Relationship between nutritional composition of plant species and infestation levels of thrips.

Levels of soluble protein and carbohydrate (raffinose, sucrose, glucose, and fructose) in leaves from a selection of plant species were measured to determine if a relationship existed between these nutrients and infestation by Frankliniella occidentalis and Heliothrips haemorrhoidalis. Most species of host plant examined contained a higher proportion of protein than carbohydrates, and overall, leaves from species of plants that supported populations of thrips had greater levels of protein than leaves from nonhost species. New leaves and flowers that supported F. occidentalis contained high levels of carbohydrate and protein. The quantity of protein in leaves at the top of the tree, Peumus boldus, was greater than in leaves from lower levels, and the amount of feeding damage accrued by H. haemorrhoidalis was greater on the upper foliage than lower foliage. Oviposition by H. haenmorrhoidalis was positively correlated to levels of protein in host plants but not to levels of carbohydrates. Overall, levels of soluble protein in plants influenced their susceptibility to thrips more than levels of carbohydrates.