F. Budia

Compatibility of spinosad, tebufenozide and azadirachtin with eggs and pupae of the predator Chrysoperla carnea (Stephens) under laboratory conditions.

Under laboratory conditions, the toxicity of three novel insecticides, spinosad (Tracer ® ), tebufenozide (Mimic ® ) and azadirachtin (Align ® ), was tested against eggs and pupae of the predator Chrysoperla carnea (Stephens). In a first series of assays, eggs were dipped in an aqueous concentration and no ovicidal activity was scored for the three insecticides. In the second, when females were ovipositing on treated substrate for 24 h, fecundity and hatching percentages were similar as compared to controls and the offspring developed normally until the adult stage. However, spinosad, at the highest concentrations tested, caused a slight, significant reduction in the adult life span and fecundity. In a third series of experiments, pupae developed into normal adults after topical treatment for the three insecticides. Herewith, a pharmacokinetic study indicated low accumulation in the body after pupal cuticle penetration when administrating 14 C-labelled insecticide. Fourthly, pupation of last-instar larvae in treated substrate was normal for spinosad and tebufenozide. Only azadirachtin caused a slight reduction in the number of pupae and adults; however, fecundity and fertility of surviving adults was normal. In conclusion, the current results indicate that the three insecticides are not toxic to eggs and pupae of C. carnea .

Laboratory effects of ingestion of azadirachtin by two pests (Ceratitis capitata and Spodoptera exigua) and three natural enemies (Chrysoperla carnea, Opius concolor and Podisus maculiventris).

The effects of azadirachtin on two pests: neonate larvae and newly emerged adults of Ceratitis capitata (Wiedemann) and last instar larvae of Spodoptera exigua (Hubner); and three natural enemies: newly emerged adults of Opius concolor Szepligeti, second instar larvae of Chrysoperla carnea (Stephens), and fifth instar nymphs of Podisus maculiventris (Say) were studied in laboratory. Adult insects were exposed to a non-oil formulation of azadirachtin (Align, emulsifiable concentrate, 3.2% azadirachtin, Sipcam Inagra, Spain) via their drinking water and immature instars were reared in the presence of the insecticide-treated diet. The natural enemies were exposed to at least the maximum field recommended concentration of the insecticide (0.15% v/v). Azadirachtin was highly toxic to neonate larvae of C. capitata and prevented adult emergence at a concentration of 1 mg a.i. l -1 . When adults were fed the insecticide at the maximum recommended concentration, their survival was not affected but egg laying was totally inhibited. Last instar S. exigua larvae were also very susceptible (LC 50 = 7.7 mg a.i. l -1 ) and at a concentration of 10 mg a.i. l -1 fecundity of surviving adults, and egg fertility, were reduced by 72 and 85%, respectively. Effects on O. concolor were large, and significant reductions in longevity, percentage of attacked hosts, and progeny size per female, were recorded. The predator P. maculiventris was much less sensitive to azadirachtin, but slight reductions in survival of emerged adults and of reproductive parameters occurred. The insecticide had no significant effect on C. carnea larvae fed with treated Sitotroga cerealella (Oliver) eggs, probably because of its inability to penetrate inside the egg.

Fungal ribotoxins: Natural protein-based weapons against insects.

Ribotoxins are fungal extracellular ribonucleases highly toxic due to their ability to enter host cells and their effective ribonucleolytic activity against the ribosome. The natural role of these proteins in the producing fungi is still unsolved. Nevertheless, recent studies showing the insecticidal properties of two ribotoxins from different origin support their involvement in defense mechanisms. Thus, it seems that not just the entomopathogen Hirsutella thompsonii expresses the ribotoxin hirsutellin A as a virulence factor but also Aspergillus, the main ribotoxin producer, does so. In this review we focus on this little known aspect of this family of proteins, their toxicity against insects, from the point of view of its biological relevance and its potential biotechnological applications.

Compatibility of Endoparasitoid Hyposoter didymator (Hymenoptera: Ichneumonidae) Protected Stages with Five Selected Insecticides

Abstract Hyposoter didymator (Thunberg) (Hymenoptera: Ichneumonidae) is a koinobiont endoparasitoid that emerges from the parasitization of economically important noctuid pests. H. didymator also is considered one of the most important native biocontrol agents of noctuids in Spain. Side effects of five insecticides with very different modes of action (fipronil, imidacloprid, natural pyrethrins + piperonyl butoxide, pymetrozine, and triflumuron) at the maximum field recommended rate in Spain were evaluated on H. didymator parasitizing Spodoptera littoralis (Boisduval) larvae and pupae of the endoparasitoid. Parasitized larvae were topically treated or ingested treated artificial diet. Parasitoid cocoons were topically treated. Host mortality when parasitized larvae were treated, as well as further development of the parasitoid surviving (e.g., percentage of cocoons spun, adult emergence, hosts attacked, and numbered progeny) were determined. Toxicity after treatment of parasitized larvae differed depending on the mode of exposure and insecticide. Fipronil was always highly toxic; imidacloprid killed all host insects by ingestion, but it was less toxic to both host and parasitoids, when administered topically; natural pyrethrins + piperonyl butoxide and triflumuron showed differing degrees of toxicity, and pymetrozine was harmless. Parasitoid cocoons provided effective protection against all the insecticides, except fipronil. RESUMEN Hyposoter didymator (Thunberg) (Hymenoptera: Ichneumonidae) es un endoparasitoide koinobionte que parasita larvas de noctuidos plaga de importancia económica, ocupando una posición destacada entre nuestros agentes nativos de control. Para poder utilizar conjuntamente el enemigo natural y los insecticidas, se evaluaron los efectos secundarios de cinco insecticidas con diferente modo de acción (fipronil, imidacloprid, piretrinas naturales+piperonil butóxido, pimetrocina y triflumuron) a la concentración máxima de campo recomendada en España para cada uno de los insecticidas en larvas de Spodoptera littoralis Boisduval parasitadas por H. didymator, y pupas del parasitoide. Las larvas parasitadas fueron tratadas tópicamente o mediante la ingestión de dieta artificial tratada, mientras que a las pupas del parasitoide se les aplicó un tratamiento tópico. Se evaluaron la mortalidad del huésped tratado tras la parasitación y también parámetros relativos al posterior desarrollo de los parasitoides supervivientes, tales como el porcentaje de capullos formados, la emergencia de adultos, la capacidad de atacar nuevos huéspedes y el porcentaje de descendientes. La toxicidad tras los ensayos con larvas parasitadas fue dependiente del modo de tratamiento y del insecticida. El fipronil fue siempre muy tóxico; el imidacloprid eliminó todos los huéspedes parasitados tratados via ingestión, pero fue menos tóxico para ambos, huésped y parasitoide, tras la aplicación tópica; las piretrinas naturales+piperonil butóxido y el triflumuron mostraron diferente grado de toxicidad y solo la pimetrocina fue inocua. Los capullos del parasitoide constituyeron una excelente protección contra todos los insecticidas, con la excepción del fipronil.

Lethal and Sublethal Toxicity of Fipronil and Imidacloprid on Psyttalia concolor (Hymenoptera: Braconidae)

ABSTRACT Psyttalia concolor (Szèpligeti) (Hymenoptera: Braconidae) is a koinobiont endoparasitoid of several species of tephritid (Diptera) larvae, such as Bactrocera oleae (Gmelin) and Ceratitis capitata (Wiedemann). Here, we report on the effects of imidacloprid and fipronil on P. concolor females, when different routes of exposure were evaluated: residual contact (cover and bait sprays) and via treatment of host species. Moreover, the persistence of the bait formulated compound also was studied. For each experiment, lethal (mortality) and sublethal effects (parasitization rate or longevity) were studied. Fipronil produced 100% mortality irrespective of exposure route, and it was very persistent, because 34-d-old residues still produced this high mortality rate, being as toxic or even more toxic than the reference product dimethoate. Toxicity of imidacloprid depends on the mode of exposure, although always remained less toxic than dimethoate. Imidacloprid caused high mortality or sublethal effect to the progeny in cover sprays and when applied via treated host, being harmless in bait sprays application. In conclusion, our results suggest that fipronil should not be used in the field when the parasitoid is present. On the contrary, although imidacloprid is physiologically active against females of P. concolor, ecological selectivity may result through the use of bait treatment.

Toxicity of Fipronil to the Predatory Lacewing Chrysoperla carnea (Neuroptera: Chrysopidae)

All the developmental stages of Chrysoperla carnea (Stephens) were treated with fipronil using different modes of exposure under laboratory conditions. Eggs were dipped in an aqueous range of concentrations and no effects were recorded, except at the highest concentration. Pupae treated topically on the silk cocoon moulted to healthy adults, without any deleterious effects on their reproduction. In contrast, larvae and adults were killed by the compound, irrespective of the mode of treatment, even at rates below the maximum field recommended rate in Spain (30 g c.p./ha). Sublethal concentrations of fipronil did not affect the fecundity or fertility of survivors. We conclude that fipronil is very toxic under laboratory conditions to this predatory lacewing.

Non-target effects of kaolin and coppers applied on olive trees for the predatory lacewing Chrysoperla carnea

Kaolin clays and copper salts might be considered as alternative chemical control products for controlling olive pests in the contexts of both organic farming and integrated pest management programmes. Chrysoperla carnea (Stephens) (Neur. Chrysopidae) represents one of the most significant generalist predators of olive grove pests. In this study, we evaluated the side effects of these compounds on the predatory lacewing. First, kaolin and two copper salts (copper oxychloride and Bordeaux mixture) were tested on C. carnea eggs to determine their effects on egg viability and larval hatching suppression by topical application. Second, L3 larvae were exposed to the pesticide residues on treated olive tree leaves. Third, a series of three residual tests in adults were sequentially performed as follows: residues on glass surfaces, on olive tree leaves and on small olive trees. Finally, kaolin- and water-treated eggs of Ephestia kuehniella Zeller (Lep. Pyralidae) were offered to L3 larvae in both dual- and no-choice tests. C. carnea egg hatching was reduced by the kaolin treatment compared to the control treatment. Residual treatments were harmless to larvae and adults, without any deleterious effects on reproduction. L3 larvae consistently preferred to feed on water-treated E. kuehniella eggs compared to kaolin-treated eggs. The larvae from the no-choice test that had fed ad libitum until pupation on kaolin-treated E. kuehniella eggs, pupated and emerged as healthy adults in reduced proportions compared with those that fed on water-treated eggs. In conclusion, our data suggest that both kaolin and copper products appeared to be largely harmless or only slightly harmful to the predator.

Effect of emamectin benzoate under semi-field and field conditions on key predatory biological control agents used in vegetable greenhouses

Abstract Predatory arthropods are commonly used as biological control agents (BCAs). They are released in commercial vegetable greenhouses as primary elements of integrated pest management programmes for some of the most devastating pests on pepper and tomato in southeastern Spain. Emamectin benzoate, a macro-cyclic lactone insecticide derived from the avermectin family of natural products, is being developed for the control of Lepidoptera pests on a variety of crops in Europe including vegetables. The compatibility of emamectin benzoate with the predatory BCAs Amblyseius swirskii Athias-Henriot and Orius laevigatus (Fieber) in field trials (direct spray and aged residues) and Macrolophus pygmaeus (Rambur) and Chrysoperla carnea (Stephens) in semi-field studies was studied. Emamectin benzoate at the highest recommended concentration (14.25 mg L−1) was compatible with A. swirskii and O. laevigatus when applied 3 days before the introduction of the arthropods, but it was toxic when directly sprayed. M. pygmaeus and C. carnea adults survived to direct spray applications.

Lethal and Sublethal Effects of Methoxyfenozide on the Development, Survival and Reproduction of the Fall Armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae)

The lethal and sublethal effects of the ecdysone agonist methoxyfenozide on the fall armyworm, Spodoptera frugiperda (J. E. Smith), were investigated by feeding a methoxyfenozide-treated diet to fifth instars until pupation in doses corresponding to the LC10 and LC25 for the compound. Larval mortality reached 8% and 26% in the low and high concentration groups, respectively, on the seventh day of the experiment. A progressive larval mortality of 12% for the LC10 and 60% for the LC25 was observed before pupation. Treated larvae exhibited lower pupal weights, higher pupal mortality, presence of deformed pupae, and more deformed adults than untreated larvae. The incorporation of methoxyfenozide into the diet had a significant effect on the timing of larval development. The development period for males and females was about seven days longer than the controls for both concentrations tested. In contrast, the compound affected neither pupae nor adult longevity. Finally, S. frugiperda adults that resulted from fifth instars treated with methoxyfenozide were not affected in their mean cumulative number of eggs laid per female (fecundity), nor percentages of eggs hatched (fertility), or the sex ratio. Our results suggest that the combination of lethal and sublethal effects of methoxyfenozide may have important implications for the population dynamics of the fall armyworm.

Differential larval age susceptibility of the medfly, Ceratitis capitata Wied. (Dipt., Tephritidae) to cyromazine

Ceratitis capitata Wied. larvae reared on an artificial diet supplemented with a range of concentrations of the IGI cyromazine, suffered severe developmental disruption depending on larval age. 100% mortality was recorded when young larvae (1‐ and 2‐day‐old) were exposed to a 10 mg/kg cyromazine‐treated diet, whereas later‐stage larvae (6‐ to 9‐day old larvae; L6 to L9) were able to pupate with 25 to 100 mg/kg concentrations. Moreover the adult emergence rate was severely affected in these cases (less than 7 % for L6 to L8, and just 36 % for L9). Larval mobility (measured as popped pupae) was drastically reduced except for L9. A significant larval growth inhibition at 3 days was observed in L2, L4 and L6, in a dependent dose manner: the median inhibitory concentration being near 1 mg/kg for young larvae, but reaching 100 mg/kg for the older ones.