Chemical control of balsam wooly aphid (Homoptera: Adelgidae) on seedlings of Abies amabilis

Assessment was made of the effectiveness of four insecticides for eradicating <i>Adelges piceae</i> (Ratz.) from Abies seedlings. Seedlings with overwintering immature aphids were top dipped in the insecticides in fall or spring (before or after cold storage), while those with mature, egg-laying aphids were treated in spring. The overwintering immature aphids were completely killed by all of the insecticides and it was recommended that any one of the following treatments would provide sanitation of <i>Abies</i> from aphid during this stage: 1.0% propoxur suspension; 2.0% carbaryl suspension: 2.0% Insecticidal Soap solution; 0.5% permethrin emulsion. Treatment of mature aphids was less effective due to relative tolerance of bwa eggs and it was recommended that treatment during this stage of the aphid be avoided

Effect of a commercial insecticidal soap on greenhouse whitefly (Hom: Aleyrod.) and its parasitoid, Encarsia formosa (Hym: Euloph.)

Safer’s Insecticidal Soap (IS) was topically applied at six concentrations to all growth stages of greenhouse whitefly as well as larvae and adults of the whitefly parasitoid, the eulophid wasp Encarsia formosa. IS at 0.5% ai caused more than 94% mortality of all whitefly larval stages and adults, and more than 82.5% mortalitv of whitefly pupae. Adults hatched from treated pupae occasionally showed altered development. E. formosa adults were more tolerant to IS than whitefly and 81.5% survived a 0.5% IS treatment. It was concluded that IS is an effective pesticide for greenhouse whitefly and should be integrated with E. formosa in greenhouse trials

Chemical control of balsam wooly aphid (Homoptera: Adelgidae) on seedlings of Abies amabilis

Assessment was made of the effectiveness of four insecticides for eradicating Adelges piceae (Ratz.) from Abies seedlings. Seedlings with overwintering immature aphids were top dipped in the insecticides in fall or spring (before or after cold storage), while those with mature, egg-laying aphids were treated in spring. The overwintering immature aphids were completely killed by all of the insecticides and it was recommended that any one of the following treatments would provide sanitation of Abies from aphid during this stage: 1.0% propoxur suspension; 2.0% carbaryl suspension: 2.0% Insecticidal Soap solution; 0.5% permethrin emulsion. Treatment of mature aphids was less effective due to relative tolerance of bwa eggs and it was recommended that treatment during this stage of the aphid be avoided

Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences

Plants can use ammonium (NH4+) as the sole nitrogen source, but at high NH4+ concentrations in the root medium, particularly in combination with a low availability of K+, plants suffer from NH4+ toxicity. To understand the role of K+ transporters and non-selective cation channels in K+/NH4+ interactions better, growth, NH4+ and K+ accumulation and the specific fluxes of NH4+, K+, and H+ were examined in roots of barley (Hordeum vulgare L.) and Arabidopsis seedlings. Net fluxes of K+ and NH4+ were negatively correlated, as were their tissue concentrations, suggesting that there is direct competition during uptake. Pharmacological treatments with the K+ transport inhibitors tetraethyl ammonium (TEA+) and gadolinium (Gd3+) reduced NH4+ influx, and the addition of TEA+ alleviated the NH4+-induced depression of root growth in germinating Arabidopsis plants. Screening of a barley root cDNA library in a yeast mutant lacking all NH4+ and K+ uptake proteins through the deletion of MEP1–3 and TRK1 and TRK2 resulted in the cloning of the barley K+ transporter HvHKT2;1. Further analysis in yeast suggested that HvHKT2;1, AtAKT1, and AtHAK5 transported NH4+, and that K+ supplied at increasing concentrations competed with this NH4+ transport. On the other hand, uptake of K+ by AtHAK5, and to a lesser extent via HvHKT2;1 and AtAKT1, was inhibited by increasing concentrations of NH4+. Together, the results of this study show that plant K+ transporters and channels are able to transport NH4+. Unregulated NH4+ uptake via these transporters may contribute to NH4+ toxicity at low K+ levels, and may explain the alleviation of NH4+ toxicity by K+

Alleviating nitrogen limitation in Mediterranean maquis vegetation leads to ecological degradation

Soils are being degraded at an alarming rate and thereby also crucial ecosystem goods and services. Nitrogen (N) enrichment is a major driver of this degradation. While the negative impacts of N enrichment on vegetation are well known globally, those on various ecological interactions, and on ecosystem functioning, remain largely unknown. Because Mediterranean ecosystems are N limited, they are good model systems for evaluating how N enrichment impacts not only vegetation but also ecological partnerships and ecosystem functioning. Using a 7-year N-manipulation (dose and form) field experiment running in a Mediterranean Basin maquis located in a region with naturally low ambient N deposition (<4 kg N ha−1 y−1), we assessed the impacts of the N additions on (i) the dominant plant species (photosynthetic N-use efficiency); (ii) plant–soil ecological partnerships with ectomycorrhiza and N-fixing bacteria; and (iii) ecosystem degradation (plant–soil cover, biological mineral weathering and soil N fixation). N additions significantly disrupted plant–soil cover, plant–soil biotic interactions, and ecosystem functioning compared with ambient N deposition conditions. However, the higher the ammonium dose (alone or with nitrate), the more drastic these disruptions were. We report a critical threshold at 20–40 kg ammonium ha−1 y−1 whereby severe ecosystem degradation can be expected. These observations are critical to help explain the mechanisms behind ecosystem degradation, to describe the collective loss of organisms and multifunction in the landscape, and to predict potential fragmentation of Mediterranean maquis under conditions of unrelieved N enrichment