Efficiency of Phytoseiulus longipes Evans as a control agent of Tetranychus evansi Baker & Pritchard (Acari: Phytoseiidae: Tetranychidae) on screenhouse tomatoes

The spider mite Tetranychus evansi Baker & Pritchard can cause severe damage to tomato crops. The predatory mite Phytoseiulus longipes Evans was recently reported in association with T. evansi in Uruguaiana, Rio Grande do Sul State, Brazil. The objective of the present study was to evaluate the effects of P. longipes on the population of T. evansi on tomatoes under screenhouse condition. The study consisted on four experiments, in each of which 80 potted plantlets were distributed in two plots of 40 plantlets each. Two weeks later, each plantlet of both plots was infested with eight adult females of T. evansi; one week after, four adult females of P. longipes were released onto each plant of one plot. The population levels of T. evansi and the damage caused by these mites were significantly lower (P < 0.05; linear mixed-effect model) in the plots where P. longipes had been released. The results indicate the potential of this predator as a candidate for classical biological control of T. evansi by inoculative releases on tomato plants.

Predatory mites associated with Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae) on native solanaceous plants of coastal Pernambuco State, Brazil / Predatory mites associated with Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae) on native solanaceous plants of coastal Pernambuco State, Brazil

The occurrence of the tomato red spider mite (Tetranychus evansi Baker & Pritchard) and predatory mites on four of the most abundant native solanaceous plants in coastal Pernambuco, Brazil, was evaluated. Monthly samples were collected from mid September 2002 to late May 2003 in Aliança, Carpina, Camaragibe, Goiana, Igarassu and Recife. A total of 5,485 mites of more than 27 species were found, of which the most common were the phytophagous species T. evansi and Brevipalpus phoenicis (Geijskes) (Tenuipalpidae), and the predaceous species Asca sp. (Ascidae), Phytoseius guianensis De Leon and Paraphytoseius orientalis (Narayanan, Kaur & Ghai) (both Phytoseiidae). Negative indexes of association were determined between T. evansi and each of four species of predaceous phytoseiids [i.e., the three most numerous species found in this study as well as Phytoseiulus macropilis (Banks)]. Laboratory tests were also conducted to evaluate the acceptability of Tetranychus urticae Koch and T. evansi as prey by the four predatory species. Only P. macropilis survived and oviposited well when fed T. urticae. Although they were able to remain alive for some days when fed T. evansi, the reproduction levels of the four predator species were very low. These results suggest that despite being commonly found on solanaceous plants in the field, these predators feed very little or do not feed at all on T. evansi in nature.

Avaliou-se a ocorrência do ácaro vermelho do tomateiro (Tetranychus evansi Baker & Pritchard) e de ácaros predadores em quatro das espécies mais abundantes de solanáceas nativas do litoral de Pernambuco. Foram feitas coletas mensais de amostras de plantas de meados de setembro de 2002 a fins de maio de 2003, nos municípios de Aliança, Carpina, Camaragibe, Goiana, Igarassu e Recife. Foram encontrados 5.485 ácaros pertencentes a mais de 27 espécies, das quais as mais numerosas foram as espécies fitófagas T. evansi e Brevipalpus phoenicis (Geijskes) (Tenuipalpidae), e as espécies predadoras Asca sp. (Ascidae), Phytoseius guianensis De Leon e Paraphytoseius orientalis (Narayanan, Kaur & Ghai) (ambos Phytoseiidae). índices de associação negativos foram determinados entre T. evansi e quatro espécies de fitoseídeos predadores [as três mais numerosas encontradas neste estudo assim como Phytoseiulus macropilis (Banks)]. Foram também realizados testes em laboratório para se avaliar a aceitação de Tetranychus urticae Koch e T. evansi como presas àqueles predadores. Apenas P. macropilis sobreviveu e ovipositou adequadamente quando alimentado com T. urticae. Embora conseguissem se manter vivos por alguns dias quando alimentados com T. evansi, os níveis de reprodução dos quatro predadores foram muito baixos. Esses resultados indicam que embora encontrados comumente sobre solanáceas no campo, aqueles predadores alimentam-se muito pouco ou não se alimentam de T. evansi na natureza.