Corn earworm activity

Figure 1.1 The three major types of hormones that regulate pheromone production in insects. A Juvenile Hormone III (C16 JH), B 20-Hydroxyecdysone and C PBANs from the corn earworm, Helicoverpa zea (Raina et al., 1989), the silkworm moth Bombyx mori (Kitamura et al., 1989) and the gypsy moth, Lymantira dispar (Master et al., 1994). The minimum sequence (pentapeptide) required for activity is indicated.

Recent publications 0,4) in regard to the latter two plants indicate that they were also toxic to two bacteria which occur in the gut of the tobacco budworm Heliothis virescens (Fab.) and the corn earworm Heliothis zea (Boddie). The compounds, rhamnetin 3-0-glucoside and isoquercitrin, were isolated (3) from H camporum based upon their activity against Pseudomonas maltophilia and Enterobacter cloacae Also, a procyanidin was isolated (4) from Mj floribundum on the basis of activity against P. maltophilia. 

Ryania is made from the ground roots of the tropical shrub Ryania speciosa. The active principle of ryania is the alkaloid ryanodine (C25H35NOu). Ryania is used for controlling aphids, cabbage loopers, Colorado potato beetles, diamondback moths, cucumber beetles, leafhoppers, corn earworms, European corn borers, codling moths, citrus thrips, and so on. Its oral LD30 in rats is 1200 mg/kg so it is practically nontoxic to mammals. 

Mating in most species of moths is mediated through the production and release of species-specific sex pheromones by the females and, in a majority of the moths, reproductive activity is limited to the hours of darkness. To achieve this diurnal periodicity of mating, production of sex pheromone must also be synchronized (JL). In the corn earworm, Helicoverpa Heliothls) zea, and in many other species of moths, this synchronization is affected by a factor produced in the head of the female (2.). The factor was identified as a peptide hormone, produced in the suboesophageal ganglion (SOG) and most likely... 

When the full structure of the pheromone biosynthesis activating neuropeptide (PBAN) from the corn earworm Heliothis zea was recently reported (28), we noted that the sequence contained the pyrokinin C-terminal pentapeptide fragment Phe-X-Pro-Arg-Leu-NH2 (X - Ser), identical to that contained in locustamyotropin I (Figure 5) (27). Indeed [Nle, Nle ]PBAN demonstrates LPK-like contractile activity in the heterologous cockroach hindgut and oviduct assays, retaining a full 25% of LPK activity on the isolated Leucophaea oviduct (Holman, G. M. and Nachman, R. J., unpublished data.). 

We recently reported the primary sequence of the pheromone biosynthesis activating neuropeptide hormone (Hez-PBAN) that controls sex pheromone production in adult female moths of the corn earworm. Heliothis zea (1), Hez-PBAN is a 33 residue C-terminally amidated peptide with a molecular weight of 3900 daltons. This paper describes the details of the isolation and characterization of this first member of a new family of insect neuropeptides. 

Ryanodine is the active, insecticidal ingredient of a tropical shrub Ryania speciosa). For years, this botanical insecticide has been recommended for use against citrus thrips, corn earworms, European corn borers, codling moths, and a variety of other pests. However, ryania is also quite toxic to mammals and water life. For this reason, it s better to rely on safer pest control measures,. such as iasecticidal soap, neem, or pyrethrin. 

Examination of the data shows that the first entry in the Table 1 had exceptionally high activity on aphids and mites with TI values of 1750 and 3192, respectively. For houseflies and corn earworms this compound was less active than the standard parathion. Increases in size of the substituent R significantly reduced the activity against all insects except the corn earworm where a major reduction only occurred when the hydrogen was replaced by ethyl and larger groups. 

This report summarizes the synthesis, insecticidal activity, and anticholinesterase activity of some novel N-dihydrobenzo-furanyl oxadiazolones. The compounds were primarily aphicides with reduced activity on houseflies, corn earworms and two-spotted spider mites. Some of these gompounds were potent anticholineterases (I-. values 1-10x10 M) that were slowly reversible. There was little relationship between in vitro... 

Table 1 contains insecticidal toxicity information on five compounds which differ only in their substituents at the 4-position of the dihydrobenzofuranyl ring. With the exception of aphids, the most broadly active compound was unsubstituted at this position. Other substituent at this site had no enhancing effect and in some cases (Cl on houseflies and corn earworms and F on mites) a strong deleterious effect resulted. The only case where a substituent, CH, increased the activity was with aphids. 

This report briefly summarizes the synthesis, insect toxicity and anticholinesterase activity of some novel dihydrobenzofuranyl oxadiazolones, a class of insecticides whose major strength lies in their toxicity to aphids with reduced activity on houseflies, two-spotted spider mites and corn earworms. This is similar to the previously reported RP 32,861, which also was most active on sucking insects. The molecule with the broadest toxicity spectrum... 

In a few Lepidoptera, like the silkworm moth Bombyx mori), hehothide species as the corn earworm (Helicoverpa zea) and the cabbage moth (Mamestra brassicae) it has been demonstrated that a neuronal hormone (PBAN, pheromone biosynthesis activating neuropeptide) is synthesised by a cephalic organ in their brain, dependent on the day/night rhythm. This mediator controls the sex pheromone production in these moths. [161, 170]... 

Corn Earworm. Bioassay for RTF activity was conducted in three- to four-day-old, adult, virgin CEW females. Neck ligations were performed 12-18 hr prior to bioassay. Five picomoles of synthetic PBAN were injected into each female in 5 ul distilled water at the onset of scotophase. One hour later this was followed with 10 ul of the test fraction. Pheromone glands were excised and pheromone titer determined as previously described (26) using a Shimadzu Model GC14A gas chromatograph equipped with a Hewlett-Packard (Avondale, PA) methyl silicone column. 

Maysin (Fig. Ic), the main representative of the third class of inhibitory compounds, the flavonoid glycosides, was shown to be active against the com earworm and was identified as the antibiotic factor in the exotic strain of corn, Zapalote Chico (10). The mode of action of maysin in inhibiting the growth of the corn earworm is similar to that of chlorogenic acid (9). 

The rice leaf binding component, prodnced in aerobic cnltures of the strain Claviceps purpurea ATCC 9605 or of a number of other microorganisms (Oishi et al., 1984), can be used to increase the rice crop. The active component increases the yield and shortens the production period. Also other metabolites of Claviceps can find application in agriculture practice. Patent of Dowd et al. (1988) describes the use of tremorgenic mycotoxins as insecticides against corn earworm and fall armyworm. Gubanski and Lowkis (1964) have demonstrated the inhibition of the tobacco mosaic virus by a substance isolated from C. purpurea. 

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