Comparison of standard (granular and drench) and novel (tablet, stick soak, and root dip) imidacloprid treatments for cottonwood leaf beetle (Coleoptera: Chrysomelidae) management on hybrid poplar.

Standard soil application methods (granular and drench) were compared with novel methods (tablet, stick soak, and root dip) for efficacy and duration in hybrid poplar (Populus spp.) against adult and larval cottonwood leaf beetle, Chrysomela scripta F. (Coleoptera: Chrysomelidae). Beetle feeding can kill saplings and significantly damage trees by reducing tree height, diameter, and biomass. Tablets offer lower risk to applicators and beneficial insects, because insecticides do not need to be measured and sprayed. In field- and container-grown plants, standard granular and drench application methods had similar efficacy and duration compared with tablets. In field-grown plants, adult and larval survivorship was reduced for 12 mo with the two highest rates of tablet (0.25 x and 0.5 x) treatments, and in container-grown plants, with all rates of tablet (0.25 x, 0.5 x, and 1 x ) treatments that were used. Two other novel application methods, stick soak and root dip, offer new methods for protecting vulnerable transplants in nursery propagation. In container-grown plants, adult survivorship was reduced for 8 mo and larval survivorship for 12 mo for all rates of stick soak (0.5 x, 1 x, and 2 x) and all rates of root dip (1 x, 2 x, and 4 x) treatments. Literature searches revealed little data on the efficacy and duration of soil-applied imidacloprid for trees, even though it is the primary insecticide used for defoliators and some borers in landscape and in nurseries for field and container production.

Professional and consumer insecticides for management of adult Japanese beetle on hybrid tea rose.

In many states, Japanese beetle, Popilliajaponica Newman (Coleoptera: Scarabeidae), is no longer quarantined, and management is left to professional applicators and consumers. Adult management in hybrid tea rose, Rosa L., was compared among biorational insecticides, novel imidacloprid applications (tablet, gel, and root dip), and conventional insecticides. Efficacy of biorational insecticides used by consumers varied widely and may not offer predictable management: mortality was 3.0% with Garlic Barrier, 5.0% with Monterey Neem Oil, 15.1% with Pygenic (1.4% pyrethrins), and 27.3% with Orange Guard (D-limonene). Only JB Killer (0.02% pyrethrins plus 0.2% piperonyl butoxide) had mortality of 90.9%, probably due to piperonyl butoxide. Professional biorationals did not show significant mortality: 7.7% with Azatin XL (azadirachtin) and 3.7% Conserve (spinosad). In contrast, conventional insecticides demonstrated significant mortality; 88.4% with Decathlon 20 WP (cyfluthrin) and 83.3% with Discus SC (imidacloprid plus cyfluthrin). New imidacloprid applications (tablet, gel, and root dip) worked as well as standard drench and granular methods, but they showed 9.1-42.7% mortality. However, beetles were incapacitated as demonstrated by inability to walk (82-106-s flip time) compared with controls (30-s flip time). No phytotoxicity was observed in any treatments. However, some imidacloprid treatments produced growth enhancement: higher leaf chlorophyll (1X, 3X granular, and one tablet), and larger leaf area and higher nitrogen (3X granular, drench). The highest (active ingredient) imidacloprid was in 3X granular treatment, which in an unplanned infestation, showed highest numbers of twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Effects of imidacloprid on leaf quality and mite outbreaks deserves research.

Soil-applied imidacloprid is translocated to nectar and kills nectar-feeding Anagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae).

Behavior was altered and survivorship was reduced when parasitoids, Anagyrus pseudococci (Girault) (Hymenoptera: Encyrtidae), were fed flowers from buckwheat, Fagopyrum esculentum L. (Polygonaceae), treated with soil applications of imidacloprid (Marathon 1% G). Parasitoids at 1 d had significantly reduced survivorship of 38 +/- 6.7% on label rate and 17 +/- 4.2% on twice label rate compared with 98 +/- 1.2% on untreated flowers. Parasitoids trembled 88% on label rate and 94% on twice label rate compared with 0% on untreated flowers. Residue analysis on a composite sample of 425 flowers showed that imidacloprid concentration was 6.6 +/- 1.0 ppm (16 ppb/flower) in label rate, 12.3 +/- 2.7 ppm (29 ppb/flower) in twice label rate, and 0 ppb in untreated flowers. The hydroxy metabolite concentration was 1.1 ppm (2.4 ppb/flower) in label rate, 1.9 ppm (4.4 ppb/flower) in twice label rate, and 0 ppm in untreated flowers. The olefin metabolite concentration was 0.2 ppm (0.5 ppb/flower) in label rate, 0.5 ppm (1.1 ppb/flower) in twice label rate, and 0 ppm in untreated flowers. Soil-applied imidacloprid used at flowering may be translocated to nectar in higher concentration compared with the imidacloprid seed treatment Gaucho. Considerable research has studied effects of Gaucho-treated canola, sunflower, and maize on behavior and mortality of Apis mellifera L. In our laboratory, we showed that translocation of imidacloprid to flowers reduced survivorship and altered behavior of pink lady beetle, Coleomegilla maculata DeGeer (Smith and Krischik 1999) and green lacewing, Chrysoperla carnea Stephens (Rogers et al. 2007).

Management of cottonwood leaf beetle (Coleoptera: Chrysomelidae) with a novel transplant soak and biorational insecticides to conserve coccinellid beetles.

Biorational foliar sprays and a novel application method of soaking transplants in imidacloprid were evaluated for control of adult and larval cottonwood leaf beetle, Chrysomela scripta F., on hybrid poplar, with emphasis on conservation of coccinellid predators. Foliar sprays of four biorational insecticides killed adult and larval C. scripta: Bacillus thuringiensis (B.t.) variety tenebrionis (Novodor), B.t. variety kurstaki (Raven), spinosad (Conserve SC), and azadirachtin (Azatin XL) (larvae only) but did not kill two species of coccinellids, Hippodamia convergens Guérin-Meneville and Harmonia axyridis (Pallas). Only imidacloprid (Admire 2) and carbaryl (Sevin XLR Plus) killed two species of coccinellids and adult and larval C. scripta. We evaluated a novel stick soak method for systemically applying imidacloprid by soaking poplar sticks in Admire 2 solutions of 3 and 6 ml/liter for 48 h before planting. The imidacloprid in the sticks was translocated to the leaves and reduced survivorship of adult and larval C. scripta for 10 mo without any symptoms of phytotoxicity. The novel stick soak method did not kill two species of coccinellids when foraging on leaves.

Control of systemically induced herbivore resistance by plant vascular architecture.

Patterns of systemically induced resistance (SIR) in Eastern Cottonwood, Populus deltoides, measured by reduced feeding of the leaf-chewing beetle, Plagiodera versicolora, were shown to be directly related to the distribution of the plant vasculature. Mechanical damage to single leaves resulted in SIR in non-adjacent, orthostichous leaves (vertically aligned on the stem) with direct vascular connections, both up and down the shoot; but no SIR in adjacent, non-orthostichous leaves with less direct vascular connections. The control that the plant vasculature exerts over signal distribution following wounding can therefore be used to predict SIR patterns, explain variation in the distribution of SIR, and relate this ecologically important phenomenon to biochemical processes of systemic gene expression and biochemical resistance mechanisms.

Generalized plant defense: effects on multiple species.

Two species of lepidopteran herbivores, Manduca sexta (Sphingidae) and Trichoplusia ni (Noctuidae), were reared on synthetic diet containing either the alkaloid nicotine or the flavonoid rutin. Survival and pupal weight of the specialist M. sexta did not differ when larvae were reared on diet containing nicotine or rutin. In contrast, the generalist T. ni did not survive on diet containing 0.125% nicotine or greater, whereas larvae survived on all concentrations of rutin. These data demonstrate that the alkaloid nicotine is inhibitory toward generalist, but not specialist herbivores, whereas the flavonoid rutin has no effect on specialist herbivores and limited effects on generalist herbivores. Five species of Pseudomonas bacterial pathogens: P. syringae, P. syringae pv. angulata, P. syringae pv. tabaci, P. fluorescens, and P. solanacearum were grown on nutrient agar containing nicotine or rutin at concentrations ranging from 0.0 to 1.0% wet weight in 0.1% intervals. No species of Pseudomonas grew at concentrations greater than 0.5% nicotine when 106 colony forming units (cfu) were used, but growth occurred at all concentrations of rutin when 102 cfu were used. These data indicate that nicotine was inhibitory to growth of both herbivores and pathogens, suggesting that certain plant secondary chemicals with high toxicity are of a generalized nature and affect multiple species. Differences in the sensitivity of organisms to allelochemicals such as generalist or specialist can make it appear that specific allelochemicals affect specific organisms, when in fact it is the tolerance of the organism to the plant chemical that is responsible. In four separate studies, the growth of M. sexta, T. ni and Helicoverpa zea was significantly lower on plants inoculated with P. solanacearum. Alteration in leaf quality by P. solanacearum was due to either reductions in leaf nutrients or increases in allelochemicals. We speculate that localized or systemic induction by both herbivores and pathogens can cause changes in leaf quality, effecting each other's subsequent colonization. The generalized nature of plant secondary compounds and potential reciprocal effects on induction by both species suggests that herbivores and pathogens may affect plant quality through induction and diffuse interactions of disparate species can alter the community of organisms colonizing a plant.