Hymenopterous parasites associated with Phyllonorycter blancardella [Lepidoptera: Gracillariidae] in Nova Scotia and Quebec

Mined leaves were collected in commercial and unsprayed (no insecticides) apple orchards of Quebec and Nova Scotia to determine the relative abundance and diversity of parasites of the spotted tentiform leafminer, Phyllonorycter blancardella [Lepidoptera: Gracillariidae]. In Quebec, 29 species of leafminer parasites were recovered, belonging to 7 families: Aphelinidae, Braconidae, Chalcidae, Eulophidae, Ichneumonidae, Pteromalidae and Scelionidae. The most prevalent species were Pholetesor ornigis (67%), Sympiesis marylandensis (11%), S. serviceicornis (7%), Pnigalio maculipes (1.5%), Tetrasticus spp. (1.2%), while all other species accounted for < 1.0%. Pholetesor pedias, a braconid released in 1983 at Frelighsburg, Quebec, was not found in the 1984 and 1985 surveys. In Nova Scotia, 19 parasite species were recovered, belonging to 5 families : Braconidae, Encyrtidae, Eulophidae, Ichneumonidae and Pteromalidae. The most prevalent species were: Pholetesor ornigis (52%), Pnigalio maculipes (14%), Sympiesis serviceicornis (12%), S. marylandensis (9.5%), Sympiesis spp. (5%), Horismenus fraternus (1.8%), Paraleurocerus sp. (1.3%), Stictopisthus flaviceps (1.1%), while all other species accounted for < 1%. Seven and five species of hyperparasites were recovered in Nova Scotia and Quebec, respectively. New records for North America for the spotted tentiform leafminer as a host are : Sticopisthus bilineatus, S. flaviceps, Euderis sp., Pnigalio epilobii, P. pallipes and Paraleurocerus bicoloripes.

EFFECT OF FOOD SOURCES ON THE LONGEVITY AND FECUNDITY OF PHOLETESOR ORNIGIS (WEED) (HYMENOPTERA: BRACONIDAE)

The fecundity of first-generation adult Pholetesor ornigis (Weed) increased when individuals were confined with flowers of creeping "Charlie" (Glechoma hederacea L.), dandelion (Taraxacum officinale Weber), and apple (Malus domesticus L.), but not with blossoms of chickweed [Stellaria media (L.) Cyrillo] or Shepherd’s purse [Capsella bursa-pastoris (L.) Medic]. Longevity of P. ornigis was little affected. The fecundity of second-generation P. ornigis increased when individuals were confined with terminal leaves of apple with honeydew of the aphid Aphis pomi DeGeer, but not when confined with terminal leaves without honeydew or with flowers of round-leaved mallow (Malva neglecta Wallr.) or red clover (Trifolium pratense L.). Longevity of P. ornigis adults also increased when they were provided with aphid honeydew. There were significant differences between the total number (oviposited and ovarian) of eggs produced by second-generation females given different food sources. Those given aphid honeydew oviposited a greater proportion of their eggs than those confined with apple leaves without honeydew or with flowers of M. neglecta or T. pratense, Adult P. ornigis fed an aqueous solution of honey (50:50, v/v) lived longest and produced more eggs than those provided with any other food source.

TOXICITY OF PERMETHRIN, AZINPHOSMETHYL, AND METHOMYL TO PHOLETESOR ORNIGIS (WEED) AND PHOLETESOR PEDIAS NIXON (HYMENOPTERA: BRACONIDAE), PARASITES OF THE SPOTTED TENTIFORM LEAFMINER, PHYLLONORYCTER BLANCARDELLA (FABR.) (LEPIDOPTERA: GRACILLARIIDAE)

The toxicity of the insecticides permethrin, azinphosmethyl, and methomyl to adult Pholetesor ornigis (Weed) and P. pedias Nixon was evaluated in laboratory bioassays. Older P. pedias (2 and 3 days old) were more susceptible than younger parasites (1 day old) to permethrin. Azinphosmethyl was slightly more toxic to female P. ornigis than to male P. ornigis or to P. pedias. There was no consistent difference in the response of adult P. ornigis compared with P. pedias exposed to permethrin or methomyl on treated paper disks. Methomyl was twice as toxic as either azinphosmethyl or permethrin. Male P. ornigis were less susceptible than female P. ornigis to permethrin, but the difference was significant in only one of four populations tested. Male P. ornigis were less susceptible than females to azinphosmethyl. In 1986, populations of P. ornigis which had been exposed previously to pyrethroid insecticides were less susceptible to permethrin than P. ornigis from orchards where pyrethroids had never been applied. The response of both Pholetesor spp. to permethrin varied significantly from 1986 to 1987.

SURVEY FOR INSECTICIDE RESISTANCE IN SOME ONTARIO POPULATIONS OF THE APPLE LEAFMINER PARASITE, PHOLETESOR ORNIGIS (WEED) (HYMENOPTERA: BRACONIDAE)

Pholetesor ornigis (Weed) from 16 orchards in seven Ontario apple production areas were tested from 1987 to 1989 to determine if their levels of resistance to permethrin and methomyl were higher than those measured earlier in two Ontario populations and if they had developed resistance to azinphosmethyl. Higher levels of resistance were not detected and there was no evidence of resistance to azinphosmethyl. Some possible reasons for the lack of higher levels of insecticide resistance and some alternatives to insecticide resistance for parasite conservation are discussed.

RELATIVE TOXICITY OF SIX INSECTICIDES TO MALE AND FEMALE PHOLETESOR ORNIGIS (WEED) (HYMENOPTERA: BRACONIDAE), A PARASITE OF THE SPOTTED TENTIFORM LEAFMINER, PHYLLONORYCTER BLANCARDELLA (FABR.) (LEPIDOPTERA: GRACILLARIIDAE)

The susceptibility of male and female Pholetesor ornigis (Weed) to the pyrethroid insecticides permethrin, fenvalerate, and deltamethrin, the organophosphorous insecticides azinphosmethyl and phosmet, and the carbamate insecticide methomyl, was compared in the laboratory using two populations from Norfolk County, Ontario. Female P. ornigis were more susceptible than males to permethrin. There was no sexual difference in the susceptibility of P. ornigis to the other five insecticides tested. The implications of these results for the biological control potential of P. ornigis in commercial apple orchards are discussed. The results obtained for permethrin, fenvalerate, azinphosmethyl, and methomyl were compared with those obtained in a study completed 6 years earlier using P. ornigis from another location in Ontario; the results suggest that P. ornigis from Norfolk County have low levels of resistance to permethrin (3.3-fold), fenvalerate (2.2-fold), and methomyl (4.1-fold).