The African bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a polyphagous pest that attacks many crops in sub-Saharan Africa. The pest is currently managed through chemical control, and by planting Bt-transgenic cotton. Trichogrammatoidea lutea Girault (Hymenoptera: Trichogrammatidae) is an indigenous egg parasitoid of H. armigera in southern Africa. The study was undertaken to determine the potential of T. lutea as a biological control agent for augmentative releases as an alternative to chemical control, and to pave the way for the development of a mass-rearing method. The biology of T. lutea was examined in the laboratory on H. armigera, Chilo partellus (Swinhoe), and Cadra (formerly Ephestia) cautella (Walker) (Lepidoptera: Pyralidae). The objectives of the study were to determine (i) the exposure time of UV-irradiation required for killing the embryos of the hosts and the effect of UV-irradiated eggs on life history parameters of T. lutea, (ii) which host(s) and temperature(s) (18, 21, 24, 27, 30 and 35 °C) are suitable for mass-rearing of T. lutea, and (iii) the longevity and age-related reproductive biology of T. lutea on H. armigera. Findings of this study showed that 13 minutes of UV-irradiation were sufficient to kill embryos of all three host species. Life history parameters were not influenced by UV-irradiation but by host species. Parasitism, number of progeny per parasitized egg, proportion of females, and developmental time of T. lutea aried on different host species at temperatures ranging from 18 to 30 °C. Trichogrammatoidea lutea did not develop at 35 °C. Overall parasitism by T. lutea was higher on H. armigera and Cadra cautella compared to Chilo partellus. The number of progeny per parasitized egg was highest on H. armigera compared to Cadra cautella and Chilo partellus. The proportion of females was highest on Chilo partellus, intermediate on Cadra cautella, and lowest on H. armigera. For all species and temperatures tested, parasitism and number of progeny per parasitized egg by T. lutea was highest on H. armigera at 27 °C. The lower threshold for development of T. lutea on all hosts was approximately 12 °C. Female T. lutea parasitized eggs of H. armigera soon after eclosion, with the highest parasitism achieved on the day of eclosion. Though T. lutea parasitized eggs for up to 14 days, it may not be economically viable to keep them in cultures for more than three days since progeny became male biased three days after eclosion. The average longevity of female and male T. lutea was 9 and 6 days, respectively. The life table parameters of T. lutea, the net replacement rate (Ro), mean generation time (T), and instantaneous rate of population increase (rm) were 25.5, 9.79, and 0.33, respectively. The timing of inundative releases of T. lutea must be synchronised with the time that eggs of H. armigera are abundant in the field. The results of this study indicate that T. lutea is a good candidate for further testing for augmentative biological control of H. armigera in the field. If successful, T. lutea may provide opportunities for expanding tactics in the management of H. armigera in southern Africa. Copyright / Dissertation (MSc)--University of Pretoria, 2011. / Zoology and Entomology / unrestricted

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-06-20T20:36:51Z No. of bitstreams: 1 2012 - Vinicius de Abreu D'?vila.pdf: 623654 bytes, checksum: 2c91585552193e53bcefc6b559fe2a2f (MD5) / Made available in DSpace on 2017-06-20T20:36:51Z (GMT). No. of bitstreams: 1 2012 - Vinicius de Abreu D'?vila.pdf: 623654 bytes, checksum: 2c91585552193e53bcefc6b559fe2a2f (MD5) Previous issue date: 2012-08-31 / CAPES / The biological control is as important method to regulate the pest populations in a system of sustainable agricultural production, because it is a promising alternative to the use of the organic synthetic pesticides that cause great ecotoxicological impacts. The predator ladybeetles are part of the biological control agents of agricultural pests, could be management by the three biocontrol strategies: classical, conservative and augmentative. In the present work, it was tried to generate knowledge for using the aphidophagous predator ladybeetle Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) under the perspective of the last two strategies. The conservative biological control involving predator insects bases on the fact that in the absence or scarceness of their preferential prey or in the presence of the other preys with inferior nutritional quality, they may use alternative foods, such as pollen, to guarantee their survivorship and, sometimes, their reproduction, and because of that botanical species that provide this floral resource might integrate the agricultural landscape, inside and/or around the agricultural property; meanwhile the augmentative control requests the multiplication of the predator in the laboratory, using natural or artificial preys. Even though some authors proved the visitation of the flowers of some species of Apiaceae by C. maculata, there are no records in the literature of the ingestion of pollen grains of this botanical family by this ladybeetle. In this context, this work was carried out with the aim to select the plant species whose flowers are source of pollen as alternative or complementary food to C. maculata in the perspective to compose the vegetation of the agroecosystems to contribute in the conservation of this ladybeetle, and /or to aid in its mass rearing in the laboratory conditions. The objective of the chapter I was to prove the ingestion of pollen of three species of the family Apiaceae [coriander (Coriandrum sativum L.), dill (Anethum graveolens L.), and fennel (Foeniculum vulgare Mill.)] from the provision of their flowers to the larvae of the 4th instar and adults of C. maculata. It was observed the presence of pollen grains in the five replicates of all treatments, proving the ingestion of the pollen of these three species of Apiaceae from their flowers by C. maculata. At 24 hours of exposition, adults fed on average more pollen of dill than pollens of coriander and fennel, while the larvae consumed more pollen of fennel. The objective of the chapter II was to determine the suitability of nine diets to C. maculata, including provision of pollen of the two species of Apiaceae (coriander and dill), under controlled conditions of the laboratory. Even though the diets with only flowers of these two Apiaceae did not provided the full development of C. maculata, they used as complementary food with eggs of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) resulted in reduction of larval period, increased the egg number by cluster, and increased the body weight. The diet with alive larvae of Drosophila melanogaster Meigen (Diptera: Drosophilidae) was proved to be an essential food as well as resulted in adults with higher body weight, and the number of eggs per cluster increased in comparison with the feeding with only eggs of A. kuehniella. / O controle biol?gico ? um importante m?todo para regular as populac?es de pragas em um sistema de produ??o agr?cola sustent?vel, pois ? uma alternativa promissora ao uso de agrot?xicos org?nicos sint?ticos que causam grandes impactos ecotoxicol?gicos. As joaninhas predadoras fazem parte dos agentes de controle biol?gico de pragas agr?colas, podendo ser manejadas pelas tr?s estrat?gias de controle biol?gico: cl?ssico, conservativo e aumentativo. No presente trabalho, buscou-se gerar conhecimento para uso da joaninha predadora afid?faga Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) sob a perspectiva das duas ?ltimas estrat?gias. O controle biol?gico conservativo envolvendo insetos predadores baseia-se no fato de que, na aus?ncia ou escassez da presa preferencial ou na presen?a de outras presas de qualidade inferior, podem usar alimentos alternativos, tais como p?len, para garantir sua sobreviv?ncia e, por vezes, sua reprodu??o e, por isso, esp?cies bot?nicas provedoras desse recurso floral devem integrar a paisagem agr?cola, dentro e/ou no entorno da propriedade agr?cola; enquanto o controle aumentativo requer a multiplica??o do predador no laborat?rio, podendo se valer de presas naturais ou artificiais. Apesar de alguns autores comprovarem a visita??o das flores de algumas esp?cies de Apiaceae por C. maculata, n?o h? relatos na literatura da ingest?o de gr?os de p?len dessa fam?lia bot?nica por essa joaninha. Nesse contexto, este trabalho foi conduzido a fim de selecionar esp?cies de plantas cujas flores sejam fonte de p?len como alimento alternativo ou complementar para C. maculata na perspectiva de compor a vegeta??o dos agroecossistemas para contribuir na conserva??o dessa joaninha, e/ou auxiliar na cria??o massal da mesma em condi??es de laborat?rio. O objetivo do cap?tulo I foi comprovar a ingest?o de p?len de tr?s esp?cies da fam?lia Apiaceae [coentro (Coriandrum sativum L.), endro (Anethum graveolens L.) e erva-doce (Foeniculum vulgare Mill.)] a partir da oferta de suas flores para larvas de 4? instar e adultos de C. maculata. Constatou-se a presen?a de gr?os de p?len nas cinco repeti??es de todos os tratamentos, comprovando a ingest?o de p?len dessas tr?s Apiaceae a partir de suas flores por C. maculata. Em 24 horas de exposi??o, os adultos consumiram em m?dia mais p?len de endro em compara??o aos polens de coentro e erva-doce, enquanto que as larvas consumiram mais p?len de erva-doce. O objetivo do capitulo II foi determinar a adequabilidade de nove dietas para C. maculata, incluindo oferta de p?len de duas esp?cies de Apiaceae (coentro e endro), em condi??es controladas de laborat?rio. Apesar das dietas apenas com flores dessas duas Apiaceae n?o proporcionarem o desenvolvimento completo de C. maculata, elas usadas com complementa??o da alimenta??o com ovos de Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) possibilitam a redu??o do per?odo larval, aumento no n?mero de ovos por postura e aumento do peso corp?reo. A dieta com larvas vivas de Drosophila melanogaster Meigen (Diptera: Drosophilidae) n?o foi s? comprovada como alimento essencial como tamb?m resultou em adultos de maior peso corp?reo e um aumento no n?mero de ovos por postura em compara??o ? alimenta??o apenas com ovos de A. kuehniella.