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Laboratory studies were done to measure physiological effects of diflubenzuron when formulated in cottonseed oil and applied at very low rates to boll weevils, Anthonomus grandis grandis Boheman. Tests were designed to measure cuticle softness, mating propensity, and effect on flight. We found significant differences within treatments in all three studies as the dose increased. Cottonseed oil formulations containing 25% diflubenzuron reduced cuticle hardness by 46.2–61.0%. Cottonseed oil formulations containing 12.5–25% diflubenzuron reduced mating by 22.2–35.4% and flight by 11.6–21.2%.

Boll weevils, Anthonomus grandis grandis Boheman, dipped into solutions containing 0.25-2.0% of CIBA-GEIGY’s CGA-184699 killed >40% after 1 wk. Feeding 0.25-1.5% of this material in the adult diet for 3 d produced mortality similar to that found in tests. Female boll weevils treated with this insect growth regulator by dipping or feeding and mated with untreated males resulted in 95-99% less egg laying compared with the control. Male boll weevils administered CGA-184699 by dipping or feeding and mated with untreated females produced 58.8-73.0% fewer eggs compared with the control. Egg hatch and adult emergence of the few eggs collected was reduced to virtually zero in dipping and feeding tests.

In 1992 and 1993, newly emerged adult boll weevils, Anthonomus grandis grandis Boheman, were released on diflubenzuron (DFB)-treated and untreated cotton plants grown in 20 screened field cages. Seven days later weevils were recovered, and the effects of DFB on adult survival, mating success of males, egg hatch, flight activity, and cuticle hardness were measured. DFB substantially reduced hatch, flight activity, and cuticle hardness in both years; survival apparently was reduced in 1992, but not in 1993. Mating success of treated males was unaffected in either year. The combined effect of reduced egg hatch, flight activity, cuticle hardness, and possibly survival demonstrates several ways in which DFB may reduce populations of boll weevils in the field.

Adult boll weevils, Anthonomus grandis grandis Boheman, were fed 100 ppm of diflubenzuron in their diet for 6 days, then exposed to 10 krads of acute irradiation. During that time, treated as well as control weevils were fed 2.5 or 10% sugar in the diet. After treatment, all weevils were fed cotton squares or diet plugs for 5 days. Both 2.5% sucrose-treated and control boll weevils fed cotton squares had higher locomotor activity for 3–4 of the 5 days tested. Treated and control weevils fed 10% sucrose during the treatment period followed by squares rather than diet plugs had significantly higher locomotor activity for 2 of the 5 days tested. Treated or control weevils fed 2.5% sucrose during treatment followed by squares after treatment had much higher responses than when they received diet plugs after treatment. Concentration of sugar in the diet during treatment did not affect locomotor activity for 4 of the 5 days tested where posttreatment diets were the same. Peaks of activity occurred at 2- to 4-h intervals each day.

In the laboratory, four substituted benzamides (LY 121342 benzamide, 2-chloro- N -[[[6-[2,4-dichlorophenyl]methoxy]-3-pyridinyl]amino]carbonyl]-6-fluoro-; LY 135926 benzamide, N -[[[6-[2,4-dichlorophenylmethoxy]-3-pyridinyl]amino]carbonyl]-; triflumuron; and CGA 112913, N -[4-(3-chloro-5-trifluoromethyl-2-pyridinyl-oxy)-3,5-dichlorophenyl-aminocarbonyl]-2,6-difluoro-benzamide) were administered to adult boll weevils, Anthonomus grandis grandis Boheman, by dipping at concentrations ranging from 0.032 to 2.5% and feeding (3 d) at concentrations ranging from 0.25 to 2.0%. In dipping tests, descending order of effectiveness of these compounds in causing progeny reduction was as follows: LY 135926, triflumuron, LY 121342, and CGA 112913. In feeding tests, descending order of effectiveness was as follows: CGA 112913, LY 121342, triflumuron, and LY 135926. Mortality was higher in dip and feeding tests with LY 121342 and LY 135926. Although all treatments reduced flight compared with the control, boll weevils that were fed these chemicals (except LY 121342) usually flew more than those that were dipped. A few days after treatment, flight of treated and controls was reduced compared with earlier flights.

Boll weevils, Anthonomus grandis grandis Boheman, 9 days after egg implantation in the larval diet were transported from the Boll Weevil Research Laboratory, Mississippi State, MS, to the Comparative Animal Research Laboratory, Oak Ridge, TN, and irradiated with 6.9 krad (test 1) or 7.2 krad (test 2) of /sup 60/Co gamma rays delivered in 25 equal doses over 100 h. In test 1, from 600 individual pairs of T (treated) males x N (normal) females, only 114 eggs hatched from a sample of 950 eggs, and 47 adults emerged from a sample of 1042 eggs. Also, from 600 pairs of T females x N males, 6 eggs hatched of a sample of 6 eggs and 12 adults emerged from a sample of 20 eggs. In test 2, from 700 individual pairs of T males x N females, 54 eggs hatched from a sample of 1510, and 10 adults emerged from a sample of 1703 eggs. Also, in T females x N males matings, 1 egg hatched of a sample of 3, and no adults emerged from a sample of 4. Transportation and handling in the 2nd test reduced adult emergence an avg of 49%. Thus the 2 replicates in testmore » 2 resulted in 3.4 x 10/sup 5/ and 4.3 x 10/sup 5/ irradiated weevils emerging/day for 7 days. Bacterial contamination of weevils was low.« less

Adult Anthonomus grandis grandis Boheman were sterilized when fed an adult diet containing 100 ppm of diflubenzuron for 5 days followed by 10 krads of acute irradiation on day 6. The diet also contained either 10% sucrose, 10% maltose, or 2.5% sucrose diet (wt/wt) as a standard comparison. Mortality of treated (T) males and females fed 10% sucrose was significantly lower than T weevils fed the standard 2.5% sucrose diet for the first 4 days after treatment. Treated males fed 10% maltose also had significantly less mortality for 4 days compared with males fed the standard sucrose diet. For the first 4 days after treatment, sperm transfer of T males fed the 10% maltose diet was significantly higher than those fed the 2.5% sucrose diet. Sperm transfer of T males fed 10% sucrose was significantly higher for 2 days after treatment compared with T males fed the 2.5% sucrose diet. Treated males fed 10% maltose flew significantly more at day 1 after treatment than T males fed the other two sugar diets. Increased sugar in the diet had no overall effect in increasing male attractiveness to virgin females.

Irradiation (10 krads in a nitrogen atmosphere) plus dipping in 0.1% diflubenzuron in acetone of 6-day-old Anthonomus grandis grandis Boheman was selected over fumigation plus dipping of adults and fractionated irradiation of pupae as the method of choice for sterilization for production of quality weevils. The results for this method were: sterility 98.5% mortality 34.5% at 7 days posttreatment; mating with sperm transfer, 78.5% and 59.6%, of normal at 3 and 7 days posttreatment, respectively; and pheromone production of 0.4 µg/adult/day. Fumigation plus pentluron produced comparable sterile males, but irradiation was more convenient and safer.

Boll weevils, Anthonomus grandis grandis Boheman, were sterilized by dipping in an aqueous suspension containing 0.4% (AI) diflubenzuron and antibiotics (0.03% kanamycin, 0.015% penicillin, and 0.015% chloramphenicol) for 10 min followed by 10 krad of irradiation. Overall, mortality was ≤16.6% after 5 d; by 7 d, male mortality was ≤59.5%. Treated males were 77–79% as attractive as untreated males to untreated females. Flight activity of treated weevils was 45–56% of that observed in the control. In competitive mating studies, numbers of females mated by untreated males were significantly greater than treated males at a ratio of 1:1. When treated males outnumbered untreated males by more than 5:1, the number of matings to untreated females was significantly higher. A 20:1 ratio of treated males to untreated males was required to significantly reduce F1 adult emergence. Sterility, mortality, and vigor were increased with this new method compared with the previous method that involved feeding diflubenzuron (100 ppm) for 5 d followed by 10 krad of irradiation.

The standard method of sterilizing Anthonomus grandis Boheman (6-day feeding of 0.1% busulfan, 1-4-butanediol dimethanesulfonate) adequately sterilizes males but does not induce a high degree of sterility in females, and mortality is less than 40% after 2 weeks. Feeding higher concentrations of busulfan alone or lower concentrations of busulfan in combinations with methotrexate, hempa, or apholate for 6 days or less, or feeding 0.1-0.2% busulfan followed by low doses of gamma radiation induces virtually complete sterility in both sexes but causes fairly high mortality. A 4-day feeding of 0.2% busulfan + 0.25% methotrexate resulted in complete sterility in females and almost complete sterility in males, and mortality was less than 40% by 3 weeks after treatment.

A device, consisting of two 5-cm cube boxes with screen tops and cone-shaped screens opening into the inside, was used to measure the attractiveness of the male Anthonomus grandis Boheman contained inside the 5-cm cube boxes in a screen-covered bottle cap above the screen cone opening. The small boxes were placed inside an enclosed cube boxes in a screen-covered bottle cap above the screen cone opening. The small boxes were placed inside an enclosed plastic box (26 by 35 by 8 cm) provided with a top to contain the loose females. Tests were run for 24 h. Sterile males used in some of the tests had been fed for 5 days on an artificial diet containing diflubenzuron at 100 ppm, followed by a 10-krad acute dose in a 137Cs irradiator. When sterile males were tested against normal males for female responsiveness, the normal males were 1.6 times more attractive for the first 5 days after treatment.

When pupae of Anthonomus grandis grandis Boheman were fumigated for 5 h in a circulating, saturated atmosphere of bisazir, 99% of the males were sterilized, and egg laying by treated females outcrossed with normal weevils was reduced by 90.6%. Sterile males transfered 11.8% more sperm than control males the 1st week post treatment but 42.6% less the 2nd week.

Overwintered Anthonomus grandis Boheman can be sterilized and egg laying can be greatly reduced in the laboratory by feeding them a diet containing busulfan (1,4-butanediol dimethanesulfonate). A feeding table designed to attract weevils as they emerged from hibernation quarters attracted a small percentage of the total overwintered weevils that were in the field on July 1.

Cotton squares containing an egg deposited by Anthonomus grandis Boheman were significantly denser than cotton squares that did not contain an egg. This increased density may cause mortality of the egg stage.

After virgin matings with sterile males (previously mated 0 to 3 times) the responsiveness of females of Anthonomus grandis Boheman to grandlure was twice that of females mated with normal males. The higher responsiveness of females mated with sterile males indicate 0 to 66 percent fewer sperm were transferred to the spermathecae and these females continued seeking other mates. After 3 matings, sperm transferred by /sup 60/Co irradiated males was reduced by 67 percent or more.