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from orchard tree branches are used to monitor abun-dance of apple maggot flies. Insecticide is appliedwhen trap captures reach economic threshold levels(Agnello et al., 1990). Under second-level IPM, odor-baited sticky red spheres are placed on perimeter appletrees to intercept immigrating adults before ovipo-sition occurs. To date, this behavioral approach tocontrol has proven to be effective under a varietyof orchard conditions (Prokopy et al., 1990, 1996;Reynolds et al., 1998). It benefits from the absenceor near-absence of adult emergence from within well-managed commercial orchards and from the fact thatapple maggot flies are univoltine.

There are, however, distinct shortcomings to exten-sive use of a sticky adhesive such as Tangletrap as theagent for killing apple maggot flies that alight on redspheres. First, it is messy to apply sticky adhesive tothe substantial number of spheres needed for control(about 40 h−1). Primarily because of such messiness,apple growers have expressed extreme reluctance todeploy sticky spheres for this purpose. Second, stickyspheres must be cleaned of insects and debris no lessthan every 2 weeks to maintain effectiveness (Duan &Prokopy, 1995b), a labor-costly process.

As an alternative to sticky red spheres, Duan &Prokopy (1995a, b) evaluated red wooden sphereswhose surface was treated with a mixture containingpesticide, feeding stimulant, and residue-extendingagent. Preliminary studies had shown that pesticidealone applied to the surface of red wooden spheresyielded insufficient fly mortality. However, when pes-ticide was mixed with an effective feeding stimulant(sucrose) and a pesticide-residue extending agent (la-tex paint), mortality of alighting flies was high forseveral months thereafter provided spheres were notsubjected to rainfall (Duan & Prokopy, 1993, 1995a).Rainfall had a comparatively minimal effect on resid-ual activity of pesticide but a strong negative effecton residual activity of sucrose, requiring re-treatmentof spheres with sucrose after every rainfall eventto maintain sphere effectiveness (Duan & Prokopy,1995a).

Three approaches have been taken for ensuring asufficient supply of sucrose on the surface of pesticide-treated red spheres throughout the 3-month periodof sphere deployment needed for season-long applemaggot fly control.

The first approach involved attempts to protect su-crose from the impact of rainfall, either by placinga cone-shaped roof above a sucrose-coated sphere todeflect rainfall, or encasing attractive odor, sucrose

and insecticide within a perforated hollow sphere andinducing flies to enter holes and feed on the interiorof the sphere. Neither of these approaches succeeded(Duan & Prokopy, 1992; Reynolds et al., 1996).

The second approach involved a variety of at-tempts to develop a mechanism for ensuring slowrelease of sucrose applied together with latex paintand pesticide to the surface of a wooden or plasticsphere. These attempts included: (a) chemically bond-ing sucrose to pregelatinized corn flour catalyzed bysodium hydroxide or calcium chloride; (b) incorporat-ing sucrose into a polymeric matrix such as agaroseor carboxymethyl cellulose or into substances com-monly used as spreader-sticker agents for pesticides;and (c) overlaying an initial coating of latex paintcontaining sucrose and pesticide with a second coat-ing of latex paint containing linseed oil or shellacto minimize the impact of rainfall. None of theseattempts proved successful (Hu et al., 1996, 1997,1998, unpubl.). Consequently, we have devoted subse-quent attention to renewing rather than preserving theamount of sucrose on the surface of a wooden sphere.

The third approach involved entrapping a largeamount of sugar (sucrose and fructose) in a mixture ofgelatinized flour and glycerin and forming the ingredi-ents into a sphere, thereby creating a large reservoir offeeding stimulant (Hu et al., 1998). Upon drying, thesphere is coated with latex paint containing pesticide.Under rainfall, sugar seeps through the paint and pro-vides a continuous supply of feeding stimulant to thesphere surface. Ideally, such spheres would maintainintegrity throughout a 3-month deployment period andbiodegrade during winter. This approach has shownconsiderable initial promise (Hu et al., 1998; Liburdet al., 1999).

Here, for each of 3 years, we compared the ef-fectiveness of odor-baited pesticide-treated woodenspheres and odor-baited pesticide-treated sugar/flourspheres with that of odor-baited sticky spheres orinsecticide sprays for controlling apple maggot incommercial apple orchards.

Materials and methods

Tests were conducted in 1997, 1998 and 1999 in eachof eight commercial apple orchards in Massachusetts.Each orchard contained four test blocks of medium-sized apple trees (M.26 rootstock) comprised almostexclusively of the cultivars McIntosh and Cortland.Each test block consisted of 49 trees in a seven x seven

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arrangement: seven perimeter-row trees and six suc-cessively internal rows of seven trees each. Test blockswithin an orchard were separated from each other byat least 30 m of orchard trees that received insecti-cide to control apple maggot. During the first weekof July each year (i.e., just before apple maggot flyimmigration), each of the 24 perimeter trees in threeblocks per orchard received an odor-baited sphere. Allspheres were red in color, 8 cm diam., baited with apolyethylene vial containing synthetic fruit odor at-tractant (butyl hexanoate) (Reissig et al., 1982), andhung 2–3 m above ground from apple tree branchesin a way that maximized visual conspicuousness andattractiveness (Drummond et al., 1984). None of thethree blocks was treated with insecticide within the 3weeks prior to sphere deployment and none receivedinsecticide after sphere deployment. The fourth blockin each orchard was treated by the grower with twoor three sprays per year of azinphosmethyl or phos-met to control apple maggot. Spheres remained untilthe end of harvest, about 12 weeks after deployment;those coated with Tangletrap captured apple maggotflies throughout the period of deployment. It wouldhave been ideal to have included in each orchard afifth test block untreated in any manner for controlof apple maggot. To have done so, however, wouldhave severely jeopardized marketability of the fruit,as the apple maggot can rapidly colonize and substan-tially damage unprotected fruit (Glass & Lienk, 1971;Prokopy, 1985).

For wooden spheres, the surface was treated oncewith red gloss enamel latex paint (Glidden, ClevelandOhio) and then after drying, was overlaid with a mix-ture containing 70% of the same paint, 20% sucrose,and 10% Provado (containing 20% imidacloprid). Asshown by Hu et al. (2000), imidacloprid is just as toxicto apple maggot flies and just as durable in latex paintas dimethoate, the insecticide of choice for previousversions of pesticide-treated red spheres (Duan et al.,1995a), and is safer than dimethoate for handling oftreated spheres. Painted spheres were allowed to dryand then equipped with a disc (2 cm tall× 4 cm diam.)of caramelized (hardened) sugar affixed to the top ofeach sphere. The intent was that during rainfall, dewor high humidity, a proportion of the sugar compris-ing a disc would be carried onto the sphere surfaceand thereby re-supply the sphere surface with feedingstimulant. In 1997, discs atop wooden spheres origi-nated from a mixture of 61% sucrose, 17% fructoseand 22% water, which, after heating to 150◦C, waspoured into 2× 4 cm moulds and allowed to cool and

harden. It turned out, however, that such discs dissi-pated in rainfall, dew or high humidity more quicklythan desired (in about 2 weeks). Therefore, in 1998,we used the same type of disc as in 1997 but placedeach disc in an open 2× 4 cm plastic Petri dish toextend residual amount available. The intent was thatdroplets of rainfall striking a disc would cause sugar tosplash onto the sphere surface. Again, rainfall, dew orhigh humidity caused too rapid a dissipation of discs(in about 4 weeks). In 1999, discs were formed froma mixture of 15% paraffin wax and 85% sucrose. Waxand sugar were heated separately to 150◦C until liquidand then were blended. After cooling, the resultinggranular mixture was compressed into a mould, whereit hardened. No Petri dishes were used beneath discs in1999, and discs did not dissipate until about 6 weeksafter deployment. Discs atop spheres were replacedat 2, 4, and 6-week intervals during 1997, 1998 and1999, respectively.

For sugar/flour spheres, ingredients of sphere bod-ies each year were very similar: 18% pre-gelatinizedcorn flour, 18% wheat flour, 22% granulated sucrose,21% corn syrup (containing fructose), 7% glycerin,8% water, 5% cayenne pepper (aimed at deterring ro-dents from feeding on spheres) and 1% sorbic acid(an anti-microbial agent). Neither cayenne pepper norsorbic acid at these doses affects feeding behaviorof apple maggot flies on sugar/flour spheres (Wrightet al., 1998). Each sphere was formed by hand arounda cord in the center and was dried in an oven for hard-ening. Drying time and temperature proved importantto sphere durability under field conditions. In 1997,spheres were dried at 50◦C for 48 h, in 1998 at 60◦Cfor 72 h and in 1999 at 90◦C for 2 h. Sphere dura-bility improved successively each year, with spheresin 1999 maintaining integrity throughout the 3-monthperiod of deployment provided they were not bitten byrodents.

After hardening, sugar/flour spheres received twocoats of latex paint, as described for wooden pesticide-treated spheres. Each year, sugar/flour spheres werereplaced once (at about 6 weeks). In 1997, and toa lesser degree in 1998, replacement was necessaryprimarily because of pre-mature crumbling of spheresfollowing rainfall. Indeed, in both years, spheresshould have been replaced more than once for com-plete continuity of sphere presence in orchard blocks.In 1999, there was little pre-mature crumbling buta greater amount of feeding by rodents, sometimesresulting in complete consumption of some spheres.

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For sticky wooden spheres, Tangletrap (Gempler’s,Mt. Horeb, WI) was applied to the sphere surface.Each sticky sphere was cleaned of all insects and de-bris every 2 weeks and retreated with Tangletrap (ifnecessary) to maintain fly capturing effectiveness.

To evaluate the success of each treatment in con-trolling apple maggot flies, we monitored comparativeamounts of fly penetration into blocks by hanging oneunbaited sticky-coated red wooden sphere from eachof four trees near the center of each block and countedboth sexes of captured flies every 2 weeks, at whichtime spheres were cleaned of insects and debris and re-treated with Tangletrap if needed. In addition, every 2weeks we examined ten fruit on each of ten randomlyselected interior trees per block (20 fruit on each often trees at harvest) for oviposition punctures madeby apple maggot flies. Fruit with suspected punctureswere dissected to confirm larval presence.

Data were transformed to logx + 1 to stabilizevariance and submitted to two-way ANOVA, followedby comparison of treatment means using the leastsignificant difference test criterion at the P= 0.05level.

Results

Assessment via captures of apple maggot flies on in-terior unbaited monitoring traps (Figure 1) showedthat each year, significantly more flies were capturedon monitoring traps in blocks surrounded by woodenpesticide-treated spheres than in blocks sprayed withinsecticide. In 1997, blocks surrounded by sugar/flourpesticide-treated spheres or sticky spheres likewise re-ceived significantly more flies on interior monitoringtraps than did sprayed blocks, but there were no sig-nificant differences among these three treatments in1998 or 1999. Each year, the rank order (most to least)in which blocks received flies on interior monitoringtraps was the same: wooden-pesticide treated spheres,sugar/flour pesticide-treated spheres, sticky spheresand insecticide sprays.

Assessment via fruit injury by apple maggot flies(Figure 1) showed no significant differences amongany of the four treatments for any year except1998, when significantly more injury occurred tofruit in blocks surrounded by wooden pesticide-treatedspheres than in blocks of any other treatment. Eachyear, the rank order (most to least) in which blocks re-ceived injury was the same: wooden pesticide-treatedspheres, sugar/flour pesticide-treated spheres, sticky

spheres and insecticide sprays. The only exceptionwas in 1999, when damage was low in all treatmentsand there was no numerical difference in injury amongthe latter three treatments.

Discussion

Our findings suggest a consistent pattern in ability ofodor-baited red spheres to (a) intercept apple maggotflies before penetration into interiors of test blocks(as measured by flies captured on interior monitoringtraps) and (b) protect fruit from injury. Each year,sticky-coated spheres were only slightly less effec-tive in these capacities than insecticide sprays. Eachyear, sugar/flour pesticide-treated spheres were onlyslightly less effective than sticky-coated spheres, withcomparative effectiveness essentially equal in 1999.Each year, wooden pesticide-treated spheres were lesseffective than sugar/flour pesticide-treated spheres,with comparative effectiveness being most similar in1999. Although yearly ranks among treatments in cap-tures of flies on interior monitoring traps correspondto yearly ranks among treatments in amount of fruitinjury, degree of correspondence varied (for reasonsunknown).

In our judgement, even though 1999 versions ofwooden and sugar/flour pesticide-treated spheres weremore durable and possibly more effective than 1997or 1998 versions, further improvements are needed. Inthe case of wooden pesticide-treated spheres, a largerdisc of wax and sucrose atop spheres is needed to en-sure a continuous replenishing of sucrose to the spheresurface over the entire 3-month season of sphere de-ployment. In the case of sugar/flour pesticide-treatedspheres, there is need for an inexpensive and moreeffective substitute for cayenne pepper for deterringfeeding on spheres by rodents. Cayenne pepper is pro-hibitively expensive at concentrations greater than the5% concentration used here, which was insufficientlyeffective. There is also a need for a private manufac-turer equipped with an extruder and/or an injectionmoulder to produce affordable sugar/flour spheres thatare more uniform in shape, size and hardness thanthe spheres used here, which were formed by hand.Ideally, manufactured sugar/flour spheres would re-main completely intact until autumn or winter, whenfreezing would cause breakdown and disintegration.

Before improved versions of wooden or sugar/flourpesticide-treated spheres can be recommended forbroad usage as a substitute for insecticide sprays to

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Figure 1. Mean number (± SE) of female and male apple maggot flies (AMF) captured per block on interior unbaited monitoring traps andmean percent of fruit (± SE) injured by apple maggot flies (averaged across all sampling periods). Means are from non-transformed data andthose superscribed by the same letter are not significantly different according to ANOVA and least significant difference tests (0.05 level).WPTS= wooden pesticide-treated spheres, SFPTS= sugar/flour pesticide-treated spheres, SS= sticky spheres, IS= insecticide sprays.

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control apple maggot flies, such spheres would needto be evaluated in larger blocks of apple trees thanused here, and deployment patterns of spheres wouldneed to be optimized so as to minimize the number ofspheres per hectare needed to achieve reliable control.Factors such as composition and arrangement of culti-vars within orchard blocks, tree size, and fruit densitycan affect degree of sphere detection by flies (J. Rull& R.J. Prokopy, unpubl.), and hence can have a strongbearing on the number and arrangement of spheresneeded for behavioral control.

Besides apple maggot flies, several other fruit-infesting pest insects have been controlled in researchplots, commercial farms or even large geographicalareas using attracticidal lures or traps. Among oth-ers, these include olive fly,Bactrocera oleae(Gmelin)(Haniotakis et al., 1991), Queensland fruit fly,Bactro-cera tryoni (Froggatt) (Fisher, 1996), codling moth,Cydia pomonella(L) (Charmillot & Hofer, 1997)and light brown apple moth,Epiphyas postvittana(Walker) (Brockerhoff & Suckling, 1999). Most of theefforts aimed at controlling these other species haveinvolved attempts to eliminate or suppress a species ina habitat containing high-ranking hosts, which in somecases are known to offer chemical or visual stimulithat compete effectively with lures or traps used forbehavioral control. Fortunately, in the case of applemaggot flies, apples are not the highest-ranking host(Prokopy et al., 1985), thereby enhancing the chancesthat artificial stimuli employed in traps can competeeffectively with host stimuli.

Acknowledgements

We thank Baruch Shasha, J. L. Willet and R. W. Behlefor assistance in constructing pesticide-treated spheresin 1997 and The Biotechnology Research and De-velopment Corporation for producing spheres used in1999. We also thank Bradley Chandler and StephenLavallee for assistance in evaluating sphere perfor-mance in orchards. This work was supported by grantsfrom the Massachusetts Society for Promoting Agri-culture, the Massachusetts Department of Food andAgriculture, the USDA CSREES Pest ManagementAlternatives Program, the USDA SARE Program, andthe Washington State Tree Fruit Research Commis-sion.

References

Agnello, A. M., S. M. Spangler & W. H. Reissig, 1990. Develop-ment and evaluation of a more efficient monitoring system forapple maggot. Journal of Economic Entomology 83: 539–546.

Brockerhoff, E. G. & D. M. Suckling, 1999. Development of anattracticide against light brown apple moth. Journal of EconomicEntomology 92: 853–859.

Charmillot, P. J. & D. Hofer, 1997. Control of codling moth byan attract and kill formulation. Technology Transfer in MatingDisruption. IOBC/WPRS Bulletin 20(1): 139–140.

Drummond, F., E. Groden & R. J. Prokopy, 1984. Comparativeefficacy and optimal positioning of traps for monitoring applemaggot flies. Environmental Entomology 13: 232–235.

Duan, J. J. & R. J. Prokopy, 1992. Visual and odor stimuli influ-encing effectiveness of sticky spheres for trapping apple maggotflies. Journal of Applied Entomology 113: 271–279.

Duan, J. J. & R. J. Prokopy, 1993. Toward developing pesticide-treated spheres for controlling apple maggot flies: carbohydratesand amino acids as feeding stimulants. Journal of AppliedEntomology 115: 176–184.

Duan, J. J. & R. J. Prokopy, 1995a. Development of pesticide-treated spheres for controlling apple maggot flies: pesticides andresidue extending agents. Journal of Economic Entomology 88:117–126.

Duan, J. J. & R. J. Prokopy, 1995b. Control of apple maggotflies with pesticide-treated red spheres. Journal of EconomicEntomology 88: 700–707.

Fisher, K., 1996. Queensland fruit fly eradication from western Aus-tralia. In: B. A. McPheron & G.J. Steck (eds), Fruit Fly Pests: AWorld Assessment of their Biology and Management. St. LuciaPress, Delray Beach, Florida, pp. 535–541.

Glass, E. H. & S. E. Lienk, 1971. Apple insect and mite populationsdeveloping after discontinuance of insecticides: 10 year record.Journal of Economic Entomology 64: 23–26.

Haniotakis, G., M. Kozyrakis, T. Fitsakis & A. Antonidaki, 1991.An effective mass-trapping method for the control ofDacusoleae. Journal of Economic Entomology 84: 564–569.

Hu, X., J. Clark & R. Prokopy, 1996. Progress in 1995 toward devel-opment of toxicant-treated spheres for controlling apple maggotflies. Fruit Notes (Massachusetts) 61 (2): 10–13.

Hu, X., A. Kaknes & R. J. Prokopy, 1997. Improved pesticide-treated wooden spheres for controlling apple maggot flies. FruitNotes (Massachusetts) 62 (2): 3–5.

Hu, X. P., B. S. Shasha, M. R. McGuire & R. J. Prokopy, 1998.Controlled release of sugar and toxicant from a novel device forcontrolling pest insects. Journal of Controlled Release 50: 257–265.

Hu, X. P., R. J. Prokopy & J. M. Clark, 2000. Toxicity and resid-ual effectiveness of insecticides on insecticide-treated spheres forcontrolling apple maggot flies. Journal of Economic Entomology93: 403–411.

Liburd, O. E., L. J. Gut, L. L Stelinski, M. E. Whalon, M. R.McGuire, J. C. Wise, X. P. Hu & R. J. Prokopy, 1999. Mortal-ity of Rhagoletisspecies encountering pesticide-treated spheres.Journal of Economic Entomology 92: 1151–1156.

Prokopy, R. J., 1968. Visual responses of apple maggot flies:orchard studies. Entomologia Experimentalis et Applicata 11:403–422.

Prokopy, R. J., 1985. A low – spray apple pest management programfor small orchards. Canadian Entomologist 117: 581–585.

299

Prokopy, R. J., 1993. Stepwise progress toward IPM and sustainableagriculture. IPM Practitioner 15 (3): 1–4.

Prokopy, R. J., S. S. Cooley & C. Kallet, 1985. Fruit acceptancepattern ofRhagoletis pomonellaflies from different geographicalregions. Annals of Entomological Society of America 78: 799–803.

Prokopy, R. J., S. A. Johnson & M. T. O’Brien, 1990. Second-stage integrated pest management of apple arthropod pests.Entomologia Experimentalis et Applicata 54: 9–19.

Prokopy, R. J., J. L. Mason, M. Christie & S. E. Wright, 1996.Arthropod pest and natural enemy abundance under second-level versus first-level integrated pest management practices inapple orchards: a 4-year study. Agriculture, Ecosystems andEnvironment 57: 35–47.

Reissig, W. H., B. L. Fein & W. L. Roelofs, 1982. Field tests of syn-thetic apple volatiles as apple maggot attractants. EnvironmentalEntomology 11: 1294–1298.

Reynolds, A. H., R. J. Prokopy, T. A. Green & S. E. Wright, 1996.Apple maggot fly response to perforated red spheres. FloridaEntomologist 79: 173–179.

Reynolds, A. H., A. M. Kaknes & R. J. Prokopy, 1998. Evaluationof two trap deployment methods to manage the apple maggot fly.Journal of Applied Entomology 122: 255–258.

Wright, S. , R. Prokopy & X. Hu, 1998. Structural refinementof spheres for controlling apple maggot. Fruit Notes (Massa-chusetts) 63 (4): 3–5