Search

Studies conducted in Israel throughout 1978 resulted in the development of an improved pheromone trap for capturing large numbers of male Spodoptera littoralis moths in the field. The dry open trap is dusted on its interior walls with 4% diazinon to prevent the escape of moths attracted therein by a dispenser releasing the insect's synthetic sex pheromone, and it remains effective for 4 weeks without replenishing either the pheromone or the insecticide. Captures were 3 times greater with diazinon than with talc or silicates (Charsit and Wessalon).

Formulations of six samples of (Z,E)‐9,11‐tetradecadien‐l‐ol acetate (9,11‐TDDA), the sex pheromone of Spodoptera littoralis Boisd., synthesized at Beltsville and a sample synthesized in Japan by another method were compared for attractiveness in the fields of Israel. The Japanese sample was 20–50% more attractive than the others, despite the fact that it was contaminated with the (E,E)‐isomer, which was shown to delay optimum attraction in the Beltsville samples (but not in the Japanese sample) during the first 4–5 nights of exposure. Beltsville 9,11‐TDDA freed of the (E,E)‐isomer was still somewhat inferior to the Japanese pheromone in attractive power. A component present only in the Japanese sample and observable by capillary column gas chromatography was at first believed to be (Z,E)‐8,10‐tridecadien‐l‐ol acetate, but total synthesis of the compound showed this not to be the case; it was neither attractive per se nor synergistic with 9,11‐TDDA of Beltsville origin. (Z,E:)‐9,12‐Tetradecadien‐...

The continuous use of gossyplure‐baited traps in 1974–1975 for monitoring infestations of the pink bollworn moth in cotton fields succeeded in reducing the percentage of infested bolls to less than 5% in the Hagilboa and Beth‐She an regions of Israel. The average number of insecticidal treatments necessary to control the pest was likewise reduced from 5.8 in 1974 to 1.64 in 1975 in Beth‐She’ an and from 2.9 to 2.21 in Hagilboa. The monitoring threshold of 8 males captured per trap per night to determine the need for pesticide treatment, instituted in 1975, proved, as expected, to be a less accurate yardstick than the threshold of 5 males per trap per night previously recommended. Crude or distilled cottonseed oil was more efficient for use in the trap cups than the aqueous detergent solution used heretofore, and the traps themselves were considerably improved by providing a plastic rooflet above the cups.

In trapping tests conducted in Israel cotton fields, propylure failed to show attractancy to male pink bollworm moths when used alone or in combination with deet, hexalure, antioxidant, or dodecyl acetate. A formulation of hexalure (and antioxidant) containing acetone was at least four times as attractive as one containing four times as much hexalure (and antioxidant) without acetone. Dodecyl acetate inhibited the response to hexalure, whereas linalyl acetate enhanced the response considerably.

Cis-7-Hexadecen-l-ol, the parent alcohol of hexalure, was found to be a powerful inhibitor of the attractant's potency. For maximum effectiveness hexalure should contain no more than 0.1% of the alcohol. A gas chromatographic procedure is described for determining the amount of the inhibitor in hexalure samples.

When hexalure was mixed with 5% by weight of N' -octyl- N -phenyl- p phenyenediamine the period of attractancy for male Pectinophora gossypiella (Saunders) moths was increased from 28 to 49 days, At all ages the potency of the 5%, formulations was equal to or better than that of neat hexalure. Field tests showed that larger proportions of antioxidant were even more beneficial, the optimum concentrations being 16-20% by weight. In addition to prolonging the period of effectiveness the inexpensive diluent makes use of the costly hexalure more economical.

A comparison of the field attractiveness of five samples of American-synthesized and one sample of Japanese-synthesized (Z,E)-9,11-tetradecadien-1-01 acetate (9,11-TDDA), the sex pheromone of Spodoptera littoralis Boisd. and S. litura (F.), showed that traps baited with one of the American-produced samples and the Japanese product were equally effective in attracting and capturing S. littoralis males in cotton and alfalfa fields of Israel. Optimum captures were obtained for periods up to three months with 4800 mug of 9,11-TDDA plus 8 mg of an antioxidant; higher doses were not advantageous. Paper squares were superior to two types of rubber septa and to closed polyethylene vials as dispensers for the pheromone; the polyethylene vials were least effective. In terms of numbers of moths captured, open polyethylene vials were as effective as paper dispensers when both were baited with 9-11-TDDA plus antioxidant. Admixture of (Z,E)-9,12-tetradecadien-1-o1 acetate (9,12-TDDA) with 9,11-TDDA was antagonistic at ratios of 1:20 and 1:50, but ratios from 1:500 to 1:1600 were synergistic, increasing moth catches up to 2.5-fold. Pheromone traps placed in Caesarea sand dunes located at least 3 km from the nearest host area captured larger numbers of males than traps placed in cultivated areas. It is therefore recommended that safety belts of pheromone traps, about 500 m apart, be used around cultivated areas to prevent invasion of the pest from outside and to attract males present inside such areas, thus reducing both the male population and mating through mass trapping and disruption of sex communication.

Gossyplure used to bait field traps at a dose of 50 micrograms admixed with 4–16 milligrams of an antioxidant attracted and captured male pink bollworm moths early in the cotton-growing season (early May) in Israel, whereas 20 milligrams of hexalure plus antioxidant was completely inactive under identical conditions. Although gossyplure without antioxidant was inactivated through decomposition within ten days, the mixtures remained attractive for at least two months; the antioxidant also increased moth catches 2.5 fold. Monitoring data obtained with 3000 gossyplure-baited traps, at one trap per 50 dunams2, in cotton fields in the Beth-Shaan region proved that capture thresholds of 5 moths/trap/night to the end of July and 8 moths/trap/night afterward were completely satisfactory for maintaining a low 2.8% average boll infestation for which only 5.8 insecticidal treatments were required during the entire growing season; results were even better in other areas of the country.

Four compounds previously identified as forming the pheromone complex of the female Spodoptera littoralis were tested alone and in combination for attraction to males in cotton and alfalfa fields. Only cis-9, trans-11- tetradecadienol acetate captured males when used to bait field traps, and admixture with the other three compounds showed no advantage. Combination of 16 micrograms of the attractant with 8–12 milligrams of a commercial antioxidant prolonged its attractive period from 48 hours to one month under natural conditions, but even 4 micrograms of the attractant was effective for a short period. The use of 0.1 or 1.0 milligram of the antioxidant was synergistic to the attractant, but the increased longevity imparted by higher concentrations makes the latter more efficient in survey and control programs for this serious pest.