NEWS FROM
PHYSIOLOGIA PLANTARUM
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Published monthly on behalf of SPPS by Wiley-Blackwell.
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Sunlight in the early season predicts quality of wine
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The chemical compound 2-methoxy-3-isobutylpyrazine (MIBP) is an important component in wine that adds a vegetal, bell pepper flavor and aroma with a very low sensory threshold. Since this contribution can be valued either positively or negatively depending on the particular wine, winemakers are interested in controlling the concentration of MIBP in the wine - and accordingly in the grapes, which is where it originates. MIBP has been found to be photolabile in the wine, but it has been unclear how sunlight affects MIBP concentration in grapes while growing on the field. Now research by Mark Matthews from University of California Davis, USA shows that the effect depends on the growing season. Their results indicate that the effect of sunlight on MIBP concentration in the harvested fruit is only important at an early stage even before the grapes start to ripen. This was observed both in natural fields during years with the appropriate weather conditions as well as in controlled environment experiments. The results might help winemakers to control quality by providing shade at the right time of the season.
Read full article here: Koch et al (June 2012) Physiologia Plantarum 145: 275
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NEWS IN BRIEF
FROM OTHER JOURNALS
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Transgenic crops promote biological control
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Source: Lu et al (13 June 2012) Nature doi:10.1038/nature11153
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Frightened grasshoppers make plant litter less digestible
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Source: Hawlena et al (15 June 2012) Science 336: 1434
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Biological control: let predation, parasitism and herbivory rule
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The lady bug beetle, Rodolia cardinalis, has been used for more than 100 years to control scale insects. From cisr.ucr.edu
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Biological control for the management of pests in agriculture has been practiced for centuries and probably dates back to ancient China. Defined as the use of natural enemies - insects, mites, parasites, pathogens or weeds - to reduce pest populations, biological control is widespread and continues to gain momentum both in the controlled environment of greenhouses and in the open field. Biological control can be viewed as an alternative to chemical pesticides and the two methods each have their benefits.
While chemical controls are cheap, readily available and show an immediate effect, they require reapplication every growing season and carry several environmental costs: they can be persistent in the environment, damage other organisms (including humans) than the target pest, and they might eventually loose effect as the pests build up resistance. Biological control, on the other hand, might take a while to show the desired effect, but once they have proved effective their effect can last forever without any additional efforts from the farmer. Thus, it can be argued that chemical control might be more economical and effective in the short term, while biological control will eventually be so in the long term.
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The parasitic wasp Aphidius colemani is one of the most widely used species for augmentative biological control of whiteflies, thrips and mites. From chem-gro.com
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Two basic methods of biological control exists, namely classical biological control and augmentative biological control. With classical biological control, a natural enemy of a pest is introduced into an area where it is not naturally present with the aim that it will reproduce and spread and thus establish a stable population in the new area. To acquire stable populations, classical biological control must be practiced outdoors and since it can influence an entire ecosystem it is only performed by public institutes. Worldwide, more than 5000 introductions selected from 2000 available species are used for classical biological control in 196 countries.
With augmentative biological control, on the other hand, a stable population is not desired. Instead, the natural enemy is only intended to survive for a single crop cycle, and it must accordingly be introduced every season. This management regime is more practical in small environments like greenhouses and is rarely practiced in open fields. Since the natural enemies used in augmentative biological control must be produced in order to get the large quantities needed to acquire an immediate effect, only a limited number of species are available. Around 170 species of natural enemies are produced and sold worldwide, but more than 90% of the market value is made up of only 25 species.
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Herbivore-induced plant volatiles affect the community members that exert pressure on plants. From Trends in Plant Science (2009) 15: 167
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The natural enemies used for both classical biological control and augmentative biological control are most often insects, mites or spiders that act as predators on the pest. Among the most popular predators in biological control is the unspotted ladybug Cryptolaemus montrouzieri that has been introduced from Australia and is used for control of mealybugs. Various predatory mites or gall midges like Phytoseiulus persimilis and Feltiella acarisuga are extensively used for control of spider mites in green houses while the parasitoid wasp Cotesia flavipes from South Asia is the preferred choice against sugar cane stem borers (Crambidae). However, the natural enemy does not have to be an arthropode, so the predatory snail Euglandina rosea are very commonly used to control other herbivory snails. Likewise, the pest does not have to be an arthropode either, so the Lantana weed (Lantana camara), a tropical shrub that acts as an invasive species and serious pest in the Australian-Pacific region, can be effectively controlled by herbivory insects like lace bugs (Tingidae) and leaf beetles (Chrysomelidae).
While natural enemies can include also bacteria, fungi and even plants (by eg masking the crop or acting as a trap for the pest), a novel approach is to control the pest by so called herbivore-induced plant volatiles (HIPVs). They are signalling compounds that a plant under attack use to either deter herbivores or attract their natural enemies. This approach has recently been tested by applied synthetic HIPVs to so diverse crops as apples, wine-grapes, sweet-corn and broccoli, and results seem promising.
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