Brunner, Jay F.

Krupke, Christian

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Section No. 6, Biology/PhenologyManagement of native vegetation for control of stink bugChristian Krupke and Jay BrunnerWashington State UniversityTree Fruit Research and Extension CenterWenatchee, WA 98801INTRODUCTIONStink bugs are anemerging pest inmany agricultural commodities worldwide,including apples and pears inWashington and Oregon. The primary stink bug (SB)species responsible for damage inNorth-Central Washington orchards is the conspersestink bug, Euschistus conspersus. This insect spends themajority of its lifecycle innative vegetation outside orchards, immigrating into orchards only in late summer/earlyfall. Research was undertaken to determine whether targeting native vegetation prior tothis immigration would bea viable management tool forreducing fruit injury at harvest.METHODS AND MATERIALS3 bordermanagement strategies were evaluated in 1999:1. Border clearing: Border vegetation containing common stinkbughostplants such asmullein and bitterbmshwasmechanically cleared to bare rock in a 100' longX 50*wide areaimmediately adjacent to orchards withhistories of highSBdamage. Thisclearing was conducted inmid-June, well before thetypical onset of immigration intoorchards in lateJuly. Fruitinjury in theblocks wasassessed immediately beforeharvest to assess efficacy of this strategy in reducing SB immigration andassociateddamage.2. Border baiting: Beginning inmid-June, andcontinuing through September, SBhostplants adjacent to orchards were baited with a lure containing the primary componentofE. conspersus aggregation pheromone. Lures were placed at 20' intervals in a200' plot, with baited sections alternating with unbaited controls of similar habitat.Fruit injury was assessed ineach of theblocks immediately before harvest to evaluatethehypothesis thatSB could be retained onnative hosts (thus delaying/reducingimmigration to orchards) by the presence ofaggregationpheromone.3. Border spraying: Throughout June, JulyandAugust many growers applied broadcastapplications of chemical insecticides to orchard borders to attempt to reduce SBpopulations priorto immigration. Experiments were conducted to attempt to evaluatea) themosteffective insecticides; andb) themosteffective method of delivery ofinsecticides to the target insect. Usingmullein plantsbaitedwith aggregationpheromone, large numbers of SB were concentrated inborder areas tobesprayed.Three insecticides were evaluated: phosphamidon (Swat®), acephate (Orthene®),formetenate (Carzol®). Eachinsecticide was applied with airblast sprayer (broadcastoverentire border) at 400gpaandwithhandgun sprayer (spray targeting onlypheromone-baited host plants) at 200gpa. Numbers of bugs were countedimmediately before spray application, and at intervals of 1,24,48 and72h post-spray.87RESULTS AND DISCUSSION1. Border clearing: Border clearing did not result in significant decreases in SB damageat harvest, suggesting that SB adults are able to immigrate into orchards (likely byflying) from distances ofgreater than 50'.Border baiting: Border baiting did not result in significant decreases in stink bugdamage atharvest, suggesting that the presence of pheromone alone is insufficient toprevent SB immigration into orchards. However, this technique willbe evaluatedfurther in 2000 in combination with targeted insecticide applications (see below), toattempt to reduce SB populations before immigration occurs.Borderspraying: The three insecticides tested all showed limited effectiveness inreducing SB numbers on pheromone-baited plants when applied with an airblastsprayer (Figure 1). However, in all cases, insecticides performed better when appliedusing ahandgun sprayer (Figure 2), suggesting that this method ismore effective indelivering spray to the underside ofthe leaf and the leaf axils, where SB are usuallymost numerous. Research in2000 will continue to evaluate the efficacy of this'attract-and-kiir strategy, as well as assessing rates of pheromone-mediatedparasitism on baited plants, relative to unbaited controls.% mortality• 1 h post-spray• 24 h post-sprayD48 h post-sprayInsecticideFigure 1. Numbers ofstink bugs on pheromone-baited plants at intervals followinginsecticide application with air-blast sprayer.% mortality•1 h post• 24 h postQ48hpostSwat Orthene-1# Carzol-1#InsecticideFigure 2. Numbers of stink bugs on pheromone-baited plants at intervals followinginsecticide application withhand-gun sprayer.88

Management of native vegetation for control of stink bug

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Management of native vegetation for control of stink bug

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