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Major differences in the feeding and olfactory behaviors of laboratory-reared and overwintered native boll weevils, Anthonomus grandis grandis Boheman, were observed. Both number of feeding punctures and damaged anthers in cotton squares (flower buds) were at least 1.5 times lower for overwintered weevils than for a laboratory-reared strain. However, overwintered females damaged a greater number of anthers with each feeding attempt (>2.5-fold). Similar to what was observed for cotton squares, decreases in the number of feeding punctures for overwintered weevils were also noted for artificial food formulations. Ingestion rates for overwintered weevils were from 1.2- to 2-fold lower for a water extract of cotton squares with and without added sucrose. However, ingestion was significantly higher (>5-fold) for overwintered weevils on a per-puncture basis; i.e., overwintered weevils appeared to ingest higher quantities of water-soluble plant material per feeding attempt. Olfactory behavior also differed significantly; overwintered weevils were 14.4–28.8% more responsive to the volatiles of cotton squares in choice olfactory studies.

The infield trap baited with grandlure is widely used to detect the movement of boll weevils, Anthonomous grandis Boheman, into cotton fields in the early spring. Computer analysis of trap spacing indicates that catch probability may be increased 10 to 20% by adjusting the traps away from the usual uniform spacing throughout a field to bring them closer to field borders where weevils are more likely to land first.

In Louisiana and in North Carolina, isolated 0.2 ha cotton plots were used to evaluate the competitiveness of male Anthonomus grandis grandis Boheman sterilized by one of 3 treatment methods: fumigation for 90 min with bisazir ( P ,, P -bis(1-aziridinyl)-N-methylphosphinothioic amide) at atmospheric pressure, followed 30 min later by a 5 sec dip in a 1.35% solution of penfluron (2,6-difluoro-N-(((4-(trifluoromethyl)phenyl)amino)carbonyl)benzamide) in acetone; 10,000 rad of gamma irradiation from a 137Cs source while the weevils were anesthetized in N2, followed by a 5 sec dip in a 0.1 % solution of diflubenzuron ( N -(((4-chlorophenyl)amino)carbonyl)-2, 6-difluorobenzamide) in acetone; and a total dose of 6750 rad administered in 25 fractions of 270 rad each in the pupal and early adult stages. Egg hatch in the plots into which the treated males and untreated males were released in a 120:40 ratio along with the 300 untreated virgin females was significantly lower than in plots into which only untreated weevils were released (

Grandlure-baited in⋅field traps used at the rate of 10/acre captured 76% of a population of overwintered Anthonomus grandis Boheman estimated to number ca. 25/acre that emerged between the time cotton was planted and the time the plants produced pinhead squares. A combination of in-field traps and insecticides captured or killed 100% of the emerging overwintered weevils during the 23 days between the pinhead square stage of plant growth (June 13) and July 6. The traps alone captured ca. 96% of a late emerging population of ca. 1 boll weevil/acre during July 6–31. The problem of clumping of F1 and F2 progeny proved to be an important factor in the efficiency of the traps.

To develop a more rapid and efficient mechanical method of detecting low level infestations of Anthonomus grandis Boheman, 4 mechanical collection systems were compared with visual observation of adult boll weevils in Cotton. The McCoy Insect Collector (a dual directional blower and vacuum system) was the most efficient system and had an efficiency of 130% compared with visual detection. Field tests indicate that ca. 10% of the oviposition damaged squares on the plants as well as adult weevils will be collected with the mechanical sampling device. The McCoy Insect Collector is capable of detecting the presence of 2 adult weevils in 10 acres of cotton either by collection of the weevils or by collection of infested squares.

In the spring of 1969, male-baited traps for Anthonomus grandis Boheman were placed around ca. 4000 acres of cotton in a large-scale field test in Monroe County, after completion of a voluntary grower-sponsored reproduction-diapause control program the fall of 1968. The few fields that had not been treated produced a population of weevils which varied from field to field. Where over wintered boll weevils numbered less than 5 per acre, the trap efficiency was estimated to be 93%, but it dropped to 21% when the populations averaged about 300 weevils/acre. Differences in the number of over wintered boll weevils collected per trap were not significant when 1, 2, 4, and 8 traps per acre were compared. However, significantly more over wintered boll weevils were found in the fields with 8 traps per acre than in fields with 2 traps per acre. Inter field movement of over wintered weevils from the fields that had not been treated appeared to be restricted to those fields that shared over wintering sites with the untreated fields. Some fields were treated with insecticides in July for control of 1st-generation boll weevils, but many fields did not require treatment until early August.

When maximum fat and minimum moisture content were used as criteria, adult Anthonomus grandis Boheman fed 11- to 15-day-old bolls and held at 26.7¼C attained firm diapause in 1 week; when the temperature was 21.1¼C during a 10-hr light period and 10¼C during a 14-hr dark period, the weevils took 3-4 weeks to attain maximum fat and minimum moisture. Thus, time required for these adult weevils to attain firm diapause was inversely related to temperature. However, the weevils held at 26.7¼C and fed 11- to 15-day-old bolls attained firm diapause more rapidly than those fed 1 to 10-day-old bolls or squares, and the diet did not influence the time to firm diapause when the weevils were held at the lower temperatures.

Six applications of a spray of methyl parathion (0.5 lb per acre) were made at 4- to 5-day intervals to isolated cotton fields in Carroll County, Mississippi, to control reproducing and diapausing boll weevils, Anthonomus grandis Boheman, during the fall. The most effective follow up procedure included chemical defoliation of cotton plants to limit the available weevil food, and a final application in October of Bidrin® (3-hydroxy- N, N -dimethyl- cis -crotonamide dimethyl phosphate) at 1 lb per acre. Examination of seedling cotton from the treated fields the following spring indicated that in 1 field only 2.7 weevils per acre had survived the control program and the winter weather. The boll weevil population in the treated fields did not rise to damaging proportions until mid-August (the 2nd generation).

A strain of boll weevils, Anthonomus grandis Boheman, with a high ability (more than 35%) to diapause (M) was crossed in the laboratory with a strain (S) with a low ability (less than 5%) to diapause. Analysis of data from the 2 strains and progeny from the reciprocal parental crosses showed 3 statistically different sets of percentage of diapause: the M strain had a high percentage; the S strain had a low percentage; and the reciprocal F, progeny had percentages approaching that of the S strain. When the pure strain, F2 and backcross progeny were exposed to diapause-inducing stimuli, the means of the percentage of weevils attaining-diapause fell into 4 statistical sets: the M strain, the backcrosses to the M strain and the F2 from (5 × M) × (5 × M), the F2 from (M × S) × (M × 5) which was not significantly different from the least responsive M backcross and the most responsive S backcross, and the backcrosses to the S strain. The percentages of diapause attained by the backcrosses to the S strain were not significantly different from those of the S strain. These results indicated partial dominance and possible simple inheritance of alleles that suppress diapause in the 5 strain. The use of insects genetically incapable of attaining diapause for a sterile-insect-release program would minimize concern that some released insects might not be sterilized because nondiapausing insects could not survive the winter and their matings to wild weevils would greatly reduce the ability of progeny to attain diapause.

Replicated tests were conducted in 1966 in semi-isolated fields in Carroll County, Mississippi, to control Anthonomus grandis Boheman by mechanically destroying fallen infested cotton squares with a flail-type machine. Control in the flail-treated fields was compared with fields treated with ultra low volume (ULV) applications of azinphosmethyl at 0.125 lb/acre applied at 5-day intervals. Flail treatments were made until the machine damaged mature fruit on the plants. Thereafter, the flail fields were sprayed with ULV applications of azinphosmethyl at 0.125 lb/acre. Results indicated that the boll weevil can be controlled with a flail-type machine by destroying fallen infested squares as long as the machine can be operated in the field. However, when the plants become heavily fruited the machine damages the mature fruit. During the season the flail machine picked up an average of 95.3% of the squares that were on the ground.

In 1960-61, tests were conducted in 3 cottonfields located on Mississippi to study the relationship between plant fruiting and the first entry of boll weevils, Anthonomus grandis Boheman, into diapause. Tests were set up also to evaluate the effectiveness of methyl parathion in controlling diapausing weevils and to measure population increases on dryland cotton. In the diapause studies, first diapausing weevils appeared in all 3 fields at cessation of flowering, when only bolls remained as the food source. In the diapause-control studies, 7 applications of methyl parathion spray applied at ½ lb/acre greatly reduced the overwintering population but did not eliminate it. In the limited studies of population dynamics, seasonal generation-to-generation increases averaged 5-fold and ranged from 1- to 9.6-fold.

In a 2-year replicated field-cage experiment with boll weevils, Anthonomus grandis Boheman, first-generation progeny from estimated overwintered populations of 0, 14, 25, 50, and 100 weevils per acre damaged 0, 28, 46, 66, and 83% of the squares, respectively. Second-generation weevils damaged from 84 to 96% (weevil-free check excluded) of the squares. Seed cotton harvested from the respective treatments averaged 2802, 1875, 1678, 1318, and 847 lb per acre. Differences in lint quality were detected between plots infested with 100 overwintered weevils per acre and those infested at the other 4 levels. These differences were observed in the first and third harvesting in 1961. No other quality differences were observed.

Azinphosmethyl applied as an ultra-low-volume spray at 0.2 and 0.25 lb per acre was as effective as a water-emulsion spray of methyl parathion (0.5 lb per acre) in a reproduction-diapause control experiment conducted in Carroll County, Mississippi, against the boll weevil, Anthonomus grandis Boheman. A lower rate of azinphosmethyl, 0.125 lb per acre, was less effective. Populations. of boll weevils sampled in woods trash adjoining treated and untreated fields were reduced 94% the fall of 1965 and 98% the spring of 1966.

Respiration and transpiration rates in A. grandis Boheman were measured with an open-system technique. Windspeed and humidity had no effect on respiration rate. There was an increase in metabolic activity, as indicated by the respiration rate, with age at temperatures above 35°C. The thermal death point in the boll weevil was fixed at 54±2°C. There was a slight (2.5°C) increase increase with age in the thermal death point from 2 to 12 days. Indirect evidence of a spiracular response to high potential transpiration rates was obtained. There appears to be no systematic change in transpiration rate with age in the boll weevil.

Calco Oil Red N-1700 dye was used to evaluate bait formulations both in the laboratory and in the field as well as to mass mark field populations of the boll weevil, Anthonomus grandis Boheman, attracted to a cottonseed-oil bait. The red dye permitted the evaluation of bait formulations without confounding the efficacy of the bait with control agents. It was not necessary to handle the insect; the marked insect was easily recognized when captured; the dye persisted throughout the life of the individual, and the dye caused no deleterious biological effects.

Regions of the visible and infrared spectrum that might be effective in suppressing diapause in Anthonomus grandis Boheman were investigated by daily exposure of immature weevils (from the 1-day-old egg through to eclosion) on artificial medium to 1 of 3 photoperiods: 11 hr of fluorescent light-time, 2 hr of irradiation with either narrow wavebands of monochromatic light or a broad band of infrared radiation, and 11 hr of dark-time (L 11 + 2: D 11); 11 hr of fluorescent light-time and 13 hr of dark-time (L 11: D 13) (this regimen induces diapause); 13 hr of fluorescent light-time and 11 hr of dark-time (L 13: D 11) (this regimen suppresses diapause). Violet light, red to far-red light, and near- to intermediate-infrared radiation were less effective than blue, green, yellow, and orange light in suppressing diapause. However, no significant differences were found in the suppressive effect of 3 energy levels (0.5, 0.1, 0.05 µw cm-2nm-1 of violet, blue, green, yellow, and orange light.

During 1958 studies of the preferred feeding and egg-laying sites of the boll weevil ( Anthonomus grandis Boheman) were conducted at Stoneville, Miss. Females damaged the fruit of the cotton plant more than males. The preferred feeding and egg-laying sites were the squares on the upper half of the plants when the population was low. As the population increased, small bolls were damaged as well as squares; the damage was intensified on the upper portions of the plants and reached into the lower fruiting branches. Bolls from 1 to 19 days old were subject to weevil damage. Exposure of the cotton plant to feeding and egg laying by the boll weevil for 4 or 5 days resulted initially in increased square abscission and slightly reduced boll abscission. No difference occurred in total boll set for the entire season between the test and check plants.

In laboratory studies conducted at Stoneville and State College, Mississippi, 5 environmental stimuli induced diapause in the boll weevil, Anthonomus grandis Boheman: (1) exposure to an 11-hour photoperiod in the larval and pupal stages; (2) exposure to night temperatures of 10 in the adult stage; (3) boll feeding in the adult stage; (4) limitation of the quantity of squares fed in the adult stage; and (5) boll feeding in the larval stage. Wild strains of weevil in Mississippi responded to these stimuli, but the State College laboratory strain did not.

In experiments at Stoneville, Mississippi, in 1957 and 1958 a Guthion-DDT mixture gave outstanding control of the boll weevil ( Anthonomus grandis Bah.). Sevin® (1-naphthyl methylearbamate), toxaphene-malathion, dieapthon, Bayer 29493 ( O,O -dimethyl O -(4-methylthio- m -tolyl) phosphorothioate), and mixtures of Monsanto CP 7769 (hexaethyl (ethylthioate ethylidyne) triphosphonate), methyl parathion, toxaphene, or malathion with DDT gave generally satisfactory control, but Thiodan® (6,7,8,9,10, 10-hexachloro-1, 5, 5a, 6, 9,9a-hexahydro-6, 9- methano-2,4,3-henzodioxa thiepin-3-oxide), runnel- DDT, toxaphene, and endrin were not effective. The mixture of DDT with runnel, Monsanto CP 7769, Guthion® ( O, O -dimethyl S -(4-oxo- 1,2,3-benzotriazin-3-(4 H )-ylmethyl) phosphorodithioate), methyl parathion, and malathion were effective in controlling the bollworm (Heliothis zea (Boddie)).

Results of tests initiated in 1967 to determine the effect of size of spray droplets on boll weevil control showed that adequate control could be obtained with 0.125 Ib per acre of azinphosmethyl applied in ultra-low-volume (ULV) sprays with droplet sizes of 140, 200, or 300 µ at 4- to 5-day intervals. The treatments were as effective as a wide spectrum of droplet sizes applied with a spinning-disc sprayer. Azinphosmethyl applied at 0.0625 lb per acre on a 4- to 5-day schedule in a ULV spray in droplet sizes of 100 and 140 µ was as effective as when it was applied in a wide spectrum of droplet sizes at 0.125 or 0.0625 lb/acre. Sprays with droplet sizes of 200µ gave marginal control when used to apply azinphosmethyl in a ULV spray at 0.0625 lb/acre on a 4- to 5-4day schedule and control with 300 µ droplets under the same conditions was inadequate.

A 3-year field study showed that ultra-low-volume formulations of azinphosmethyl (0.125 lb/acre) or malathion (0.5 lb/acre), when they were applied on a 4- or 5-day schedule, gave in-season control of Anthonomus grandis Boheman.

Tests in field plots showed that size of spray droplets, dose, and volume of ULV azinphosmethyl applied per acre were all highly significant in determining mortality of Anthonomus grandis Boheman when exposed to the residues. As volume applied per acre was increased, kill decreased. Kill by direct impingement of the droplets was less than 32%. The overall ratio between kill by residue and by direct impingement was over 4.0. With spray droplets in the size range of 100–200 μm, kill by direct impingement is less important than kill by residue.

In-field evaluations of proposed modifications to in-field traps Anthonomus grandis Boheman, clear plastic cylinders (5 by 5 cm) were found to be equal to clear plastic boxes (5 by 5 by 5 cm) as capture containers, clear lids on the capture containers were found to be superior to opaque lids, molded screen cones were found to be equal to stapled cones, and traps with holes in the top of the base were found to be superior to traps without holes. A modified trap with all four evaluated trap components captured 42% more boll weevils than a standard infield trap.

Within the limits of the droplet sizes tested, smaller droplets provided better plant coverage and, thus, insect control, but also increased drift. Therefore, a compromise was necessary in determining an acceptable droplet size that would provide good coverage without increasing drift. For ULV applications of azinphosmethyl with ground equipment, a droplet size between 140 and 200 μ provided an adequate solution for control of Anthonomus grandis Boheman and drift problems.

When 4-, and 16-row trap plots were planted to cotton 2 weeks earlier than normal, both types of plots were equally effective in attracting overwintered Anthonomus grandis Boheman. When the plots were treated with aldicarb, a large proportion of the boll weevils that emerged before the squaring of the normal crop was attracted to the special plots and killed. When the plots were baited with grandlure, they attracted more of the boll weevil populations than plots that were not baited. Also, when trap plots were treated for control of Heliothis spp. 3 weeks after the sidedress application of aldicarb, the remainder of the fields did not require treatment against this pest until after insecticide was applied to control boll weevils. Plots sprayed with methyl parathion resulted in fewer Heliothis larvae than did aldicarb treatments.

In the laboratory, Thompson-Hayward TH-6040 ( N -4-chlorophenyl)-N′-(2,6-difluorobenzoyl) urea) formulated in cottonseed oil and applied to cotton plants was effective in preventing hatch of eggs laid by female Anthonomus grandis Boheman for 4–7 days after the females were exposed. In the field, TH-6040 (0.25 AI/acre) in cottonseed oil applied every 4 or 5 clays from initiation of squaring in mid-June until late Aug. either caused all eggs to fail to hatch or caused emerging larvae to die in the 1st instar. As a result, no 1st field-generation boll weevils could be detected by in-field trapping until Aug. 20. Even then, the population was very low and could be attributed partially to rainfall that washed off 2 successive treatments of TH-6040 in late July.

Regions of the near-ultraviolet and visible spectrum effective for inducing diapause suppression in the boll weevil, Anthonomus grandis Boheman, were investigated. One group of weevils was exposed to 11 hours of fluorescent light-time and 13 hours of dark-time that initiated diapause (L11:D13); the 2nd group was exposed to 13 hours of fluorescent light-time and 11 hours of dark-time that inhibited diapause (L13:D11). A 3rd group was exposed to 11 hours of fluorescent light-time followed by 2 hours of illumination with narrow wavebands of light of different spectral compositions and 11 hours of dark-time (L11+2:D11). The spectral region most effective for suppressing diapause was found to be between 400-665 nm. The 359-390 nm and 670-1000 nm spectral regions were less effective.

A rotary disc device was developed for ground applications of ultra-low-volume (ULV) undiluted pesticides. The applicator consists of 2 rotating discs powered by a small electric motor and a metering nozzle. One applicator is used on each row. Experimental application of ULV azinphosmethyl (2 lb per gallon), applied to cotton with this device at 0.25 lb per acre gave boll weevil, Anthonomus grandis Boheman, control equivalent to standard methyl parathion applied as a water-emulsion spray at 0.5 lb per acre. Particle deposition within the plant and across the swath was compared with a mist blower ULV applicator. Both gave equivalent particle deposition within the plant, but the rotary disc device gave more uniform coverage across the swath.

The ratio of proteins and carbohydrates in the adult diet of Anthonomus grandis Boheman was varied to study its effect on the initiation of diapause. Removal of germinated cottonseed puree from the standard diet greatly increased the incidence of diapause, but this effect was offset partially by increasing the level of protein and decreasing the level of sucrose. Similarly, a reduction of protein and an increase in sucrose caused greater numbers of insects to enter diapause. We were not able to extract the component (s) of germinated cottonseed that prevent initiation of diapause with chloroform, acetone, water, and dilute NaOH, in succession. A cottonseed flour or the alkali-soluble protein of that flour was equal to or better than germinated cottonseed in preventing the initiation of diapause.

In field experiments conducted in DeSoto County, Mississippi, in 1961-62, selected procedures were evaluated for effectiveness in preventing the boll weevil, Anthonomus grandis Boheman, from entering diapause. Methyl parathion spray (0.5 lb/acre) was applied at 7- to 9-day intervals in the fall of 1961, when the first boll weevils were found in diapause. A desiccant, pentachlorophenol, was used to terminate plant growth in mid-October. Control measures reduced both fall and spring weevil populations, but these reductions were not large enough to substantially reduce the number of insecticide applications needed for boll weevil control in the next crop season. Population pressure in September decreased effectiveness of methyl parathion in October, and an abundance of food (squares, flowers, and bolls) for surviving boll weevils in treated fields contributed to the less-than-desired effectiveness of the control program.

Initial entry into diapause by segments of populations of the boll weevil ( Anthonomus grandis Boheman) were studied in one field in 1958 and in seven fields in 1959. In the 1958 field diapause occurred by August 26. In the 1959 fields it was observed as early as August 11 and as late as September 8. Weevil populations generally entered diapause in two distinct periods. Gross observations indicated that entry into diapause in the first period was related to the maturity of the plants in the different fields, An adequate food supply appeared to be necessary. Diapausing weevils were first recovered from ground trash on September 10 in 1958 and September 9 in 1959, which indicated movement by diapausing segments of the weevil populations to overwintering quarters well in advance of the first killing frost.

The effect of four different levels of infestation by the boll Weevil ( Anthonomus grandis Boheman) on earliness, yield, and quality of cotton lint was evaluated in a replicated field-cage experiment at Stoneville, Mississippi, in 1959-60. Seasonal square (Hower-bud) infestation levels of about 0%, 25%, 50%, and 75% were used. As infestation level increased, plant fruiting was delayed, with a subsequent delay in time of harvest. Plots held at 0% infestation yielded the earliest cotton; those at the highest infestation level produced the latest harvestable cotton. Yield data indicated an inverse relationship between total yield and percentage of squares damaged throughout the season. Grade indexes and lint values indicated no significant loss in quality of lint at the different infestation levels. Differences in value of lint per acre for the four treatments actually reflected differences in yield.

The male boll weevil, Anthonomus grandis Boheman, after feeding on cotton plants, emits an airborne pheromone which attracts both sexes of emerged overwintered adults prior to squaring of cotton plants. Cross et al. (1969) reported that male-baited sticky wing traps attracted female boll weevils. Hardee et al. (1969), in concurrent tests, observed that both male and female boll weevils responded to male-baited traps in the spring and in the fall. However, relatively few boll weevils responded to traps around cotton fields during the fruiting period from late June until late August. Mitchell and Hardee (1974) found that pheromone-baited traps placed in cotton fields during mid-season captured females primarily. Thus, the pheromone appears to serve as an aggregating attractant for both sexes of overwintered boll weevils and as a mating attractant for females seeking mates in cotton fields.

A polyester-wrapped cigarette filter was found to be at least as effective in field tests at several locations in dispensing grandlure as the ordinary paper-wrapped filter placed inside a 1-dr glass vial. The new dispenser saved considerable time in rebaiting traps in the Boll Weevil Eradication Trial in North Carolina during 1978 and 1979.

In small field plots, azinphosmethyl, malathion, and methyl parathion were equally effective in controlling populations of Anthonomus grandis Boheman. In a caged bioassay test, maximum boll weevil suppression was obtained with azinphosmethyl, and residual control was 84% after 4 days.