Paulo R. R. Barbosa

Predatory behavior and life history of Tenuisvalvae notata (Coleoptera: Coccinellidae) under variable prey availability conditions

Abstract Prey availability for predaceous insects can be uncertain in row crop ecosystems, requiring predators to employ flexible reproductive strategies to maintain their populations. In this study, we examined life history parameters and predatory behavior of the ladybeetle, Tenuisvalvae notata (Mulsant) (Coleoptera: Coccinellidae) under different conditions of prey availability. Females of T. notata exhibited a type III functional response when preying upon neonate striped mealybug [Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae)] nymphs and a type II response when preying upon third instars and female adults. On average, T. notata females consumed 157.9 neonate nymphs, 3.6 third-instar nymphs and 2.2 adult females of F. virgata per day. When subjected to a one-day period of prey deprivation, T. notata females exhibited significant reductions in reproduction and survivorship. After 150 days of exposure 47, 13 and 20% of females were alive when fed daily or subjected to repeated one- or 2-day periods of prey deprivation, respectively. Prey consumption increased as a function of prey availability. Daily oviposition was observed for females fed daily, but a sharp reduction in egg production was observed under conditions of prey scarcity. These findings show that T. notata exhibits a positive response to prey availability preying upon the striped mealybug F. virgata.

Suitability of Two Prey Species for Development, Reproduction, and Survival of Tenuisvalvae notata (Coleoptera: Coccinellidae)

ABSTRACT The coccinellid Tenuisvalvae notata (Mulsant) (Coleoptera: Coccinellidae) has been observed recently in association with the striped mealybug Ferrisia virgata Cockerell (Hemiptera: Pseudococcidae) and the false cochineal scale Dactylopius opuntiae Cockerell (Hemiptera: Dactylopiidae) in the semiarid region of Pernambuco, Brazil. The latter species are important pests of cotton and prickly pear, respectively. In this study, we tested the two scale insects as prey for T. notata. In addition, eggs of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) were tested as possible alternative prey for rearing T. notata. In this work, the survivorship, reproduction, and predation of T. notata were investigated. The coccinellid T. notata was able to complete development only on F. virgata with 83% larval and pupal viability. Females of T. notata fed F. virgata produced 7.6 eggs a day with an eclosion rate of 61.9%. No oviposition occurred while feeding on A. kuehniella eggs. The highest consumption rate of F. virgata occurred during the last larval instar. Our results support the use of T. notata as an agent for the biological control of F. virgata, a highly polyphagous pest worldwide.

Dual resistance to lambda-cyhalothrin and dicrotophos in Hippodamia convergens (Coleoptera: Coccinellidae).

Insecticide resistance is usually associated with pests, but may also evolve in natural enemies. In this study, adult beetles of three distinct North American populations of Hippodamia convergens Guérin-Méneville, and the progeny of reciprocal crosses between the resistant and most susceptible population, were treated topically with varying concentrations of lambda-cyhalothrin and dicrotophos. In addition, the LD50s of both insecticides were applied in combination to resistant individuals. The developmental and reproductive performance of each population was assessed in the absence of insecticide exposure to compare baseline fitness. California and Kansas populations were susceptible to both materials, whereas Georgia (GA) beetles exhibited a resistance ratio (RR50) of 158 to lambda-cyhalothrin and 530 to dicrotophos. Inheritance of lambda-cyhalothrin resistance was X-linked, whereas inheritance of dicrotophos resistance was autosomal. Mortality of resistant beetles treated with a mixture of LD50s of both materials was twice that of those treated with lambda-cyhalothrin alone, but not significantly different from those receiving dicrotophos alone. Life history parameters were largely similar among populations, except that Georgia beetles had higher egg fertility relative to susceptible populations. We conclude that the high levels of resistance to lambda-cyhalothrin and dicrotophos in Georgia beetles reflect heavy loads of these insecticides in local environments, most likely the large acreage under intensive cotton cultivation.

TOXICITY OF NEEM (AZADIRACHTA INDICA) SEED CAKE TO LARVAE OF THE MEDITERRANEAN FRUIT FLY, CERATITIS CAPITATA (DIPTERA: TEPHRITIDAE), AND ITS PARASITOID, DIACHASMIMORPHA LONGICAUDATA (HYMENOPTERA: BRACONIDAE)

ABSTRACT The objective of this study was to evaluate the interaction of Diachasmimorpha longicaudata (Ashmead) parasitism and the toxicity of neem seed cake (NSC) on survival of Ceratitis capitata (Wiedemann), the Mediterranean fruit fly (medfly). Groups of 1600 – 1700 third instar C. capitata larvae were each wrapped in organdy cloth (“unit of parasitism”) and exposed to approximately 500 couples of sexually mature D. longicaudata parasitoids (5-d old) for one hour. C. capitata larvae exposed or not to parasitism were transferred to plastic cups containing vermiculite with different proportions of neem seed cake (NSC): 0% NSC (control), 5% NSC, 10% NSC, 15% NSC, 20% NSC, 25% NSC, 30% NSC. Both NSC and the parasitism caused larval/pupal mortality and reduced the emergence of C. capitata flies. NSC affected parasitoid emergence negatively. The effect of parasitism coupled to NSC did not provide greater reduction in the medfly emergence than when parasitism was used alone. However, each of these 2 methods affect a different life stage of medfly, larvae and pupae, respectively, and their joint use may increase the probability of controlling medfly populations in 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 predators 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.

Extending the “Ecology of Fear” Beyond Prey: Reciprocal Nonconsumptive Effects Among Competing Aphid Predators

Abstract Nonconsumptive effects of predators on prey are well known, but similar effects among competing predators are not. Aphidophagous insect larvae are notorious for cannibalism and intraguild predation, as they compete for aggregated but ephemeral prey. We tested for indirect effects of competitors on the development of Coleomegilla maculata DeGeer and Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae), and a green lacewing, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae), with all larvae reared on eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). Control larvae were reared singly, while treatment larvae were reared pairwise, with either a conspecific or heterospecific, in partitioned Petri dishes that allowed the passage of chemical cues. Larvae of C. maculata, a dietary generalist, appeared stressed by the presence of competing larvae, whether con- or heterospecific, and suffered fitness costs (longer pupation times, lower male adult mass). In contrast, H. convergens and C. carnea, both aphid specialists, responded to competing larvae with accelerated development, and without any apparent costs in terms of adult size or reproductive performance. Adult C. carnea in some treatments were heavier than solitary controls, suggesting a higher consumption rate by the induced phenotype, and those exposed to H. convergens began oviposition earlier. Thus, the phenotypes induced in the specialized aphid predators were adaptive for development in aphid colonies, whereas that induced in the generalist was not. These results indicate that nonconsumptive effects are not simply a vertical force acting on prey, but can also impact conspecific and heterospecific competitors on the same trophic level.

High Concentrations of Chlorantraniliprole Reduce Its Compatibility with a Key Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

Abstract Diamides are a novel insecticide group that act by disrupting insect muscle contraction. Recommended field rates (FRs) vary greatly among target pests and cropping systems, leading to variable risks for non-target organisms. We evaluated the toxicity of chlorantraniliprole to the predator Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae) by exposure to residues, topical application, and consumption of contaminated food.We also estimated lethal concentrations (LCs) of chlorantraniliprole in two target pests, cotton leafworm, Alabama argillacea (Hübner) (Lepidoptera: Erebidae), and tobacco budworm, Chloridea virescens (F.) (Lepidoptera: Noctuidae), by exposing larvae to treated cotton, Gossypium hirsutum L., leaves and assessed residual activity at various intervals after application to cotton plants. Exposure to dried residues and ingestion of treated moth eggs resulted in similar toxicity to H. convergens, whereas topical application was a less toxic route of exposure. Regardless of exposure route, the LC50s and LC90s obtained for H. convergens were higher than those calculated for the pests. Residues at the upper limit of the LC90 for C. virescens remained effective against this pest for up to 16 d, while exhibiting minor impacts on H. convergens. In contrast, the FR concentration of C. virescens caused significant mortality in H. convergens. The results suggest that the current FR for C. virescens is too high to be safe for H. convergens, and given the LCs observed for this pest in the present study, trials to explore the potential efficacy of lower FRs are justified. Depending on the concentration and route of exposure, this insecticide has the potential to be compatible with H. convergens.