Another Root PestLectures 15 and 16 Root-feeding insectsWeevilsRostrumRostrumThree importantexamples of theroot weevil complex. Black vine weevilOtiorhyncus sulcatus Strawberry root weevilO. ovatus Woods weevilSciopithes obscurus(1) grow strong varieties ofstrawberries,(2) allow poultry to run in thestrawberry patches(3) trap adults under boards orstraw(4) spray, if you feel you must, witharsenate of lead, two pounds of powder to 100 gallons of water(5) clean up and burn old leaves andrefuse in the fields or gardensA 1926 version of what we would call, IPM!The black vine weevilTypical leaf damage caused byroot weevils. Females have tofeed on leaves to mature theirovaries.More Adult WeevilDamageWeevils beforefeeding on foliageWeevils afterfeeding on foliageThe root weevils are common to the northern half of U.S. and southern half of Canada.The most destructive form is the larval form as grubs feed on roots and lower stems. There are hundreds of hosts, a few would be: yews, rhododendrons, strawberries, many green house plants and Douglas-firs in nurseries.• The flightless, parthenogenic females hide under boards, litter, and trash during the day. •At night they climb plants and feed on leaves. Egg laying occurs during early summer through July. Eggs are found at the base of host plants. After hatching the grubs move into the soil and feed on roots. • Later instars move to the root crown, feed on the stem and pupate just under the soil. • Adults then emerge and continue to feed during warm fall and winter days. Adults are long lived, often more than 3-yrs.Grubs feedingon roots ofrhododendronsLeaf notchingSharon Collman picking weevils outof nursery containersLarvae found in containersIntense root andstem damagecaused by grubsBlack vine weevilSevere damage causedby root-feeding weevilgrubsDamage by root weevils onrhododendron in PNWPest mgt. -- Adult controlshould begin when adultsemerge in May-June. Larvalcontrol is done in autumn.Azadirachtinbifenthrincyfluthrinacephatebeneficial nematodesBeauvaria bassianaPlant weevil-resistant Rhododendrons:R. edgeworthiiR. leuteumR. mergeratumR. trichostomumAnd others.•2 0 0 4The Scarabaeidae: Scavengers and Herbivores Dung beetle -- scavengersaprophageLeaf chafers -- herbivoreA good illustration on theimportance of saprophagousinsects is what happened inAustralia. Cattle were introducedinto vast areas of northernAustralia, an area with few saprophagous insects thatfed on dung.A suite of saprophages were introduced into Northern Australia to recycle the large amounts of accumulatingcattle dung. Introduction of these beetles was a resounding success.Processing bythe beetles wasbeneficial to pasture growth.Dung rollers are fascinating to watchSome scarabs are metallic coloredand used in jewelryThe root and leaf-feeding scarabs (the leaf chafers)severely damage grasses, crops and nurseries.The ten-lined June beetle is a scarab.• Larvae feed on roots•Adults feed on leaves of hardwoodsLeaf chafer adults feed on foliage, while the grubs feed on rootsLeaf chafers include the May beetle, June beetle,Japanese beetle, rain beetle and others. The onesdestroying lawns belong to the Phyllophaga spp.In the PNW these are the June beetles that includeseveral species. Adults are nocturnal andattracted to lights. June beetlesemerge from pupal cells in thesoil during April- June (dependson the weather). Adults feed onfoliage of birch, elm, ash, maples,and other hardwoods.Later each female lays 150-200 eggs inthe soil and larvae feed on rootsof turf or pasture grass.The population overwinters as larvae and the last instar constructsa pupal cell.White grubs -- Larvae are variable in size with robust, cream-colored bodiesand black heads. Grubs feed on roots. Turf damage generally appearsas patches of dead turf that are not anchored to the soil. Symptoms mayoccur from spring through fall.Control -- beneficial nematodes,imidaclopridBacillus popillaeMACH 2Other insecticidesHow -- Treat when grubs are activenear the soil surface.irrigate treated area immediatelyafter application.2 0 0 4Another Root PestThe European cranefly whose larvae feed on stems, root crowns and roots of grassesThe Crane Flies: TipulidaeTipulid larva(“leather jacket”)More on the tipulidsLeather jacketsC.P. AlexanderAlexander, born 1889 and died 1981. During his career he described almost 11,000 species of Tipulidae and he wrote 1017 articles, 20,000 pages of books, and produced 15,000 of his own illustrations. His contribution to entomology is immense.The Tipulidae – crane fliesJ. R. VockerothRecipient of the 2003 C.P. AlexanderAward by the International Societyof DipterologyThe European crane fly: Tipula paludosa Alex., a turf pestLeatherjackets feeingon roots of turfEuropean craneflyLarvae hatch in the late summer and feed onroots, root crowns and shoots through winter and into spring, causing turf damage anytimebetween Jan-May. Affected lawns often thin out severely in early spring when normal turf starts vigorous growth. Starlings and other birds are attractedto infested lawns and may cause accelerated turf damage as they search for larvae.Cranefly larvae can be controlled easily withrecommended insecticides. Monitor turfstarting in Jan, and consider treating whenlarval populations reach 25+ per sq. ft or when damage is apparent.European crane flyin LaurelhurstLeather jacketsAnother Root-feeding Insect: Sod WebwormBelong to the moth family Pyralidae whichinclude the snout moths.Sod webworm damageDamage most common on wetparts of the lawnSod Webworms (Chrysoteucia topiara)Larvae feed at bases of grass blades and onnew tender roots.You can look at the base of the dying sod and observe the chopped-off bladesDamage begins as relatively small, irregular spots of dead and dying grass. During sod webworm outbreaks the spots coalesce and major damage ensues.May-June (Late Spring)• See erratic flying moths hovering over your lawn at dusk;• Erratic flying moths attracted to lights;• Lay eggs in slight lawn irregularities – aeration holes;Summer• Larvae feed on grass blades and succulent roots:Fall & Winter• Pupate in early fall and overwinter as pupaeLate Spring• Next adult generation emergesRemember we said that the sod webworm prefers a wet site? What site is wetter than cranberry bogs?When this insect, Chrysoteucia topiara, is found killing cranberries, it’s called the cranberry girdler.When this insect girdles