Plants Repel Insect Pests

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Here are two recent articles which document the fact that plants repel insect pests. Of course, the ability of plants to repel insects pests is greatly enhanced by the availability of the 72+ natural trace elements, many of which are needed to make the repellent volatile compounds - which are sadly lacking in our modern agriculture.

What is most remarkable is that plants are not only able to repel insect pests - but also, and simultaneously, produce compounds which are attractive to the natural predators of the insect pests. Hence, the more than 90% efficiency of pest control, as documented in the first article, does not come as a surprise. This, of course, requires the availability of a wide range of trace elements - most of which by far, are not part of our modern chemical agriculture - to produce those intricate repellent and attractive compounds.

All of these natural pest control compounds are - by the way, and naturally - completely harmless to humans.

Again, use a fishmeal or seaweed fertilizer - once or twice a year - for the complete spectrum of the 72+ natural trace elements. This has to be done every year, to compensate for the trace elements shipped away in your products.

And if you can introduce the "Wolf spider" into your croplands - which needs to be done only once - insect control will be all but perfect. And you'll never ever need any pesticides again. See POISON-FREE AGRICULTURE in these pages.

Original Abstracts:

Defensive Function of Herbivore-induced Plant Volatiles

In many land-based ecosystems, the major autotrophs are plants, and the major heterotrophs feeding on plants are insects. One of the more intriguing ecological relationships in nature is that of the "trophic triangle", an often remarkable instance of co-evolution among different species. One example is the insect- plant-insect trophic triangle, in which a species of plant, prey to a predatory insect species that destructively feeds on it, evolves a defense mechanism that sends out a signal that attracts another species of insect that feeds on the first species of insect.

Such co-evolutionary triangles, delicate minuets of prey and predation, have become an important focus of experimental ecology. Researchers now report a study in which they quantified volatile emissions from plants growing in natural populations during attack by 3 species of leaf-feeding herbivores. Three compounds increased egg predation rates by a generalist predator, and the complete blend decreased lepidopteran egg-deposition rates. As a consequence, a plant could reduce the number of herbivores by more than 90 percent by releasing volatiles. (A. Kessler and I.T. Baldwin: Science 16 Mar 01 291:2141)

Caterpillar-induced Nocturnal Plant Volatiles Repel Conspecific Females

CONSUELO M. DE MORAES, MARK C. MESCHER & JAMES H. TUMLINSON
Plants respond to insect herbivory by synthesizing and releasing complex blends of volatile compounds, which provide important host-location cues for insects that are natural enemies of herbivores. The effects of these volatile blends on herbivore behaviour have been investigated to only a limited extent, in part because of the assumption that herbivore-induced volatile emissions occur mainly during the light phase of the photoperiod. Because many moths—whose larvae are some of the most important insect herbivores—are nocturnal, herbivore-induced plant volatiles have not hitherto been considered to be temporally available as host-location cues for ovipositing females.

Here we present chemical and behavioural assays showing that tobacco plants (Nicotiana tabacum) release herbivore-induced volatiles during both night and day. Moreover, several volatile compounds are released exclusively at night and are highly repellent to female moths (Heliothis virescens). The demonstration that tobacco plants release temporally different volatile blends and that lepidopteran herbivores use induced plant signals released during the dark phase to choose sites for oviposition adds a new dimension to our understanding of the role of chemical cues in mediating tritrophic interactions. NATURE 410, 577 - 580, 29 March 2001

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