Infestation and natural parasitism of aphids in single and mixed pastures of black oats and ryegrass

• Published in: Revista brasileira de entomologia Vol. 56; no. 3; pp. 363 - 367
• Main Authors: Sturza, V S, Poncio, S, dos Santos, AB, Lopes-Da-Silva, M
• Format: Journal Article
• Language: Portuguese
• Published: 01-07-2012
• Subjects: Aphididae; Aphidius colemani; Avena strigosa; Cereals; Crops; Data processing; Grasses; Infestation; Lolium multiflorum; Natural enemies; Parasitism; Parasitoids; Pasture; Pests; Poaceae; Rhopalosiphum padi; Sitobion avenae; Species composition
• ISSN: 0085-5626

Some species of aphids are major pests on cereal crops and grass pastures. Usually these pests are not adequately controlled in pasture lands that become sources of aphid infestations to cereal crops. The dynamics of aphids and the incidence of natural enemies are less known in pasture systems than in cereal fields. The objective of this work was to assess the aphid infestation and natural aphid parasitism in different pasture composition. Three hypotheses were tested: 1- the aphid species composition in pastures may vary according to the cereal species in the field; 2- the mixture of two plant species can modify the amount and diversity of aphids; 3- the plant species composition of pasture fields influences the parasitism of aphids. Empirical data were obtained from three Poaceae fields: black oats (Avena strigosa L.), ryegrass (Lolium multiflorum L.), and a mixed field of black oats and ryegrass. The most abundant aphid species was Rhopalosiphum padi followed by Sitobion avenae. Plant species composition increases the amount and the parasitism rates of aphids. The mixture of heavily infested black oats with a poorly infested ryegrass resulted in reduction of aphid infestation in comparison with heavily-infested single plant species field. This is possible because the conditions are favorable for the development of parasitoid populations. Aphidius colemani was the main parasitoid found in these areas.Original Abstract: Algumas especies de pulgoes sao importantes pragas de cereais, atacando tambem pastagens de gramineas. Normalmente, essas pragas nao sao controladas nas pastagens e podem tornar-se fontes de infestacao dos afideos para os cereais cultivados. A dinamica dos afideos e de seus inimigos naturais e pouco conhecida em sistemas de pastagem. O objetivo deste trabalho foi avaliar a infestacao de pulgoes e seu parasitismo natural em areas com diferentes composicoes de pastagens. Tres hipoteses foram testadas: 1 - a composicao de especies de afideos em pastagens pode variar de acordo com as especies de plantas na area; 2 - a mistura de duas especies de plantas pode modificar a quantidade e diversidade de afideos; 3 - a composicao de especies de plantas da pastagem influencia no parasitismo de afideos. Os dados empiricos foram obtidos a partir de tres areas avaliadas: um campo de aveia preta (Avena strigosa L.), um campo de azevem (Lolium multiflorum L.) e um campo misto de aveia preta e azevem. A especie de afideo mais abundante foi Rhopalosiphum padi, seguida por Sitobion avenae. A mistura de especies de plantas aumenta a quantidade e as taxas de parasitismo de afideos. A combinacao de plantas altamente infestadas de aveia preta com poucas plantas de azevem infestadas resultou na reducao da infestacao de pulgoes, em comparacao com um campo altamente infestado de uma unica especie de planta. Isto deve-se as condicoes favoraveis para o desenvolvimento das populacoes de parasitoides. Aphidius colemani foi o principal parasitoide encontrado nessas areas.