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Plant Growth Affected by Prior Plants in the Same Soil

Not long ago, it was discovered that root-feeding insects cause plants to release volatiles in the air, which leaf-feeding insects cue in on to avoid the plant. Recently, Netherlands Institute of Ecology scientists found that ragwort plants grown in soil previously containing insect-fed plants will also release those same volatiles. The changes in the new plant reflected whether the old plant was fed on by root- or leaf-feeding insects, thus repelling both those insect types. The soil fungal community was found to relegate these changes.

Varroa Mites Alter Bee-Infecting Virus

Research conducted in Hawaii by scientists from the University of Sheffield, the Marine Biological Association, the Food and Environment Research Agency and the University of Hawaii, and reported in Science Magazine, found that the newly introduced varroa mites to Hawaiian hives increased the prevalence of deformed wing virus (DWV) in Hawaii bee colonies from 10% to 100%. As a result, the number of viral particles increased by a million fold and the number of viral strains was reduced, leading to the predominance of a single virulent strain. Deformed wing virus is naturally transmitted in bees through feeding or sex but the mites change the disease so it becomes more deadly, shortening the bees’ lifespan. The authors conclude that the worldwide spread of varroa mites has led to the selection of DWV strains that are widely distributed and highly contagious.

Bed Bugs Survive OTC Foggers

Scientific evidence by Oregon State University entomologists conclusively shows that over-the-counter foggers are ineffective against bed bugs. The researchers found that three different commonly found brands had no effects on five different bed bug populations. The insects survive the applications due to resistance, and their habit of residing in protected locations.

Historic Presence of Plant Disease can Affect its Strength

The virulence of a plant pathogen is sometimes related to the host plant from which it was transmitted, according to NSF and NIH funded research out of University of California and USDA Agriculture Research Service, published in the journal PLoS ONE. The authors showed, for the first time, the genetic process by which pathogens’ environmental history can change their behavior. One disease they studied was sudden oak death, caused by Phytophthora ramorum. They examined identical strains of the pathogen from different plant hosts and found that they were strikingly different in their virulence and their ability to proliferate. The results of this study may provide scientists with future approaches to control a disease, such as manipulating gene expression to artificially reduce the aggressiveness of plant pathogens.

Assessment of Climate Change and Forest Diseases

The USDA Forest Service’s Pacific Southwest Research Station conducted a review of the impact of climate change on forest diseases in the Western U.S. and Canada. They considered eight pathogens and two climate change scenarios (warmer and drier and warmer and wetter), and assigned a high, moderate, or low risk value for each pathogen and each scenario. Diseases that could become more prevalent in hot, dry conditions are armillaria root rot, cytospora canker, yellow-cedar decline, and dwarf mistletoes. The warm and wet scenario favors Phytophthora diseases such as sudden oak death. The full report, “A Risk Assessment of Climate Change and the Impact of Forest Diseases on Forest Ecosystems in the Western United States and Canada,” is available here.

"Medicinal Plants" used by Sick Bees

North Carolina State University entomologists found that when honey bees that are infected with a harmful fungus, worker bees will increase the amount of plant resins they bring to the hive. Honey bees typically collect propolis (a mixture of plant resin and wax) to line their hives for protection. But the presence of a pathogenic fungus resulted in a 45% increase in the amount of propolis collected. They also found that bees were able to discern pathogenic fungi from harmless fungi, since colonies did not bring in increased amounts of propolis when exposed to harmless fungal species. Oddly, the presence of pathogenic bacteria did not affect the bees’ propolis collection. This new knowledge will help beekeepers to understand the reasoning for the collection of propolis. This paper was published in PLoS ONE.

How Imidacloprid can Affect Honey Bees

University of California at San Diego (UCSD) entomologists found various ways that imidacloprid affects honey bees (Journal of Experimental Biology). They exposed bees to the insecticide in an amount equivalent to that found in nectar from a treated plant, and then observed feeding preferences, and communication with other bees. They found that the exposed bees preferred to feed on sweeter nectar and refused less sweet nectars, as compared to the untreated bees. In addition, the treated bees recruited nest mates (“waggle dance”) to good food less often than the untreated bees. These changes may lead to a reduction in resources brought back to the colony due to the preference for sweetness and lack of communication.