Since the initial suggestion of using insect hormones or their mimics as the third-generation insecticides, great strides have been made in the discovery of three classes of such insect growth-disrupting insecticides We propose the use of the term “insect growth disruptors” instead of the mis-named term “insect growth regulators” We review the commercial insecticides that mimic the mode of action of the insect growth and development hormones, the sesquiterpenoid juvenile hormones and the steroidal 20-hydroxyecdysone and the third class of insecticides that disrupt growth and development by interfering with chitin synthesis in target insect pests In this chapter, the emphasis is on the application of these insecticides to control insect pests and development of resistance Since the non-steroidal ecdysone agonist insecticides have been extensively reviewed in other chapters of this volume and elsewhere, only salient features of these novel insecticides are discussed

An Overview of Insect Growth Disruptors; Applied Aspects

Abstract Potentially selective and integrated pest management (IPM)-compatible pesticides for the citrus leafminer Phyllocnistis citrella Stainton and its parasitoid Ageniaspis citricola Logvinovskaya were compared under nursery field conditions at Gainesville, FL. In 1996, replicated blocks of young grapefruit trees were treated with 2% petroleum oil and 1× the lowest recommended field rate (LRFR) of diflubenzuron + oil (0.4%). Untreated and treated controls (avermectin at 1× the LRFR + oil) were included. In 1997, blocks were treated with oil (3%), 1× the LRFR of azadirachtin + oil, 1× the LRFR of diflubenzuron + oil and 0.1× the LRFR of avermectin + oil. Untreated and treated controls were again included. Oil at 3%, azadirachtin at 1× the LRFR + 0.4% of oil, and diflubenzuron at 1× the LRFR + 0.4% of oil were shown to be IPM-compatible pesticides. In 1997, these blocks had fewer mines per leaf and P. citrella pupae parasitized by A. citricola per total leaves sampled compared with the untreated control but more than the treated control (α = 0.05). Avermectin at 0.1× the LRFR + 0.4% of oil was not considered an IPM-compatible pesticide because, while it reduced the number of P. citrella mines per leaf, it reduced the number of A. citricola to levels as low as the treated control. Actual P. citrella infestation levels had no detectable effect on tree growth and vigor. Pesticide applications were not justified when P. citrella infestations were <1 mine per leaf and the biological control agent A. citricola was present.

Field evaluation of integrated pest management-compatible for the citrus leafminer Phyllocnistis citrella (Lepidoptera : Gracillariidae) and its parasitoid Ageniaspis citricola (Hymenoptera : Encyrtidae)

Gas exchange and hydraulic features were measured in leaves of three different Citrus species (Citrus aurantium L., Citrus limon L., Citrus × paradisii Macfad) infested by Phyllocnistis citrella Staiton, with the aim to quantify the impact of this pest on leaf hydraulics and, ultimately, on plant fitness. Infested leaves were characterized by the presence on the leaf blade of typical snake-shaped mines and, in some cases, of a crumpled leaf blade. Light microscopy showed that leaf crumpling was induced by damage to the cuticular layer. In all three Citrus species examined: (a) the degree of infestation did not exceed 10% of the total surface area of infested plants; (b) control and infested leaves showed similar values of minimum diurnal leaf water potential, leaf hydraulic conductance and functional vein density; and (c) maximum diurnal values of stomatal conductance to water vapour, transpiration rate and photosynthetic rate (An) were similar in both control leaves and the green areas of infested leaves. A strong reduction of An was recorded only in mined leaf areas. Our data suggest that infestation with P. citrella does not cause conspicuous plant productivity reductions in young Citrus plants, at least not in the three Citrus species studied here.

Does citrus leaf miner impair hydraulics and fitness of citrus host plants

Abamectin, in aqueous solutions of dose rates 0.0625, 0.125, 0.25, 0.5, and 1 mL/L, was sprayed on different feeding stages of the tick Argas (P.) persicus. The results revealed a marked increase of immobile and dead male or female ticks following a single treatment with the above doses, particularly the higher ones, and during the 5 weeks after treatment. Abamectin seriously decreased the percentage of fed ticks as well as that of oviposition and hatching. A decrease in the amount of emitted coxal fluid was observed also following treatment. Although the amount of ingested blood increased following abamectin treatment, digestion remained similar. The study also revealed that spraying a dose of 0.5 mL/L of abamectin in fowl shelters, i.e., floor, walls, ceiling, etc., is sufficient to eradicate A. persicus population.

Efficacy of abamectin against the fowl tick, Argas (Persicargas) persicus (Oken, 1818) (Ixodoidea: Argasidae)

The developmental thresholds for Marmara gulosa Guillen & Davis (Lepidoptera: Gracillariidae) were investigated in the laboratory by using 17, 21, 25, 29, and 33° C. The lowest mortality occurred in cohorts exposed to 25 and 29° C. Other temperatures caused >10% mortality primarily in egg and Þrst and second instar sap-feeding larvae. Linear regression analysis approximated the lower developmental threshold at 12.2° C. High mortality and slow developmental rate at 33° C indicate the upper developmental threshold is near this temperature. The degree-day (DD) model indicated that a generation requires an accumulation of 322 DD for development from egg to adult emergence. Average daily temperatures in the San Joaquin Valley could produce up to seven generations of M. gulosa per year. Field studies documented two, Þve, and three overlapping gen­ erations of M. gulosa in walnuts (Juglans regia L.; Juglandaceae), pummelos (Citrus maxima (Burm.) Merr.; Rutaceae), and oranges (Citrus sinensis (L.) Osbeck; Rutaceae), for a total of seven observed peelminer generations. Degree-day units between generations averaged 375 DD for larvae infesting walnut twigs; however, availability of green wood probably affected timing of infestations. Degree-day units between larval generations averaged 322 for pummelos and 309 for oranges, conÞrming the laboratory estimation. First infestation of citrus occurred in June in pummelo fruit and August in orange fruit when fruit neared 60 mm in diameter. Fruit size and degree-day units could be used as management tools to more precisely time insecticide treatments to target the egg stage and prevent rind damage to citrus. Degree-day units also could be used to more precisely time natural enemy releases to target larval instars that are preferred for oviposition.

/pdf/temperature-thresholds-and-degree-day-model-for-marmara-4fc0xze5ha.pdf

Temperature Thresholds and Degree-Day Model for Marmara gulosa (Lepidoptera: Gracillariidae)

BACKGROUND: Egg and larval stages of citrus peelminer Marmara gulosa Guillen and Davis infesting zucchini squash Cucurbita pepo L. var ‘Revenue’ were exposed in the laboratory to a wide range of insecticide classes used in California citrus (organophosphate, carbamate, pyrethroid, neonicotinoid, insect growth regulator, fermentation products and sulfur) to determine peelminer response with and without a non-ionic adjuvant or oil.



RESULTS: All of the insecticides tested except sulfur reduced egg hatch and mine initiation. When the larval stage was treated, only buprofezin failed to reduce larval and pupal development. Cyfluthrin and spinosad, with the addition of adjuvant or oil, and abamectin combined with oil allowed no survivors at 7 days after treatment (DAT). The slower-acting insect growth regulators pyriproxyfen and diflubenzuron applied in combination with adjuvant or oil allowed no survival of peelminer 21 DAT. A field trial showed 62.6–68.5% reduction in mined citrus fruit after two applications of diflubenzuron and no significant improvement of control with the addition of cyfluthrin.



CONCLUSION: Bioassays indicate that M. gulosa is relatively susceptible to a wide range of insecticide classes in the laboratory. Lack of efficacy experienced in field trials would then be due to characteristics of the fruit or canopy that limit coverage, rather than to the effectiveness of the insecticides. Copyright © 2008 Society of Chemical Industry

Response of citrus peelminer Marmara gulosa Guillén and Davis (Lepidoptera: Gracillariidae) stages to various insecticides.

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Response of citrus peelminer Marmara gulosa Guillén and Davis (Lepidoptera: Gracillariidae) stages to various insecticides.