When larvae of Pieris brassicae (L.) were fed on leaves of plants showing symptoms of deficiency of nitrogen, phosphorus, potassium or iron, some or all of the following effects were recorded in each experiment: —Reduction of larval weight (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).Reduction of relative growth rate (deficiency of (1) N throughout larval life, (2) Fe from time of hatching, from sixth day and for last two larval instars).Increased larval mortality (deficiency of N, Fe from time of hatching).Delayed pupation (deficiency of (1) N, P, K throughout larval life, (2) Fe from time of hatching, from sixth day and for the last two larval instars).The more detailed experiments with iron-deficient diet showed that similar effects were produced at whatever stage of larval development it was first supplied.Larvae fed on iron-deficient leaves from the time of hatching appeared to have received a severe initial check to growth, but this was followed by some degree of recovery so that they showed a higher relative growth rate, a few days later, than larvae given the same diet six days after hatching.Preliminary trials were made on the effects of the addition to diets of iron-deficient leaves of various nutrient substances sprayed on to them. No markedly beneficial results were noted.
Insecticidal Effects of Different Application Techniques for Silica Dusts in Plant Protection on Phaedon cochleariae Fab. and Pieris brassicae L.