SPATIOTEMPORALLY VARIABLE AREA MASS RELATIONSHIP OF RUSSET-BURBANK POTATO LEAFLETS - IMPLICATIONS TO POTATO PRODUCTION MODELS/

The relationship between area and mass of fresh Russet Burbank potato leaflets tvas monitored in two fields throughout two growing seasons i n southern Manitoba. A simple ratio was adequate to describe the relat ionship between leaflet area and mass. The ratio changed non-linearly over the growing season in each field; this time trend differed among fields. During the middle of the growing season, the ratios differed s ignificantly among all trials. In one season, Colorado potato beetles completely defoliated plants in one field; from shortly after plant em ergence until no leaves remained, the area:mass ratio in this field wa s significantly lower than in all other fields. When the area:mass rat io is assumed to be constant or to change linearly over time, estimate d leaf area per plant is consistently erroneous. Where models make eit her assumption, such bias may contribute to site-specificity, or to th e inability to accurately simulate the effects of insect attack.