Side effects of a mixture of essential oils on Psyttalia concolor.

Integrated Pest Management programs do not always prioritize natural enemies when selecting control methods; too often these important pest reducing agents are negatively affected by the action of other methods in agroecosystems. The aim of this research was to evaluate side effects of a bioinsecticide, developed from the mixture of cedar (Cedrus atlantica), eucalyptus (Corymbia citriodora) and lemon grass (Cymbopogon citratus) essential oils (EOs), in a ratio of 1:1:1, on Psyttalia concolor (Szèpligeti) (Hymenoptera: Braconidae) which is a parasitoid of some pests of the Tephritidae family, as Ceratitis capitata. The LD50 of the EOs mixture for C. capitata females was 3.09 µl/g, whereas the LD50 for P. concolor females was 20.45 µl/g which suggests the natural enemy is more tolerant to the EOs mixture. P. concolor parasitized L3 larvae of C. capitata through a voile treated with the mixture of EOs at 1.8% without causing any deleterious effects neither on the percentage of attacked hosts nor on the emergence rate, whereas at the highest concentration tested, 4.8%, decreased both parameters during the 2 first days after treatment. Semi-field assays showed that mixture of EOs was harmless to P. concolor when released 4 h after treatment whereas killed 55 ± 3.9% males and 37.5 ± 1.6% females of C. capitata. The mixture of EOs used jointly with lambda-cyhalothrin or kaolin, both compounds applied against C. capitata in conventional and organic farming, respectively, did not increase the toxicity and/or persistence against the pest.

Composition and Toxicity of a Mixture of Essential Oils Against Mediterranean Fruit Fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae).

A natural insecticide developed from the mixture of the essential oils (EOs) of Cymbopogon citratus (DC.) Stapf (Poaceae), Cedrus atlantica (Endl.) Manetti ex Carriére (Pinaceae), and Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson (Myrtaceae) was studied. The mixture of oils caused high mortality (LD50 = 0.018 µl/insect) to the Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), a globally important pest, after topical application on adults. Based on the chemical characterization of biopesticide using gas chromatography-mass spectrometry (GC-MS) analysis, many of the constituents had known insecticidal properties (the monoterpenes α-citronellal and E-citral and the sesquiterpernes α-himachalene and ß-himachalene, all at concentrations above 15%). Phytotoxicity tests on orange trees demonstrated that this natural product was harmless when the mixture was applied diluted in water with a surfactant. The mixture of EOs was also harmless (1, IOBC category) to the biological control agent responsible for reducing populations of tephritids, the parasitoid Psyttalia concolor (Hymenoptera: Braconidae), following exposure to treated orange trees in a semifield assay within a greenhouse, but killed 46.2% of C. capitata (Szépligeti) adults after 72 h. Our results suggest that mixture of EOs has potential for use as an adulticide against medfly, although the production price was exceedingly high compared with that of commercial synthetic insecticides. Therefore, we discuss the advantages and disadvantages related to the potential use of this natural insecticide.

Impact of Feeding on Contaminated Prey on the Life Parameters of Nesidiocoris Tenuis (Hemiptera: Miridae) Adults.

Insecticide selectivity to natural enemies is an important concern in integrated pest management programs. Although there is a wide range of information concerning pesticide lethal and sublethal effects on contaminated surfaces, little is known when the route of exposure occurs at a trophic level. This study evaluates this route of pesticide intake on the omnivorous predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) for the first time. Under laboratory conditions, prey treated with six insecticides (flubendiamide, spirotetramat, deltamethrin, flonicamid, metaflumizone, and sulfoxaflor) were offered to N. tenuis adults for 3 days. Mortality (24, 48, and 72 h after treatment), offspring production (third until eighth day) and longevity were documented. Metaflumizone and sulfoxaflor were classified as moderately harmful products because although the percentage of mortality was only 28 and 36%, respectively, both products caused a severe decrease in offspring production and longevity. Flonicamid and flubendiamide were classified as slightly harmful products; although they did not have a lethal effect, sublethal impact was important on the parameters studied. Spirotetramat and deltamethrin were insecticides categorized as harmless. This information could be useful for selecting the most appropriate insecticides to control pests in tomato crops in which N. tenuis is a relevant biological control agent.

Toxicity of Insecticides on Various Life Stages of Two Tortricid Pests of Cranberries and on a Non-Target Predator.

Laboratory and extended laboratory bioassays were conducted to determine the residual toxicities of various insecticides against two key pests of cranberries, Sparganothis sulfureana and Choristoneura parallela (Lepidoptera: Tortricidae), and their non-target effects on the predatory Orius insidiosus (Hemiptera: Anthocoridae). The effects of nine insecticides with different modes of action on S. sulfureana and Ch. parallela eggs, larvae, and adults were tested in the laboratory, while the efficacy of a post-bloom application on larval mortality and mass of these pests and on adult O. insidiosus was evaluated in extended laboratory experiments. The organophosphate chlorpyrifos and the spinosyn spinetoram provided long-lasting (seven-day) control against all stages of both pests. The growth regulator methoxyfenozide and the diamides chlorantraniliprole and cyantraniliprole had strong (1-7 days) larvicidal, particularly on young larvae, and growth inhibitory activity, but only the diamides were adulticidal. Among neonicotinoids, acetamiprid had stronger ovicidal and adulticidal activity than thiamethoxam, showing within-insecticide class differences in toxicities; however, both were weak on larvae. Lethality of novaluron and indoxacarb was inconsistent, varying depending on species and stage. Chlorpyrifos was most toxic to O. insidiosus. These results show species- and stage-specific toxicities, and greater compatibility with biological control, of the newer reduced-risk classes of insecticides than older chemistries.

Residual Acute Toxicity of Some Modern Insecticides Toward Two Mirid Predators of Tomato Pests.

The successful integration of chemical and biological control strategies for crop pests depends on a thorough evaluation of the effects of pesticides on the natural enemies of pests. A case-by-case review is difficult to achieve because of the many combinations of pests, natural enemies, and crops that need to be tested. Within this framework, we tested and compared seven insecticides representative of four different modes of action (MoAs) groups on closely related predators (Miridae): flubendiamide, spirotetramat, metaflumizone, and sulfoxaflor on Nesidiocoris tenuis Reuter and flubendiamide, spiromesifen, indoxacarb, and imidacloprid on Macrolophus basicornis (Stal). We follow the standardized methodology of the International Organization for Biological Control, a sequential testing exposure scheme. The lethal effect of each insecticide was evaluated in adults after three days of contact with treated surfaces in the laboratory, extended laboratory, and semifield tests (inert substrate, tomato leaves, and tomato plant as the treated surface, respectively). Flubendiamide, spiromesifen, and spirotetramat were classified as harmless (class 1), metaflumizone was slightly harmful (class 2) but persistent, indoxacarb was harmless (class 1), and sulfoxaflor and imidacloprid were toxic (class 4) and exhibited a long residual activity. Our results suggest similarities in the acute toxicities of insecticides from the same MoA group on related species of natural enemies.