Cotton harvest at 40% versus 75% boll-splitting on yield and economic return under standard and proactive boll weevil (Coleoptera: Curculionidae) spray regimes

The standard practice of two or three preemptive insecticide applications at the start of pinhead (1-2-mm-diameter) squaring followed by threshold-triggered (when 10% of randomly selected squares have oviposition punctures) insecticide applications for boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), control does not provide reliable protection of cotton, Gossypium hirsutum L., lint production. This study, conducted during 2004 and 2005, showed that three to six fewer spray applications in a "proactive" approach, in which spraying began at the start of large (5.5-8-mm-diameter) square formation and continued at approximately 7-d intervals while large squares were abundant, resulted in fewer infested squares and 1.4- to 1.7-fold more lint than the standard treatment. Fewer sprays and increased yield made proactive spraying significantly more profitable than the standard approach, which resulted in relatively low or negative economic returns. Harvest at 75% boll-split in the proactive spray regime of 2005 resulted in four-fold greater economic return than cotton harvested at 40% boll-split because of improved protection of large squares and the elimination of late-season sprays inherent to standard spray regime despite the cost of an extra irrigation in the 75% boll-split treatments. The earlier, 40% harvest trigger does not avoid high late-season boll weevil pressure, which exerts less impact on bolls, the predominant form of fruiting body at that time, than on squares. Proactive spraying and harvest timing are based on an important relationship between nutrition, boll weevil reproduction, and economic inputs; therefore, the tactic of combining proaction with harvest at 75% boll-split is applicable where boll weevils are problematic regardless of climate or region, or whether an eradication program is ongoing.     

Relationships of different cotton square sizes to boll weevil (Coleoptera: Curculionidae) feeding and oviposition in field conditions

Feeding and oviposition preferences of the boll weevil, Anthonomus grandis grandis Boheman, for four different cotton square size classes in field conditions of the Lower Rio Grande Valley of Texas were studied during 2002 and 2003. Percentages of large (5.5-8-mm-diameter) squares used for oviposition and feeding were greater than pinhead or match-head squares. The preference for large squares as food and associated accelerated fecundity explain the substantial boll weevil population buildups that occur after large squares form. Medium-sized (3-5.5-mm-diameter) squares also were used but less than large squares. Feeding and oviposition on pinhead (1-2-mm-diameter) and match-head (2-3-mm-diameter) squares were negligible. Although planting date did not affect oviposition or feeding preferences for squares larger than pinhead and match-head sizes, the least amount of either damage to large squares was found in the earliest plantings during both years. This study indicates that pinhead and match-head squares, regardless of planting date, do not require pesticide applications to protect against boll weevil feeding and oviposition.     

Effects of planting dates on boll weevils (Coleoptera: Curculionidae) and cotton fruit in the subtropics

The effects of planting dates 2-3-wk apart on boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), field-level populations, and feeding and oviposition damage to cotton, Gossypium hirsutum L., squares and bolls, were studied during 2002 and 2003 in the Lower Rio Grande Valley of Texas. Squares were 44-56% more abundant in some later planted treatments than in the earlier planted treatments, but mean cumulative numbers of oviposition- and feeding-damaged squares were 2.7 - 4.8-fold greater in some later planted treatments than in earlier treatments. Increased square production in later planted cotton was offset by boll weevil infestations that occurred when squares are most vulnerable and contribute most toward the pest's reproduction. Early planting avoided boll weevil population buildups in the field when large squares were abundant. Lint yields in 2002 did not differ significantly between the planting date treatments, but in 2003, mean yield in the middle treatment was 23% greater than in the early and late-planted treatments. Insecticide sprays in the earliest planted treatment of each year, based on the 10% damaged squares threshold, were >33% and >43% fewer than in the corresponding middle and latest planting treatments, respectively. Delayed planting, relative to the onset of favorable cotton-growing weather, at the field level, even when not applied uniformly on an areawide scale, is more cost-effective than planting too early or too late.     

Effects of kaolin-based particle film application on boll weevil (Coleoptera: Curculionidae) injury to cotton

This study examined a non-insecticidal tactic for suppressing boll weevil, Anthonomus grandis grandis Boheman, damage to cotton, Gossypium hirsutum L. In cage assays, kaolin, a reflective white mineral, applied to excised cotton squares or to the cotton foliage, initially resulted in lower levels of boll weevil injury to squares than nontreated squares. Boll weevil oviposition and feeding on kaolin-treated squares and squares on kaolin-treated cotton plants increased when nontreated squares and cotton plants were in short supply. A laboratory assay and field trials suggested that boll weevils distinguished between cotton plots based on color differences caused by kaolin and this appeared to influence levels of damage to squares. Random sampling in small plots indicated that oviposition damage to squares in plots treated with kaolin was reduced (P < 0.05) compared with nontreated controls, except when rain washed the kaolin off the foliage. Lint yield differences were not detected between the small plots, but the kaolin-treated small plots yielded as much as 2.36 times more cotton lint than a large but unreplicated adjacent nontreated control plot, and up to 1.39 times more than another large but unreplicated adjacent plot sprayed twice with preemptive applications of azinphosmethyl when cotton squares were first developing (pinhead stage). Potentially important avenues for future research on boll weevil injury suppression using kaolin are discussed.     

Relationships of abscised cotton fruit to boll weevil (Coleoptera: Curculionidae) feeding, oviposition, and development

Abscised cotton, Gossypium hirsutum L., fruit in field plots planted at different times were examined to assess adult boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), use of squares and bolls during 2002 and 2003 in the Lower Rio Grande Valley of Texas. Although boll abscission is not necessarily related to infestation, generally more bolls abscised than squares and abundances of fallen bolls were not related to the planting date treatments. During 2003, fallen squares were most abundant in the late-planted treatment. Although large squares (5.5-8-mm-diameter) on the plant are preferred for boll weevil oviposition, diameter of abscised squares is not a reliable measurement because of shrinkage resulting from desiccation and larval feeding. Fallen feeding-punctured squares and bolls were most abundant in late plantings but differences between fallen feeding-punctured squares versus fallen feeding-punctured bolls were found in only one treatment in 2003. During the same year, fallen oviposition-punctured squares were more numerous in the late-planted treatment than in the earlier treatments. Treatment effects were not found on numbers of oviposition-punctured bolls, but fallen oviposition-punctured squares were more common than bolls in the late-planted treatment compared with earlier treatments each year. Dead weevil eggs, larvae, and pupae inside fallen fruit were few and planting date treatment effects were not detected. Living third instars and pupae were more abundant in fallen squares of the late-planted treatment than in the earlier treatments and bolls of all three treatments. This study shows that fallen squares in late-planted cotton contribute more to adult boll weevil populations than bolls, or squares of earlier plantings.     

Influence of cotton fruit stages as food sources on boll weevil (Coleoptera: Curculionidae) fecundity and oviposition

Boll weevil, Anthonomus grandis grandis Boheman (Coloeoptera: Curculionidae), populations in the Lower Rio Grande Valley of Texas increase strongly during the squaring stage, and preemptive insecticide sprays at the pinhead square stage were designed to capitalize on that association. Laboratory assays showed that cotton plant volatiles, or leaves as a food source, do not elicit egg production in wild weevils. Boll weevils fed on large (5.5-8-mm diameter) squares for 7 d resulted in > or = 3.8-fold more gravid females that developed 4.8-fold more chorionated eggs per female than weevils fed on match-head-sized squares, or postbloom, young (5-10-d-old), or old (3-5-wk-old) bolls. When presented with a choice, nongravid females preferred to feed on young and old bolls 4.7- and 8.4-fold more, respectively, than on large squares. In the field, large squares had 7.8- and 25-fold more feeding punctures than match-head-sized squares and bolls, respectively. Oviposition increased > or = 2.7-fold when females fed on large squares compared with match-head-sized squares and bolls. Greater feeding on large squares during squaring and the associated greater fecundity explain rapid weevil population buildups shortly after large squares become well established.     

Evaluation of Catolaccus grandis (Burks) (Hym., Pteromalidae) as a biological control agent against cotton boll weevil

Abstract: An evaluation of augmentative releases carried out at the Agreste site of the state of Paraiba, Brazil, provided significant insight into the ecology and potential impact of Catolaccus grandis (Burks) against the boll weevil, Anthonomus grandis Boheman in that cotton agroecosystem. The rate of increase in density of C. grandis was higher than the boll weevil. Catolaccus grandis showed ability to effectively search and reproduce within the release environment and revealed pronounced host and habitat preferences. Parasitism by C. grandis was largely confined to third instar weevil larvae, the majority of which (86.9%) occurred in abcised cotton squares. Catolaccus grandis inflicted significant mortality on third instar weevil larvae in the plot resulting in a significant level of suppression. The net effect was a higher boll weevil mortality in the release plot in comparison with the control. The use of augmentative releases of C. grandis has a very high potential for supplementing and enhancing available technology for suppressing boll weevil populations in the Agreste Paraiba.     

Reducing boll weevil populations by clipping terminal buds and removing abscised fruiting bodies

Cotton pests damaging fruiting bodies (squares and young bolls) are difficult to control and their damage results in direct yield loss. Small growers, with low technological inputs, represent a large portion of cotton growers worldwide comprising more than 76 countries; they rely mainly on cultural practices to counteract pest attack in their crops. Boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae), oviposition involves puncturing cotton squares and young bolls, causing abscission. We examined the impact on boll weevil population of collecting abscised cotton fruiting bodies and clipping plant terminals at 50% boll maturation in the field during two cotton‐growing seasons and under field cage conditions. Greatest numbers of damaged squares occurred ca. 117 days after planting and clipped plants resulted in reduction of abscised structures and adult boll weevils compared with non‐clipped plants, irrespective of cotton variety. Damaged young bolls were found ca. 128 days after planting in 2009 and 2011, but clipping had no effect. Numbers of boll weevils found in plants of the varieties BRS 201 and BRS Rubi (both in 2009) and BRS Rubi (in 2011) were, respectively, 13‐, 17‐, and 20‐fold greater when clipping plus collecting abscised fruiting bodies were not practiced. Furthermore, the average percentage of the boll weevil parasitoid Bracon vulgaris Ashmead (Hymenoptera: Braconidae) emerging from abscised and collected structures was similar between clipped and non‐clipped plant terminals in both seasons. Clipping plant terminals did not result in yield reduction and reduced adult boll weevil production. Collecting abscised reproductive structures, clipping plant terminals, and using both practices together reduced boll weevil populations by as much as 63, 57, and 79%, respectively, in cage trials. Thus, these practices cause significant impact on boll weevil populations and are feasible of adoption, especially for smallholder cotton growers.     

Early-season colonization patterns of the boll weevil (Coleoptera: Curculionidae) in Central Texas cotton

It is commonly believed that colonization of early-season cotton, Gossypium hirsutum L., by overwintered boll weevils, Anthonomus grandis grandis Boheman, is concentrated on field margins. However, supporting experimental evidence is not available. In 1999 and 2000, we examined colonization patterns of overwintered boll weevils in Central Texas cotton on the bases of adult collections by a pneumatic sampler and hand collections of abscised infested squares. Samples were taken from sites arranged in a grid that extended inward >70 m from the field margin. Adults were collected from shortly after seedling emergence until the flowering stage, and infested squares were collected during the one-third grown square stage. Despite numerical trends, the numbers of adult weevils collected were not significantly different between years or sexes, or among plant phenological stages. Field-to-field variation among collections was considerable and likely prevented detection of differences among these factors. Spatial patterns represented by adult weevil and infested square collections were examined by logistic regressions fitted to the respective probabilities of weevil detection at each designated sample site. Although we observed trends for slightly decreased probability of weevil detection with increased distance from the field margin, these trends were too weak to be demonstrated statistically. Our results indicate the boll weevil does not consistently exhibit a strong edge-oriented colonization pattern, and that management tactics that are predicated on these patterns, such as border sprays, should be used with caution.     

Boll weevil (Coleoptera: Curculionidae) damage to cotton bolls under standard and proactive spraying

In some parts of the boll weevil's, Anthonomus grandis grandis (Boheman) (Coleoptera: Curculionidae), distribution from the United States to Argentina, insecticides are applied after cut-out (end of square production) when bolls are the predominant stage of fruiting body. This study demonstrates that the standard spray regime in southern Texas, which involves insecticide applications after cut-out, did not result in more bolls than a nonsprayed control. An alternative "proactive" spray regime focusing on protecting large squares before cut-out resulted in 1.9- to 2.5-fold more bolls in the lower half of the canopies than the control. At one of two experimental field locations, the percentage of damaged boll carpels was 3-fold greater in the standard spray regime's lower canopy than in the proactive spray regime, and the percentage in the control was 1.6-fold greater than in the standard regime. At both experimental field locations, the upper canopy control had 2.1- to 2.3-fold greater percentages of carpel damage than the proactive spray regime. The standard spray regime resulted in 2.3-fold greater percentage of carpel damage than the proactive regime. In the control and the standard spray regime, percentages of upper canopy nondamaged bolls were mostly lower than or not different from percentages of bolls with one, two, three, or all four carpels damaged, but in the proactive regime, percentage of nondamaged bolls in the upper canopy was greater than percentages of bolls with one or more damaged carpels. Reasons for the ineffectiveness of the standard spray regime and the benefits observed in the proactive approach are discussed.     

Effects of burial and soil condition on postharvest mortality of boll Weevils (Coleoptera: Curculionidae) in fallen cotton fruit

Effects of soil condition and burial on boll weevil, Anthonomus grandis grandis Boheman, mortality in fallen cotton, Gossypium hirsutum L., fruit were assessed in this study. During hot weather immediately after summer harvest operations in the Lower Rio Grande Valley of Texas, burial of infested fruit in conventionally tilled field plots permitted significantly greater survival of weevils than in no-tillage plots. Burial of infested squares protected developing weevils from heat and desiccation that cause high mortality on the soil surface during and after harvest in midsummer and late summer. A laboratory assay showed that burial of infested squares resulted in significantly greater weevil mortality in wet than in dry sandy or clay soils. Significantly fewer weevils rose to the soil surface after burial of infested bolls during winter compared with bolls set on the soil surface, a likely result of wetting by winter rainfall. A combination of leaving infested fruit exposed to heat before the onset of cooler winter temperatures and burial by tillage when temperatures begin to cool might be an important tactic for reducing populations of boll weevils that overwinter in cotton fields.     

Effects of routine late-season field operations on numbers of boll weevils (Coleoptera: Curculionidae) captured in large-capacity pheromone traps

Flat and cylindrical adhesive boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), pheromone traps captured significantly more (P < or = 0.05) boll weevils than the Hercon (Hercon Environmental, Emigsville, PA) trap during the late cotton-growing season, and larger adhesive areas were associated with higher captures; a flat plywood board collected the most boll weevils because it had the largest surface area. The flat board trap, chosen for measuring large late-season adult boll weevil populations common to the Lower Rio Grande Valley of Texas in 2000 and 2001, collected more (P < or = 0.05) weevils when deployed in proximity to natural and cultivated perennial vegetation, and mean numbers of captured boll weevils were higher (P < or = 0.0001) on the leeward sides of the board traps than on the windward sides. The board trap had an estimated potential capacity of approximately 27,800 boll weevils, and the large capacity of the board trap allowed for more accurate measurements of large adult boll weevil populations than the more limited Hercon trap. Measurement of adult boll weevil numbers after the routine field operations of defoliation, harvest, shredding, and stalk-pulling, demonstrated that large populations of boll weevils persist in cotton fields even after the cotton crop has been destroyed. Increases (P < or = 0.05) in the percentage variation of trapped boll weevils relative to the numbers collected just before each field operation were observed after defoliation, harvest, shredding, and stalk-pulling, but the percentage variations followed a quadratic pattern with significant correlation (P < 0.0001; 0.59 < adjusted r2 < 0.73). Numbers of adult boll weevils caught on board traps deployed at 15.24-m intervals on windward and leeward edges of cotton fields suggested that boll weevil populations in flight after field disturbances might be affected by large-capacity trapping.     

Short-range dispersal and overwintering habitats of boll weevils (Coleoptera: Curculionidae) during and after harvest in the subtropics

Field experiments in the subtropical Lower Rio Grande Valley of Texas were conducted to determine the extent of adult boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), dispersal from cotton, Gossypium hirsutum L., fields during harvest operations and the noncotton-growing ("overwinter") period between 1 September and 1 February. Using unbaited large capacity boll weevil traps placed at intervals extending outward from commercial field edges, boll weevils did not move in substantial numbers during harvest much beyond 30 m, primarily in the direction of prevailing winds. From traps placed in fallow cotton; citrus; lake edge; pasture; treeline; sorghum, Sorghum bicolor (L.) Moench, and sugarcane, Saccharum spp., habitats during the overwinter period, the most boll weevils were collected in the fallow cotton fields and adjacent treelines during the fall. However, the greatest abundances of boll weevils were found in citrus orchards in the spring, before newly planted cotton fields began to square. One of the three lake edges also harbored substantial populations in the spring. Egg development in females was not detected between November and April, but in cotton fields most females were gravid between May and August when cotton fruiting bodies were available. Mated females, as determined by discoloration of the spermatheca, made up 80-100% of the female population during November and December but declined to approximately 50% in February. The lower incidence of mating indicates a reduction in physical activity, regardless of overwinter habitat, until percentages increased in March and April after cotton fields had been planted and squares were forming.     

Reproductive potential of field-collected overwintering boll weevils (Coleoptera: Curculionidae) fed on pollen in the laboratory

Abstract  The reproductive potential of overwintering boll weevil, Anthonomus grandis grandis (Boheman), females collected from pheromone traps in September, November and January, fed for 1, 3, and 5 weeks on plant pollens, and then provided cotton squares, was determined in the laboratory at 27 ± 1°C, 65% RH, and a photoperiod 13 : 11 (L : D) h. Duration of pollen feeding by overwintering boll weevils did not significantly influence egg and feeding punctures, or puncture ratios (egg to total punctures) for any of the three months of parent weevil collections when provided cotton squares on a daily basis. However, punctures and puncture ratios are significantly different when comparing mean data between months of boll weevil collections. When boll weevils were provided with cotton squares daily, the pre-ovipositional periods of female parents captured in September, November and January were 5, 9 and 14 days, respectively. The rate of eggs by females was significantly lower during November and January than September. Female parents collected in September produced a significantly higher percentage of eggs yielding adult progeny than those collected in November and January. Life table parameters indicated that net reproductive rate ( R _o) of boll weevil females collected in September was 1.2-fold higher than those collected in November and 10.7-fold higher than those collected in January. Except for testes size, no differences in male reproductive parameters were observed during the cotton-free period compared with males captured during mid-cotton (June). The number of oocytes in the ovarioles and the number of oocytes containing yolk were significantly lower during September, November and January compared with June. The reproductive potential of overwintering boll weevil females collected in different months is an important consideration in determining the success of any control strategy.     

Potential for escape of live boll weevils (Coleoptera: Curculionidae) into cottonseed, motes, and cleaned lint at the cotton gin

Reintroductions of the boll weevil, Anthonomus grandis grandis Boheman, into areas of the United States where it has been eradicated or suppressed are very expensive to mitigate. There is concern that a cotton gin in an eradication zone may serve as a site of boll weevil reintroductions when processing cotton harvested in a neighboring infested zone. Similarly, there is a question whether weevil-free areas can safely import gin products, such as cottonseed and baled lint, from infested areas without risking an introduction. Many countries require fumigation of imported U.S. cotton bales to protect against boll weevil introductions, costing the U.S. cotton industry millions of dollars annually. In previously reported experiments, we quantified the potential for boll weevils to survive passage through precleaning machinery in the gin. In this study, we quantified survival potential of boll weevils passing through the gin stand and segregating into the cottonseed, mote, or lint fractions. We also examined boll weevil survival when passed with ginned lint through a lint cleaner. We present a flow chart of experimentally determined survival potentials of boll weevils passing through the various subprocesses of the gin, from which one can calculate the risk of a live boll weevil reaching any point in the process. Our data show that there is virtually no chance of a boll weevil being segregated alive into the cottonseed or of one surviving in the lint to approach the bale press. Therefore, quarantine or fumigation of cottonseed and cotton bales to guard against boll weevil introductions is unnecessary.     

Common subtropical and tropical nonpollen food sources of the boll weevil (Coleoptera: Curculionidae)

It is known that substantial boll weevil, Anthonomus grandis grandis Boheman, individuals can survive mild subtropical winters in some habitats, such as citrus orchards. Our study shows that endocarp of the fruit from prickly pear cactus, Opuntia engelmannii Salm-Dyck ex. Engel.; orange, Citrus sinensis L. Osbeck.; and grapefruit, Citrus paradisi Macfad., can sustain newly emerged adult boll weevils for >5 mo, which is the duration of the cotton-free season in the subtropical Lower Rio Grande Valley of Texas and other cotton-growing areas in the Western Hemisphere. Cotton, Gossypium hirsutum L., and the boll weevil occur in the same areas with one or all three plant species (or other citrus and Opuntia species that might also nourish boll weevils) from south Texas to Argentina. Although adult boll weevils did not produce eggs when fed exclusively on the endocarps of prickly pear, orange, or grapefruit, these plants make it possible for boll weevils to survive from one cotton growing season to the next, which could pose challenges to eradication efforts.     

Competition betweenBracon mellitor [Hym.: Braconidae] andCatolaccus grandis [Hym.: Pteromalidae] for their hostAnthonomus grandis [Col.: Curculionidae]

BioControl - Laboratory studies of competition between populations of 2 parasitoids of the cotton boll weevil,Anthonomus grandis Boheman, showed that populations ofCatolaccus grandis (Burks)...     

Ecology and phenology of the boll weevil (Coleoptera: Curculionidae) on an unusual wild host, Hibiscus pernambucensis, in southeastern Mexico.

The phenology and ecology of Hibiscus pernambucensis Arruda and its interaction and importance in maintaining populations of the boll weevil, Anthonomus grandis Boheman, were studied over a period of 3 yr in the Soconusco Region of the state of Chiapas, Mexico. H. pernambucensis is a small tree of Neotropical distribution, restricted to lowland areas, and generally associated with halophytic vegetation. This species is found exclusively along the shores of brackish estuaries, in or near mangrove swamps in southeastern Mexico. In this region, H. pernambucensis has a highly seasonal flowering pattern in which the greatest bud production occurs shortly after the start of the rainy season in May and the highest fruit production occurs in July and August. Boll weevil larvae were found in buds of H. pernambucensis during all months but February and densities of buds and weevils were highest from May through September. The percentage of buds infested with boll weevil larvae rarely exceeded 30%. Because plant densities and reproductive output of H. pernambucensis is relatively low and, consequently, the number of oviposition and larval development sites for boll weevils is limited, the importance of this plant as a source of boll weevils with potential of attacking commercial cotton is minimal in comparison with the quantity produced in cultivated cotton. However, the plant could be important as a reservoir of boll weevils in areas of boll weevil quarantine and eradication programs. The factors and circumstances that may have led to this apparent recent host shift of the boll weevil in this region are discussed.     

Potential for transport of boll weevils (Coleoptera: Curculionidae) to the cotton gin within cotton modules

There is concern that cotton gins located in boll weevil, Anthonomus grandis grandis Boheman, eradication zones serving customers in adjacent infested zones may serve as a site for boll weevil reintroductions if weevils are transported alive inside cotton modules. We surveyed fields in three distinct areas of Texas and found that weevils can be present in large numbers in cotton fields that have been defoliated and desiccated in preparation for harvest, both as free adults and as immatures inside unopened bolls. Harvested cotton taken from module builders indicated that approximately = 100-3700 adult boll weevils were packed inside modules constructed at the sampled fields. Marked weevils were forced through a laboratory field cleaner (bur extractor) commonly mounted on stripper-harvesters, and 14% were recovered alive in the seed cotton fraction and lived at least to 24 h. Survival of weevils placed inside modules declined over time up to 7 d, but the magnitude of the decline varied with experimental conditions. In one experiment, 91% of the weevils survived to 7 d, whereas under harsher environmental conditions, only 11% survived that long. Together, our results indicate that when cotton is harvested in an infested area, boll weevils likely will be packed alive into cotton modules, and many will still be alive by the time the module is fed into the gin, at least up to 7 d after the module's construction.     

Molecular cloning of a cysteine proteinase cDNA from the cotton boll weevil Anthonomus grandis (Coleoptera: Curculionidae)

The cotton boll weevil (Anthonomus grandis) causes severe cotton crop losses in North and South America. This report describes the presence of cysteine proteinase activity in the cotton boll weevil. Cysteine proteinase inhibitors from different sources were assayed against total A. grandis proteinases but, unexpectedly, no inhibitor tested was particularly effective. In order to screen for active inhibitors against the boll weevil, a cysteine proteinase cDNA (Agcys1) was isolated from A. grandis larvae using degenerate primers and rapid amplification of cDNA ends (RACE) techniques. Sequence analysis showed significant homologies with other insect cysteine proteinases. Northern blot analysis indicated that the mRNA encoding the proteinase was transcribed mainly in the gut of larvae. No mRNA was detected in neonatal larvae, pupae, or in the gut of the adult insect, suggesting that Agcys1 is an important cysteine proteinase for larvae digestion. The isolated gene will facilitate the search for highly active inhibitors towards boll weevil larvae that may provide a new opportunity to control this important insect pest.