Revista Brasileira de Milho e Sorgo (Apr 2006)
EFFECT OF SOIL MOISTURE ON THE BIOLOGY OF Rhopalosiphum maidis (FITCH, 1856) (HEMIPTERA: APHIDIDAE) ON MAIZE
Abstract
The effect of soil moisture on the biology of Rhopalosiphum maidis (Fitch) fed on maize plants (Zea mays L.) was evaluated under greenhouse conditions. A completely randomized experimental design with three treatments (20%, 40% and 100% water availability) and four replications was used. Each experimental plot was a 5 liter plastic pot containing two corn plants at the third developmental plant stage and 10 adult aphids confined into micro-cages (10 mm high x 10 mm diameter) (five aphids/microcage/ plant) and total of 40 aphids per treatment. The biological variables of the aphids recorded were: duration of each instar, duration of the pre-reproductive, post-reproductive and reproductive periods; daily production of nymphs and winged adults, and life-cycle of R. maidis. The amount of water supply to the corn plants affected the duration of the developmental time of the nymphs, in each one of the four instars, as well as on duration of the total nymph phase. The aphids that developed on corn plants with 80% of water deficit completed the nymph instars in shorter period of time. Similarly, the reproductive period and longevity of adults were shorter for aphids that developed on plants under 20% of the field capacity. There was no effect of treatments, however, on duration of the post-reproductive period. Adult aphids on plants with 80% water deficit (only 20% of the needed water) produced the first nymph in shorter period of time than those on plants that received 40% of water to reach field capacity. Aphids whose nymphs developed on corn plants under 80% water deficit disappeared more rapidly from the plants than those developed on plants under a 60% water deficit. These results indicate that the water management on maize field might be an important strategy to control the population as well as the number of generations of R. maidis in the environment, reducing the need of chemical control.
