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Studies were conducted in Phoenix, Ariz., to determine the occurrence of boll weevil, Anthonomus grandis grandis Boheman, infestations in late-season cotton bolls, and the pattern of boll weevil emergence and survival and mortality in the bolls. Boll weevils emerged from bolls buried in moist vermiculite over a period of 232 to 239 d, from 29 January to 2 August. Higher percentages of emergence and lowest mortality in bolls occurred in bolls collected in November as compared with bolls collected in December. Few boll weevils emerged from bolls held under dry conditions in an outdoor in sectary for 174 d. However, an average of 16% of the weevils were found alive in the dry bolls in late May.

After ethephon and thidiazuron were applied in late season to small plots of Upland cotton ( Gossypium hirsutum L.) to terminate fruiting chemically, the numbers of green bolls and pink bollworm, Pectinophora gossypiella (Saunders), diapausing larval populations, and yields were determined. Tests were conducted during 1985 and 1986 on the Maricopa Agricultural Center, Maricopa, Ariz., and on the Irrigated Desert Research Station, Brawley, Calif. Also, at Brawley in both years, we determined the combined effects of early irrigation cut-off and chemical termination. Results show that rates of 1.12 kg (AI)/ha of ethephon or higher and rates of 0.056 or 0.112 kg (AI)/ha of thidiazuron were needed for effective termination of cotton fruiting as indicated by reductions in number of green bolls. These rates of each chemical also reduced the number of squares and blooms after treatment, and sequential applications resulted in greater reductions than a single application. Last irrigation in mid-July resulted in reduced yields. However, irrigation cut-off in late July or early August resulted in yields as high as when the last irrigation was in September. Yields were not reduced by chemical termination treatments except by thidiazuron at Brawley in 1986, when last irrigation was in mid-July. Diapausing pink bollworm larval populations were reduced by chemical termination treatments and early irrigation termination.

Constant temperatures between 32–35°C or higher and fluctuating temperatures with a mean of 32°C or higher generally resulted in reproductive failure of pink bollworms, Pectinophora gossypiella (Saunders), if the exposure occurred in the larval and pupal, pupal, or adult stages. This failure usually occurred because the male exposed to high temperature did not mate and/or effectively transfer sperm to the spermatheca of the female. Short exposures to high temperature in the late larval-early pupal stage caused mortality but had little effect on reproduction. Sperm was often found in the transferred spermatophores, an indication that death of the sperm, reduced sperm motility, or some other mechanism prevented movement of sperm to the spermatheca. Both eupyrene and apyrene sperm were affected. Females exposed to these temperatures had reduced egg laying and egg viability.

In comparative tests, Allied Chemical Corp. compound GL-6506 (dimethyl p -(methylthio) phenyl phosphate) applied as a stern treatment to cotton in small-plot field tests gave more effective control of the bollworm, Heliothis zea (Boddie), and the tobacco budworm, H. virescens (F.), than monocrotophos or methomyl; however, no stem treatment was as effective as foliar applications of monocrotophos. The Heliothis nuclear polyhedrosis virus ( Heliothis NPV), applied as a foliar spray 3 times/week, was as effective as monocrotophos (applied as a foliar spray at 5-, to 7-day intervals) in increasing the yields of cotton, but when the Heliothis NPV was applied 1 or 2 times/week, yields were inferior to that achieved with monocrotophos.

Boll weevils, Anthonomus grandis Boheman, in Arizona continued to emerge until 23 May from infested bolls collected in December and placed above or on the soil surface under emergence cages during January or early February. Practically no emergence occurred when infested bolls were buried under 15 cm of soil under cages. Boll weevil captures in grandlure-baited traps were near zero during the summer (June–August), began to increase in the fall, reached maximum numbers in January and February, and began to decline in April of each year. The decline in numbers caught occurred at approximately the same time that the emergence from bolls was nearly complete. The relatively large catches of boll weevils during periods when no host was available suggests that emergence from bolls is occurring throughout this period and that large segments of the populations during the winter are not in a resting state, but are actively seeking host material or mates.

Survival of pink bollworm moths, Pectinophora gossypiella (Saunders), during the diapause period was reduced ca. 50% by irrigations during the winter and early spring. Fewer insects emerged from buried bolls than from bolls above or on the soil surface, and earlier burial of bolls resulted in greater mortality than later burial. The emergence patterns of the moths were affected by some of the treatments. Moths emerged earlier (as a percentage of total emergence) and at a faster rate from irrigated treatments than from nonirrigated treatments in 1981, but not in 1980. Moths from larvae in bolls emerged slower than moths from larvae that had cut out of bolls. The date on which 50% accumulated emergence had occurred was 11 May in 1980 and 25 April in 1981. However, the accumulated heat units (based on 12.8°C as the threshold for development) were 1,176 and 1,174 at the time of 50% emergence for 1980 and 1981, respectively. Thus, accumulated heat units may provide a more consistent indication of time of emergence than the calendar date.

Comparative toxicities of 23 insecticides to adult pink bollworm, Pectinophora gossypiella (Saunders), were determined by topical application. The smaller male was more susceptible than the female; however, the values were not significantly different. The moths were slightly more susceptible when the insecticides were applied to the thoracic dorsum than when they were applied to the abdominal venter. For doses applied to the dorsum, LD50, values at 48 h after treatment ranged from 0.0016 µg per male for cyfluthrin to 1.81 µg per male for malathion. These data may serve as reference values to determine if resistance to any of the insecticides develops in field populations of the pink bollworm; they may also aid in the selection of an insecticide for use in a spray program aimed at the adult moth or for use as an adulticide in a sex pheromone-insecticide (attracticide) system.

Pink bollworm, Pectinophora gossypiella (Saunders), moths treated with low doses of certain insecticides had a lower percentage of mating, laid fewer eggs, and, in some cases, had a reduced number of eggs hatch. The synthetic pyrethroids cyfluthrin, fenpropathrin, fenvalerate, flucythrinate, and permethrin all caused reductions in mating during the first 24-h period after treatment. The insecticides also reduced the number of eggs laid. Reductions in mating and oviposition caused by treatment with azinphosmethyl, methylparathion, trichlorfon, carbaryl, and chlordimeform were usually associated with or were the result of high mortality. Avermectin B1, an experimental compound from Merck, Sharpe and Dohme (MK-936), completely prevented mating and oviposition at the LD10 and LD50 with little mortality among the treated insects. Hatching of eggs was also reduced by these treatment levels of Avermectin B1. These tests show that, in addition to causing mortality, treatments of moths with certain insecticides may cause population suppression through reduced mating, fecundity, and hatching of eggs.

The numbers of diapausing larvae of Pectinophora gossypiella (Saunders) found in soil and trash in the fall after harvest in cotton were reduced by early irrigation cut-off and chemical termination treatments. Also, the number of moths that emerged the following spring was reduced by the combination of the 2 treatments. The early irrigation termination reduced pink bollworm infestations in bolls and Heliothis spp. oviposition in the fall, but there was no effect due to the chemical termination.

Adult pink bollworms, Pectinophora gossypiella (Saunders), that emerged from hibernation before small squares were on the cotton plant (21 days before blooming) usually failed to produce any progeny in field cage tests. Thus all emergence up to this time may be considered suicidal. Rate of reproduction by overwintered moths ranged from

In tests conducted in Riverside County, California, in 1970, overwintered pink bollworm moths, Pectinophora gossypiella (Saunders), migrated at least 35 miles to infest an isolated field of cotton. Then high temperatures during late June and early July drastically reduced the population. However, later migrants during August and September of 1970, and also in 1971, produced sufficient larvae to cause significant damage to the crop

Chemical control of Pectinophora gossypiella (Saunders) increased yield of cotton lint and seed and reduced amounts of bright greenish-yellow fluorescence associated with Aspergillus flavus Link and thus associated with aflatoxin. Levels of aflatoxin were maintained below 20 ppb when populations of pink bollworms were held at or below the economic threshold, but this was only achieved by numerous insecticide applications.

Fewer Bucculatrix thurberiella Busck were present and less leaf damage was done in plantings of nectariless cotton, Gossypium hirsutum L., than in plantings of nectaried cotton. Also, numbers of Lygus spp. were reduced, as well as total predator populations. Consistently fewer Chrysopa spp. and Geocoris spp. were present.

Native populations of Pectinophora gossypiella (Saunders) in 7.3×3.7×1.8-m field cages were suppressed by continuous releases of moths of a laboratory strain irradiated as adults with 10 krad. Cages receiving moths irradiated with 20 krad had populations not significantly different from those in control cages. The 1st generation of native moths increased 4–5 fold in all cages. In the 2nd generation, which developed in bolls, the control cages increased by a 36-fold rate vs. a 15-fold rate for cages receiving moths irradiated with either 10 or 20 krad. Results indicated that moths irradiated with 10 krad were more effective in suppressing native populations than moths irradiated with 20 krad.