Aspects of the biology and management of Froggatt's apple leafhopper (Typhlocyba Froggatti baker) in New Zealand

Froggatt's apple leafhopper (FALH) is a minor pest of apple in New Zealand although it has the potential to increase its pest status through insecticide resistance and any reduction of insecticide use aimed at 'key pests'. This thesis gathered basic biological information to rationalise any future management of this insect. Yellow sticky boards were used to sample FALH adults in three orchards under different management regimes and the adults of the egg parasite Anagrus armatus in two orchards. Sampling of overwintering eggs, summer eggs and nymphal instars occurred only in an abandoned orchard. Regular insecticide applications in a commercial orchard reduced the numbers of FALH and A. armatus to very low levels compared to those trapped in an abandoned orchard. All life stages of FALH sampled over two seasons in an abandoned orchard strongly suggested the presence of at least two, and possibly a partial third, generation. A similar temporal distribution was found in blackberry adjacent to an abandoned orchard. Overwintering eggs, summer eggs and nymphs showed no consistent preference for any of the examined positions within the tree. Adult numbers trapped on yellow sticky boards increased with height, due to a disproportionate increase of males with height in relation to females. The description of the pattern of distribution was established using the indices of Taylor's power law and Iwao's patchiness regression for overwintering eggs (randomly dispersed, cohesive groups of eggs), for two seasons of summer eggs (a clumped distribution with a basic component of individuals in both seasons) and two seasons of nymphal instars (basically random or clumped groups of individuals). Of the 27 distributions analysed, Taylor's power law gave the better data fit on 26 occasions. Only four distributions were described differently by the two models. FALH numbers built up quickly in a previously uninfested orchard through natural increase and migration. Migration over short distances was mainly influenced by the condition of the host plant and the prevailing wind. Conservative estimates of parasitism by A. armatus were established for overwintering FALH eggs (30-53%) and summer FALH eggs (20-100%) in an abandoned orchard. Yellow sticky board samples indicated that the life cycle of A. armatus was well synchronised with that of FALH. The appropriate base temperatures for different development stages of FALH were found to be between 9.7 and 11.0°C by laboratory studies and field measurement. A thermal constant of 463.5 ±10.5D° from egg to adult was established from laboratory studies. Acetate sheets placed on the yellow sticky boards only reduced the spectral reflectance by a small amount but improved sampling efficiency and trap storage. The yellow sticky boards were found to sample larger proportions of the FALH population in relation to the D-Vac (at all densities) and Johnson and Taylor suction trap (only at high densities). Sticky boards appeared to preferentially sample males in relation to females. Higher placement of sticky boards in the tree reduced the number of leafhoppers, other than FALH, caught. A rational approach to control, based on all available data for this insect, is discussed.