Southern corn rootworm

Symptoms Southern corn rootworms feed on corn roots, often killing young plants and weakening older ones. Striped cucumber beetle larvae feed on the roots of squash-family plants only, killing or stunting the plants. Adults of both species feed on leaves, stems, flowers, and fruit of squashes and other crops. 

Southern corn rootworm. The structure of the southern corn rootworm has been defined as 10-methyl 2-tridecanone, XI (Figure 16) (5J3). Alkylation of undecanoic acid with n-propyl bromide was followed by conversion to the diastereomeric amides with either (S)- or (R)-a-methylbenzylamine that had been purified previously by recrystallization of D and L tartaric acid salts, respectively. Recrystallizations of these amides from ethanol (4 was sufficient) gave 32% yields of pure (>99.5%) diastereo-mers (Figure 16). Hydroxyethylation labilized the amides toward hydrolysis. It was convenient to intercept the aminoesters and reduce them with LAH. The resulting carbinols were than carried forward in standard manner to provide the ketones. 

The pheromone of the southern corn rootworm (SCR), D. undedmpunctata howardii Barber, was identified as (R)-10-methyl-2-tridecanone (40). Since it has only one asymmetric carbon, it can exist in only two enantiomeric forms. Synthesis of both the (R)- and (S)-enantiomers by Sonnet (41) in high enantiomeric purity again provided material for field tests. SCR males respond only to the (R)-enantiomer in the field. 

Spotted cucumber beetle larvae (also called southern corn rootworms) are white with brown heads and grow up to A" long. Adults are A", greenish yellow beetles with black spots. Treat infested plants with a commercial pyrethrin spray if the damage is severe. P revent problems by covering plants with... 

Southern (see Southern corn rootworms) spotted, 285.285 Corn smut, 80,390,390 Corn spurry, as attractant crop,... 

Diabrotica undecimpunctata howardi. See Cucumber beetles Southern corn rootworms Diagnosis... 

The insecticidal activity and structure-activity relationships of novel pyrethroids prepared by reacting methyl phenyl substituted pyrazole methanols with dichloro chrysanthemic acid chloride are reported. These pyrethroids are active on tobacco budworm, fall armyworm, southern corn rootworm, and aster leafhopper, generally in the concentration range of 1000-250 ppm. Although less active than the pyrethroid standard bifenthrin, the overall structure-activity of these pyrazole pyrethroids with regard to substitution patterns is similar to that previously observed with bifenthrin analogs. 

TBW = Tobacco Budworm FAW = Fall Armyworm SCRW - Southern Corn Rootworm ALH = Aster Leafhopper... 

The compounds were evaluated for insecticidal and acaricidal activity against the following species cabbage looper (Trichoplusia ni [Hubner]), Mexican bean beetle (Epilachna varivestis Muls), southern armyworm (Spodootera eridania [Cram]), pea aphid (Acvrthosiphon pisum [Harris]), twospotted spider mite (Tetranvchus urticae [Koch]) and southern corn rootworm (Diabrotica undecimpunctata Howardi). 

Each cup of treated topsoil was capped with a plastic lid and stored for 7, 1A, and 28 days. On the terminal day of the storage period, the cups were infested with southern corn rootworm larvae (10 specimens for each of the two replicates for each compound), and a kernel of germinating corn was added to each cup as a food supply. The cups were recapped and returned to storage for three days. At the end of this time the dead and living rootworms were counted and the percent mortality was calculated. 

The southern corn rootworm is a member of the genus Diabrotica, family Chrysomelidae. This genus contains a large number of pest species that feed upon include corn, cucumber, squash and melon. Mint and mesquite grass have also been attacked by an occasional species (13). 

The sex pheromone structure, 10-methyl-2-tridecanone, was synthesized using the carboxyl group as the source of the methyl branch (lA) (Figure 6). Undecylenic acid was a-propylated and resolved via amides. The procedure followed allowed us to obtain the alcohols,(R)- and (S)-2-propyl-10-undecenol (>99.6% ee). The corresponding bromide was reduced with lithium triethylborohydride (15) then the double bond was converted to a methyl ketone by a) oxymercuration, b) reduction of the C-Hg bond with sodium borohy-dride, and c) oxidation with dichromate. The male southern corn rootworm responds only to the (R)-configuration no biological activity was noted for the (S)-enantiomer. Therefore, in this instance the racemic compound would be predicted to monitor this species adequately. 

Figure 6. Synthesis of the southern corn rootworm sex pheromone stereoisomers...

Secondary Screening Methods. Compounds 2 and 3 underwent additional evaluation against the 2-spotted spider mite (SSM, P-resistant strain, Tetranvchus urticae) and the western potato leafhopper adult (WPL, Empoasca abrupta). In these tests, the 2-spotted spider mites were either allowed to infest a Sieva lima bean test plant which was then dipped in the test solution, or they were directly sprayed with a test solution. Activity against the western potato leafhopper was determined using the cut-stem systemic test in which Sieva lima bean plants were allowed to take up an emulsion formulation of the test compound. Compounds 1 and 3 were further evaluated against the tobacco budworm (TBW, Heliothis virescens) and the southern corn rootworm (SCR, Diabrotica unde-cimpunctata howardi). Solutions of the test compounds were applied topically. 

Asymmetric syntheses directed toward construction of enantiomers of the western and southern corn root-worm pheromones are described. A brief review of the subject of asymmetric synthesis as it is related to the synthesis of insect sex pheromones is presented. The laboratory s previous research with chiral pheromones is summarized (Japanese beetle, white peach scale, and lesser tea tortrix) before detailing synthetic work on the pheromones of the aforementioned rootworm species. Throughout the course of the synthetic effort, cholesteric stationary phases for GLC have found use. Their superior ability to separate crucial diastereomeric intermediates for synthesis is detailed. 

Figure 10.6 Relationship between generations per year and development of resistance in species selected by soil application of aldrin/dieldrin. 1 and II, root maggots III, southern potato wireworm IV, northern corn rootworm V, European chafer VI, Japanese beetle VII, sugarcane wireworm. (From Georghiou, G.P. and Taylor, C.E., in Pesticide Resistance Strategies ami Tactics for Management, National Academy Press, Washington, D.C., 1986,157 With permission.)...

Southern corn leaf blight, com and, 78 Southern com rootworms, 75,285, 285 Southernwood. See Artemisia abrotanum... 

This is a review of synthetic efforts made at these laboratories in recent years. Stereoisomers of sex pheromones of various insect species were synthesized in order to facilitate identification and permit more thorough evaluation of their potential in insect control programs. Syntheses are described for pheromones of the stable fly, tsetse fly, southern and western corn rootworms, and the Mediterranean fruit fly attractant, trimed-lure. In each instance centers of asymmetry were generated that made use of diastereomer formation using readily available (R)- and (S)-a-methyl-benzylamine. Resolutions were achieved either by preparative HPLC, or fractional crystallization of amides. The latter technique was rendered synthetically useful for the preparation of configurationally pure acids by virtue of transformations wrought upon the amides that made them subject to cleavage under very mild conditions. 

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