GM pollen 'harmless to Butterflies

[sumairp at operamail.com]

http://news.bbc.co.uk/hi/english/sci/tech/newsid_1814000/1814068.stm


Monday, 11 February, 2002, 17:59 GMT 
GM pollen 'harmless to butterflies'

The monarch butterfly: GM risk is definitively discounted, researchers
say (Noaa)

By Alex Kirby
BBC News Online environment correspondent



US scientists say monarch butterflies suffer no significant harm from
pollen from genetically- modified (GM) maize plants. 

A two-year study led by the US Agricultural Research Service (ARS) has
concluded that the risk of harm is negligible. 

A group of federal, university and biotechnology industry scientists
was involved in the study. 

The ARS says it shows definitively that the pollen poses no "immediate
significant risk". 

The research was published in the Proceedings of the National Academy
of Sciences (PNAS). 

The debate over a possible risk to the butterflies from GM pollen on
maize plants (known also as corn) has been simmering for several
years. 

In 1999 researchers from Cornell University reported that maize
genetically engineered with the bacterium Bacillus thuringiensis (Bt)
to resist the corn-borer pest killed monarch caterpillars in the
laboratory. 

Problem strain

In 2000 researchers from Iowa State University said monarch
caterpillars were seven times likelier to die from eating milkweed
near GM maize than those eating milkweed leaves with no GM pollen on
them. 


Milkweed, the monarch's staple (USFS)
The ARS scientists sought to establish how much Bt pollen was needed
to cause toxic effects in the caterpillars, and how likely they were
to encounter that level in natural conditions. 

It assessed the feeding behaviour of caterpillars on milkweed leaves
dusted with pollen from six Bt maize types, with no-pollen and no-Bt
pollen controls. 

The lead ARS scientist was Richard Hellmich, an entomologist from the
Corn Insects and Crop Genetics Research Unit, Ames, Iowa. 

He said: "We looked at larval weight and survival and found it took
large amounts of pollen to get any statistically significant effect." 

Below 1,000 pollen grains per square centimetre, the caterpillars'
weight and survival rate were unaffected. Above that level the
caterpillars were smaller, but they survived as long as the controls. 

The exception was one of the six types of maize, BT176, which caused
some harm at levels of ten grains per square cm. 

Results corroborated

ARS says this was the earliest Bt maize developed and is likely to be
phased out entirely by 2003. 

To find how likely the caterpillars were to be exposed to significant
amounts of pollen, one team measured pollen deposition around seven
fields in Iowa. 


Pesticides harm insects too
Dr Hellmich said: "We found that, on average, less than 30% of the
pollen that corn produces ends up on milkweed leaves, even when
conditions are perfect, and most of that gets deposited on milkweed
within the cornfield." 

Similar studies in Maryland, Nebraska and Ontario in Canada confirmed
this pattern: they showed average pollen density on milkweed leaves
within cornfields was about 170 grains per square cm, and seldom went
above 600 grains. 

Chemical decline

Dr Hellmich said this meant caterpillars in the fields would encounter
the lowest observable effect dose less than 1% of the time. 

He said maize pollen was too heavy to blow far, and rain easily washed
it off milkweed leaves. 

He added: "You need to compare the potential for risk to monarchs from
Bt corn with the alternative, which is chemical insecticide use." 

The US Environmental Protection Agency says use of insecticides
recommended against European corn borers has fallen by about one-
third since Bt maize was introduced to the marketplace. 


Cheers,

 
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