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.

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.

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.

[Behavioral response and adaptive cost in resistant and susceptible Plutella xylostella to Chlorantraniliprole]

Diamides have been used worldwide to manage the diamondback moth (DBM), Plutella xylostella L. (Lepidoptera: Plutellidae), however some strains showed resistance to these molecules. Also, pheromone traps could be used to manage this pest, hence reducing the use of insecticides in the field. Resistant DBM strains may have biological disadvantages in comparison to susceptible strains in areas without sprays, including reduction in fitness or behavioral changes. Therefore, the aim of this study was to investigate whether DBM strains resistant to chlorantraniliprole showed adaptive costs that could alter male attraction to the sex pheromone, in comparison to susceptible strains in the laboratory and semi-field conditions. First, the LC1, LC10, LC25, and LC50 of DBM to chlorantraniliprole were established, which were 0.003, 0.005, 0.007, and 0.011 mg a.i. liter-1, and 5.88, 24.80, 57.22, and 144.87 mg a.i. liter-1 for the susceptible and resistant strains, respectively. Development and reproduction of DBM strains subjected to those concentrations were compared. Later, male response to the sex pheromone was investigated in a Y-tube in the laboratory and in a greenhouse to pheromone traps. Resistant DBM strain showed an adaptive cost in comparison to the susceptible strain that can result in a delay in population growth in the field when selection pressure is absent. Conversely, resistant males have no olfactory response alteration in comparison to susceptible males, consistently at 3 (P = 0.6848) and 7 days (P = 0.9140) after release, suggesting that pheromone traps continue to be a viable alternative to manage DBM in an IPM system.

Mating system, age, and reproductive performance in Tenuisvalvae notata, a long-lived ladybird beetle

The long-lived polygynandrous ladybird beetle Tenuisvalvae notata (Mulsant) found in Brazil was evaluated in the laboratory for the effects of multiple mating and aging on its reproductive performance. This species is native to South America and is an important predator of mealybugs. Specifically studied were partner choice, female reproductive success, adult longevity, male virility, and offspring development. Young (5-10 days old) and older virgin females (95-100 days old) were subjected to either a single mate or multiple mating with the same or different males of various mating status (virgin or previously mated once, twice, and thrice). Results revealed a preference in both genders to mate with previously known partners. Additionally, younger females had higher fecundity and greater longevity when mated only once in comparison to those mated multiple times. Fecundity, fertility, and offspring development were similar across the treatments regardless of the number of mating or male mating history. Fecundity and fertility decreased throughout the oviposition period regardless of mating treatment.

Sexual behavior in ladybird beetles: Sex with lights on and a twist for Tenuisvalvae notata (Coleoptera: Coccinellidae)

The ladybird beetle Tenuisvalvae notata is an important predator of mealybugs (Pseudococcidae); however, little is known about its reproductive behavior. Thus, in order to improve methods of its rearing, this work studied several aspects regarding the sexual behavior of T. notata. We investigated its sexual activity period, age of the first copulation, mating frequency over 24h, and oviposition during a 30-day interval. Sexual activity of T. notata is diurnal with peak between 1100h and 1500h. Males need about 4days to first copulation, whereas females can mate at emergence. Adults mate 1.17±0.16-1.91±0.29 times over 24h with an average duration of 84±19.70s (ranging from 27 to 130s) per mating. Females produced an average of 54±6.42-64±7.08 offspring over 30days. An ethogram was also constructed to depict the events that occurred during copulation as follows: the male mounts the female, inserts the aedeagus, touches its back with palps and mandibles, and attempts to hold it simultaneously. The female can walk while copulating or remains motionless; the male retracts its aedeagus and twists on the females' back before moving apart.

Performance of the Striped Mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae) under Variable Conditions of Temperature and Mating

Mealybugs have strong associations with their host plants due to their limitations for dispersal. Thus, environmental conditions and host quality may impact the biological traits of mealybugs. To the best of our knowledge, we are the first to report on the biology of a Brazilian population of the striped mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae), which has recently been reported to infest cotton in Brazil. We evaluated the development and reproductive performance of F. virgata reared under different temperatures (25, 27, and 28°C) and mating status. The type of reproduction was also studied with insects reared on a factitious host and on cotton plants. Shorter development was obtained at 28°C as follows: nymphs generating males and females exhibited three and four instars with a mean duration of 19.1 and 20.5 days, respectively. The nymphal viability ranged from 77 to 96%, and was highest at 25°C. Females reared at 28°C initiated reproduction earlier (16.4 days), but the reproductive period was similar in all temperatures (∼16.2 days). Females produced more nymphs at 27 and 28°C (440 and 292 neonates) than at 25°C (277 neonates), although they lived longer at 25°C (63 days). Ferrisia virgata females exhibited only sexual reproduction. Thus, only mated females produced offspring, whereas unmated females died without reproducing. Therefore, the studied population of F. virgata exhibited only sexual reproduction with high survival and offspring production when fed cotton. Furthermore, pumpkin is a feasible host for mass rearing this mealybug species in the laboratory, an opening avenue for future studies.

Survival and behavioural responses of the predatory ladybird beetle, Eriopis connexa populations susceptible and resistant to a pyrethroid insecticide

The ladybird beetle, Eriopis connexa (Germar) (Coleoptera: Coccinellidae), is one of the commonest predators of aphids (Hemiptera: Aphididae) in the cotton agroecosystem and in many other row and fruit crops in Brazil, and has been introduced into other countries such as the USA for purposes of aphid control. In addition, the boll weevil, Anthonomus grandis Boheman (Coleoptera: Curculionidae) is the most serious cotton pest where it occurs, including Brazil. Controlling boll weevils and other pests such as cotton defoliators still tends to involve the intense application of insecticides to secure cotton production. The pyrethroid insecticide lambda-cyhalothrin (LCT) is commonly used, but this compound is not effective against aphids; hence, a desirable strategy would be to maintain E. connexa populations in cotton fields where LCT is applied. Using populations of E. connexa resistant (Res) and susceptible (Sus) to LCT, we compared behavioural responses on treated cotton plants and under confinement on partially and fully treated surfaces, and assessed the insects' survival on treated plants compared with that of the boll weevil. The E. connexa resistant population caged on treated plants with 15 and 75 g a.i. ha-1 exhibited ≫82% survival for both insecticide concentrations compared with ≪3% and ≪17% survival for susceptible E. connexa populations and boll weevils, respectively. The response of E. connexa Res and Sus populations when released, either on the soil or on the plant canopy, indicated avoidance towards treated plants, as measured by elapsed time to assess the plant. When compared with susceptible individuals, resistant ones took longer time to suffer insecticide knockdown, had a higher recovery rate after suffering knockdown, and spent more time in the plant canopy. Based on behavioural parameters evaluated in treated arenas, no ladybird beetles exhibited repellency. However, irritability was evident, with the susceptible population exhibiting greater irritability compared with the resistant population and a subgroup comprising resistant individuals that had recovered from knockdown. The outcomes for the E. connexa Res population indicate a promising strategy for its maintenance when using the insecticide LCT in integrated pest management schemes to control boll weevil or other non-target pest of ladybird beetles in cotton fields.

New records of natural enemies of Plutella xylostella (L.) (Lepidoptera: Plutellidae) in Pernambuco, Brazil

We report the occurrence of natural enemies of Plutella xylostela (L.) in organically farmed kale in Pernambuco, Brazil. Seven natural enemies were observed parasitizing or preying on larvae and pupae of P. xylostella--three parasitoids: Cotesia plutellae Kurdjumov (Hym.: Braconidae), Conura pseudofulvovariegata (Becker) (Hym.: Chalcididae) and Tetrastichus howardi (Olliff) (Hym.: Eulophidae), and four predators: Cheiracanthium inclusum (Hentz) (Araneae: Miturgidae), Pheidole sp.Westwood (Hym.: Formicidae), nymphs and adults of Podisus nigrispinus (Dallas) (Hem.: Pentatomidae), and one unidentified species of solitary wasp. Beyond recording these natural enemies, data on predation of P. xylostella larvae in the field and laboratory by C. inclusum are presented.

[Effect of age, photoperiod and host availability on the parasitism behavior of Oomyzus sokolowskii Kurdjumov (Hymenoptera: Eulophidae)]

The high reproduction rate, potential to cause damage, wide geographic distribution and resistance to insecticides of Plutella xylostella (L.) makes difficult its efficient control. However, larvae and pupae of this pest are naturally parasitized by Oomyzus sokolowskii (Kurdjumov), providing opportunities to improve the natural parasitism. This study investigated the effects of the age of adult parasitoids, host availability and time of exposure on O. sokolowskii parasitism behavior. The number of larvae encounters by parasitoid females and the parasitism rate increased with parasitoid age up to 96h. The parasitization was higher when wasps received a constant number of hosts daily in comparison with a random number (13.3 versus 8.9 larvae parasitized). Female parasitization activity was maintained up to the age of 20 days in both treatments and exhibited similar longevity (constant host = 33.5 d; and random host = 34.7 d). The progeny produced per female and the number of parasitoids emerged per host significantly decreased as wasps aged. There was no significant effect of the light regime (12h darkness or 12h light exposure) on the parasitization, although parasitoid was more active after 3h of light exposure. Therefore, further studies on field application of O. sokolowskii should consider the release of 48 h- to 72 h-old parasitoids at dawn as a way to increase the success of host parasitization.

Relative effects of the insecticide thiamethoxam on the predator Podisus nigrispinus and the tobacco whitefly Bemisia tabaci in nectaried and nectariless cotton

The predaceous stinkbug Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) feeds on plants as well as on arthropod prey. The question arises whether feeding on plants might expose the predator to systemic insecticide via ingestion of the active ingredient or its metabolites through plant sap of treated plants. This interaction was investigated with nectaried and nectariless cotton plants cropped in pots and treated with the systemic insecticide thiamethoxam at 0.5, 1.0 and 2.0 mg per plant as a root drench. Development of P. nigrispinus fed on prey and on treated nectaried and nectariless cotton plants and confined at 15, 30 and 45 days after insecticide application, and adult reproduction from nymphs caged 30 days after treatment were determined. Podisus nigrispinus life history traits were unaffected by the type of cotton plant, nectaried or nectariless, but were significantly affected by insecticide dose and time after application. Developmental time was extended and fresh adult body weight was reduced by feeding on prey and treated plants. Nymphs caged on treated plants with the highest thiamethoxam concentration at 15 days after application produced only 13.2% of adults. Females emerged from nymphs caged on both plants and at all thiamethoxam concentrations at day 30 after application presented similar reproductive characteristics, except for age of first oviposition, which was delayed on plants treated with the highest thiamethoxam concentration. Thiamethoxam at 0.5 mg per plant restrained tobacco whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) colonization only during the first 15 days after application to either cotton plant, and similar immature densities were sampled at day 35 after application on treated and untreated plants. However, plants treated with 1.0 and 2.0 mg per plant as a drench and cropped in pots were protected from tobacco whitefly for up to 45 days after exposure to a whitefly colony.