Comparative Residual Toxicities of Pesticides to the Predator Euseius mesembrinus (Acari: Phytoseiidae) on Citrus in Florida

Experimental and Applied Acarology 25: 461–474, 2001.© 2001 Kluwer Academic Publishers. Printed in the Netherlands.

Comparative residual toxicities of pesticides to thepredator Agistemus industani (Acari: Stigmaeidae) oncitrus in Florida

CARL C. CHILDERS∗, RAUL VILLANUEVA, HUGO AGUILAR,RYAN CHEWNING and JOHN P. MICHAUDUniversity of Florida, Citrus Research and Education Center, 700 Experiment Station Road,Lake Alfred, FL 33850, USA

Received 10 January 2001; accepted 13 May 2001

Abstract. Residual toxicities of registered and selected experimental pesticides used on cit-rus against Agistemus industani Gonzalez (Acari: Stigmaeidae) were compared. Pesticidesconsidered highly toxic to A. industani were: abamectin 0.15 EC at 731 ml/ha + FC 435-66petroleum oil at 46.8 l/ha, pyridaben 75 WP at 469 g/ha, ethion 4 EC at 7.01 l/ha + FC 435-66 petroleum oil at 46.8 l/ha, propargite 6.55 EC at 3.51 l/ha, chlorfenapyr 2 SC at 1.46 l/haapplied alone or in combination with FC 435-66 petroleum oil at 46.8 l/ha, sulphur 80 DF at16.81 kg/ha, dicofol 4 EC at 7.01 l/ha, fenbutatin oxide 50 WP at 2.24 kg/ha, benomyl 50 WPat 2.24 kg/ha, benomyl 50 WP at 1.68 kg/ha + ferbam 76 GF at 5.60 kg/ha, ferbam 76 GF at11.21 kg/ha, neem oil 90 EC at 46.8 l/ha, and copper hydroxide DF (40% metallic copper)at 4.48 kg metallic copper/ha + FC 435-66 petroleum oil at 46.8 l/ha. Pesticides that weremoderately to slightly toxic included: copper sulphate 98% at 4.48 kg metallic copper/ha + FC435-66 petroleum oil at 46.8 l/ha, fenbuconazole 2 F at 280 ml/ha + FC 435-66 petroleum oilat 46.8 l/ha, FC 435-66 petroleum oil applied alone at 46.8 l/ha or 23.4 l/ha, and diflubenzuron25 WP at 1.40 kg/ha. Pesticides that were non-toxic included: fenbuconazole 2 F at 585 ml/ha,malathion 57 EC at 5.85 l/ha, FC 435-66 petroleum oil at 46.8 l/ha, carbaryl 80 S at 3.36 kg/ha,chlorpyrifos 4 EC at 4.68 l/ha, and formetanate 92 SP at 1.12 kg/ha. Understanding the toxiceffects of field weathered pesticides against key predacious mite species is important for ef-fective IPM. The results of this study provide a comparison of direct and indirect toxic effectsof various pesticides to A. industani under field conditions.

Key words: acaricides, fungicides, insecticides, integrated pest and disease management,toxicity, non-target arthropods

Introduction

The citrus rust mite, Phyllocoptruta oleivora (Ashmead), and the pink citrusrust mite, Aculops pelekassi (Keifer), are recognized as key pests of Flor-ida citrus (Childers and Achor, 1999). Both species cause feeding injury to

∗ Author for correspondence: Tel.: (863) 956-1151, Ext. 274; Fax: (863) 956-4631;E-mail: [email protected]

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leaves, twigs and fruit. Rind blemish damage to the fruit surface can eliminatefruit for fresh market and reduce both fruit size and bonding force, increasefruit drop and decrease juice quality (Allen, 1978, 1979a, b, 1980). Approx-imately 171 million dollars are spent annually for chemical control of miteson citrus including combined costs of chemicals and application equipmentbased on estimates for central, east coast and southwest Florida (Muraro andHebb, 1997; Muraro et al., 1997a, b). Control recommendations for mites inthe 2001 Florida Citrus Pest Management Guide consisted solely of pesti-cides (Childers et al., 2001a, b) ignoring the optimization of predacious mitepopulations for pest mite suppression.

Mites in the family Stigmaeidae are recognized as potentially importantpredators of phytophagous mite pests on both apple and citrus in differentareas of the world (Nelson et al., 1973; Childers and Enns, 1975; Muma,1975; Childers, 1994; Searle and Smith Meyer, 1998; Villanueva and Harm-sen, 1998). In addition, stigmaeid species have been reported as predators ofvarious tetranychid and tenuipalpid mite species on grapes, tea, cotton, sweetpotato and potato (Santos and Laing, 1985) or various eriophyoid mite specieson peach, nectarine, citrus, tomato, grape, sweet potato, and fig (Thistle-wood et al., 1996). Recognition of their potential importance as predators ofvarious eriophyoid, tetranychid and tenuipalpid mites continues to increase.Agistemus floridanus Gonzalez occurs in abundance in many Florida citrusorchards with modified to non-spray programs (Childers, unpublished data).

An experiment was conducted to evaluate the effects of different pesticidesagainst A. industani in the field during 1998. This predacious mite specieshas shown considerable promise as an exotic candidate for release on Flor-ida citrus (Childers, unpublished data). Different pesticides were applied andweathered in the field to assess their impact on gravid female A. industani,oviposition and the survival of eclosing larvae.

Materials and Methods

Field application

Five series of field applications were completed between 27 April and 15June 1998 in a 4 ha block of ‘Ruby red’ grapefruit located at the CitrusResearch and Education Center in Lake Alfred, Florida. The treatment treeswere healthy, vigorous and measured 3.2–3.9 m tall and 3.9–5.2 m in dia-meter. Trees were spaced 7.47 m within the row and 8.11 m between rows( = 187 trees/ha). Different trees were selected for each of the series of pesti-cide treatments with a minimum of four trees separating single tree treatmentswithin the row and with two buffer rows between treatment rows.

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Treatments were applied using a tractor-drawn FMC 352 airblast sprayerbeginning each morning after the dew on citrus leaves had dried. The sprayerwas calibrated to deliver 2,338l of spray/ha. Each single tree treatment wassprayed while traveling at 2.4 km/h. Tractor speed was properly adjustedseveral tree spacings ahead of the sample tree before engaging the sprayeron either side within the rows. The pesticides, application dates, water pH,formulations and rates per ha are shown in Table 1.

FC 435-66 represents a medium, narrow-range petroleum oil with a mid-distillation temperature of 224◦C ( = 435◦F) that meets the designated Floridacitrus standards established by Simanton and Trammel (1966). T-Mulz (Har-cros Chemicals, Inc., Kansas City, KS), a non-ionic surfactant, was mixedat 10 ml per liter of petroleum oil as the emulsifier. Pesticides tested areregistered for use on Florida citrus except chlorfenapyr, an experimental aca-ricide of American Cyanamid Co., Princeton, NJ and fenbuconazole (RH-7592), an experimental fungicide of Rohm and Haas Co., Philadelphia,PA.

Maximum air temperatures in the field during the 1998 experiment rangedfrom 28 to 36◦C and one significant rain event occurred on 5 May after thesample leaves were collected for Series II pesticides.

Field sampling

Twelve or more hardened spring flush leaves were collected at random fromthe outer exposed canopy around each sample tree at waist to chest height(1.2–1.6 m) 1 day after each series of pesticide treatments was applied dur-ing 1998. Leaves were always collected first from the unsprayed check treesfor each treatment series. Disposable rubber gloves were changed betweentreatments both in the field and laboratory to avoid potential contamination.Individual dry leaves were collected into a paper bag by picking the leaf atthe base of the petiole without touching the leaf surface. Each paper bagwas then placed on the floor of a running air conditioned vehicle out ofdirect sunlight. Sampling and travel time required less than 1 h beforeprocessing.

Laboratory preparation

Untreated check leaves were always processed first. Leaves from each treat-ment were removed from a paper bag and briefly placed on a clean papersurface and then individually selected and prepared for double whole leaf testarenas (Figure 1). Contact with treated leaf surfaces was avoided as much aspossible. Four leaves ( = 4 replicates) were selected per treatment based onsize, vigor and minimal leaf blemishes. Two leaf arenas with two leaves each

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Table 1. Survival (×± SE) of Agistemus industani gravid females and egg production after infestation on 24 h post-treated pesticideleaves and survival of eggs and larvae after 72 h exposure

Series Date of application Pesticide Formulationb Usec Rate per ha Gravid female arenasa Arenas with 10 eggs on cotton fibersa

and water pH Surviving Live eggs Live larvae Live eggs+♀ ♀ produced larvae

I 27 April – pH 7.3 1. Fenbutatin 50 WP A 2.24 kg 0.7 ± 0.7 b 7 ± 4 b 3.3 ± 1.4 b 4.0 ± 1.7 cd

oxide

2. Formetanate 92 SP A, I 1.12 kg 8.3 ± 0.7 a 65 ± 2 a 6.0 ± 1.0 a 6.0 ± 1.0 abc

3. Chlorpyrifos 4 EC I 4.68 l 8.3 ± 0.3 a 58 ± 9 a 6.0 ± 1.1 a 6.0 ± 1.1 abc

4. Abamectin + 0.15 EC A, I 731 ml

petroleum oil FC 435-66 F, A, I 46.8 l 7.7 ± 0.3 a 53 ± 3 a 0 ± 0 d 0 ± 0 e

5.Carbaryl 80 S I 3.36 kg 7.3 ± 0.9 a 43 ± 8 a 4.0 ± 0 ab 4.0 ± 0 bcd

6. Pyridaben 75 WP A 469 g 0 ± 0 b 7 ± 4 b – –

7. Ethion + 4 EC A, I 7.01 l

petroleum oil FC435-66 F, A, I 46.8 l 0 ± 0 b 3 ± 2 b 1.3 ± 0.3 c 6.3 ± 0.9 ab

8. Dicofol 4 EC A 7.01 l 1 ± 1 b 5 ± 5 b 3.0 ± 0 b 3.0 ± 0 d

9. Propargite 6.55 EC A 3.51 l 0 ± 0 b 5 ± 5 b 0 ± 0 d 8.0 ± 0 a

10. Untreated – – – 9.3 ± 0.7 a 60 ± 3 a 6.3 ± 0.3 a 6.7 ± 0.3 ab

II 4 May – pH 7.3 1. Benomyl 50 WP F 2.24 kg 5.0 ± 1.5 bc 9 ± 4 de 0.5 ± 0.3 e 7.5 ± 0.5 ab

2. Ferbam 76 GF F 11.21 kg 2.3 ± 0.9 d 6 ± 2 e 4.7 ± 0.7 a 6.2 ± 0.5 abc

3. Benomyl 50 WP F 4.68 kg

+ Ferbam 76 GF F 5.60 kg 4.0 ± 0.6 cd 13 ± 3 cde 0.7 ± 0.2 cde 2.2 ± 0.9 d

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Table 1. (continued)

Series Date of application Pesticide Formulationb Usec Rate per ha Gravid female arenasa Arenas with 10 eggs on cotton fibersa

and water pH Surviving Live eggs Live larvae Live eggs+♀ ♀ produced larvae

4. Petroleum oil FC 435-66 F, A, I 23.4 l 6.0 ± 0.6 abc 26 ± 3 abc 2.5 ± 0.5 ab 5.5 ± 0.6 abc

5. Petroleum oil FC 435-66 F, A, I 46.8 l 4.7 ± 1.2 abc 39 ± 3 ab 1.7 ± 0.5 bcd 4.7 ± 1.5 bc

6. Malathion 57 EC I 5.85 l 7.7 ± 0.3 ab 31 ± 5 abc 3.0 ± 0.4 ab 4.5 ± 0.9 abc

7. Copper 98% F 4.48 kg

sulphate metallic

+ petroleum oil FC 435-66 F, A, I 46.8 l 6.7 ± 1.2 abc 21 ± 5 abc 1.7 ± 0.2 bc 4.0 ± 1.5 cd

8. Sulphur 80 DF A 16.8l kg 4.3 ± 1.9 cd 23 ± 9 abc 1.5 ± 0.3 bcd 4.0 ± 0.4 bc

9. Copper 40% metallic F 4.48 kg

hydroxide metallic

+ petroleum oil FC 435-66 F, A, I 46.8 liters 8.0 ± 0.6 ab 17 ± 5 bcd 0.7 ± 0.5 de 5.5 ± 0.9 abc

10. Untreated – – – 9.0 ± 0.6 a 52 ± 12 a 3.7 ± 1.4 ab 8.7 ± 0.6 a

III 7 May – pH 7.3 1. Fenbuconazole 2 F F 585 ml 5.3 ± 1.3 ab 44 ± 5 a 2.5 ± 1.2 a 3.2 ± 1.6 a

2. Fenbuconazole 2 F F 280 ml

+ petroleum oil FC 435–66 F, A, I 46.8 l 6.3 ± 0.9 a 31 ± 10 a 1.5 ± 0.9 a 7.2 ± 0.7 a

3. Neem oil 90 EC F, A, I 46.8 l 3.3 ± 1.3 b 22 ± 4 a 0.7 ± 0.5 a 3.0 ± 1.9 a

4. Diflubenzuron 25 WP A, I 1.40 kg 9.0 ± 0.6 a 42 ± 8 a 1.0 ± 0.7 a 5.7 ± 1.1 a

5. Untreated – – – 8.0 ± 1.0 a 35 ± 1 a 3.2 ± 0.5 a 7.0 ± 1.6 a

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Table 1. (continued)

Series Date of application Pesticide Formulationb Usec Rate per ha Gravid female arenasa Arenas with 10 eggs on cotton fibersa

and water pH Surviving Live eggs Live larvae Live eggs+♀ ♀ produced larvae

IV 13 May – pH 7.6 1. Chlorfenapyr 2 SC A, I 1.46 l 0 ± 0 b 17 ± 3 b 0.2 ± 0.2 a 0.7 ± 0.2 a

2. Chlorfenapyr 2 SC A, I 1.46

+ petroleum oil FC 435-66 F, A, I 46.8 l 0.3 ± 0.3 b 18 ± 8 b 0.5 ± 0.3 a 1.2 ± 0.5 a

3. Sulphur 80 DF A 16.81 kg 0.3 ± 0.3 b 13 ± 4 b 0 ± 0 a 0 ± 0 a

4. Untreated – – – 7.3 ± 1.2 a 42 ± 7 a 2.0 ± 1.3 a 2.2 ± 1.3 a

V 15 June – pH 7.2 1. Fenbutatin- 50 WP A 2.24 kg 6.0 ± 1.1 a 14 ± 3 b 0.2 ± 0.2 c 0.2 ± 0.2 c

oxide

2. Formetanate 92 SP A, I 1.12 kg 7.7 ± 0.9 a 71 ± 6 a 7.0 ± 0.7 a 7.0 ± 0.7 a

3. Petroleum oil FC 435-66 F, A, I 46.8 l 7.3 ± 0.7 a 47 ± 11 a 3.2 ± 0.9 b 3.2 ± 0.9 b

4. Untreated – – – 7.7 ± 0.3 a 56 ± 5 a 7.5 ± 0.7 a 7.5 ± 0.7 a

aMeans within each column within each series followed by the same letter are not significantly different (P ≥ 0.05).bWP = wettable powder, EC = emulsified concentrate, S, SP = soluble powders, DF = dispersible flowable, FC 435-66 = Florida citrus 435 oil (Simanton andTrammel, 1966), SC = soluble concentrate, F = flowable, GF = granular flowable.cA = acaricide, F = fungicide, I = insecticide.

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from the same treatment were prepared with the lower leaf surfaces facingup based on using established methods (Abou-Setta and Childers, 1987). Inaddition, an aluminum foil sheet was placed beneath the foam padding toprevent contact of water with the plastic container and to avoid potentialcontamination. The sides and petiole areas of each whole leaf were coveredwith absorbent cotton stripping to keep the leaf in position and provide a non-toxic barrier to minimize escape of the gravid females (Figure 1). Treated leafarenas were maintained in the laboratory between 26 and 28◦C and held inopen boxes to assure adequate ventilation.

Mite cultures

The strain of A. industani studied was first collected in Egypt in November1993 on apple at Cairo University in Giza. Additional specimens were addedto the laboratory colony from Egypt again in February 1997 that had beencollected from apple and citrus. This strain has no known history of exposureto pesticides. The colony has been maintained on a diet of ice plant pollen,Malephora crocea (Jacquin), and eggs of the citrus red mite, Panonychus citri(McGregor).

Agistemus industani males and females were transferred to several newuntreated rearing leaf arenas (Figure 1) for 24 h to establish a synchron-ous cohort of eggs ± 12-h-old. The following day, all motile mites were re-moved from the leaf arenas and the eggs were allowed to develop. Gravid A.industani females were then collected from the arenas after 11–12 days. Cot-ton fibers were placed on the surface of each leaf for use as an ovipositionsubstrate along with a piece of black construction paper about 4 mm wide by8–10 mm long that served as a refuge for aggregation. A total of 10 gravidfemales was transferred individually using a 5-0 sable brush directly onto theblack construction paper (to avoid contaminating the brush with pesticides).Mites injured during transfer were immediately replaced.

Agistemus industani egg development required more than 3 days com-pared with egg development of the phytoseiid Euseius mesembrinus (Dean)(Childers, unpublished data). Therefore, sufficient time did not elapse betweenplacement of gravid females on leaf arenas and subsequent eclosion of eggswithin 72 h in the first experiment. Therefore, a second series of leaf arenaswas prepared to determine possible egg mortality or mortality to eclosinglarvae. There were four replicates for each treatment. Cotton fibers containing10 A. industani eggs nearing eclosion were transferred onto each leaf arena.The treated leaf arenas in this second experiment were maintained in thelaboratory between 26 and 28◦C and held in open boxes to assure adequateventilation.

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Figure 1. Citrus leaf arenas used for pesticide evaluations against Agistemus industani.

Laboratory assessment

Each arena was examined 72 h after infestation to determine mortality ofgravid females. Three categories were recorded for adults: dead, alive ormissing. A mite was considered dead if it was unable to move forward. Inaddition, the number of live eggs per arena was recorded after 72 h. Eggswere recorded as live when their size, bright yellow color and oval shapewere consistent. In the second series of arenas, numbers of both live eggsand live larvae present were recorded after 72 h after transfer of A. industanieggs.

Statistical analysis

All data on surviving or missing adults and oviposition in the first exper-iment/assay and surviving eggs and larvae in the second experiment/assaywere analyzed in each experiment by analysis of variance (ANOVA) andmeans were separated using LSD (GLM procedures; SAS Institute, 1991).Means and standard errors reported here were calculated using non-trans-formed data.

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Results and Discussion

Gravid females

Pesticides that resulted in less than 30% survival of gravid female A. indus-tani included: fenbutatin oxide, pyridaben, ethion + petroleum oil, dicofol,propargite, carbamate, neem oil, chlorfenapyr alone or in combination withpetroleum oil or sulphur (Table 1). Pesticides that resulted in 30 –70% sur-vival of gravid females included: benomyl, benomyl + ferbam, sulphur 80DF at 16.81 kg/ha, fenbuconazole, alone or in combination with petroleumoil (Table 1). In general, gravid females appeared to be tolerant of petroleumoil applied alone, of some organophosphate compounds such as chlorpyrifosor malathion, and some carbamate insecticides such as formetanate or car-baryl. Exceptions included the organophosphate, ethion + petroleum oil andthe dithiocarbamate fungicide, ferbam. Both of these pesticides were toxic toboth adults and eclosing larvae.

For comparison, most organophosphate pesticides tested on apple inMichigan were not toxic to A. fleschneri Summers females using a slidedip method (Nelson et al., 1973). However, propargite, cyhexatin, karathane,and Dikar (a combination product containing karathane and mancozeb) werehighly toxic. A. longisetus Gonzalez was not directly affected by DDT, or theorganophosphates: azinphos-methyl or demeton-methyl on various deciduousfruit crops in New Zealand (Collyer, 1964). Field toxicity studies on applein Missouri demonstrated the high toxicity of both sulphur and benomylto A. fleschneri populations (Childers and Enns, 1975). Hagley and Biggs(1989) reported that the fungicides: captan, mancozeb and flusilazole wereall highly toxic to the stigmaeid mite Zetzellia mali (Ewing) on apples inCanada. Difficulties in attempting to rear A. fleschneri on apple or A. florid-anus on citrus have impeded efforts to identify the spectrum of pesticide tox-icities for both species to date. Field evidence suggests that Z. mali on applein North Carolina has developed resistance to azinphos-methyl (Motoyamaet al., 1970). Croft (1994) identified Z. mali as tolerant to organophosphatepesticides and similar results were obtained with the pyrethroid, cypermethrin12.5 WP (Villanueva and Harmsen, 1998).

The pesticides listed in Table 2 had significantly higher numbers ofmissing A. industani gravid females from treated leaf surfaces comparedto the untreated checks and other treatments tested. We suspect thatthese products were repellent, irritating, and/or excitatory to gravid fe-males.

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Table 2. Pesticides with significantly greater numbers of missing Agistemus industanigravid females after 72 h exposure on treated leaf surfaces 1 day after spray application,1998

Series Pesticide Rates Missing femalesa

per ha ×± SE

II Ferbam 76 GF 11.21 kg 2.3 ± 0.7 a

Petroleum oil FC 435-66 46.8 l 2.3 ± 0.7 a

Copper sulphate 98% 4.48 kg metallic

+ petroleum oil FC 435-66 46.8 l 2.0 ± 0.6 a

Sulphur 80 DF 16.81 kg 2.0 ± 0 a

Untreated – 0.3 ± 0.3 bc

III Fenbuconazole 2 F 585 ml 3.3 ± 0.7 a

Trilogy (Neem oil) 90 EC 46.8 l 3.7 ± 0.9 a

Untreated – 0.3 ± 0.3 b

aMeans within each column within each series followed by the same letter are notsignificantly different (P ≥ 0.05).

Fecundity

Pesticides that were not toxic to gravid females but resulted in a 50% orgreater reduction in egg production after 1 day post treatment included: cop-per hydroxide combined with petroleum oil and febutatin oxide applied alone(Table 1). Metallic copper formulations and petroleum oil are the two prin-ciple fungicides currently recommended for control of the fungal pathogen,Mycosphaerella citri Whiteside on Florida citrus (Roberts and Timmer, 2001).Use of copper has an adverse effect on citrus IPM.

Larval survival and combined egg and larval survival

Surviving larvae in the untreated checks II, III and IV were significantly lowerthan the untreated checks in the remaining two series (Table 1). The treat-ments: abamectin + petroleum oil, ethion + petroleum oil, propargite, be-nomyl, benomyl + ferbam, copper hydroxide + petroleum oil and fenbutatinoxide resulted in larval mortalities more than 50% higher than in the un-treated checks (Table 1). All of these products can be considered highlytoxic to eclosing larvae. When remaining live eggs and larvae were com-bined abamectin + petroleum oil, dicofol, benomyl + ferbam, copper sulph-ate + petroleum oil, sulphur, fenbutatin-oxide, and FC 435-66 petroleum oil

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at 46.8 l/ha applied alone were considered highly toxic compared with therespective untreated checks in each of the series.

Comparative toxicities

Our data often showed differential toxicity to various life stages of A.industani. Therefore, a simple method to compare toxicities between pesti-cides was used where (mean number of surviving gravid females), (meannumber of live eggs produced/arena), and (mean number of live larvae) weremultiplied. The lower the value obtained then the more toxic was the pesti-cide. Based on these criteria, pesticides evaluated in this study were determ-ined to be highly toxic with values below 200, moderately toxic with valuesbetween 200 and 400 and slightly to non-toxic with values greater than 400(Table 3).

Understanding the toxic effects of field weathered pesticides against keypredacious mite species is important for all commodities, especially thosegrown under different environmental conditions. Climatic conditions in Flor-ida are characterized by warm temperatures, high humidity and moderate tohigh annual rainfall. During the summer (i.e., May through October), humid-ity conditions at night approach 100% and result in prolonged hours of leafand fruit wetness that often continue to mid morning. In addition, afternoonrain showers frequently occur between May and October. Accelerated de-gradation of many pesticides has been shown as a consequence (Nigg et al.,1983). One possible reason that chlorpyrifos and malathion were not toxicto A. industani in this study is the rapid degradation of these compoundsunder Florida conditions (Nigg et al., 1977; Thompson et al., 1979; Niggand Stamper, 1981). The sulphur applied in Series II and IV appeared to bemoderately toxic in one instance and highly toxic in the other. One explan-ation for such differences may be a longer leaf wetness interval that resul-ted from higher humidity conditions following spray application in SeriesII on 4 May. An 18 mm rainfall occurred on 5 May following collection ofleaves.

The results of this study provide a comparison of direct and indirect toxiceffects of various pesticides to A. industani under field conditions. Previ-ous studies have shown that toxicity of certain pesticides to populations ofpredacious mites and consequent reductions in their effectiveness againstphytophagous mite pests (Childers and Enns, 1975; Childers and Abou Setta,1999). Longer term field studies are in progress to identify possible subtleand/or delayed negative effects of copper formulations alone or combinedwith petroleum oil for use in arthropod and fungal disease control on Floridacitrus.

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Table 3. Highest to lowest comparative toxicities of various pesticides and untreatedchecks to Agistemus industani

Treatment Series Calculated Toxicity

ratinga rating

Abamectin + petroleum oil I 0 Highly toxic

Pyridaben I 0 –

Ethion + petroleum oil I 0 –

Propargite I 0 –

Chlorfenapyr IV 0 –

Sulphur IV 0 –

Chlorfenapyr + petroleum oil IV 3 –

Dicofol I 15 –

Fenbutatin oxide I 16 –

Fenbutatin oxide V 17 –

Benomyl II 23 –

Benomyl + Ferbam II 36 –

Neem oil III 51 –

Ferbam II 65 –

Copper hydroxide + petroleum oil II 95 –

Sulphur II 148 –

Copper sulphate + petroleum oil II 239 Moderately to

slightly toxic

Fenbuconazole (280 ml) +petroleum oil III 293 –

Petroleum oil (46.8 l) II 312 –

Diflubenzuron III 378 –

Petroleum oil (23.4 l) II 390 –

Fenbuconazole (585 ml) III 583 Non-toxic

Untreated (IV) IV 613 –

Malathion II 716 –

Untreated (III) III 896 –

Petroleum oil (46.8 l) V 1098 –

Carbaryl I 1256 –

Untreated (II) II 1732 –

Chlorpyrifos I 2888 –

Untreated (V) V 3234 –

Formetanate I 3237 –

Untreated (I) I 3515 –

Formetanate V 3827 –

aCalculations based on (X No. surviving ♀♀) × (X No. live eggs produced/arena) × (XNo. live larvae) per treatment.

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Acknowledgements

The authors thank H. N. Nigg for his review comments to improve this ma-nuscript. This research was supported by the Florida Agricultural ExperimentStation, and approved for publication as Journal Series No. R–08156.

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