Charlotte Marie Bisgaard Nielsen

Soil as an environment for winter survival of aphid-pathogenic Entomophthorales

The survival of Pandora neoaphidis was studied for both discharged primary conidia and hyphal bodies inside aphid cadavers after storage on moist soil at different temperatures. The activity of the inoculum was quantified by the ability to produce replicate conidia as well as the ability to infect aphids. No effect of inoculum type was found. Conidia were produced after storage for at least 32 days at 20C, 64 days at 10C, and 96 days at 5C. Inoculum retained the ability to initiate infections in aphids after storage for at least 14 days at 20C, 32 days at 10C, and 64 days at 5C. Morphological studies of the inoculum suggest that P. neoaphidis may survive unfavorable conditions as thick-walled conidia also known as loricoconidia. Furthermore, P. neoaphidis and Conidiobolus obscurus were documented for the first time in field-collected soil in early spring by baiting the soil with aphids. We hypothesize that germination of overwintering inoculum is stimulated by host-induced factors since inoculum apparently responded to the presence of aphids. 2003 Elsevier Science (USA). All rights reserved.

Conservation through utilization: a case study of the Vulnerable Abies guatemalensis in Guatemala

Conservation through utilization is a controversial strategy that deserves more attention from researchers and practitioners. This case study focuses on Abies guatemalensis, a Vulnerable Mesoamerican conifer that is illegally used for timber, shingles, charcoal and Christmas tree production. Conservation of the remnant populations would preserve some unique montane forests, with concomitant benefits for local water supplies and prevention of landslides. As a conservation tool we suggest establishment of additional A. guatemalensis Christmas tree plantations. These could generate income for local farmers and help halt poaching from natural stands. So far, 51 such plantations have been established in Guatemala but practical knowledge of cultivation is limited and production dominated by a few large plantations. Seed for Christmas tree plantations needs to be carefully selected because there aremarked differences among populations in germination, seedling height increment and greenery quality. Insect pests such as the balsam twig aphid Mindarus sp. could limit cultivation. A market study showed that c. 23% of households in the major Guatemalan cities buy A. guatemalensis Christmas trees but currently only 2.3% of these are plantation-grown. The prices of illegal and certified Christmas trees are, however, converging, making plantation trees more competitive. Because of the market characteristics and the potential for establishment of plantations, we are moderately optimistic that the conservation through utilization strategy may be successful for this species in Guatemala.

Nondormancy in Entomophaga maimaiga azygospores: effects of isolate and cold exposure.

Azygospores (resting spores) of the fungal pathogen Entomophaga maimaiga are produced in later larval instars of the gypsy moth Lymantria dispar and normally enter constitutive dormancy. In the laboratory cadavers of recently dead larvae containing immature azygospores were placed on 1.0% water agar at 20 C for 2 wk after host death, allowing time for azygospore maturation. We found that some azygospores produced in this way did not enter dormancy. To investigate nondormancy, suspensions of azygospores from individual cadavers were transferred to moist, sterile soil at 15 C. Groups of gypsy moth larvae were exposed sequentially to azygospores for consecutive 4 d periods for 196 d. Infections first were seen among larvae exposed 24–28 d after bioassays began, and infection potential continued 196 d. Germination tests confirmed azygospore germination. Additional cadavers containing azygospores produced under the same conditions were maintained at 4 C for 1–8 mo, and each month new sequential bioassays were initiated. There was a general trend of earlier initiation of infection with longer durations of 4 C exposure; after 6–8 mo at 4 C first infections occurred 6–10 d after bioassays began. With 5–8 mo at 4 C infection levels declined after 96 d of sequential bioassays. Activity of azygospores differed by the individual larval cadaver in which they were produced; azygospores from 29.2% of cadavers yielded only 0–0.3% infection. Infection from non-dormant azygospores did not differ among three Japanese isolates and two North American isolates, although azygospores from a third North American isolate caused no infections in 84 d, suggesting that dormancy had not been prevented.

BIOLOGICAL CONTROL OF SCARABS AND WEEVILS IN CHRISTMAS TREES AND GREENERY PLANTATIONS

In Danish forestry the economically most important insect problems and consequently the most intensive use of chemical insecticides occur in the production of Christmas trees and decoration green (Kirkeby-Thomsen and Ravn, 1997; Ravn, 2000). Nordmann fir (Abies nordmanniana) and noble fir (Abies procera) are the dominant tree species in this production today. Abies nordmanniana is mostly used for Christmas trees, while A. procera is mostly used for decoration green. Other conifer species to be used for the same purposes are only grown on a negligible scale. Christmas trees and decoration green are both important for the home market and export. In several countries in Central and Northern Europe with Germany as the main recipient. The prices obtained by the producers vary depending on quality, but can typically be around EUR 10 per tree of 200 cm height and EUR 1 per kg decoration greenery. The total export value for Denmark was thus above EUR 150 mio in 2003. The market demands a very high product quality, and no damage from feeding of insect pests is accepted. Only the highest quality with the required shiny, dark green needle colour of Christmas trees and decoration greenery without any signs of insect feeding on the needles are saleable at reasonable prices. It is therefore a prerequisite for the producers to ensure pest control. Control of insect pests in the Danish production of Christmas trees and decoration green has historically been based on the use of chemical pesticides. However no chemical pest control have been permitted in state forestry since 2003 (The Danish Environmental Protection decoration greenery. For privately owned forests there is a political wish from the state authorities to phase out chemical pesticides (Ravn, 2000). Further, there is an increasing desire from consumers to buy organically grown Christmas trees produced without chemical pesticides. The products are associated with strong emotions among consumers: Christmas trees and decoration green are linked to family traditions during the Christmas period, which in Denmark lasts about one month. Biological control using natural enemies of the pest populations may thus provide an attractive alternative to conventional chemical treatment. This chapter provides a short review

A New Species of Mindarus (Hemiptera: Aphididae) on the Endangered Guatemalan Fir

Abstract A pestiferous species of Mindarus (Hemiptera: Aphididae: Mindarinae) presents challenges for the cultivation and conservation of the endangered Guatemalan fir, Abies guatemalensis Rehder. The aphid, Mindarus guatemalensis n. sp., is described.