Potential displacement of the native Tenuisvalvae notata by the invasive Cryptolaemus montrouzieri in South America suggested by differences in climate suitability.

Tenuisvalvae notata (Mulsant) (Coccinellidae) is a predatory ladybird beetle native to South America. It specializes in mealybugs prey (Pseudococcidae), but relatively little is known about its ecology. In contrast, the ladybird beetle Cryptolaemus montrouzieri Mulsant (Coccinellidae) is indigenous to Australia and has been introduced to many countries worldwide including Brazil for biological control of mealybugs. The potential impacts of these introductions to native coccinellids have rarely been considered. The software CLIMEX estimated the climate suitability for both species as reflected in the Ecoclimatic Index (EI). Much of South America, Africa, and Australia can be considered climatically suitable for both species, but in most cases, the climate is considerably more favorable for C. montrouzieri than T. notata, especially in South America. The CLIMEX model also suggests seasonal differences in growth conditions (e.g. rainfall and temperature) that could affect the phenology of both species. These models suggest that few locations in South America would be expected to provide T. notata climatic refugia from C. montrouzieri. Although other ecological factors will also be important, such as prey availability, this analysis suggests a strong potential for displacement of a native coccinellid throughout most of its range as a consequence of the invasion by an alien competitor.

Selective insecticides secure natural enemies action in cotton pest management.

Cotton hosts a variety of arthropod pests requiring intensive control mostly with insecticides, which in turn may impact beneficial insects and the environment. Therefore, insect control in cotton fields preconizes the use of selective insecticides that offer pest control but conserve natural enemies. In this work, we measured the impact of recommended insecticides on the abundance of predatory insects and predation upon sentinel preys in the field. Further, the survival of four key selected predatory insects of cotton ecosystem, representing chewing and sucking feeding habits and different pest species attacked [Chrysoperla externa Hagen, Eriopis connexa (Germar), Podisus nigrispinus (Dallas) and Orius insidiosus (Say)], were assessed when exposed to the dried residues of the tested insecticides. Mortality of sentinel prey caused by natural enemies was higher in areas treated with selective insecticides relative to the non-selective ones, and most of time similar to the untreated areas. Furthermore, areas treated with non-selective insecticides experienced prolonged impact between sprays depending on the insecticide applied. Seasonal abundance of predatory insects was 2× greater in fields under selective and untreated fields compared to those under non-selective recommendation. Survival of predators exposed to the dried residues of the selective insecticides pymetrozine, chlorantraniliprole, pyriproxyfen, and cyantraniliprole were greater than when exposed to the non-selective lambda-cyhalothrin, malathion, dimethoate, and thiamethoxam. Among the non-selective insecticides, malathion and dimethoate exhibited shorter residual time compared to the thiamethoxam and lambda-cyhalothrin + thiamethoxam. Therefore, the recommendation of selective insecticides provides benefits for cotton pest management by maintaining the action of the natural enemies present in the field.

Differential impacts of six insecticides on a mealybug and its coccinellid predator.

Broad-spectrum insecticides may disrupt biological control and cause pest resurgence due to their negative impacts on natural enemies. The preservation of sustainable pest control in agroecosystems requires parallel assessments of insecticide toxicity to target pests and their key natural enemies. In the present study, the leaf dipping method was used to evaluate the relative toxicity of six insecticides to the striped mealybug, Ferrisia dasylirii (Cockerell) (Hemiptera: Pseudococcidae) and its predator, Tenuisvalvae notata (Mulsant) (Coleoptera: Coccinellidae). Three neurotoxic insecticides, lambda-cyhalothrin, methidathion and thiamethoxam, caused complete mortality of both pest and predator when applied at their highest field rates. In contrast, lufenuron, pymetrozine and pyriproxyfen caused moderate mortality of third-instar mealybug nymphs, and exhibited low or no toxicity to either larvae or adults of the lady beetle. At field rates, lufenuron and pymetrozine had negligible effects on prey consumption, development or reproduction of T. notata, but adults failed to emerge from pupae when fourth instar larvae were exposed to pyriproxyfen. In addition, pyriproxyfen caused temporary sterility; T. notata females laid non-viable eggs for three days after exposure, but recovered egg fertility thereafter. Our results indicate that the three neurotoxic insecticides can potentially control F. dasylirii, but are hazardous to its natural predator. In contrast, lufenuron and pymetrozine appear compatible with T. notata, although they appear less effective against the mealybug. Although the acute toxicity of pyriproxyfen to T. notata was low, some pupal mortality and reduced egg fertility suggest that this material could impede the predator's numerical response to mealybug populations.

Toxicity of three aphicides to the generalist predators Chrysoperla carnea (Neuroptera: Chrysopidae) and Orius insidiosus (Hemiptera: Anthocoridae).

Recent widespread infestations of the invasive sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), in sorghum fields in the southern USA have created demand for insecticides that will provide effective control of sugarcane aphid, while conserving those beneficial species that contribute to biological control of the pest. We tested the susceptibility of both adult and immature stages of two aphid predators, the green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), and the insidious flower bug, Orius insidiosus (Say) (Hemiptera: Anthocoridae), to three aphicides, flonicamid, sulfoxaflor and flupyradifurone. Flonicamid was innocuous to both species regardless of life stage or route of exposure. Lacewing adults were more susceptible to sulfoxaflor and flupyradifurone than were larvae, and had higher mortality when fed contaminated honey solution than when contacting residues on an inert surface. When laid in sunflower stems treated with these two materials, eggs of O. insidiosus hatched successfully, but nymphs experienced significant mortality when exposed to treated stems, likely due to phytophagous behavior that resulted in some insecticide ingestion. Despite these impacts, we conclude that both sulfoxaflor and flupyradifurone are likely to be relatively innocuous in comparison to more broad-spectrum insecticides and are thus potentially compatible with biological control and overall management of M. sacchari in grain sorghum.

Indigenous Aphid Predators Show High Levels of Preadaptation to a Novel Prey, Melanaphis sacchari (Hemiptera: Aphididae).

The performance of four aphid predators, Hippodamia convergens Guerin-Meneville, Coleomegilla maculata DeGeer, Chrysoperla carnea Stephens and Orius insidiosus Say was compared on three prey species: Schizaphis graminum Rondani, Melanaphis sacchari (Zehntner), and Ephestia kuehniella Zeller eggs. Species predatory in both life stages (all except Ch. carnea) were reared on E. kuehniella eggs and switched to aphid prey for assessment of reproduction. Differences were greater between the E. kuehniella and aphid diets than between the two aphid species. Juvenile survival was high for all predators on all prey, except for O. insidiosus, which had survival on E. kuehniella > S. graminum > M. sacchari. The fastest development of Ch. carnea and O. insidiosus was obtained on E. kuehniella, whereas H. convergens developed fastest on S. graminum, and C. maculata did not differ among diets. S. graminum also yielded the largest H. convergens adults, whereas the largest adults of other predators were obtained on E. kuehniella. Female fecundity and egg viability were similarly high on both aphid diets for H. convergens and C. maculata, whereas, on E. kuehniella, 50% of the former entered reproductive diapause and the latter species had reduced fecundity. Reproductive success of Ch. carnea was S. graminum = M. sacchari > E. kuehniella, but it was similar among treatments for O. insidiosus, although female infertility ranged from 25 to 37.5%. We concluded that all the predators studied are preadapted to utilize sugarcane aphid as prey and have excellent potential to provide sustainable biological control of this newly invasive pest.

Enzymes mediating resistance to lambda-cyhalothrin in Eriopis connexa (Coleoptera: Coccinellidae).

Resistance to widely used insecticide, lambda-cyhalothrin, was recently reported in the predatory lady beetle Eriopis connexa (Germar) (Coleoptera: Coccinellidae). However, to understand whether metabolic mechanisms underlie such resistance, synergism bioassays and in vitro studies were carried out by using inhibitors and model substrates for enzymatic assays, respectively. The LD50s estimated for susceptible and resistant populations ηg of lambda-cyhalothrin/insect, and thus, a 22-fold difference in resistance ratio. Synergism ratios for the susceptible population with piperonyl butoxide (PBO), diethyl maleate (DEM), triphenyl phosphate (TPP), and S,S,S-tributylphosphorotrithioate (DEF) were respectively 33.8-, 0.24-, 0.35-, and 4.25-fold, while for the resistant population, they were 1463.0-, 0.79-, 0.85-, and 282.6-fold, respectively. The synergized resistance ratios were 0.50-, 2.00-, 6.75-, and 8.77-fold with PBO, DEF, DEM, and TPP, respectively, while resistance was virtually suppressed with DEF. The esterase exhibited 4.16-, 4.03-, and 5.38-fold greater activity towards formation of α-naphthol, ß-naphthol, and 4-nitrophenol in the resistant population of E. connexa than in the susceptible population. The activity of esterase depended on concentrations of DEF applied, either using α-naphthol or ß-naphthol, which completely inhibited the activity at 636 ηM. The PBO inhibited the ß-naphthol formation in approximately 50%, suggesting it as inhibitor of esterases. The activities of glutathione-S-transferase were similar and corresponded to 0.36-0.47 ηmol(-1) min(-1)µg of protein, for S and R populations, respectively. Similarly, the activities of cytochrome P450-dependent microsomal monooxygenases were 0.04 and 0.05 ηmol(-1) min(-1)µg of protein. The native gel indicated that the formation of ß-naphthol was completely inhibited by methyl-paraoxon, but only partially inhibited by eserine, TPP, and PBO. Although other studies with DEF and PBO have demonstrated strong inhibition of type B carboxylesterase associated with insecticide resistance, the results reported here do not rule out metabolism by cytochrome P450-dependent microsomal monooxygenases as a factor conferring E. connexa resistance to lambda-cyhalothrin and confirmed that PBO may also act by inhibiting esterases of insects.

Fungal seed treatments of cotton affect boll weevil development.

BACKGROUND: Nonpathogenic fungi associated with plants can enhance plant defenses against stress factors, including herbivory. This study assessed whether cotton plants grown from seeds treated with different fungi affected boll weevil, Anthonomus grandis grandis Boheman, development and reproduction along with plant tolerance. We used whole plants grown from seeds treated with different fungi (Chaetomium globosum TAMU520 and TAMU559, Phialemonium inflatum TAMU490, and Beauveria bassiana) versus non-treated controls to test insect growth, reproduction, and plant tolerance assays in a greenhouse. RESULTS: Regarding boll weevil reproduction, fewer larvae hatched and fewer adults emerged from fungal-treated plants. In addition, the developmental time from oviposition to adult emergence was delayed in the plants treated with all fungi. For plant tolerance, B. bassiana-treated plants attacked by boll weevils shed fewer squares than nonfungal-treated plants. CONCLUSION: Fungal treatments can affect boll weevil performance and reproduction on cotton plants, with potentially negative effects on population growth. Collectively, these results support the potential for cottonseed treatments with fungi as a novel tool for boll weevil management in the field. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Response of different populations of seven lady beetle species to lambda-cyhalothrin with record of resistance.

Simultaneous use of biological and chemical controls is a valued and historic goal of integrated pest management, but has rarely been achieved. One explanation for this failure may be the inadequate documentation of field populations of natural enemies for insecticide tolerance or resistance because natural enemies surviving insecticide application do not create problems like resistant pest species. Therefore, this study investigated 31 populations of lady beetles (Coleoptera: Coccinellidae) regarding their susceptibility to lambda-cyhalothrin, a pyrethroid insecticide that is widely used in cotton and other crops to control lepidopteran and coleopteran pests that are not targeted as prey by lady beetles. The study focused on seven coccinellid species common in cotton fields Coleomegilla maculata De Geer, Cycloneda sanguinea (L.), Eriopis connexa Germar, Harmonia axyridis (Pallas), Hippodamia convergens Guérin-Méneville, Olla v-nigrum (Mulsant), and Brumoides foudrasi (Mulsant) and one lady beetle species [Curinus coeruleus Mulsant] from a non-cotton ecosystem for comparisons. Dose-mortality curves were estimated after topical treatment of adult lady beetles with lambda-cyhalothrin. Statistically significant variations in lady beetle susceptibility were observed between species and between populations of a given species. Seven and eighteen populations of lady beetles exhibited greater values of LD50 and LD90, respectively, than the highest recommended field rate of lambda-cyhalothrin (20g a.i./hectare≈0.2g a.i./L) for cotton fields in Brazil. Furthermore, based on LD50 values, 29 out of 30 tested populations of lady beetles exhibited ratios of relative tolerance varying from 2- to 215-fold compared to the toxicity of lambda-cyhalothrin to the boll weevil, Anthonomus grandis Boh. (Coleoptera: Curculionidae). Four populations of E. connexa were 10.5-37.7 times more tolerant than the most susceptible population and thus were considered to be resistant to lambda-cyhalothrin, the first record of resistance for this species. These findings demonstrate that field selection for resistance to lambda-cyhalothrin in common lady beetles is occurring, opening up possibilities to effectively integrate biological control where the popular insecticide lambda-cyhalothrin is used.

Olfaction Response and Fertility Life Table Parameters of Tetrastichus howardi (Hymenoptera: Eulophidae) Parasitizing Plutella xylostella (Lepidoptera: Plutellidae) and the factitious host Tenebrio molitor (Coleoptera: Tenebrionidae).

Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) parasitizes the diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae), but not much is known about its potential as a biocontrol agent. A rearing protocol has been established for this parasitoid on pupae of the factitious host Tenebrio molitor (L.) (Coleoptera: Tenebrionidae), with the aim of releasing it in the field to manage several lepidopteran species. The potential population growth of a parasitoid can be measured through fertility life tables and provide supporting information for using T. howardi in the management of P. xylostella. Also, the fitness and behavior of T. howardi reared on a factitious host can be indicators of its potential to control P. xylostella. Thus, in this study, the fertility life table parameters of T. howardi parasitizing P. xylostella were determined, as well as the effects of the natal host on the behavior of T. howardi towards host volatiles and parasitism rate. The results showed that net reproduction rate (Ro) and the intrinsic rate of population growth (rm) of T. howardi parasitizing P. xylostella were 13.6 (♀/♀) and 0.124 (♀/♀*day), respectively, whereas the mean generation time was 20.9 days. Moreover, the natal host (T. molitor or P. xylostella) did not affect the fitness, parasitism rate, or olfactory response of T. howardi. In general, regardless of the natal host, parasitoid females responded to volatiles of both host species and exhibited the same rate of parasitism on P. xylostella. Therefore, T. howardi reared on the factitious host maintains its attraction and potential to parasitize P. xylostella, and can contribute to the biological control of this pest.

Planting Date of Cotton in the Brazilian Cerrado Drives Boll Weevil (Coleoptera: Curculionidae) Infestation.

Although the boll weevil (BW), Anthonomus grandis grandis (Coleoptera: Curculionidae) has been attributed to the significant losses caused to cotton yield in the Americas, the categorization as a quarentenary pest in places where it is still not occurring has increased its relevance worldwide. In areas where it is widespread, pest suppression relies on many broad-spectrum insecticide applications. However, other control tactics are sought. Considering that early-flowering cultivars escape from boll weevil infestation, we investigated if three different planting dates (November, December, and January) could alter the plant life cycle, allowing the plants to escape from boll weevil infestation. Field trials were run in two seasons (2014/2015 and 2017/2018), and variables (days required to reach each flowering stage, fruiting plant structures-undamaged and damaged by the BW, and totals-number of boll weevils on plants and that had emerged from fallen structures on the ground) were assessed over 29 and 33 weeks, respectively. Based on the number of days required to initiate and terminate the flowering stage, the time to reach the economic threshold (ET), the number of undamaged, damaged, and the total reproductive structures, we concluded that planting dates in December for the Central Cerrado of Brazil should be preferred over the other two tested dates. Cultivations run at this planting date, anticipating the flowering period initiation and termination, reduced infested flowering structures, and delayed the decision making to control the pest, when compared to the other two planting dates.

Sexual maturity, lack of partner choice and sperm precedence in the promiscuous ladybird beetle Eriopis connexa (Germar): Who is my father?

Ladybird beetles present as key predator of many agricultural pests. Among them, Eriopis connexa stands out due some important traits for pest management programs such as common occurrence, population selected for resistance to pyrethroid insecticides, and possibility to be commercially available by rearing using alternative prey. Despite that, little is known about the role of polyandry and its effect on paternity in this species. Ladybird beetles engage in multiple matings, raising questions about the benefits of polyandry and paternity. We studied the selection of mating pair, sperm precedence, and offspring paternity by performing experiments on (1) the age of sexual maturity, (2) the frequency and refractory mating behavior within a photophase period, (3) the preference of insecticide-susceptible females to mate with either susceptible or resistant male phenotypes; and (4) the effect of multiple matings, on progeny paternity. Sexual maturity in E. connexa was found to begin within 3 days of adult emergence for both sexes, but fully developed after 5 days. The highest frequency of mating exhibited by sexual mature pairs occurred within first hour of pairing and the phenotype for insecticide resistance did not affect the choice of a mating partner. The resistance trait marker in the resistant beetle phenotype indicates that progeny paternity results from a mixture of available sperm and do not depend on mating order. These data suggest that released beetles would have a simple prospect for progeny production for both insecticide resistant and susceptible beetles.

Dispersal of boll weevil toward and within the cotton plant and implications for insecticide exposure.

BACKGROUND: Immature stages of boll weevil complete development endophytically leaving only the adult stage accessible for chemical control. We tested the hypothesis that boll weevil colonization of the cotton plants significantly affects their exposure to sprayed insecticides. We determined the adult dispersal toward and within cotton plants, lethal time (LT), and residual control by recommended insecticides (malathion, carbosulfan, thiamethoxam, fipronil, beta-cyfluthrin, lambda-cyhalothrin, and thiamethoxam + lambda-cyhalothrin) through dried residue exposure and residual control regarding the leaf position in the upper and the lower thirds of the treated plant canopy. RESULTS: Newly emerged adults from fallen buds reached the cotton plants by walking (80%) and most of the time settling on cotton bolls in the lower part of the plants (78%). Irrespective of sex and mating status, adults released on the upper part of the plant remained longer on the same release site than the lower part, with some individuals remaining up to 50 h on the same flower bud. The shortest LT90 was found with thiamethoxam (106 h). Fipronil and malathion, respectively, provided the longest (>144 h) and shortest (24 h) residual control times and caused boll weevil mortality above 80%. CONCLUSIONS: These findings suggest that weevils accessing the cotton plants exhibited within-plant distribution that minimizes their contact with insecticide residue on plant foliage. Furthermore, short residual control with malathion, the most used insecticide against boll weevil, and the low susceptibility exhibited by the tested population to pyrethroids highlight the current challenges faced for boll weevil control in Brazilian cotton fields. © 2020 Society of Chemical Industry.

Field-evolved resistance to beta-cyfluthrin in the boll weevil: Detection and characterization.

BACKGROUND: Insecticide resistance in arthropods is an inherited trait that has become a major cause of insect pest control failure. Monitoring the level of susceptibility and characterization of the type of resistance of key pest species aims to determine the risk of resistance selection in time to take action to mitigate control failures. Seven populations of the boll weevil, Anthonomus grandis grandis, collected from cotton fields in the Semiarid and Cerrado areas of Brazil, were screened for their resistance to malathion and beta-cyfluthrin, insecticides widely recommended for control of boll weevil and other pests. RESULTS: The levels of adult mortality were variable for beta-cyfluthrin (0-82%) but invariant (100%) for malathion. Bioassays of concentration-mortality were used to determine lethal concentrations (LCs) for each insecticide. The LC-values corroborate the lack of resistance to field rates of malathion but high levels of resistance to beta-cyfluthrin from 62.7- to 439.7-fold. Weevils resistant to beta-cyfluthrin were found through genome sequencing to possess a kdr mutation through the L1014F substitution in the voltage gated-sodium channel gene. CONCLUSIONS: This study found boll weevil resistance to beta-cyfluthrin to be not mediated by carboxylesterases, but with cross-resistance to DDT and carbaryl, and kdr mutation as the major mechanism of the resistance in our samples. Caution is recommended in further use of beta-cyfluthrin against boll weevil due to potential resistance. Monitoring studies using other boll weevil populations are recommended to determine the geographic pattern and extent of pyrethroid resistance. © 2021 Society of Chemical Industry.

Determination of an Economic Injury Level for Old World Bollworm (Lepidoptera: Noctuidae) in Processing Tomato in Brazil.

Tomato plants host various herbivores, including the Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), recently introduced into South and Central America. It is a harmful pest for tomato crops, damaging mainly the flowers and fruits. The assessment of losses and the establishment of economic injury level (EIL) and economic threshold (ET) are core steps toward establishing a control program. We determined losses caused by H. armigera on processing tomato and estimated EIL/ET values. Trials were run during two growing seasons using tomato plants caged in the field. The field cage experiment consisted of six densities of H. armigera second instar larvae (0, 1, 3, 6, 12, and 24 larvae per row meter) at two infestations periods spaced 15 d apart with the first infestation done 90 d after transplanting. The larvae were placed individually on the third upper fully developed leaf. The number of healthy and damaged fruits, size, and weight of the fruits were measured. Yield losses as a function of infestation of 1-24 larvae per row meter ranged from 4 to 34% and resulted in a yield reduction of 1.22-12.77 kg per row meter. The EIL ranged from 1.41 to 1.72 and from 2.11 to 2.58 larvae per row meter of plants in 2017 and 2018 cropping seasons, respectively. Helicoverpa armigera causes significant reduction of tomato yield. These EIL values will enable better control decision-making in processing tomato.

Mortality of the defoliator Euselasia eucerus (Lepidoptera: Riodinidae) by biotic factors in an Eucalyptus urophylla plantation in Minas Gerais State, Brazil.

Euselasia eucerus (Hewitson, 1872) (Lepidoptera: Riodinidae) is a Brazilian native species commonly found in Eucalyptus plantations. Biotic mortality factors of this defoliator were studied in a Eucalyptus urophylla plantation in Minas Gerais State, Brazil aiming to identify natural enemies and their impact on this insect. Euselasia eucerus had biotic mortality factors during all development stages. The most important were Trichogramma maxacalii Voegelé and Pointel, 1980 (Hymenoptera: Trichogrammatidae) during egg stage (48.9%), a tachinid fly (Diptera: Tachinidae) during larval stages (10%) and Itoplectis sp. (Hymenoptera: Ichneumonidae) during pupal stage (52.2%). The parasitism rate was higher in the basal part of the plant canopy (37.8%).

Susceptibility of Cotton Boll Weevil (Coleoptera: Curculionidae) to Spinosyns.

The control of boll weevil, Anthonomus grandis grandis Boh., relies primarily on synthetic insecticides. Although insecticides are registered to spray cotton fields against boll weevils, only a few offer satisfactory control and most have broad-spectrum action. Alternatively, spinosyns have been recommended against lepidopteran pest species in cotton and are considered comparatively of reduced risk to nontargets. The susceptibility of nine populations of boll weevil to spinosad and spinetoram was determined through dried residue on squares and cotton leaves. Furthermore, control efficacy of spinosad and spinetoram compared with the standard organophosphate malathion was determined for caged adults at two different positions within the plant canopy or treated cotton leaves after different spray intervals. Boll weevil susceptibility varied across the nine populations and tested spinosyns. The lethal concentrations (LC50s and LC90s) varied from 8.62 to 32.25 and 49.86 to 281.70 mg a.i./l for spinosad and from 2.17 to 15.36 and 8.58 to 69.36 mg a.i./l for spinetoram. The location of boll weevil within the plant canopy affected the insecticide efficacy with higher mortality when caged on upper parts rather than on lower parts of cotton plants (>85% vs <45% of control) across all three insecticides. In addition, dried residues of spinosyns resulted in adult mortality >80% until the end of the evaluation period (8 d), while the standard malathion caused only 10% at this last evaluation time. Thus, we can conclude that both spinosyns promoted prolonged adult mortality using recommended field rates compared with the standard malathion.

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.

Spermatogenesis, changes in reproductive structures, and time constraint associated with insemination in Podisus nigrispinus.

Males of the predatory stinkbug, Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae), accomplish long and multiple matings. We hypothesize that this behavior is due to time requirement for spermatozoa production and their transference to the females. Thus, this work investigated the effect of mating status of males and mating duration on spermatozoa transference to the females and the location of spermatozoa in the male reproductive tract during mating. On females, morphological alterations on female spermatheca and associated structures during a mating were investigated. Analyses of male reproductive tract showed presence of spermatozoa in the lumen of vas deferens was independent of mating status (ca. virgin, 0, 12 and 24 h after having a full mating), indicating continuous spermatogenesis which is supported by the absence of a seminal vesicle for spermatozoa storage. Female spermatheca had no changes associated with the duration of mating. However, females exhibited spermathecal elastic duct swelling by 30 min of mating duration. The success of males in filling the female spermatheca with spermatozoa depends on duration of mating. Thus, the results indicate that multiple mating is a requirement for reproductive success in the species by transference of spermatozoa and accessory substances stored in the female spermathecal duct. Likewise, the long mating is a male requirement to transfer materials in appropriate amount to the female but it is not dependent on spermatozoa alone.

Effect of some biorational insecticides on Spodoptera eridania in organic cabbage.

BACKGROUND: To reduce pest attack, several biorational products are allowed for use on organic vegetables in Brazil. This study investigated eight biorational products applied singly or in combination against Spodoptera eridania Cramer in field plots of cabbage intercropped with coriander. The treatments were applied once a week over a 5 week period, beginning 34 days after transplanting. The evaluations consisted of counting the larvae of S. eridania on the day before and 7 and 21 days after spraying. The damage to leaves and cabbage head, the commercial weight of head and the percentage of head losses were evaluated. RESULTS: Leaf injury in plots treated with Beauveria bassiana and neem oil (Dalneem) yielded scores of 1.3 and 2.5 (scale ranging from 0 to 4) respectively, in comparison with a score of 3.6 from untreated plots. Head weight losses were 6.1, 5.3 and 4.9% with an aqueous extract of neem leaves, neem oil and B. bassiana respectively, compared with 24.6% lost from untreated plots. CONCLUSION: Dalneem, B. bassiana and the extract of neem leaves at 20% exhibited the best performance for control of S. eridania.

Relative Toxicity of Two Aphicides to Hippodamia convergens (Coleoptera: Coccinellidae): Implications for Integrated Management of Sugarcane Aphid, Melanaphis sacchari (Hemiptera: Aphididae).

Flupyradifurone and sulfoxaflor present novel insecticide chemistries with particular efficacy against aphids, and the recent emergence of sugarcane aphid, Melanaphis sacchari (Zehntner), as a pest of sorghum in the United States has resulted in their widespread use. We examined their toxicity to Hippodamia convergens Guerin-Meneville, an important aphid biocontrol agent. We exposed beetles to topical applications of the field rate (FR) of these insecticides, fed them contaminated food (eggs of Ephestia kuehniella Zeller), and gave first-instar larvae 24-h exposures to leaf residues. More than half of fourth-instar larvae receiving topical applications of sulfoxaflor at FR survived, whereas flupyradifurone at 0.1× FR caused 90% mortality. Adults survived topical treatments better than larvae and without measurable mortality, except flupyradifurone at FR, which killed more than 80% of beetles. Survivors of all treatments had fertility similar to controls, whether treated as larvae or adults. Ingestion of contaminated food caused significant mortality in all treatments (15-40% for adults and 55-85% for larvae), with no significant differences between insecticides at FR. Leaf residues of sulfoxaflor at 1.0 and 2.0× FR caused approximately 60 and 80% mortality of first instars, respectively, whereas flupyradifurone at 0.1 and 1.0× FR caused > 90% mortality. Although sulfoxaflor was less toxic to H. convergens than flupyradifurone, the tested FR of flupyradifurone has now been reduced by half. We conclude that neither insecticide appears as toxic as other nicotinic acetylcholine receptor agonists, and that both materials are compatible with integrated pest management programs for M. sacchari.