Juvenoids effects

Each chamber was infested before treatment with a population of 750 Blattella germanica consisting of 250 nymphs of mixed age, 250 adult males, and 250 adult females. Populations were sampled monthly with monitoring traps made from baby food jars baited with bread soaked in beer. These escape proof jars were placed in the chambers for a period of 24 hours once per month. Trapped cockroaches were counted as male, female, gravid female, adults showing juvenoid effects, large and small nymphs. 

Methoprene and hydroprene are first-generation juvenoids that iacorporate minor stmctural optimisation of neotenin to increase persistence. Methoprene, 1-isopropyl (E,E)-ll-methoxy-3,7,ll-tnmethyl dodecadi-2,4-enoate (129) (bp 100 C/6.7 Pa, vp 3.5 mPa at 25°C), is soluble ia water to 1.4 mg/L. The rat oral LD q is >34,000 mg/kg. Methoprene has been used as a mosquito larvicide, ia baits for ant control, and as a catde feed-through treatment for horn fly control. Hydroprene, methyl (H,H)-3,7,ll-trimethyl-dodecadi-2,4-enoate (130) (bp 174°C at 2.5 kPa, vp 2.5 mPa at 25°C), is soluble ia water to 0.54 mg/L. The rat oral LD q is >34,000 mg/kg. Hydroprene is especially effective against aphids and cockroaches. 

At least two events were responsible for a change in this attitude and provided the incentive to select and develop an effective juvenoid for cockroach control a) the success achieved with the juvenoid methoprene in the control of breeding flea populations in household carpets and upholstery (17, 18) b)... 

In a further development of the juvenoid control approach, there appeared to be a very good promise also for combinations of conventional insecticides (whether really effective or only perceived as such) with effective long term juvenoid control agents. 

Many different effects have been described as a result of juvenold treatment on cockroaches, primarily Blattella germanlea. In none of the tests we undertook have we seen a significant mortality attributable to either a direct effect of the compounds tested, (13, 14, 23), an inability to molt properly, or a failure to molt (5. 8, 11). On the contrary, many of the morphogenetically affected adults or adultoids appeared to suffer no ill effect from the indignities inflicted by the juvenoids, other than failure to reproduce. Although the treatment methods may be partly responsible for differences between the results of different authors, it is more likely that qualitative differences between types of juvenoids are partly responsible. Delays in the final molt were frequently observed in batches affected by juvenoids. Most, if not all, of these nymphs made it eventually to viable, but non reproducing, adultoids. 

According to expectation based on pharmacological analogies, fixation of part of the molecule by a relatively rigid cyclic structure enhanced the species specificity, as compared with acyclic juvenoids. Thus, compounds 27 and 28 seem to be the most potent juvenoids presently available against Blattodea and Lepidoptera. At the same time, they are but moderately effective against their dipterous and hymenopterous parasites, honey bees and other useful insects. 

The N-[4-(benzyloxy)benzyl]anilides obtained by DeMilo and Redfern (1979) proved to be highly effective juvenile hormone mimics, though their structure does not reflect even the intention of preparing terpene inspired juvenoids. The most effective member of this class was N-[4-(3-chlorobenzyl)oxy]benzyl-2,6-difluoro-aniline (69). 

It cannot be decided on the basis of experimental results available so far whether the action of the synthetic juvenoids is a hormonomimetic effect exerted according to the same mechanism as that of endogenous juvenile hormones. The fact that compounds with a very different structure from that of natural juvenile hormones also display morphogenetic activity seems to suggest that at least an important part of synthetic juvenoids acts according to another mechanism. According to Bowers... 

The compound should demonstrate the ability to mimic JH at the three principle stages of insect development the eggs, the juvenile and the adult (female). Therefore, observation of ovicidal effects is suggestive of juvenoid activity but not definitive. 

These effects should represent the biological situation. For example, many of the studies described below have been performed using topical application of the putative juvenoid this may not reflect the insect s natural contact with the chemical. 

Plant secondary metabolites which mimic JH activity appear to be active on a narrow range of host species. What account(s) for this effect The majority of bioassays used last larval instars of P. apterus, O. fasciatus and pupae of T. molitor to test for activity of the juvenoids. Are these the most sensitive insects Six JHs have been identified to date different homologs have been isolated from specific insect orders. Juvenile hormone III appears to be ubiquitous [12, 13] and, in most species, is the only JH present. Juvenile hormone I and II are important in the regulation of metamorphosis and ovarian maturation in Lepidoptera [5] and the bis-epoxide appears to be the principle JH in higher Diptera [20]. Therefore, the nature of the JH in the test insect and the role that it plays in development must be considered in the selection of the bioassay a compound which mimics the action of JH in P. apterus (Hemiptera) is unlikely to be active in a Lepidopteran insect. 

Juvenile Hormones and Juvenoids Modeling Biological Effects and Environmental Fate, James Devillers, 2013... 

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