A DISCUSSION OF SOME ECOLOGICAL FACTORS AFFECTING COCCIDENCYRTUS MALLOI BLANCHARD (HYMENOPTERA, ENCYRTIDAE) AS A PARASITOID OF DIASPIDID SCALES UNDER GLASS IN FRANCE. The encyrtid parasitoid Coccidencyrtus malloi Blanchard has been recorded in orchid glasshouses of south-eastern France where its diaspidid host, Diaspis boisduvalii Signoret (Hemiptera, Diaspididae), is sometimes a pest of ornamentals. In order to study its biology and potential as a biological control agent, it was cultured on a bromeliad and released into several hot temperate commercial houses. It was found to have a very restricted distribution which appeared to be determined by deep shade and very high humidities. Key words: Argentina, Boisduval scale, parasitoid development, thelytokous parthenogenesis, Diaspis bromeliae, D, coccois, Laeliocattleya, Vriesea, Aechmea, Cattleya, Citrullus, Cymbidium, Coccos, Dendrobium, Neodypsis, Hohenbergia

Panis, A.

Pinet, C.

Italian

Università degli Studi di Bari: Open Journal Systems

Entomologica, Bari, 33, (1999): 419-422PANIS, A.1; PINET, C.INRA, Laboratoire de Biologie des Invertébrés, Antibes, France114 Avenue Schubert, 83440 Montauroux, FranceA DISCUSSION OF SOME ECOLOGICAL FACTORS AFFECTINGCOCCIDENCYRTUS MALLOI BLANCHARD (HYMENOPTERA:ENCYRTIDAE) AS A PARASITOID OF DIASPIDID SCALES UNDER GLASSIN FRANCE.ABSTRACTA DISCUSSION OF SOME ECOLOGICAL FACTORS AFFECTING COCCIDENCYRTUS MALLOI BLANCHARD(HYMENOPTERA, ENCYRTIDAE) AS A PARASITOID OF DIASPIDID SCALES UNDER GLASS IN FRANCE.The encyrtid parasitoid Coccidencyrtus malloi Blanchard has been recorded in orchidglasshouses of south-eastern France where its diaspidid host, Diaspis boisduvalii Signoret(Hemiptera, Diaspididae), is sometimes a pest of ornamentals. In order to study its biology andpotential as a biological control agent, it was cultured on a bromeliad and released into severalhot temperate commercial houses. It was found to have a very restricted distribution whichappeared to be determined by deep shade and very high humidities.Key words: Argentina, Boisduval scale, parasitoid development, thelytokous parthenogenesis,Diaspis bromeliae, D, coccois, Laeliocattleya, Vriesea, Aechmea, Cattleya, Citrullus, Cymbidium,Coccos, Dendrobium, Neodypsis, Hohenbergia.INTRODUCTIONCoccidencyrtus malloi Blanchard (Hymenoptera: Encyrtidae) had onlybeen reported as a parasitoid of the Boisduval scale, Diaspis boisduvaliiSignoret (Coccoidea: Diaspididae), on an undetermined orchid in Argentina(Buenos Aires Province) (De Santis, 1964). In 1970, it was found for the firsttime in south-eastern France (Alpes-Maritimes department) on orchids in aglasshouse. According to Noyes (1980), the species malloi should be correctlyplaced in Coccidencyrtus. In Argentina, both sexes are known but malesappear to be completely lacking in France and so the parasitoid reproducesby thelytokous parthenogenesis. This paper considers some ecological factorsaffecting its distribution in glasshouses in France.MATERIALS AND METHODSThree species of Diaspis (D. boisduvalii, D bromeliae (Kerner) and D.coccois (Lichtenstein)) were found to be parasitised by C. malloi. Adultfemale D. boisduvalii and D. bromeliae were separated using the illustrationsin Williams & Watson (1988). D. coccois was validated by Miller (1996), wholisted it separately from the Boisduval scale as a new record on coconutpalms in Mexico.In 1970, Coccidencyrtus malloi was bred from the Boisduval scale on afairly shaded x Laeliocattleya plant which had recently been imported fromBrazil within a hot and humid temperate glasshouse whose sides were belowground level (Glasshouse 1). From this initial collection, the parasitoid wasmaintained in a culture (Culture 1) of the Boisduval scale raised on uncagedand potted Vriesea splendens (Brongn.) (Bromeliaceae) at 15-18°C and 60-80% RH, in a small, north-facing, greenhouse against a high wall whichprovided shade in the afternoons for about 6 months of the year. Under thesesame conditions, it failed to parasitise the Boisduval scale on anotherbromeliad, Aechmea fasciata (Lindl.) which has upright leaf blades. C. malloifrom Culture 1 was then released into two commercial orchid houses, one ofwhich was used to grow Cattleya x (Glasshouse 2) and the other Cymbidiumx (Glasshouse 3), where it successfully parasitised D. boisduvalii.The second glasshouse (Glasshouse 2), which was used to grow 10 yearold potted-Cattleya x plants, was 75m2 and was maintained at 18°C constanttemperature and 60-70% RH (except when pots were outdoors in summer)and periodically shaded between November and early April for floweringrequirements. Infestations of D. boisduvalii on the sheathing leaf bases whichenclosed the flower stem and on the pseudobulbs resulted in flower spotting,indicative of economic loss for grower, even though the level of infestationhad been scored as low to medium on many plants. After high pressuresprays of petroleum white-oil had failed to control the scale, 200 C. malloiwere released during April and May 1971, when the RH was obviously lessthan normal and with little shade.C. malloi was also released in another glasshouse (Glasshouse 3) with 7year old potted Cymbidium x (Orchidaceae) plants. This glasshouse was200m2 and, between October and late April (during flowering), it wasmaintained at 15-18°C and 60-65% RH but from spring to early autumn, thetemperatures were maintained at 14-15°C nightly and 20-26°C daily, with anRH of 50-65%. The glasshouse was shaded according to the sky conditionsfrom February to April. Many of the plants had a light infestation of Boisduvalscale towards the base of their pseudobulbs. In November 1971, about 200 C.malloi were released during a rather long cloudy and rainy period (more than65% RH was measured from time-to-time indoors). The effectiveness of theparasitoid was estimated by roughly counting the number of live scales onthe same infested plants before and after release. –– 420 ––In March 1991, a second “wild” population of C. malloi was discovered ina small orchid collector’s glasshouse (Glasshouse 4) which backed onto anorthern wall, fairly humid and hot temperate, and somewhat shaded duringthe morning and evening between mid-autumn and early spring. Theparasitoid was probably introduced in parasitised D. boisduvalii on the flowerstem of a Cattleya plant imported from Brazil; it was also found on thepseudobulb of a Dendrobium sp. imported from Thailand. The parasitoid wascollected and maintained in culture on caged water-melon fruit, Citrulluslanatus (Thunb.), previously contaminated with Boisduval scale, in a rearingchamber at 25°C, 60-70% RH and artificial overhead lighting (L:D 16:8 h)(Culture 2). Parasitoids from this second culture were not subsequently usedexperimentally under glass.In 1996-1997, yet more C. malloi of undetermined origin were found in alarge, 2.3 hectare, wet-tropical house with a special plastic roof (Glasshouse5). The tallest vegetation was about 6m tall, while the understorey provided awide variety of conditions, some of which were permanently shadedthroughout the day. Gradients of temperature (22-28°C) and RH (60-85%)were present depending on the situation and vegetational strata in theglasshouse. Control of the temperature and RH (misted water from above thetop vegetation) was automatic, so that the temperature above the vegetationwas 17°C at night and 20-25°C daily from October to late in March and 20°Cat night and (at most) 25°C during the day from April to September. The RHabove the canopy was controlled at 75-80% between February and Octoberand at 70% between November and January. Three species of Diaspis werepresent: D. boisduvalii was widespread on various tropical plant-species,either scattered on both leaf surfaces or on the sheathing leaf bases whichenclosed the stem; it also formed mixed infestations with D. coccois on twopalms (Coccos nucifera L. and Neodypsis decaryi Baill.). In addition, D.bromeliae was present on both leaf surfaces of three bromeliads:Hohenbergia stellata Schult., Vriesea hieroglyphica (Carr.) and V. spendens,but only in very small groups.RESULTS AND DISCUSSIONThe development of the C. malloi under the conditions of Culture 2 lasted20-25 days, with the eggs being laid in the 2nd-instar nymphs and youngadult females only. Parasitoid emergence was from young female scales priorto ovarian maturation. Adult parasitoids were mainly found beneath the watermelons and were never found to lay their eggs in scales on the upper –– 421 ––surface. Similarly, in the first culture (Culture 1) which had been raised on V.splendens, the parasitoid rarely emerged from scales on the upper leafsurface, preferring to remain beneath the leaves. All the populationsintroduced into glasshouses (Glasshouses 1, 3, 4 and 5) preferred to rest andoviposit in fairly to very shady situations.In the case of Glasshouse 2, it is considered that the failure of theparasitoid to establish was due to too low a humidity. Glasshouse 3 had amuch higher RH and the pseudobulbs were very shaded and it is consideredthat these conditions were suitable for biological control on Cymbidium,which remained undamaged up to October 1972 when observations ceased.Again, in Glasshouse 5, C. malloi was restricted to D. bromeliae infesting twobromeliad plants: H. stellata (0.7m high) and V. hieroglyphica (0.5m high)growing on the margin of a small pond in deep shade in a nearly water-saturated atmosphere. About 2m away from these two bromeliads, in fairlyshady situations but with sunny areas at times and with 70-80% RH, werethree plants of Vriesea splendens (0.4m tall) infested with D. bromeliae and aplant of Vriesea imperialis Carr. (1.25m tall) infested with D. boisduvalii.These plants grew under brighter light conditions and lower RH and were notattacked by C. malloi; nor was a mixed colony of D. boisduvalii and D.coccois on the two palm species. It is concluded that Coccidencyrtus malloirequires high humidity and deep shade for it to become established inglasshouses in France.REFERENCESDE SANTIS, L., 1964 - Encirtidos de la Republica Argentina (Hymenoptera:Chalcidoidea). Anales de la Comision de Investigacion Cientifica, 4: 9-392.MILLER, D.R., 1996 - Checklist of the scale insects (Coccoidea: Homoptera) of Mexico.Proceedings of the Entomological Society of Washington, 98: 68-86.NOYES, J.S., 1980 - A review of the genera of Neotropical Encyrtidae (Hymenoptera:Chalcidoidea). Bulletin of the British Museum (Natural History), EntomologySeries, 41: 107-253.WILLIAMS, D.J., WATSON, G.W., 1988 - The Scale Insects of the Tropical South PacificRegion. Part 1. The Armoured Scales (Diaspididae). CAB International Institute ofEntomology, Wallingford. 290pp. –– 422 ––

A DISCUSSION OF SOME ECOLOGICAL FACTORS AFFECTING COCCIDENCYRTUS MALLOI BLANCHARD (HYMENOPTERA: ENCYRTIDAE) AS A PARASITOID OF DIASPIDID SCALES UNDER GLASS IN FRANCE

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A DISCUSSION OF SOME ECOLOGICAL FACTORS AFFECTING COCCIDENCYRTUS MALLOI BLANCHARD (HYMENOPTERA: ENCYRTIDAE) AS A PARASITOID OF DIASPIDID SCALES UNDER GLASS IN FRANCE

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