Southern armyworm

Mayer and coworkers128 discovered that kojic acid is a moderately effective activator for nicotine insecticides. When tested against the melon worm (Diaphania hyalinata L.) and the southern armyworm (Prodenia eridania Cram.), kojic acid (alone) was not toxic but the toxicity of a 5% nicotine sulfate-pyrophyllite dust was increased 35 %, and that of a 5 % nicotine bentonite-bentonite spray by some 50%, by the addition of 5% of kojic... 

Highly toxic substances, such as cyanides, are sometimes feeding cues and stimulants for specialized insects. For example, instar larvae of the southern armyworm (Spodoptera eridania) strongly prefer cyanogenic foods, such as foliage of the lima bean, a plant with comparatively elevated cyanide content — up to 31 mg/kg in some varieties — in the form of linamurin (Brattsten et al. 1983). Feeding was stimulated in southern army worms at dietary levels up to 508 mg KCN/kg... 

Experimental studies with southern armyworm larvae and thiocyanate — one of the in vivo cyanide metabolites — showed that 5000 mg thiocyanate/kg diet reduced pupation by 77%, completely inhibited oviposition, and reduced adult emergence by 80% (Brattsten et al. 1983), strongly suggesting that thiocyanate poisoning is the primary effect of high dietary cyanide levels in southern army worms. 

Resistant species, such as southern armyworms, require injected doses up to 800 mg KCN/kg BW (332 mg HCN/kg BW) or diets of 3600 mg KCN/kg for 50% mortality (Brattsten et al. 1983), but data are scarce for other terrestrial invertebrates. Exposure to 8 mg HCN/L air inhibits respiration in the granary weevil (Sitophilus granarius) within 15 min and kills 50% in 4 h some weevils recover after cessation of 4-h exposure (Towill et al. 1978). 

Brattsten, L.B., J.H. Samuelian, K.Y. Long, S.A. Kincaid, and C.K. Evans. 1983. Cyanide as afeeding stimulant for the southern armyworm, Spodoptera eridania. Ecol. Entomol. 8 125-132. 

In vitro dieldrin production increased proportionally to larval concentration (enzyme concentration) up to 5 larvae/ml and each 10X increase in substrate (aldrin) concentration tripled and doubled, respectively, dieldrin formation. An approximation of 2 X 10-5 M aldrin as the Km value for midge epoxidase was obtained from a double reciprocal plot of data in Table VII, which closely corresponds to values for aldrin epoxidase in the house fly (28) and the southern armyworm (11). 

Electron microscopic examination of midge microsomes prepared by a slightly different procedure than Table VIII revealed a homogeneous mixture of vesicles derived from rough and smooth endoplasmic reticulum, ribosomes and a few mitochondria. Midge preparations are similar in composition to microsomal fractions of southern armyworm fat body and gut (44). 

Although southern armyworms were used for the development of QSARs the other insects listed in Figure 2 were used in topical or foliar assays to monitor spectrum and performance under field conditions. 

It was clear, from even a qualitative inspection of the data, that the presence of a methyl or fluoro group in the meta position had the effect of not only increasing activity versus the design insect, the southern armyworm, but also lead to dramatic increases in level of topical activity against other species. 

Figure 2. Growth from fourth instar to pupation on control or pulegone-containing diet of fall armyworm larvae (11) (top) and southern armyworm larvae (13) (bottom). Key , control A, O.OI % pulegone and A. 0.1 % pulegone.

Effects of larval dietary pulegone on development and ovlposltlon In the southern armyworm... 

Several different molecular mechanisms could be involved in the reproductive Inhibition observed In the southern armyworm. 

The microsomal cytochrome P-A50 system In the midguts of southern armyworm larvae oxidises pulegone vitro. The two major products, 9-hydroxypulegone and 10-hydroxypulegone are formed by mlcrosomes from larvae Induced with either pentamethylben-zene or a-plnene. Mlcrosomes from control (un-lnduced) larvae only oxidise trace amounts of the compound. The 9-hydroxypulegone rearranges spontaneously to menthofuran (38). 

Terpene Induction of mldgut microsomal cytochrome P-450 and pyrethrum-dependent NADPH oxidation In southern armyworm larvae (42)... 

Table VII shows the Increase In cytochrome P-450 content In mlcrosomes from southern armyworm larval midguts resulting from dietary exposure to several cyclic monoterpenes ( ). It also shows a closely corresponding Increase In the rate of NADPH oxidation when pyrethrum Is the substrate (R) being oxidised. The microsomal cytochrome P-450 system Is arranged as outlined In Figure 6, consisting of a terminal heme-lron protein that In the oxidised (Fe3+) state binds the substrate (R). The complex undergoes two reductions during which bound molecular oxygen Is converted to free radical species, one of which Is Inserted In the substrate molecule, and the other one forms water. The reductions...

The Inducing effects on the southern armyworm cytochrome P-450-medlated metabolism shown In Tables VII and VIII resulted from 3 days feeding on diets containing 0.2% of the terpene. 

C/5 content in midgut microsomes form southern armyworm larvae (38). ... 

Z)-9-tetradecenyl acetate [16725-534] CH3(CH2)3CH=CH(CH2)8OOCCH3 southern armyworm, Spodoptera eridania (with (Z)-9,(E)-12-tetradecadienyl acetate) beet armyworm, Spodoptera exigua... 

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