JUNE 1991 VERTICALDrstRIsuttoN Qr P. enrsnt'tlra 287

VERTICAL DISTRIBUTION OF PSYCHODAALTERNATA (DIPTERA: )IN SOIL RECEIVINGWASTEWATER UTILIZED FOR TURF CULTIVATION

ARSHAD ALI, MOH LENG KOK-YOKOMI EUO J. BRUCE ALEXANDER

[Jniuersity of Florida, IFAS, Central Florida Researchand Education Center,2700 East CelcryAuentr'e, Sanford, FL 32771-9608

ABSTRACT. Vertical distribution of immature Psychodaalternata in soil to a depth of 15 cm was studied in Jacksonville, FL. Samples were randomly taken from large circular land areas receiving a brewery wastewaterutilized for commercial turf cultivation and included turfed and bare habitats. Total organic matter was quantified at various soil depths. Overall, 88.5 and 95.8Volawae and 91.3 and 94.0% pupae were recoveredfrom the top 2.5 cm of soil at turfed and bare habitats, respectively.The highest concentration of total organic matter at both habitat t5,peswas in the top 2.5 cm. There were strong positive relationships beiween the number of Iarvae and pupae and total organic matter, indicating highest concentrationsof immatures in nutrient-rich topsoil with an abundant supply of larval food. We suggestthat insecticidal treatment directed against immature P. alternatabreedingin such habitats need not penetrate to a depth of more than a few centimeters to affect almost all of the population of this pestiferousinsect.

INTRODUCTION vertically in the soil were determined and cor- related with the populations of P. alternata. An Psychodaalternata Say,which breedsin semi- understandingof this aspectof the ecologyof P. aquatic habitats, occurs in a variety of sources alternata is essential for the development of suchas hay infusion (Haseman1907), decaying control measuresagainst the pest. vegetables,cow and horse dung (Turner 1925) and seaweedpiles (Saunders1928). It is one of only 3 speciesin its subfamily able to live under MATERIALS AND METHODS heavily polluted conditions, and capitalizes on The turf farm is located at approximately the rich enerry resourcesavailable in biological 80'46' W longitudeand 30'31'N latitude,Duval filter beds of sewagetreatment plants; popula- County, FL. At the farm, several areas ranging tions reach such levels that it is commonly "trickling from 6 to 40 ha are under turf cultivation. Each known as the filter " (Quate 1955). cultivated area receives approximately 123,000 The tolerance of P. alternata for strong sewage liters/ha of the wastewater 2-3 times a week allows it to thrive free from interspecific com- dischargedthrough a long largeboom containing petition in many habitats heavily polluted with several nozzles and moving at a set speed in a organic material (Rutz et al. 1980).In biological circular manner. filter beds,the larvae may perform an important pivot, "zoog- Under each there is an elaborate net- function by grazingon the algal scum ot work of underground drains approximately 60 Iea" that coversthe stonesofthe filter bedsand cm abovethe water table. which is ca. 1-1.5 m thus prevent clogging.However, the adults from below the surface.The subterraneandrains col- such sourcesemerge in Iarge numbers and can lect and carry any leached wastewater into becomea nuisancein the vicinity of their breed- ditches situated at the periphery of each pivot. ing sites (Tomlinson and Stride 1945,Woods et The ditchesempty into small man-madeponds. al. 1978).This type of a problem exists in one Some ditches and ponds are equipped with re- situation in Jacksonville, FL, where 6-8 million leasegates used when necessary.The soil under Iiters ofwastewater derived daily as a by-product the pivots was considered to be the primary of a beerbrewing processare dischargedthrough breeding sourceof P. alternata, with turfed and pivot irrigation systemsonto large circular land bare sites which were apparently the 2 distinctly areas to cultivate turf. The nutrient-rich was- different types ofP. alternata habitats. tewater, discharged over several hundred ha, Soil samplesfrom the turfed and bare habitats createsfavorable conditions for the development under various pivots were randomly obtained by of very large populations of P. alternata. Large driving a 3.8-cm (inner diam) plexiglasscore numbers of adults disperseto neighboring resi- tube (Ali 1984) into the ground to a depth of dences,posing considerabledistress to local in- 20-25 cm with a rubber mallet. The collected habitants. column of soil was extracted from the tube with This study reports the vertical distribution of a plunger and its upper 15 cm length was sepa- immature P. alternata in the irrigated soil. Con- rated and fractioned into 2.5-cm-longsections centrations of total organic matter distributed and transferred into 6 separate, labeled poly- 288 JounNer, or rnr AnrsRrcln Mosqutro CoNrRor,Assocrnrlotv VoL.7,No.2

Table 1' Vertical distribution of Psychod.aalternata larvae and pupae and percent total organic matter in soil (turfandbare habitats)in largecircular land areascultivatedto turfiniacksonville, Fi (October19g9- February1990). + Mean no. SD of immat:ul.ePsychoda alternata per 10 cores"or mean % concentration of total organicmatter per 5 cores . Soil depth Total Vo organtc (cm) L1b L3 L4 larvae' Pupae" matter ,TURF 0.0-2.5 1.0+ 0.8 5.0+ 3.3 28.0+ 11.3 88.7{- 31.4 1.22.7a 38.7a -f 2.60+7.07 2.5-5.0 1.0 1.4 3.0+ 2.9 3.8-f 5.2 13.0b 2.0b 1.59+0.14 5.0-7.5 0.0 + 0.0 0.7+ 0.9 0.3 + 0.5 1.0+ 1.4 2.0b 0.7b t.26+0.17 7.5-10.0 0.0+ 0.0 0.0 + 0.0 0.3+ 0.5 0.0 t 0.0 0.3b 1.0b 0.95+0.12 10.0-12.5 0.0+ 0.0 0.0+ 0.0 0.0 r 0.0 0.3+ 0.5 0.3b 0.0b 1..25r- 0.12 12.5-15.0 0.0+ 0.0 0.3+ 0.5 0.0+ 0.0 0.0+ 0.0 0.3b 0.0b r.22+0.12 BARE -{- 0.0-2.5 33.3+ 38.7 163.3 187.4 70.7+ 18.5 74.3+ 95.2 347.7a 30.0a 3.36+ 0.32 2.5-5.0 0.3+ 0.5 4.7+ 3.3 4.7+ 3.7 2.0-f 0.0 11.7b 1.3b 2.22+ 0.02 5.0-7.5 0.0+ 0.0 0.0+ 0.0 0.0+ 0.0 1.0-f 0.8 1.0c 0.0b 1.99+ 0.30 7.5*10.0 0.0+ 0.0 0.0+ 0.0 0.0+ 0.0 1.0-f 1.4 1.0c 0.3b 1.83+ 0.18 -f 10.0-12.5 0.0+ 0.0 0.0 0.0 0.3+ 0.5 1.0-f 1.4 1.3c 0.3b 2.02+ 0.28 -r 12.5-15.0 0.0{- 0.0 0.0 0.0 0.0+ 0.0 0.0 -f 0.0 0.0 c 0.0b 1.52-f 0.16 'Each core 3.8 cm in diam and 2.5 cm deeo. r'Ll-L4: larval instars I to 4. " Means in a column followed by the same latter are not significantlydifferent (P > 0.01)as analyzedby ANOVA and Duncan's multiple range test.

thene bags. At each habitat, 10 such cores ofsoil to elucidate relationship betweenpopulations of were collected and the fractioned subcores ofthe immature P. alternata and the total organic same depth were pooled. Larval and pupal sam- matter at various depths. ples were collected on 3 occasions between Oc- tober 1989 and February 1990. An additional 5 cores of soil from equivalent depths were col- RESULTS AND DISCUSSION lected each time for the determination of total Among immaturesof psychodids,only P. ol- matter organic at different depths. ternata larvae and pupae were recognizedin the In the laboratory, each soil sample collected collectedsamples. The mean numbersof P. al- for assessment of immature P. alternato popu- ternata per 10 soil corestaken at various depths Iation was washedthrough a series of U.S. stand- arepresented in Table 1; a total of 30 coresfrom ard sieves. Large pieces of vegetation were eachhabitat were collected.Generally, the bare washed clean of soil and discarded. The residue habitat supported higher populations of larvae on the finest screen (250-pm pore size, U.S. than the turfed habitat. As expected,the first Standard sieve No. 60) was collected, preserved instars in both habitat categoriesoccurred only in 707o alcohol and examined under a binocular in the top 5 cm of soil since the eggsare laid at microscope (10X magnification) to identify and or near the soil surface. Overall, 88.5% latvae count psychodid larvae and pupae. Each sample and,91.3%pupae recoveredfrom soil samples was examined in parts by placing small portions collected from turfed habitats were in the top in a 8.5-cm diam Petri dish with a l-cm grid 2.5 cm. At bare locations,the percentagesfor marked on the bottom. The taxonomic keys in this upper most level werc 95.8Volarvae and Quate (1955) were used. 94.0% ptqae. These proportions of larvae and To determine total organic matter, soil sam- pupaein the top 2.5cm of soil weresignificantly ples were dried at 40"C and ground to pass different (P < 0.01) from those encounteredin through a 4O-mesh sieve. The wet oxidation the variousdepths below 2.5 cm. The numberof method of Nelson and Sommers (1982) was used larvae or pupae collected5 cm below the surface to determine percent total organic matter in was 13Vo of the total larvae or pupae collected each sample. from either habitat. Negligible numbers oc- Populations of total larvae and pupae of P. curredbelow 12.5cm. alternata at various soil depths were compared Mean values of percent total organic matter by analysis of variance and Duncan's multiple at different soil depths in turfed and bare habi- range test. A correlation analysis was performed tats are shown in Table 1. The highest concen- JUNE 1991 Venrrcer, DrsrnrsurloN or P. etrenNern' tration of total organic matter was in the top 2.5 with those of Solbeet al. (1967)made in water cm. The mean values of total organic rnatter, treatment plant filter beds, a more common 3.36%rn the top 2.5 cm soil and 2.22%in 2.5to sourceof suchinfestations. Based on our results, 5.0cm soil depthin bareareas, were significantly we suggestthat insecticidal treatment directed different (P < 0.01).Below 5 cm from the sur- against immature P. alternnta in such habitats face, the total organic matter content did not need not penetrate to a depth of more than a significantly differ in the various depths sam- few centimeters to affect almost all of the pest pled. In turfed sites, the mean value of total population of this .This high concentra- organic matter in the top 2.5 cm soil amounted tion of immatures near the soil surface also to 2.6%. makes the larvae and pupae of P. alternata par- Simple correlation analysis of P. alternata ticularly vulnerable to dry conditions as they larval and pupal populations at various depths require at least moderate amounts of moisture with the prevailingtotal organicmatter concen- in their niches(Quate and Vockeroth 1981). trations showedstrong positive relationship be- tween the number of larvae and total organic matter (r : 0.789,P < 0.01, n : 36), and the ACKNOWLEDGMENTS (r : number of pupae and total organic matter This is Florida Agricultural Experiment Sta- : 0.584,P < 0.01,n 36). This indicatesthat the tions Journal SeriesNo. R-01181. greatest numbers of immatures were located in the nutrient-rich topsoil which had more abun- dant Iarval food supply than the lower depths. REFERENCES CITED AIso, the of P. alternata is air-breathing A. 1984.A simple and efficient sediment corer for and amphipneustic. It bears nonfunctional an- Ali, shallowlakes. J. Environ. 13:63-66. projections Qual. terior spiracleslocated on raised on Fair, G. M. 1934.The trickling filter fly (Psychoda the prothorax. The posterior spiraclesare situ- alternata), its habits, and control. SewageWorks J. ated at the apex of a respiratory siphon on the 6:966-981. eighth abdominal segment, equipped with hy- Haseman,L. 1907.A monographof the north Ameri- drofuge hairs arising from 4 finger-like papillae. can Psychodidae,including ten new speciesand an The larva of P. alternalio must therefore main- aquatic psychodid from Florida. Trans. Am. Ento- tain direct contact with the atmosphere to ob- mol. Soc.33:299-333. tain oxygen. This requirement for atmospheric Nelson,D. W. and L. E. Sommers.1982. Total carbon, carbon,and organicmatter. pp. 539-579.In: oxygenis also one of the most important factors organic Methods of soil analysis. Part 2. Chemical and regulating the vertical distribution. The oxygen microbialproperties.Am. Soc.Agron., Madison, WI. is obtained either at the surfaceofthe substrate Quate, L. W. 1955. A revision of the Psychodidae or from air spaceswithin the medium in which (Diptera) in Americanorth of Mexico. Univ. Calif. it lives. The Iarva of P. alternato is apparently Publ. Entomol. 10:103-273. able to tolerate submergencein water for 24 h Quate,L. W. and J. R. Vockeroth.1981. Psychodidae. under normal conditions, although entrapment pp.293-300.In: J.F. McAlpine et al. (eds.).Manual of an air bubble in the breathing tube may allow of Nearctic Diptera, Vol. 1. Res. Branch Agric. it to survive for twice as long (Fair 1934). The Canada,Monograph 27. T. D. Edwards.1980. pupa is generally immobile, but is able to move Rutz, D. A., R. C. Axtell and of organic pollution levels on aquatic insect Pupal Effect if necessaryby abdominal contractions. abundancein field pilot-scale anaerobic breathing is through paired thoracic horns. wastelagoons. Mosq. News 40:403-409. Previous studies in which larvae, pupae and Saunders,L. G. 1928.Psychoda alternoto Say breeding even adults of theseinsects have been reported in the sea.Entomologist 61:209. at depthsof 1 m or more (Solbeet al. 1967)refer Solbe.J. F.. N. V. Williams and H. Roberts.1967. The to populations in sewagefilter beds.In the filter colonization of a percolating filter by invertebrates beds,the substratecontains a higher concentra- and their effect on settlement of humus solids.Wat. tion of air spacesthan the often water-logged Pollut. Control 66:423-448. soil encounteredin the study area.Larvae ofP. Tomlinson,T. G. and G. O. Stride.1945. Investigation percolating alternata maintained in a laboratory colony in into the fly populations of filters. J. Proc.Inst. SewagePurif. 1945:140-148. damp sand observedto remain closeto the were Turner, C. L. 7925.The Psychodidae(moth-like ) surface at all times, with their bodies buried in as subjectsfor studiesin breedingand heredity. Am. the sand and the posterior siphon projecting at Nat. 57:545-559. the surface(A. Ali, personalobservation). Woods,D. R., J. M. Williams and J. Croydon.19?8. Observations on vertical distribution of im- Fly nuisance control in treatment systems.Water. mature P. alternata made in this studv contrast Pollut. Control 77 :259-27 0.