Abstract
The anti-juvenile hormone, precocene-2, showed multiple biological activity against the whitebacked rice planthopper, Sogatella furcifera. When newly hatched nymphs were released on rice plants treated with 500ppm of precocene-2 and continuously contacted with the chemicals, about half of the insects died within the first stadium (rapid toxicity). The other half survived through the following two or three nymphal stadia and then developed into precocious adults in the fourth or fifth stadium (prothetely). In this case, the insects seem to have been rather strongly affected by the anti-JH activity of precocene-2. On the other hand, when the insects were transferred from the treated rice plants to untreated ones on two, four and six days after the release, a large portion of the surviving insects (41.9% at maximum) developed into supernumerary nymphs in the sixth stadium (metathetely). In this case, the insects were supposed to have been incompletely affected by the activity of precocene-2. A juvenile hormone analog, NC-170, induced metathetely by itself, but none of the natural JH-1, JH-2 and JH-3 showed any morphogenetic effect. In addition, NC-170 rescued the prothetely induced by precocene-2, but the three natural JH's did not.
