Biological Control: A Major Component of the Pest Management Program for the Invasive Coconut Scale Insect, Aspidiotus rigidus Reyne, in the Philippines.

The coconut scale insect, Aspidiotus rigidus Reyne, caused a major pest outbreak in coconut plantations and stands in the Southern Tagalog region of Luzon Island in the Philippines between 2010 and 2015. To determine if parasitism by Comperiella calauanica Barrion, Almarinez and Amalin, a native encyrtid, could have been a factor in the eventual management of the outbreak by 2015, we estimated and assessed its parasitization levels on A. rigidus colonies on field-collected samples from selected points in three provinces in the Southern Tagalog Region across three sampling periods. We observed that C. calauanica consistently occurred only in areas where A. rigidus populations occurred, with high parasitization levels in the Southern Tagalog sites from 2014 to 2015. Results of correlation and regression of total scale count against parasitized scale count suggest putative host density-dependent parasitism by C. calauanica in the field. A marked decrease in the abundance of A. rigidus was recorded concurrently with visually observable recovery of coconut trees from the third quarter of 2014 up to the second quarter of 2016. Similar results of significant reduction in A. rigidus populations concurrent with high percent parasitization by mass-reared and released C. calauanica were found in the Zamboanga Peninsula from 2018 to 2020. Our findings and observations altogether suggest that host-specific parasitization by C. calauanica effected biological control, which may have contributed to the eventual management of the A. rigidus outbreak in the Southern Tagalog Region, and also in the Zamboanga Peninsula where similar recovery of coconut trees were observed within a year after inoculative releases of C. calauanica.

Parasitism of Tuta absoluta in tomato plants by Trichogramma pretiosum Riley in response to host density and plant structures / Parasitismo de Tuta absoluta por Trichogramma pretiosum Riley em resposta a densidade do hospedeiro e estruturas da planta

One important factor determining the efficacy of parasitoids is the way they exploit different host patch. This study evaluated the response of females of Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) to the oviposition sites of Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) on processing tomato plants. In fully developed caged tomato plants T. absoluta moths were released, followed by the release of T. pretiosum females 12h later. After 24h of parasitoid release, the moth oviposition sites were mapped according to the plant canopy, and levels of parasitism assessed. The parasitism rate varied from 1.5 to 28 percent. There was not influence of plant structures on parasitism, except for the absence of parasitism on the plant apex. Levels of both T. absoluta oviposition and parasitism by T. pretiosum were higher on the upper third of the plant, decreasing downward along the plant canopy.

Um dos fatores que podem determinar a eficácia de parasitóides é como esses agentes de controle biológico exploram o habitat de seus hospedeiros. Este estudo avaliou a resposta de fêmeas de Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) à oviposição da praga Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) em tomate industrial. Mariposas de T. absoluta foram liberadas em gaiolas contendo plantas de tomate e, após 12h, foi realizada a liberação de fêmeas de T. pretiosum. Após 24h da liberação do parasitóide, a oviposição da praga foi mapeada de acordo com as estruturas no dossel da planta de tomate e, posteriormente, foram determinados os níveis de parasitismo. O parasitismo de ovos da praga variou de 1,5 a 28 por cento. Não houve influência significativa das estruturas da planta na taxa de parasitismo dos ovos da praga, exceto pela ausência de parasitismo na parte apical da planta. Ambos os níveis de oviposição de T. absoluta e parasitismo por T. pretiosum foram maiores no terço superior da planta de tomate.

Ecological aspects of lepidopteran caterpillar parasitoids from Caryocar brasiliense Camb. (Caryocaraceae) in a cerrado sensu stricto of Central Brazil / Aspectos ecológicos de parasitóides em lagartas de Lepidoptera em Caryocar brasiliense Camb. (Caryocaraceae) em um cerrado sensu stricto do Brasil Centra

This study quantified parasitoid occurrence on five lepidopteran caterpillars species that use Caryocar brasiliense as host plant, trying to verify if there was a direct relationship between host abundance and the proportion of parasitism; if leaf shelters served as cues or protection from parasitoids; if host size influenced the proportion of parasitism, and if attacks by Diptera were more frequent than by Hymenoptera. Searches for external folivorous caterpillars were carried out in an area of cerrado sensu stricto, from July/2003 to June/2004. Caterpillars were more parasitized when occurred on mature leaves. Nola sp. (Noctuiidae) had the highest proportion of parasitism and a negative correlation between their body size and parasitoid attack. Caterpillars that constructed shelters suffered lower parasitism than those exposed. Hymenopteran parasitoids were more abundant than Dipteran parasitoids attacking caterpillars on C. brasiliense leaves. In general, parasitoid species richness and the proportion of parasitism in lepidopteran caterpillar on C. brasiliense showed associations with host population density, their life strategy, diet and leaf nutritional quality.

Este estudo quantificou a ocorrência de parasitóides em cinco espécies de lagartas de Lepidoptera que possuem Caryocar brasiliense como planta hospedeira, verificando se existe uma relação direta e positiva entre a abundância do hospedeiro e a proporção de parasitismo; se os abrigos utilizados pelas espécies de Lepidoptera atuam como pistas ou proteção contra os parasitóides; se o tamanho do hospedeiro influencia as taxas de parasitismo e se existe uma maior ocorrência de ataques de Diptera em comparação com Hymenoptera nas lagartas de Lepidoptera no cerrado do Distrito Federal, Brasil. O estudo foi realizado em uma área de cerrado sensu stricto da Fazenda Água Limpa no período de julho de 2003 a junho de 2004, à procura de lagartas folívoras externas. As lagartas foram mais parasitadas quando ocorreram em folhas maduras. Nola sp. (Noctuidae) apresentou a maior proporção de parasitismo em comparação com as outras espécies e foi a única espécie em que se verificou uma correlação negativa entre as taxas de parasitismo e o tamanho de seus indivíduos. As espécies de lagartas que constroem abrigos apresentaram menores porcentagens de parasitismo em comparação com as que vivem expostas. Os parasitóides da ordem Hymenoptera foram mais freqüentes que os Diptera. No geral, para as espécies de Lepidoptera em C. brasiliense, a riqueza de espécies de parasitóides e a porcentagem de parasitismo apresentaram associações com a densidade, a estratégia de vida, a dieta do hospedeiro e a qualidade nutricional da folha de C. brasiliense.

Parasitism of Nematodes by the Fungus Hirsutella rhossiliensis as Affected by Certain Organic Amendments.

Experiments were conducted to determine whether the addition of organic matter to soil increased numbers of bacterivorous nematodes and parasitic activity of the nematophagous fungus Hirsutella rhossiliensis. In a peach orchard on loamy sand, parasitism of the plant-parasitic nematode Criconemella xenoplax by H. rhossiliensis was slightly suppressed and numbers of C. xenoplax were not affected by addition of 73 metric tons of composted chicken manure/ha. In the laboratory, numbers of bacterivorous nematodes (especially Acrobeloides spp.) and fungivorous nematodes increased but parasitism of nematodes by H. rhossiliensis usually decreased with addition of wheat straw or composted cow manure to a loamy sand naturally infested with H. rhossiliensis. These results do not support the hypothesis that organic amendments will enhance parasitism of nematodes by H. rhossiliensis.