Studies on the relationship between cotton aphids feedding, excretion, absorption and ability of cotton varieties resisting aphids using radioactive tracer 14C

The experments were conducted in 1980-1982. The aphids were placed on the plants after the cotton plants were exposed to 14CO2 under the sunlight for 1 hr. and then coverd with paper covering in the special photosynthesis chambers. The honey dew excreted by aphids was collected on the paper covering. Then the aphids and the paper coverings both put into scintillation liquid, and the radioactivity was determined. The results indicated that the aphids being different instars had different approximate rate of 14C absorption. 71.2% of total absorption was excreted in the form of honey dew; 28.8% of total absorption was taken by the aphid bodies (included milts) in the nymph stage, while 23.5% of total absorption was uptaken in the adult stage. The aphids feeding on the aphid-resistant cotton varieties (such as 'Junhai 1', 'Shanghai 605') had 23.5-26.7% approximate absorbing rate, whereas those on the aphid-sensitive cotton varieties (for example 'Uganda 2') had over 28.1% approximate absorbing rate. These results showed no difference from the results of field experiments