A method of rearing fungus gnats of Corynoptera sp. (Diptera: Sciaridae) is described, based on a diet of bean seed and horticultural peat. The gnats completed development from egg to adult in 13-15 days at 24 + 2° C. Oviposition and longevity were increased by a honey supplement to the adults

Gillespie, David R.

A method of rearing fungus gnats of &lt;i&gt;Corynoptera&lt;/i&gt; sp. (Diptera: Sciaridae) is described, based on a diet of bean seed and horticultural peat. The gnats completed development from egg to adult in 13-15 days at 24 + 2° C. Oviposition and longevity were increased by a honey supplement to the adults

Journal of the Entomological Society of British Columbia

J. Er-:T0\10L Soc. BRrJ . COL li Wll f\ K3 ( 19t>61 . DI :C. :II. 1'100 A SIMPLE REARING METHOD FOR FUNGUS GNATS CORYNOPTERA SP. (DIPTERA:SCIARIDAE) WITH NOTES ON LIFE HISTORYI DAVID R. GILLESPIE Agricu lt ure Ca nada Saanichton Research and Pla n! Quarantine Station 880 I East Saanich Road Sidney. B. C. V8L I H3 ABSTRACT A method of rearing fungus gnats of Cor."lIoplera sp. (Diptcra:Sciaridae) is described. bascd on a diet of bean seed and hort icultural peat. The gnats completed development from egg to adu lt in 13- 15 days at 24 ± 2 ° C. Oviposit ion and longevi ty were increased by a honey ;,u ppJcment to the ad ult s. INTRODUCTION Various species of fungus gnats (Dipte ra:Sciar idae) arc comlllon pests in greenhouse crops (Lindquist. Faber and Casey 1985 ; Wilkinson and Daugherty 1970a. b). Larvae reported ly damage the roots of seedl ings and mature plants (Wilkinson and Daugherty 1970a: Dennis 1978). and adu lts are a source of annoyance and ir ritation to workers and consumers. The species most commonly reported causi ng damage in greenhouses i;, Brad,'si(1 coprophilia (L intncr) (Lindquist. Faber and Casey 1985) . Wilk inson and Daugherty (1970a) re[1orted B. illlpaliCIIs (Johannsen) feeding on root s of soybean plants in a gree nhouse. In the fa ll of 1982 larvae of a spec ies of Sciaridae were noted tCeding on and around the roots of GerlJerajwlleso-lIii in a greenhouse. These were coll ected . reared and subsequentl y identified as COr\'llOplem sp, This species was sucecss full y placed in cont inuous rearing. The fol -lowing report s rearing Icchniques for Ih is species wh ich may be adaptable tn olher species of Sciaridae . The li fe hi story of Corrlluprera ;,p. is described. MATERIALS AND METHODS Rearing The rearing mixture was prepared by fir st soaking 100 g of dried pinto or small red beans in water for 24 h. These were rinsed under co ld run ning water and ground wi th 500 ml of water in a blender. The ground beans we re the n added to 2 t' of sieved ( 16 mesh) horticult ural peat and suffi cient water was added to produce a moist mixture. This was stored in the refrigerator at 2°C unt il needed . Cyl ind rical plasti c I I' refrigerator containers coated on the outside with black paint were u;,ed a;, rea ring contain -er;,. A hole 01'2.5 cm d iam. in the lid was covered with 80 mesh screen to provide ventil ati on. Approximately 100 ml of the rea ring mix was added to these contai ne rs and lCunlrihulion NIl. :!90 Saani..::htull R~:-ciJr(" h and Plant Qllar'lllI ine SI.t tHIll . 8~Ol Ea~1 Saamchtllll Rd .. Sldnc}. B.C. packed firm ly into the bottom. A small quantity of ho ney was then smeared on the lid . Twenty- live to 50 1- to 2-day-old grav id lemale fu ngus gnats and an equal quantity of males were brielly anesthetized wiih CO2 and placed in the container. Colonie;, were renewed by anestheti zing fresh ly emerged adults in the or ig inal con tainer and then placing the appropriate number into a new container. Life History Eggs for life history studies were co llected by placing large numbers of lemale and male COrl'llOl'lera sp. in sealed containe rs with l1loist paper towell ing. Eggs were rinsed from the towelling after 24 h and col lected on a 200 mesh screen. Approxi mately :WOO freshly laid eggs were pu t into each of fi ve containers as described above. with :WO mt of rea ring mix. These were he ld at 24 ± 5°C. On the following day and each day thereafle r a 10 ml sample of mix was taken frolll each container. Sample~ wt;:re teased apart with dissecting needles. Fungus gnats at all stages were extrac ted from the mediu m by gentl e ag ita -tion in a 40 % sucrose sol ution as suggested by Fordyce and Cantelo ( 1981 ). They were rellloved from the solu-ti on as Ihey iloated to the surface. This ac ti vi ty was maintai ned unt il no further indi vidua l;, could he ex-tracted . All fungu s gnats ex tracted from each sample were counted and identi fied by stage. i.e . egg. larva. pupa or empty pupal case ( = adult) . Adu lt Fecundity and Longevit., The eflects of carbohyd rate >upplcmelll on fecundit} and adult longevity were tested. One freshly-emerged ullmated lCmale and one male were placed in each of 30 in ve rted, ve nted petri di shes. Blott ing paper disc;, on the bottom of the d ishes were kept moist throughout. A small po rt ion of rea ring mix tu re \Va;, provided to focus egg laying. In 15 of the dishes a drop of honey (approx imately O.lml) was placed on the blotting paper asa carbohydrate ;,u pplement. Ov iposit ion was assessed dail). Data were analysed by t-test ( = 0.05 ). 46 J. E NTOMOL SOc. BRIT. C OLU MBIA 83 ( 1986). DEC. 3 1. 1986 RESULTS Rearing . .. . The method desc ribed was e lfectl ve lor rea rIng Cor-y" oplera sp . Cultures have been mainta ined continuously for three yea rs with occasional supple menting from wild stocks collected in greenhouses. Yield of indi vidual cul-ture vesse ls ranged from 500 to 1000 insects . A culture normally took 16 to 18 days to cyc le at lab te mpe ratures 18 to 24 QC). The rearing mi xture deve loped a luxuri ant covering of mold that rap id ly disappeared whe n the larvae hatched and began feeding. After the visible fungus had been consume rd . the larvae turned to the large r bean pieces le ft in the mi xtu re as well as the mi xture itse lf. By the time larval development was complete. the mi xture had been reduced to a ric h compost. Life History Overall deve lopment requi red sli ghtly less than 13 days to 50 % emergence of adults (Fig I). The egg stage lasted between I and 2 days. La rval deve lopme nt required 7 days and the pupal stage lasted about 4 days. Emergence of ad ults was essenti ally complete by day 15 . Males began emerging I day before the fe males (Table I) . The ma le: le-male ratio was I : 1.3. Adult Fecund ity and Longevity Females lived for 7.3 ± 1.72 days and la id 149.6 ± 42.39 eggs when provided with a honey supple ment. In contrast. fe males li ved onl y 3.8 ± 0. 68 days and laid I I I . I ± 47. 18 days without the honey supplement. Males lived 10 .6 ± 2 .12 days with honey supplement and 4.5 ± 0 .53 days without honey supplement. All diffe r-ences are significant (t-test. p < 0 .0 I). In a separate expe rime nt. all fe ma les without mates laid eggs on the day of death and these eggs we re infertil e . Eggs from the mated fe ma les in the previous experiment we re gene rall y fe rtile although the leve l of ferti lity was not checked . Most of the eggs were laid on day 3 of the ex periment in both honey and no honey treatments (Table II ). Without honey. all ov iposition took place in a 3-day span whereas with honey. ov ipos ition occurred during an 8-day span. DISCUSSION The rea ring system desc ribed above is similar to that of Wilkinson and Daughe rty ( 1970a). In the ir studies. Bm-dysia impaliellS was reared on fine ly ground soybeans mi xed in distilled water. A mixture of ground beans and disti ll ed water proved too odoriferous for use in a labora-tory env ironment. particularl y when large numbers we re being rea red in vented containers. Othe r rearing methods fo r B. coprophilia used ingred ients ranging from a ste ri-lized manure/straw mi xture inoculated with mushroom spaw n (T homas 1929) to ste rilized. blended grass cut-tings on aga r slant s (Kennedy 1973). Horticultura l peat was chosen because it closely simulates the substrate used by fungus gna!s in greenhouses. In add ition. it and the beans are more readily avail able than the exotic ingred i-ent s. Fig . I Development or CorYlloplera sp. over ti me in a rearing mi xture of peat and ground beans. 100 80 I- 6 0 Z w () a: w 40 0... 20 0 0)- ---0 EG G 0------ - 0 PU P A e ------ . L A RV A e--- ~. E M E RG ED e -- -... ----e -- - e- --e - - " ' , t ' ~ . . \ I \ I \ I \ I '. I \ \ \ \ ,0.- _ _ q , \ ;' \ I \ , \ -. 9 \ 2 3 4 5 6 7 , , I I ~o 8 \ \ \ , \ , I, \ ,' 1 \ I \ 9 \ \ ~ , \ 9 10 DA Y " , 'q , , , , 18 J. ENTOtvlOL soc. BRIT. COLUM BI A 83 ( 1986). D EC. 3 1. 1986 TABLE I. Cumulative percen'. emergence of COn'noprera sp. adult male, and females from a rearing mi xture of peat and ground beam .. Day Mal es Female s 1 1 0 0 1 2 33 . 2 . 2 13 7 1 . 0 55 . 5 1 4 93 . 7 92 . 5 1 5 97 . 9 95 . 8 1 6 98 . 9 98.4 17 9 9 . 8 99 . 4 1 8 100 . 0 10 0 . 0 TABLE II. Mean daily egg production (S . D.) of Cor)'/ lOprera sp. fe males wi th and without honey supplement. With Without Day Honey Honey N=14 N = 1 5 0 0 2 1 . 1 4 .0 1 ) 2 . 4 6 . 51 ) 3 74 . 1 (63 . 18 ) 83.4 (5 7 .2 8 ) 4 1 9 . 4 (2 8 . 10 ) 25 . 2 ( 46 . 36 ) 5 33 . 8 ( ;, 7 . 65 ) 0 6 8 . 4 ( 1 9 . OR ) 0 7 3 . 9 ( 8.70 ) n 8 ') . 6 ( 7 . 88 ) 0 9 3 . 6 ( 13 . 63 ) 0 H) 0 0 Gra nd X 149 . 6 ( 42.~9 ) 111.1 ( 47 . 18 ) 48 1. ENTOMOL SOc. BRIT. COLUMBIA 83 ( 1986) . D EC. 3 1. 1986 The li fe cycle of Corynoptera sp. is cons iderab ly shorter unde r our condit ions than that of B. coprophilia as desc ribed by Wil ki nson and Daugherty ( 1970b). They found the optimum for that species to be approxi mately 20 days at 18.9-30.0 °C as opposed to 13 days fo r Cor· ynoptera sp. at 24 ± 2 °C. The apparent increase in nu mbers of pupae afte r day 16 (Fig. I) was probably spurious and due perhaps to wate rl ogging or disinteg ra-ti on of empty pupal cases. Kennedy ( 1973) observed adult s of B. impatiens appa r-entl y feeding on "ooze" from rea ring cultures , although Wilkinson and Daugherty (l 970a) did not observe feed-ing by adults of this spec ies. I have many times obse rved fungus gnat females of undetermined spec ies apparentl y feed ing on honeydew depos its from Trialeurodes vapora-riorum (Homoptera :Aley rodidae). It appears from the feeding experiment that thi s behav ior could increase the ov ipos ition and lifespan of females . perhaps to the degree that in cases of white fl y outbreak. fungus gnat popula-tions should be monitored carefull y. ACKNOWLEDGEMENTS I thank B.L. Marchand. N. Williams and S. Hart for technica l ass istance at va rious stages of the project, and 1. R. Voc keroth (Agriculture Canada, Biosystematics Re-search Institute, Onawa, Onta rio) fo r identification of specimens. REFERENCES Dennis , 0 .1. 1978. Observations of fungus gnat damage to glasshouse curcubits. N .Z.l . Exp. Agric. 6 : 83-84. Fordyce, c., lr. and WW Cante lo. 198 1. Techniques to extract immature stages of Lycoriella mali from mushroom grow ing media. 1. econ. Ent. 74 : 253-254 . Kennedy, M. K. 1973. A cu ltu re method for Bradysia impatiens (Dipte ra :Sc iaridae). Ann . Entomol. Soc. Am . M: 11 63-11 64. Lindquist, R.K., Faber, WR ., and Casey, M .L. 1985. Effect of various soiless root media and insecticides on fungus gnats. HortSc ience 20: 358-360 . Thomas , C. A. 1929. A method for rearing mushroom insects and mites. Entomol. News. 40: 222-225. Wilkjnson, 1.0 . and Daugherty, D.M. I 970a . The biology and immature stages of Bradysia impatiens (Dipte ra:Sc iari -dae) . Ann . Entomol. Soc. Am . 63: 656-660 . Wilk inson, 1.0. and Daughe rty, D .M. 1970b. Comparati ve development of Bradysia impatiens (Diptera:Sc iaridae) under constant and va riable temperatures. Ann . Entomol. Soc. Am. 63: 1079- 1083. 

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A simple rearing method for fungus gnats Corynoptera sp. (Diptera: Sciaridae) with notes on life history

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A simple rearing method for fungus gnats Corynoptera sp. (Diptera: Sciaridae) with notes on life history

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Journal of the Entomological Society of British Columbia