Greenhouse and field studies were conducted to assess the effects of systemic insecticides and plant age on beet curly top virus (BCTV) transmission to sugar beet, tomato, pepper, melon, and cowpea. Sugar beets were the most susceptible to BCTV infection. For all BCTV-susceptible plants tested, younger plants showed greater susceptibility to infection than did older plants, even when inoculations were delayed by only 1 week. Systemic insecticides applied to test plants resulted in increased beet leafhopper (Circulifer tenellus) mortality and decreased the percent BCTV transmission. Soil treatment with imidacloprid (250 g a.i./ha) gave significantly better reductions in BCTV transmission than did dimethoate foliar sprays (280 g a.i./ha). These data suggest that the use of specific systemic insecticides only when crop plants are most susceptible to BCTV infection could be an effective alternative component of the curly top disease control program.