Leguminous cover crops to enhance population development of Euseius tularensis (Acari : Phytoseiidae) in citrus

Pollens from various field-grown legumes, including clovers, vetches, pea, and bell bean plants, were fed to laboratory colonies of the predacious mit e Euseius tularensis (Congdon). The survival, sex ratio, and reproduction o ff. tularensis were compared with those for colonies fed pollen from ice pl ant, Malephora crocea (Jacquin). Predacious mites fed a diet of pollen from bell bean, Vicia faba L.; 'Austrian winter' pea, Pisum sativum (L.) var. ' arvense' Poir.; and New Zealand white clover, Trifolium repens L. survived and reproduced as well as those fed ice plant pollen. Predacious mites fed common vetch, Vicia sativa L.; woollypod vetch, Vicia villosa Roth ssp. das ycarpa Ten. var. 'Lana'; and crimson clover Trifolium incarnatum L. var. 'F lame' pollens exhibited reduced fecundity E. tularensis did not survive mor e than one generation when fed pollens from rose clover, Trifolium hirtum A llioni var. 'Hykon' or red clover, Trifolium pratense L. var. 'Kingsland'. When E. tularensis was released into a held-grown cover crop mixture of woo llypod vetch, bell bean, and 'Austrian winter' pea, the predacious mite pop ulation exhibited a significantly greater population increase on the cover crop over a 4-week period than in nonrelease areas. Addition of ice plant p ollen did not significantly improve population growth off. tularensis on th e cover crop. The majority of the E. tularensis population was recovered fr om the bell bean plants in the cover crop mixture. When E. tularensis-infes ted cover crop was cut and placed in young citrus trees that had low natura l densities of predacious mites, densities on trees were significantly incr eased. (C) 1999 Academic Press.