IMP – Scouting and Monitoring for Pests in Commercial Greenhouses

IMP –Scouting and Monitoringfor Pests in CommercialGreenhousesF-6711Linda A. TopliffGreenhouse IPM CoordinatorMichael A. SchnelleExtension Ornamentals/Floriculture SpecialistKenneth N. PinkstonExtension EntomologistGerrit W. CuperusExtension IPM CoordinatorSharon von BroembsenExtension Plant PathologistEnvironmental issues, restricted labeling of pesticides,and pest resistance are all concerns causing the commercialgrower to seek alternative forms of pest control. Integratedpest management (IPM) is a holistic approach to pest controlin which multiple practices are implemented throughout theentire production period of the crop. Some of these practicesare preventative—good sanitation and sound cultural practices.Other practices are implemented as control methods—applying less toxic and/or environmentally sensitive pesticidesand introducing biological control agents, as well as thejudicious use of traditional pesticides.Crop monitoring is the foundation of an IPM program.Crop monitoring provides heightened awareness of pestpresence, activity, and control. It addresses the real needs ofthe crop, reduces pesticide use by eliminating unnecessary,routine applications, and assures that pesticides are appliedat the proper life-cycle stage to insure effectiveness.PrerequisitesA successful IPM program depends upon a successfulmonitoring program. There are several prerequisites whichmust be satisfied to accomplish this. An implementor of anIPM program must:1. Commit enough time and sufficient money to expand pestcontrol practices from total dependence on pesticides toa truly integrated system.2. Establish an IPM team and decide who is going to makethe pest management decisions.3. Provide team members with the proper equipment including:10X hand lens, books with pictures for proper identificationof pests, maps of greenhouses, etc.4. Divide the greenhouses into logical units and then makemaps of these units so all members of the IPM team cancommunicate pest and crop information uniformly.Oklahoma Cooperative Extension Fact Sheetsare also available on our website at:http://www.osuextra.com5. Provide adequate training to team members to allowthem to identify pests in all life cycles.6. Hire a consultant or professional scout if employees arealready overworked.Scouting MethodsThe primary goals of monitoring are to locate and identifyinsect, mite and disease problems, and to observe changesin the severity of infestation. These are accomplished byrandom plant inspections throughout the production area andby the use of sticky traps and indicator plants.Random plant inspections should be performed weeklyor, preferably, twice weekly during the entire productionseason. Scouting procedures should be as routine as possible.Monitors should establish a pattern that will cover allareas of the greenhouse and follow the same pattern everytime. Scouting must be intensive; the more plants monitoredthe better. Scouting should start from a major doorway. Thisis often the location where disease and pest problems begin.Special attention should be paid to plants around any openingsin the greenhouse, especially those plants on the outsiderows of benches.Monitors should walk every aisle and move from benchto bench in a snake-like or zig-zag pattern. At least 10 minutesshould be spent inspecting 20 or more plants from every 1,000square feet of production area. The number and size of plantswill affect the scouting pattern, as well as the location and sizeof the benches in the greenhouse. At least three plants onevery bench should be inspected, from the edge, the middleand as far into the bench as can be reached. Individual plantsshould be chosen at random and inspection should includechecking for insects, mites, or disease symptoms. Inspectionis begun at the bottom of the plant and proceeds upwards,from older leaves to younger leaves to new growth. Specialattention should be paid to buds and blooms. Pots should betipped sideways for inspection of the underside of the leaveswhere many of the pests reside. Root examinations should beperformed on crops that are highly susceptible to root diseaseby inverting and removing the pot. Hanging pots and basketsmust also be inspected. Since most pests that attack greenhousecrops do not distribute themselves evenly throughoutthe crop, one should never assume to know exactly where thepests are, or a serious misjudgment could occur and an entireinfestation overlooked.Division of Agricultural Sciences and Natural Resources • Oklahoma State University

In addition to random plant monitoring, a daily inspectionof indicator plants and sticky traps is necessary. The firstdiseased or pest-infested plant found on a bench becomes anindicator plant. This plant is marked with a stake or in somemanner that allows the employee to check the same plantdaily. Checking the same plant daily allows for an ongoingclose examination of pest populations or symptoms as theyspread to surrounding plants. The scout can also follow thedevelopment of a pest problem, noting the rate at which the lifecycle is progressing. Tracking the development rate providesthe manager with necessary information regarding the besttime for pest control measures, if necessary. Indicator plantscan also be used to check if treatments were effective. Ahighly susceptible host plant is an excellent indicator plant.Grown among the commercial crop, it is the first plant tobecome infested or diseased and helps simplify crop monitoring.Some highly susceptible host plants and the pests theyattract are as follows:1. Whiteflies—tomatoes, lantana, gerbera daisies, andfuschias.2. Spider mites—marigolds, roses, and parlor palms.3. Aphids—sweet peppers and fuschias.4. Thrips—petunias and gloxinias.5. Tomato Spotted Wilt Virus—petunias and glaxinias.While indicator plants are useful as monitoring devices, caremust be taken so that they do not become sources ofreinfestation.Another method of monitoring a greenhouse for insectpests is the use of sticky traps. The traps come in two colors,a bright yellow and a medium blue. Most greenhouses use theyellow traps which attract flying aphids, fungus gnats, whiteflies,leafminers, thrips, and others. Blue sticky traps are usedto attract mainly thrips. These brightly colored cards arecovered with a sticky substance that traps the insects. Thesemay be purchased pre-made or materials may be purchasedseparately and the traps made by hand, which is moreeconomical. When using only one color, yellow traps shouldbe chosen because of their general attractiveness.Sticky traps should be placed throughout the greenhouse.They should be placed in a grid-like fashion, at leastone card per 1,000 square feet of production area. More trapsper square foot of production area are beneficial. They areplaced just above the plant canopy to 16 inches above thecrop. Sticky traps should be placed in the same position everytime. This allows for accurately determining the increase ordecrease of pest populations as the production seasonprogresses. Sticky traps should be checked at least once aweek. Most growers prefer to check them every three days.Daily monitoring of the traps is recommended if time andpersonnel permit.Time counting insects on sticky traps may be reduced bycounting the insects within an one inch wide vertical columnon the trap. Aphids and thrips tend to be caught on the bottomhalf of the traps. Leafminers are caught more often along thetop, and leafminer wasps and whiteflies tend to be spreaduniformly over the trap. Aphids tend to be caught in the middlevertical columns. Since insects are not distributed evenlyhorizontally across the trap, columns counted should bevertical towards the middle of the trap.To identify insects on the sticky traps, a 5X to 10X powerhand lens will be necessary. When handling the sticky traps,it is beneficial to have some waterless hand cleaner nearby.The adhesive used on the traps is a polybutene-naphtharubber polymer that remains viscous for long periods. It isdifficult to examine the traps without getting adhesive on thehands. The following is a list of characteristics to help in theidentification of insects on sticky traps (Figure 1):1. Aphids. The wings of aphids often settle symmetricallyinto the adhesive to either side of the body. They sometimesgive birth to one to five nymphs before they die. Thefront wings usually have two parallel veins close to thefront edge. These veins end at a dark, skinny spot on thefront edge. The legs and antennae seem to be long andskinny.2. Fungus Gnats. These are small, dark, mosquito-likeinsects with gray wings. The wing has a distinct, Y-shaped vein at the tip. They have long, skinny legs andantennae.3. Leafminer Flies. Unless the specimen is totally embeddedin the adhesive, it is possible to see a conspicuousyellow spot on each side. They have short antennae andmoderately long legs.4. Parasitic Wasps. These usually have antennae withelbows like an ant, and the forewings have only one veinwhich zigs toward the front margin and zags away.Usually parasitic wasps are more pointed at the rear thanshore flies.5. Shore Flies. These are the largest common fly usuallyfound on sticky traps. They have pale spots on the wings,the antennae are short and the legs are moderately long.Care should be taken when identifying, since shore fliesare often confused with fungus gnats.6. Thrips. These are the tiniest insects found in any numberson the trap. Most appear spindle-shaped with thewings protruding neatly at the rear. Hairs line the edgesof the wings. Often, the stocky antennae protrude in a V-shape at the front.7. Whiteflies. Whiteflies lose their white, waxy bloom asthey are entrapped by the adhesive. They are only a littlelarger than thrips and show up orange on the traps.Usually enough of a wing or leg protrudes above theadhesive so that the white bloom reveals the identity.Record KeepingWithout proper records, scouting will be ineffective. IPMprograms depend upon keeping detailed records. Incomingplant material inspections, random and indicator plant inspections,sticky trap information, and crop treatments must berecorded. All production inputs must be noted concisely andaccurately (Tables 1 and 2). Managers trying to diagnose aproblem without records are at a disadvantage and willoverlook potential causes of the problem. Maps of the greenhousesshowing where benches, sticky traps, and indicatorplants are located should be maintained. Disease, mite, andinsect infestations can be penciled in on these maps, andmovement of the infestation can be monitored. As the seasonprogresses, pest trends develop, and a direction for pestmanagement decisions will be seen.6711-2

Table 1. Incoming Plant Material Inspection Sheet.Location_________________________________________Plant and Number Date Date Pot Date Number InspectionCultivar Received Received Planned Size(s) Inspected Inspected Comments6711-4

Table 2. Yellow Sticky Card Data.Location Card Date WF Thr Aph Fg Sf OtherNo. PlacedWF=Whitefly Aph=Aphids Thr=Thrips SF=Shore Files FG=Fungus Gnats6711-5

Table 3. Plant Pest Scouting Report Greenhouse #_______ Month Of_______, 20______Pest Week#1___ Week #2___ Week #3___ Week #4___ Week #5___Encountered Local General Local General Local General Local General Local GeneralAphidsBeneficialsCaterpillarsFungus GnatsPathogensScalesSpider MitesThripsWhitefliesOther0 = None Found3 = LightPopulation6 = ModeratePopulation10 = HeavyPopulationIndicate localpopulationson maps.List problematicplants below.Abbreviate w/the model asexample.N NN N N6711-6

Table 4. Pesticide Application Log.Pesticide Time Dilution Quanity Appli- Area/ Appli-Trade Active Regist. Target Rate spray cation No. cator’sDate Name Ingred. % No. Start End pest* Crop (eg. ml/L) mix used rate Pots Initials*WF = whiteflies APH= Aphids THR=Thrips SF= Shore Flies FG= Fungus Gnats SM=Spider Mites OTH=Other (Identify)6711-7

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