Vine phenological stage during larval feeding affects male and female reproductive output of Lobesia botrana (Lepidoptera : Tortricidae)

The effect of vine phenological stage during larval feeding on the reproduc tive output of Lobesia botrana (Denis & Schiffermuller) adults was assessed . Larvae were reared under field conditions on vine inflorescences, unripe or ripe berries simulating the first, second and third insect generations r espectively. The resulting adults showed significant differences in body we ight, longevity and reproductive output as measured by oviposition period, total fecundity and reproductive efficiency (viable eggs/body weight) for f emales, and spermatophore number and volume of the first spermatophore for males. Viable egg number was positively correlated with female body weight for all treatments but male reproductive efficiency (spermatophores/body we ight) was not. The reproductive output of females from larvae reared on a s tandard semisynthetic diet was comparable to that of females reared on ripe berries whereas males showed a higher reproductive output when reared on s emisynthetic diet. These results clearly show that data obtained from insec ts reared on artificial diet cannot be extrapolated to 'field-derived' adul ts. The results suggest that the variation in L. botrana reproductive outpu t due to the larval food source should be taken into account as a potential factor affecting insect population dynamics. It is suggested that differen t intervention thresholds, such as those based on pheromone catches, may be needed for each of the three moth generations, to compensate for the incre ased fecundity and potential to cause larger amounts of crop damage of late r generations.