Integrated Control of the Alfalfa Weevil, Hypera Postica (Gyllenhal) (Coleoptera: Curculionidae), in Ontario
| dc.contributor.advisor | Ellis, C.R. | |
| dc.contributor.author | Abu, J.F. | |
| dc.contributor.other | University of Ghana, College of Basic and Applied Sciences, School of Biological Sciences, Department of Animal Biology and Conservation Science (DABCS) | |
| dc.date.accessioned | 2016-02-29T11:29:30Z | |
| dc.date.accessioned | 2017-10-13T15:24:47Z | |
| dc.date.available | 2016-02-29T11:29:30Z | |
| dc.date.available | 2017-10-13T15:24:47Z | |
| dc.date.issued | 1976-01 | |
| dc.description | Thesis ( PhD) - University of Ghana, 1976 | |
| dc.description.abstract | The distribution of the established parasitoids of the alfalfa weevil, Hypera postica (Gyllenhal) in western Ontario was determined during 1973 to 1975. Potasson luna (Girault), a parasitoid of eggs, was found in 13 out of 17 counties surveyed, but parasitism was only 0.7-17-0$. Tetrastichus incertus (Ratz.), a parasitoid of the larva, was recovered from only two sites and parasitism was less than k.0% at both places. Bathyplectes curculionis (Thomson), another parasitoid of the larva, was widespread and parasitism ranged from to 75-0$. Microctonus aethiopoides Loan, a parasitoid of the adult weevil, was recovered at only one site where parasitism was 33.3% in 19739 56.6% in 197^9 and 76.6% in 1975. The relationships between the alfalfa weevil and each of its two major parasitoids in Ontario, B. curculionis and M. aethiopoides, were investigated. Parasitism by B. curculionis was only 6.3-33.3% at the peak of the host population, but increased to 56.0-68.0% later in the season, when host population was low. The incidence of diapause as well as winter survival of B^ curculionis were highest among parasitoid cocoons obtained towards the end of the season. The populations of the first generation adults of M. aethiopoides was synchronized well with those of the overwintered adult weevils, resulting in parasitism of 76.6-82.0%. The second generation of the adult parasitoids and the summer adult weevils overlapped for about two weeks and parasitism was 1+1.6-60.0$. Some adults of M. aethiopoides were present in the field when hosts were unavailable and this may have significance in the establishment of the parasitoid at new release sites. Parasitism by M. aethiopoides did not significantly affect the overwintering mortality of the alfalfa weevil. The toxicity of five insecticides, carbofuran, carbaryl, malathion, phosmet, and methoxychlor was determined by topical application in the laboratory on adult B. curculionis, adult M. aethiopoides, third-instar larvae of H . postica, third-instar larvae of H. postica parasitized by B. curculionis, adult H. postica and adult H . postica parasitized by aethiopoides. The effect of these five insecticides in an integrated control program was assessed, using selectivity ratios calculated as the of the parasitoid divided by the of weevil larva or adult. Each of the insecticides was more toxic to the two parasitoids than to the host larvae but, comparatively, carbofuran and carbaryl were 2 to 3 times safer to the parasitoids than malathion, phosmet, or methoxychlor. Carbofuran, the only insecticide which was selective in favour of both parasitoids over the adult weevils, had selectivity ratios 2 to i times those of malathion, phosmet, carbaryl, and methoxychlor. Parasitized larvae and adults of H^_ postica were more susceptible to the insecticides than were their non-parasitized counterparts and most of the parasitoid larvae died within the susceptible hosts. The weevil larvae were much more tolerant to all the insecticides than were the adults. Based on the selectivity ratings, carbofuran and carbaryl are preferable to malathion, phosmet, or methoxychlor in the integrated control of the alfalfa weevil. Because adults are more susceptible than larvae and since there is a period in the spring when adult weevils are active in the field while adult parasitoids are not, the feasibility of chemical control against the adult weevil should be investigated further. Such a recommendation could have application in alfalfa seed production where early cutting is not an alternative and control is usually required each year | en_US |
| dc.format.extent | ix, 96p. :ill | |
| dc.identifier.uri | http://197.255.68.203/handle/123456789/7694 | |
| dc.language.iso | en | en_US |
| dc.publisher | University of Ghana | en_US |
| dc.rights.holder | University of Ghana | |
| dc.title | Integrated Control of the Alfalfa Weevil, Hypera Postica (Gyllenhal) (Coleoptera: Curculionidae), in Ontario | en_US |
| dc.type | Thesis | en_US |
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