512

Table 1. LT50 Valuesa for German Cockroach Second Instars

compound type

natural

synthetic

a Number of days before death of 50% of the population following exposure to toxic baits at a dose of 1000 ppm.

Table 2. LT50 Valuesa for German Cockroach Fifth Instars

compound type

natural

synthetic

a Number of days before death of 50% of the population following exposure to toxic baits at a dose of 1000 ppm.b There was a single response value to cypermethrin; no lethal time estimate was made.

Most of the acetogenins tested performed better than the conventional insecticides against both stages of both strains (Tables 1 and 2). No growth-regulation effects were caused by any of the compounds tested. Low resistance ratios (RRs) were obtained for most compounds (except chlorpyrifos) (Table 3). Low resistance ratio values for second instars ranged from Q9 to 22 with the natural acetogenins and from 1.0 to 38 with the synthetic compounds; the fifth instars ranged from Q2 to 3.9 with the natural acetogenins and from Q6 to 80 with the synthetic compounds (Table 3). Hydromethylnon, an electron-transport complex III inhibitor, not surprisingly, showed the lowest RR among the synthetic pesticides.[22] The high mortality observed with the low resistance ratios, shown in this study,[22] suggested an excellent potential for the use of Annonaceous acetogenins in baits against cockroaches, and it is predictable that such pesticide-resistance also includes ATP-dependent factors.

These compounds are proven to induce emesis in pigs; this is a definite safety factor should someone ingest excessive amounts of these materials either intentionally or unintentionally; indeed, a fluidextract of paw paw seeds was once sold as an emetic by the Eli Lilly Co. (Asta Laboratories, unpublished data).[107] The methanolic-soluble fraction, FOO5, of paw paw bark, gave negative results in the Ames mutagenicity test (Sitek Research Laboratories, unpublished results); nine out of 10 tests were negative on the histidine mutants of Salmonella typhimurium, and one slight positive (2.5% above control) occurred after enzyme activation of the extract. Further research is now needed to develop more refined treatment strategies for the inclusion of effective baited formulations, containing mix-

b

Figure 11. Effects of Annonaceous acetogenins (1000 ppm in bait) on development of fifth instars of (a) the Jwax and (b) Muncie strains of Blattella germanica.

Table 3. Resistance Ratios for Annonaceous Acetogenins and Conventional Synthetic Toxicant Baits for Second and Fifth Instars of Blattella Germanica

compound type

natural

synthetic

a Resistance ratios (95% confidence limits, CL) at LT50 value estimates. There was a single response value for cypermethrin against fifth instars of the Jwax strain; no lethal time was estimated, and the RR was not calculated. In some instances, the use of a large t value caused nonrealistic confidence limits (CL) to be calculated. Whenever the 95% CL of a ratio includes 1 (values with an asterisk), no significant differences exist between the probit levels of mortalities being compared.

tures of acetogenins obtained from plant extracts, into integrated pest management programs to control resistant B. germanica.

The activities of 44 Annonaceous acetogenins were evaluated in the yellow fever mosquito larva microtiter