QuotientF = Average No. EggsSR = No. FemalesNo. Females + MalesThe iris bulb fly:Fecundity = 150Out of 1000 puparia you collected, 500are males. There is one generation/yrof the gladiola bulb fly.Mq = (150)(0.5) - 1( 150)(0.5)150 X 0.986 = 148So: 150 - 148 = 2 (a male and a female) 150 eggs= 0.986(75) - 1(75)Mq = (100)(1) - 1(100)(1)= 0.99/generationi.e., 100 eggs - 99 killed = 1 female!BWAManagement of BWA in the urban environment:• Avoid planting subalpine fir• Maintain a high vigor in plantingsof other Abies spp.• Consider applied control of BWA-infested firs if they have special intrinsic value, e.g. a historical fir planting within the Japanese Garden.• Consider applied control when the aesthetic value of a commercial Abies spp. planting is threatened,e.g. the Christmas tree industry.With valuable trees, you may have to treat -- about bud-break time.Apply insecticideat time of budburst,you should see tinycrawlers.7The balsam twig aphid, Mindarus abietinusEggsStem mothersTwistingnew growthBTA on the stemThe balsam twig aphid can severely damage true firs:¾In nurseries, the terminal needles twist and become deformed.¾ In urban plantings, BTA suck on twigs and foliage producing great amounts of honey dew and sooty mold -- firs become unsightly.April - May: stem mothers sucking on stem next to new buds or on new foliage – needles twist. May - Mid June:vivipary in action:2 or more generationsof wingless females.Mom?Mom?Mom?Mom?Mom?Mom?Mom?Mom?Mom?Mom?June: a winged generationflies off to an alternatehost.July - August:both males and femalesare produced and theyfly back to true firsMaleFemaleUnknown host?True fir: primaryhostLate summer:males & femalesoccurAugust - September: egg laying and the winter is spent in the egg stage. Early next spring eggs hatch and stem mothers start inserting their stylets at the bases of buds.Mating AphidsThe bowlegged aphid, Cinara curvipes; occurs in California Oregon, Washington, Colorado and Utah -- on firs, Engelmann spruce,and deodar cedar.The Cinara spp. aphids have a typical conifer-aphid life cycle and they feed on trunks, stems, and roots. These aphids often are herded by ants, typicallyFormica spp. (e.g. western thatching ants) and Camponotus spp., the carpenter ants.Ants tending Cinara aphidsand Cinara curvipes onbark of white pine.What to do?Aphids:Pest description and crop damage: Soft-bodied insects that suck sap on stems, branches, leaves etc.Biological control: Aphids have many natural enemies.Cultural control: A strong spray of water often effectively removes these suckers.Chemical control: It’s important to cover foliage thoroughlyas well as stem and branches with:o azadirachtino insecticidal soapo acephateo horticultural oils as dormant sprayso


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UW ESRM 451 - Stempests

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