Survival Of Weevils Research Articles

Evaluation of long-term residual activity of insecticides against Acanthoscelides obtectus (Say) on common bean in laboratory tests

There are insufficient data about long-term (longer than six-months) residual effects of insecticides against Acanthoscelides obtectus (Say) as an important economic insect pest of stored bean. Therefore, we evaluated, in laboratory conditions, the insecticide potential of recommended rates of commercial formulations: organophosphate malathion (10 mg active ingredient - AI/kg), spinosyns bioinsecticide spinosad (1 mg AI/kg) and pyrethroid deltamethrins (0,25 mg AI/kg, with and without the synergist piperonil butoxide – PBO) after 210-, 265-, 310- and 365-days of post-treatment. Testing was performed on two types of beans with kidney- and cranberry-shaped kernels to evaluate the insecticide residual effects on the survival of weevils, progeny production, and related levels of kernels damage. Survival of weevils depends mainly on adults exposure/living period in treated beans and on the recovering period. Small differencies in weevils survival in each insecticide were recorded. We found increases in progeny and thus higher damage in beans, as manifested effects of sublethal doses only in malathion treated bean. In spinosad treated bean we recorded low levels of progeny and damage, below the economic threshold. In deltamethrin treatments, we recorded weevils avoiding contact with beans, no progeny and no damages. The effect of bean type was very low or non existent. It can be concluded that bioinsecticide spinosad can provide long-term protection of common beans against A. obtectus, while organophosphate malathion has low control potential. Pyrethroid deltamethrins residues cause adults to avoid treated beans and no offspring to appear. The obtained results might have significant impact on better understanding of weevils behaviour in the presence of insecticide residues and on the creation of sustainable pest management programmes.

Synergistic effect of Balanites aegyptiaca essential oil and storage materials on cowpea seeds

The cowpea (Vigna unguiculata L.) is a legume produced and consumed all over Africa and especially in Nigeria. These beans are a major source of protein in the region. The cowpea weevil (Callosobruchus maculatus L.) is a major pest that affects cowpea seeds. Therefore, cowpea farmers need effective non-toxic pesticides to replace synthetic chemicals. The present research tested the effect of Balanites aegyptiaca L. essential oil on cowpea weevils.
 This research quantified weevil proliferation and cowpea seed qualities. The samples were treated with 5, 10, and 15 mL of B. aegyptiaca essential oil diluted in 1 mL of acetone and stored in five storage materials, i.e., jute bags, polythene bags, sacks, plastic containers, and glass bottles. The study featured a completely randomized design with three replications of each treatment: treatment time – 90 days, storage temperature – 30 ± 5°C, check – 0.125 g of aluminum phosphide, control – acetone.
 B. aegyptiaca essential oil proved to be an effective insecticide against cowpea weevils. The treatment achieved 100% mortality rate at 10 and 15 mL of B. aegyptiaca essential oil after 72 h of exposure in glass bottles, plastic containers, and jute bags. In addition, B. aegyptiaca essential oil demonstrated a potent activity against oviposition and survival of immature cowpea weevils. Cowpea seeds packaged in glass bottles, plastics containers, and jute bags showed significantly less damage than those stored in sacks and polythene bags. Glass bottles were the best storage material in terms of safety and shelf stability, followed by plastic containers and jute bags. 
 B. aegeptica essential oil has potent insecticidal properties and can be used as pest control during grain storage.

Dry bolls and their association withAnthonomus grandis grandisBoheman (Coleoptera: Curculionidae) survival through cotton fallow periods

AbstractThe boll weevil,Anthonomus grandis grandisBoheman (Coleoptera: Curculionidae), can remain inside dry and deformed reproductive structures of cotton,Gossypium hirsutumLinnaeus (Malvaceae), known as dry bolls, during the cotton fallow to infest the next cotton crop. In this study, the influence of cotton cultivars and sowing densities on the formation of dry bolls was evaluated. In addition, dry bolls were dissected and internal structures that were related to boll weevil development were estimated. Finally, the presence and survival of boll weevils inside dry bolls were evaluated. The results indicate that the number of dry bolls, empty pupal cells, and emergence holes was influenced by cultivar and not by sowing density. Almost one-quarter (22.53%) of adult boll weevils examined was found alive inside the dry bolls after 10 weeks, which is slightly longer than the duration of cotton fallow in Brazil’s main cotton-producing regions. Therefore, remaining inside the dry bolls is an important survival strategy for boll weevils during the cotton fallow period, and cotton cultivars with a greater propensity for the formation of dry bolls might favour survival of the pest during this period.

Sublethal Effects of Insect Growth Regulators on Boll Weevil (Coleoptera: Curculionidae).

Immature stages of the boll weevil, Anthonomus grandis grandis Boh. (Coleoptera: Curculionidae), develop protected inside cotton fruiting structures. Therefore, the adult beetles have become the main target of insecticide applications. The use of insect growth regulators (IGRs) is recommended against immatures, even though they may also affect the survival and reproductive traits of adult insects. The present study evaluated the impact of a juvenile hormone analog (pyriproxyfen), an ecdysteroid agonist (methoxyfenozide), and a chitin biosynthesis inhibitor (lufenuron) on adult cotton boll weevils, a key cotton pest. Mated and virgin beetles were treated by feeding them contaminated squares and cotton leaf discs that were previously immersed into pyriproxyfen, methoxyfenozide, and lufenuron solutions at field-rate concentrations. After exposure, treated couples were caged onto cotton plants, and survival, fecundity, and egg viability were evaluated. The IGRs neither affected the survival nor fecundity of adult boll weevils. On the other hand, egg viability was significantly reduced by lufenuron, regardless of whether the females were treated premating or postmating or whether their pairs were either treated or untreated. However, egg viability increased as the females aged since the initial exposure date to lufenuron, indicating a potential transovarial effect of this insecticide. Our results indicate that pyriproxyfen and methoxyfenozide do not affect adult boll weevils, whereas lufenuron temporarily reduces the egg viability of this key cotton pest.

EFFECT OF DIFFERENT INSECTICIDES ON THE SURVIVAL OF THE OIL PALM POLLINATOR, ELAEIDOBIUS KAMERUNICUS (COLEOPTERA:CURCULIONIDAE)

This study investigated the effects of nine insecticides used in young mature oil palm plantations for bunch moth control and their effect on the survival of the oil palm pollinating weevils especially on the newly emerged young adult weevils from the spent male inflorescence spikelets. Ten male inflorescences were randomly selected from an eight-year-old oil palm field and sprayed with 1 litre each of selected insecticides five days before anthesis. Field sampling of the male inflorescence spikelets for weevil counting was conducted when the flowers began to open from the base of the spikelets and continued until pollen shedding is over and no more aniseed smell was detected. Results show that three insecticides namely Dinotefuran, Fipronil and Cypermethrin at 0.0056 per cent ai, 0.0048 per cent ai and 0.015 per cent ai respectively at 1 litre spray solution per inflorescence showed significantly detrimental effects on both survival of adult weevils and newly emerged adult weevils per spikelet. The mean percentages of survival weevil per spikelet for Dinotefuran, Fipronil and Cypermethrin were at 20.48 per cent, 12.09 per cent and 55.18 per cent respectively. The mean number of newly emerged adult weevil count per spikelet for male inflorescence treated with Dinotefuran, Fipronil and Cypermethrin at 0.58, 4.74 and 6.05 respectively were significantly lower as compared to control (43.06). There were no significant differences in both mean percentages of survival adult weevil and newly emerged adult weevil per spikelet by the other six insecticides as compared to control. The study concludes that prolonged usage of these three insecticides in the young mature oil palm plantation to control bunch moth will inevitably lead to detrimental effects on the survival and proliferation of the oil palm pollinators in the oil palm ecosystem in the long run. Extra precaution is therefore required when handling these insecticides in the fields in order to have more sustainable way of controlling oil palm bunch moth in peat. Keywords: Bunch moth, insecticides, Elaeidobius kamerunicus, oil palm.

Evaluation of the Pathogenicity of Isolates ofBeauveria bassiana1AgainstRhyssomatus nigerrimus2

Abstract. The soybean weevil, Rhyssomatus nigerrimus Fahraeus, seriously damages vegetative and reproductive stages of soybean, Glycine max (L.) Merr., in Mexico. The weevil is currently controlled with conventional insecticide, and it is necessary to generate effective, sustainable control measures to reduce the negative impact of this new pest. The fungus Beauveria bassiana (Balsamo) Vuillemin has shown potential for management of some coleopteran pest species. The objective of this study was to assess the virulence of eight strains of B. bassiana against R. nigerrimus under laboratory conditions. Results showed that B. bassiana is a microbial agent that can potentially be incorporated into a program to control R. nigerrimus. All of the B. bassiana strains reduced survival of adult weevils, relative to the check. The most aggressive strains were Bb-Hy, Bb-Rhy, and Bb-13, with LC50 of 1.07 x 107, 1.55 x 107, and 1.31 x 1010 conidia per milliliter of suspension, respectively. Lethal time means (LT50) were...

Effects of ultraviolet-C and microwave irradiation on the expression of heat shock protein genes in the maize weevil (Coleoptera: Curculionidae)

The maize weevil, Sitophilus zeamais (Motschulsky), is a major pest of stored grain kernels. Irradiation is an established technique for controlling insects in stored grain and is a major stress factor affecting these insects. Since heat shock protein (hsp) genes respond to this stress, we proposed that hsps may be associated with irradiated stress tolerance in S. zeamais. The responses of the maize weevil to exposure to ultraviolet-C (UV-C) and microwave irradiation were assessed at four developmental stages: egg, larva, pupa and adult. The results revealed that exposure to UV-C (254 nm, < 8 h) did not affect the survival of the maize weevils; however, Szhsp70, Szhsc70 and Szhsp90 mRNA levels significantly increased during the first 1 h of UV-C exposure. The median lethal time (LT50) of exposure to microwave irradiation indicated that the adult stage was more tolerant of microwave irradiation than the other developmental stages. Microwave irradiation enhanced the expression of the three hsps, but the intensity of up-regulation differed among the three genes, with Szhsp70 the most highly up-regulated. Our experiments revealed that UV-C and microwave irradiation influenced the expression profile of hsp genes in S. zeamais. At the tissue level, the gene responses to UV-C and microwave irradiation varied greatly in different tissues.

Repeated Cold Exposure Effects on Mortality and Feeding Activity of the Salvinia Weevil, Cyrtobagous salviniae (Coleoptera: Curculionidae).

Biological control of the aquatic fern, Salvinia molesta D. S. Mitchell, by Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae), in temperate regions has been less reliable relative to tropical and subtropical regions. High mortality of overwintering adults is presumed to be an important factor. At temperate sites, overwintering adult C. salviniae may experience multiple exposures to low temperatures that could compound to lethal levels. We examined the effects of repeated cold exposure (RCE) on the overwintering mortality and feeding rate of adult C. salviniae. Mortality rate of adults following exposure to 2, 4, and 6 cycles of RCE was 22, 70 and 82%, respectively. Mortality in the RCE treatment was similar to that in the matched-cold treatment for 2 and 6 cycles but was significantly less than in the matched-cold treatment for the 4 cycles. The relationship between the number of RCE and adult mortality rate was modeled and model results were compared to adult survival of caged weevils during four winters on two lakes in northeast Texas. Also, the feeding activity of adult weevils surviving RCE declined following exposure to 4 and 6 cycles of RCE. These results provide insight into how cold impacts overwintering survival of C. salviniae and should assist in anticipating the need for inoculative releases of C. salviniae the following spring to achieve consistent biological control of S. molesta at temperate locales.

Desiccation resistance and water balance in populations of the maize weevil Sitophilus zeamais

Water balance is a challenge for insects due to their small size and body with high surface area-to-volume ratios, and it is particularly important for insects that inhabit dry environments, such as stored grains, and warm climates. This subject has been curiously neglected in stored product insects, including the maize weevil Sitophilus zeamais Motschulsky, were broad population differences have been reported with management consequences. Here, we assessed variation in desiccation resistance and water balance among three strains of the maize weevil exhibiting differences in body mass. The survival of male and female weevils from three strains was therefore assessed at relative humidities ranging from 0 to 100%, in which their water content and water loss were also assessed. The effect of insect aggregation (1–25 insects per group) on water balance was also assessed, as was the water gain by the drinking of free water and drinking preference when exposed to insecticide-contaminated water. The median survival time (LT50) of individual insects increased with relative humidity and varied significantly among the weevil strains. The larger strain exhibited 60–80% higher LT50 at 50% relative humidity (r.h.) and above, with little difference between strains at 0% r.h. Heavier weevils exhibited higher water content and lower overall rates of water loss; these qualities made heavier weevils more resistant to dehydration. Larger groups of weevils facilitate water retention in individual insects. Weevils actively drink water to achieve favorable water balance when dehydrated, which is a major source of water intake. Under dehydration, weevils in general were not able to discriminate between insecticide-contaminated and uncontaminated water. However, females of the insecticide-susceptible strain avoided contaminated water.

Systemic Insecticides Reduce Feeding, Survival, and Fecundity of Adult Black Vine Weevils (Coleoptera: Curculionidae) on a Variety of Ornamental Nursery Crops

Systemic activity of the neonicotinoids clothianidin, dinotefuran, and thiamethoxam and the anthranilic diamide chlorantraniliprole was tested against adult black vine weevils, Otiorhynchus sulcatus (F.) (Coleoptera: Curculionidae), on Astilbe, Euonymus, Heuchera, Rhododendron, Sedum, and Taxus. Insecticide treatments were applied to the soilless substrate of containerized plants. Bioassays were conducted 12 or 13, 26, and 42 d after treatment (DAT) and ran for 7 d; and feeding, mortality, and weight gain or loss by weevils were evaluated. Foliage was removed from test plants and then placed in arenas with adult black vine weevils. The neonicotinoids reduced feeding and weight gain by adult black vine weevils on most plant species with residual activity 42 DAT on some plant species. At 12 DAT, mortality was caused by the three neonicotinoids on Astilbe and by thiamethoxam on Sedum; and at 26 DAT dinotefuran caused mortality on Astilbe. Chlorantraniliprole reduced feeding on Taxus at 12 DAT, with no activity detected in other bioassays. Another set of bioassays was conducted to examine survival and fecundity of adult black vine weevils during prolonged feeding on Heuchera and Taxus systemically treated with dinotefuran or thiamethoxam. Bioassay procedures were similar to those described above, except they ran continuously for 56 d. Prolonged feeding on dinotefuran and thiamethoxam treated Heuchera and Taxus resulted in high mortality of adult black vine weevils and reduced fecundity. These studies show that the systemic activity of neonicotinoids is influenced by plant species and that systemic neonicotinoids have the potential to suppress black vine weevil populations in containerized nursery crops.

Influence of tillage on adult and immature pea leaf weevil (Coleoptera: Curculionidae) densities in pea.

The pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), has been a major pest of pea, Pisum sativum L., in eastern Washington and northern Idaho since its introduction to the region in the early 1970s. Eggs are deposited in the spring on the soil surface and first instars hatch and move to pea root nodules, where larvae feed before they pupate and adults emerge in mid- to late summer. No-tillage practices are known to reduce pea leaf weevil colonization in pea, but the effects of tillage on larval densities and subsequent adult emergence have not been examined. During 2005, 2006, and 2007, we compared densities of colonizing adult and immature pea leaf weevils on pea plots grown using conventional tillage and no-tillage. In 2005 and 2006, emergence of adult pea leaf weevil was monitored in the same plots. Densities of colonizing adult and immature pea leaf weevil were significantly higher in conventional tillage plots. Larvae in conventional tillage were further along in development than larvae in no-tillage plots during June and July. Densities of emerging adult pea leaf weevil were significantly greater from conventional tillage than no-tillage plots. Based on densities of colonizing and subsequent emerging adults, survival of weevils from egg through adult was greater in conventional tillage plots. Soils under no-tillage are cooler, resulting in later emergence of the pea crop and delayed root nodule development, possibly affecting the ability of first-instar pea leaf weevil to locate host plant roots. Our results indicate no-tillage fields are less suitable for pea leaf weevil colonization and survival than conventional tillage fields.

Effects of Photoperiod on Boll Weevil (Coleoptera: Curculionidae) Development, Survival, and Reproduction

Effects of photoperiod on development, survival, feeding, and oviposition of boll weevils, Anthonomus grandis grandis Boheman, were assessed under five different photophases (24, 14, 12, 10, and 0 h) at a constant 27 degrees C temperature and 65% RH in the laboratory. Analyses of our results detected positive relationships between photoperiod and puncturing (mean numbers of oviposition and feeding punctures per day), and oviposition (oviposition punctures/oviposition+feeding punctures) activities, and the proportion of squares attacked by boll weevil females. When boll weevil females developed in light:darkness cycles, they produced a significantly higher percentage of eggs developing to adulthood than those developed in 24-h light or dark conditions. In long photoperiod (24:0 and 14:10 h), the number of female progeny was significantly higher and their development time was significantly shorter than those developed in short photoperiod (0:24 and 10:14 h). Lifetime oviposition was significantly highest at 12- and 14-h photophase, lowest at 0- and 10-h photophase, and intermediate at 24 h of light. Life table calculations indicated that boll weevil populations developed in a photoperiod of 14:10 and 12:12 (L:D) h will increase an average of two-fold each generation (Ro) compared with boll weevils developed in 24:0- and 10:14-h photoperiods and 15-fold compared with those at 0:24 h. Knowledge of the photoperiod-dependent population growth potential is critical for understanding population dynamics to better develop sampling protocols and timing insecticide applications.

Seasonal Patterns in Host-Free Survival of the Boll Weevil (Coleoptera: Curculionidae) in the Subtropics

The overwintering ecology of the boll weevil, Anthonomus grandis Boheman, in the subtropics is poorly understood. Knowledge of seasonal patterns of host-free survival may be important to eradication efforts in the Lower Rio Grande Valley of Texas. The host-free survival of weevil cohorts emerging between 1 June and 3 November 1994 was examined. Weevils were fed either outdoors for 21 d (9 cohorts), outdoors for 28 d (6 cohorts), or under controlled conditions (29.4 ± 1°C, 13:11 [L:D] h photoperiod; 5 cohorts) for 21 d. Weevils were fed cotton (Gossypium hirsutum L.) squares or bolls, depending on availability in the field, and were subsequently held without food in the same environment in which they were fed. Survival of weevils fed outdoors exhibited a marked seasonal pattern in which greater survival was associated with the later cohorts. However, survival of cohorts fed and held under controlled conditions exhibited no seasonal pattern. When survival was adjusted for degree-day accumulations, using a base temperature of 12.8°C, differences in survival curves of weevils fed outdoors were reduced but not eliminated. During the periods of highest degree-day accumulations, most cohorts fed outdoors for 21 d exhibited greater survival than those fed outdoors for 28 d, and survival tended to be greater for weevils fed under controlled conditions than for weevils fed outdoors. These observations suggest the feeding period duration influenced subsequent survival. The observed influence of temperature on host-free survival suggests the opportunity to reduce overwintering weevil populations in subtropical regions through a delayed planting tactic.

Effects of mulching and insecticides on establishment and growth of Norway spruce

Establishment of Norway spruce (Picea abies (L.) Karst.) seedlings is often restricted by competition from vegetation, drought, and damage by pine weevils. In this study, effects of mulching on these factors were investigated. Norway spruce seedlings were planted on fresh and 1-year-old clearcuts treated with mulch on three sites in southern Sweden. Mulch was made of slash from the old stand and applied on whole blocks at three different depths: 0, 10, and 20 cm. Both insecticide-treated and untreated seedlings were planted. By reducing the competing vegetation and improving soil moisture and mineralization, mulching created a favorable growth environment. Mulching significantly improved growth in terms of height, diameter, and volume of the seedlings. Growth continued to increase over time in mulched treatments, probably as an effect of increased nutrient availability. The 20 cm mulch layer generated the greatest increase in growth throughout the 10-year experimental period. Soil moisture was preserved under the isolating mulch layer and during periods of drought soil water potential was significantly higher in mulched treatments. After 2 years, percent cover of competing vegetation was 50%–60% without mulch and 10%–20% with a mulch depth of 20 cm. Insecticide-treated seedlings achieved a survival rate close to 100% in all mulching treatments, whereas survival among untreated seedlings was only 40% on some clearcuts. Mulching alone did not affect survival or abundance of pine weevils.

Host-Free Survival of Boll Weevils (Coleoptera: Curculionidae) Previously Fed Vegetative-Stage Regrowth Cotton

The need to minimize populations of overwintering boll weevils (Anthonomus grandis Boheman) in eradication programs is widely recognized, but the potential contribution of nonfruiting regrowth cotton (Gossypium hirsutum L.) to weevil survival has not been directly examined. We conducted experiments in 2002 and 2003 to examine the host-free survival of weevils previously supplied vegetative-stage regrowth cotton. Weevils, 1–3 d after eclosion, were caged with vegetative regrowth cotton under ambient environmental conditions (2002), or in a controlled environment (23.9 ± 2°C, 13:11 [L:D] h photoperiod, 2003). Four cohorts of each weevil sex were examined each year. Of the 60 weevils dissected in 2002, 12% possessed the hypertrophied fat bodies associated with diapause and extended host-free survival. In both years, the majority of weevils (&amp;gt;75%) died during the initial 3 wks of the host-free period. No differences in host-free survival were detected between weevil sexes, but differences were observed among replicates of the experiment established on different dates. Survival patterns among replicates, however, did not strictly follow a seasonal pattern. Overall, approximately 5% of the weevils survived ≥12 wks beyond the feeding period. Maximum observed host-free longevities were 21 wks in 2002 and 19 wks in 2003. Our findings suggest vegetative-stage regrowth cotton should not be disregarded in eradication zones, particularly in those experiencing unsatisfactory progress or resurgence of weevil populations.

Boll Weevil (Coleoptera: Curculionidae) Survival through Cotton Gin Trash Fans

There is concern that cotton gins may serve as loci for reintroduction of boll weevils, Anthonomus grandis grandis Boheman, to eradicated or suppressed zones when processing weevil-infested cotton from neighboring zones. Previous work has shown that virtually all weevils entering the gin in the seed cotton will be removed before they reach the gin stand. Those not killed by the seed cotton cleaning machinery will be shunted alive into the trash fraction, which passes through a centrifugal trash fan before exiting the gin. The objective of this study was to determine survival potential of boll weevils passed through a trash fan. Marked adult weevils were distributed in gin trash and fed through a 82.6-cm (32.5-in.) diameter centrifugal fan operated across a range of fan-tip speeds. A small number of boll weevils were recovered alive immediately after passage through the fan, but all were severely injured and did not survive 24 h. In another experiment, green bolls infested with both adult- and larval-stage weevils were fed through the fan. Several teneral adults survived 24 h, and there was no evidence that fan-tip speed affected either initial survival of weevils, or the number of unbroken boll locks that could harbor an infesting weevil. Thus, designating a minimum fan-tip speed for ensuring complete kill is not possible for the boll weevil. Experiments suggest that a device installed in a gin that partially crushes or cracks bolls open before entering a trash fan will increase mortality, possibly enough that further precautions would be unnecessary.

Boll weevil (Coleoptera: Curculionidae) survival through the seed cotton cleaning process in the cotton gin.

There is concern that gins located in boll weevil, Anthonomus grandis grandis Boheman, eradication zones may become points of reintroduction when they process cotton grown in a neighboring infested area. We estimated boll weevil survival through two typical machine sequences used in commercial cotton gins to clean and dry the seed cotton in advance of the gin stand, as well as separately through two incline cylinder cleaners or one or two tower dryers operating at different temperatures. Large numbers of laboratory-reared adult boll weevils were marked with fluorescent powder, fed into the test system, and recovered with the assistance of blacklights. We found no evidence of survival through the seed cotton cleaning systems even when the dryers were not heated, or when passed separately through the two incline cleaners alone. Upper confidence limits (95%) were calculated for the observed zero recoveries based on sample size and the binomial distribution, and these represent the statistical worst-case (i.e., highest) survival potential. Survival through heated tower dryers declined rapidly to zero at higher temperatures, especially when two dryers were running. Although we conclude that the potential for survival of weevils in the seed cotton to the gin stand is zero or close to zero, a small percentage of live weevils was recovered in the green boll/rock trap, which may represent the greatest threat of reintroduction at the gin. Escape of live weevils with the gin trash is also possible, and studies addressing this issue will be presented elsewhere.

Boll Weevil (Coleoptera: Curculionidae) Survival Through the Seed Cotton Cleaning Process in the Cotton Gin

There is concern that gins located in boll weevil, Anthonomus grandis grandis Boheman, eradication zones may become points of reintroduction when they process cotton grown in a neighboring infested area. We estimated boll weevil survival through two typical machine sequences used in commercial cotton gins to clean and dry the seed cotton in advance of the gin stand, as well as separately through two incline cylinder cleaners or one or two tower dryers operating at different temperatures. Large numbers of laboratory-reared adult boll weevils were marked with fluorescent powder, fed into the test system, and recovered with the assistance of blacklights. We found no evidence of survival through the seed cotton cleaning systems even when the dryers were not heated, or when passed separately through the two incline cleaners alone. Upper confidence limits (95%) were calculated for the observed zero recoveries based on sample size and the binomial distribution, and these represent the statistical worst-case (i.e., highest) survival potential. Survival through heated tower dryers declined rapidly to zero at higher temperatures, especially when two dryers were running. Although we conclude that the potential for survival of weevils in the seed cotton to the gin stand is zero or close to zero, a small percentage of live weevils was recovered in the green boll/rock trap, which may represent the greatest threat of reintroduction at the gin. Escape of live weevils with the gin trash is also possible, and studies addressing this issue will be presented elsewhere.

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 ≈100–3,700 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.

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.