Pollen as alternative food for Neoseiulus californicus (Acari: Phytoseiidae)

GUGOLE OTTAVIANO, M. F.; CÉDOLA, C. ; SÁNCHEZ, N.E.; GRECO, N.M.

Recife

Congreso; XIII International Congress of Acarology; 2010

The increase of plant diversity in agricultural systems can enhance the abundance of some natural enemies, by improving the availability of alternative foods (nectar, pollen and honeydew). Strawberry is an important crop in the orchards of La Plata (Buenos Aires, Argentina). Neoseiulus californicus is a generalist predatory mite of spontaneous presence in strawberry crops and associated wild plants. It plays an important role in limiting the abundance of the main pest of this crop, Tetranychus urticae (Acari: Tetranychidae). Plant diversity could promote the persistence, in space and time, of this predator in the crops. The aim of this work was to determine if pollen of strawberry and some wild plants constitute alternative foods to N. californicus in the orchards. Leaves and flowers of wild plants associated to strawberry crop were monthly sampled from April 2005 to March 2009. N. californicus and T. urticae presence was registered. Flowers of strawberry and the wild plants where the predator was observed were collected and pollen of each one was extracted. Eggs 24h old were put individually on strawberry discs, in a Petri dish. After eclosion pollen of each plant was offered “ad libitum” to the nymphs. The control treatment was N. californicus fed with T. urticae eggs, nymphs and adults. The experimental conditions were 25ºC, 60-70% HR and 14:10h L:D. Developmental time from egg to adult of N. californicus was registered in each treatment. Data were analyzed by ANOVA. The predator was registered in 13 out of 56 sampled plant species and it was along with T. urticae on Urtica dioica, Convolvulus arvensis, Dipsacus fullonum, Lamium amplexicaule, Morus alba and Picris echioides. On Sonchus oleraceus, Polygonum aviculare, Lolium multiflorum, Galega sp., Taraxacum officinale, Echinocloa crusgalli and Anoda cristata,  this predator could be feeding of pollen since it presence was coincident with the flowering of these plants and the T. urticae absence. The pollen of U. dioica, S. oleraceus, L. multiflorum, P. echioides, E. crusgalli, P. aviculare, L. amplexicaule was tested as food. The developmental time of N. californicus differed significatively among foods.  Feeding on S. oleraceous pollen developmental time (6.96 ± 1.02d) was higher than on strawberry pollen (6.00 ± 0.98d), U. dioica pollen (5.71 ± 0.76) and the prey T. urticae (4.53 ± 0.79).  Feeding on pollen of P. echioides, E. crusgalli and P. aviculare, N. californicus did not complete development and only reached protonymph stage. The present results indicated that N. californicus feeding on pollen of some wild plants can reach the adult stage but at lower developmental rate than when preying T. urticae. These plants bloom in different seasons, so alternative food for the predator would be available throughout the year. While is not yet known if the predator can be reproducing with this food, its persistence in strawberry orchards would be favored.