Pink bollworm larvae

The growth-inhibitory activity of azadirachtin fed in artificial diet to three species of agricultural pests, gossypiella, H. zea, and frugiperda, was compared to the activity of a number of limonoids isolated from plants in the Meliaceae and the Rutaceae (Table VI). After azadirachtin, the most active limonoid was cedrelone (Figure 13). Cedrelone was unique among the compounds tested in Table VI since it was the only limonoid, besides azadirachtin, to cause an inhibition in ecdysis (LC50 = 150 ppm) when fed to pink bollworm larvae (54). 

Table 1. Effects of 5 phytoecdysones on growth and development of pink bollworm larvae.

A number of other llmonolds which were Isolated from plants In the Mellaceae and the Rutaceae were tested for ecdysis and growth Inhibitory activities (Table V). Cedrelone (Figure 9) was unique among the compounds tested In Table V since it was the only llmonold, besides azadlrachtln, whose toxicity (LC50 - 150 ppm) Included ecdysis Inhibition when fed to pink bollworm larvae (43). 

Figure 3. Mean pink bollworm larva found from gossyplure-treated and check plots. Reprinted with permission from Journal of Economic Entomology, c. 1981, Entomological Society of America.22... 

Figure 7. Electron Micrograph Illustrating Ecdysls Inhibition of a Larva of the Pink Bollworm, Pectlnophora gossyplella after Ingestion of 2 ppm Ponasterone A In an Artificial Diet (Magnification x 100)...

Figs. 3 and 4 are electron micrographs of a fall armyworm, and a pink bollworm, respectively. Both Insects have three head capsules because they underwent two failed molting cycles before death. That Is, even though feeding became Impossible after the first Inhibited ecdysls because the adhering second head capsule covered the mouthparts, these larvae could synthesize a third head capsule. ... 

Homeosoma electellum) contain high concentrations of tra-chyloban-19-oic acid (70) and ( —)-16-kauren-19-oic acid (71) in their florets. As sunflower florets that contain only small amounts of these compounds are a major portion of the diet of first instar larvae of this insect, it is likely that these acids serve as feeding inhibitors. At the 1% level, both kaurenoic and trachylobanoic acids decreased the growth of sunflower moth larvae and tobacco budworm (Heliothis virescens) by about 50%. At the 0.5% level, both reduced larval growth of the cotton bollworm and the pink bollworm to less than 5% (Fig. 22.23) (Mabry and Gill, 1979). The Z-and -isomers of (- )-ozic acid (72) have been isolated from Helianthus occidentalis and may be associated with resistance to insect attack (Stipanovic et al., 1979). 

Figure 31. Diterpene resin acids tested for biological activity against pink bollworm (Pectinophora gossypiella) larvae.

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