Efficacy of systemic insecticides on the gall wasp Quadrastichus erythrinae in wiliwili trees (Erythrina spp.).

BACKGROUND: Erythrina gall wasp (EGW), Quadrastichus erythrinae Kim, was first found on Oahu Island, Hawaii, in April 2005. Its rapid spread and infestation in wiliwili trees (Erythrina spp.) have brought an urgent need to suppress its population. Little is known about the control of EGW in wiliwili trees. RESULTS: Among the systemic insecticides abamectin, dinotefuran and imidacloprid, applied via trunk injections or soil drenches, injections of imidacloprid showed better control of EGW in wiliwili trees. All the imidacloprid injection treatments had varying levels of effectiveness against EGW, but not the soil drench. The levels of imidacloprid were higher in lower canopies than those in the other parts within a tree. Imidacloprid remained detectable 1 year after treatment. The trees injected with the products IMA-jet and Merit 200 SL via Arborjet had lower infestation severity ratings for the entire growth season and carried more imidacloprid than those with Imicide via Mauget or Pointer via Wedgle injections. CONCLUSION: The results indicate that, among the three insecticides tested, imidacloprid is most effective against EGW in the trees. Concentrations of imidacloprid in the leaves need to be 4 mg kg(-1) or higher for good EGW control.

Application of an enzyme-linked immunosorbent assay for the analysis of imidacloprid in wiliwili tree, Erythrina sandwicensis O. Deg, for control of the wasp Quadrastichus erythrinae.

A monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) for the neonicotinoid insecticide imidacloprid was evaluated for its reproducibility, accuracy, and comparability to results from a conventional high-performance liquid chromatography (HPLC) for the analysis of imidacloprid in the endemic wiliwili tree (Erythrina sandwicensis O. Deg) found in dryland forests and landscapes in Hawaii. Imidacloprid was applied to these wiliwili trees in an attempt to control the newly introduced erythrina gall wasp, Quadrastichus erythrinae Kim. Leaf samples were freeze-dried and extracted with acidic aqueous methanol followed by methylene chloride partitioning. After solvent removal, the extract residue was reconstituted in 1 mL of water/methanol (1:1, v/v) for ELISA; no significant matrix interference was observed at 10-fold or more dilution. The average recoveries of imidacloprid from fortified samples ranged from 78% to 100% by ELISA. The correlation between the ELISA and HPLC results was excellent (r2 = 0.98). Imidacloprid was detected with the ELISA in all treated samples and its level varied in the samples among different treatments and in those from different parts of the trees. The infestation severity rating of leaf samples was inversely related to the concentration of imidacloprid. It is clear that imidacloprid effectively controls the wasps. The ELISA is a suitable method for quantitative and reliable determination of imidacloprid in wiliwili trees and the application provides information to understand how to control the wasps.

Hot water immersion for surface disinfestation of Maconellicoccus hirsutus (Homoptera: Pseudococcidae).

Mealybug Maconellicoccus hirsutus (Green) adults, nymphs, crawlers, and eggs were tested for their susceptibility to hot water immersion at 47, 48, and 49 degrees C. Eggs inside ovisacs were found most tolerant with prolonged survival compared with other stages at all temperatures. Ovisacs required an average of 1.38, 1.46, and 1.62 times longer treatment duration than adults, nymphs, and crawlers, respectively, for 99.9% predicted mortality at 47, 48, and 49 degrees C. Lethal time estimations were calculated from inverse predictions of regressions derived from logit-transformed data as well as those created using a kinetic model. LT 99.9 estimations were 47.0, 21.2, and 11.9 min at 47, 48, and 49 degrees C, respectively, by using regressions with logit transformations. The kinetic model predictions were 43.9, 19.6, and 11.1 min at 47, 48, and 49 degrees C, respectively. During the study no emergence from eggs inside ovisacs was found after treatments of 52, 24, and 14 min at 47, 48, and 49 degrees C, respectively. Results from this study provide efficacious temperature-time treatments.

Irradiation of Maconellicoccus hirsutus (Homoptera: Pseudococcidae) for phytosanitation of agricultural commodities.

Studies on the tolerance of pink hibiscus mealybug, Maconellicoccus hirsutus (Green), to ionizing irradiation were undertaken to determine the dose needed to disinfest commodities of this pest. Overall, radiotolerance of M. hirsutus was found to increase with maturity. Target doses of 50 Gy reduced eclosion of eggs to <50%, but doses as great as 750 Gy did not eliminate hatching during the study. At 100 Gy, M. hirsutus eggs, crawlers, and nymphs were controlled, because progeny were not produced despite crawlers and nymphs living for much longer periods than unexposed individuals. Fecundity of treated crawlers and nymphs was greatly impacted by treatment of 100 Gy; crawlers developing into adults produced no eggs, and 10 adults of 3,983 treated nymphs (0.25%) produced 309 eggs. Few adult females exposed as nymphs deposited eggs because male nymphs died during development, which left the females unfertilized. By comparison, 89% of female nymphs treated at 100 Gy and mated as adults with nonirradiated males produced a total of 1,447 eggs (19 eggs per female). Evidence from this study suggests M. hirsutus reproduces sexually, not parthenogenetically. Adults, the most resistant stage, exposed to target doses of 100 Gy produced eggs that were 1.2% viable, from which a small portion of individuals successfully completed development and produced progeny. A target dose of 250 Gy was sufficient to control adult M. hirsutus because, at that dose, none of the eggs produced by 3,093 irradiated adults eclosed. The minimum dose needed to ensure quarantine security is between 100 and 250 Gy.