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Spent yeast from beer breweries could be fruit fly bait

The sludge, left over from making beer, may be the next best tool for fruit growers to control spotted-winged drosophila (Drosophila suzukii), according to Chinese researchers.

This might be good news for beer brewers, too. Disposing of the dregs remaining after beer production can be a difficult and costly. Moreover, improper discharges could run a brewery afoul of the Clean Water Act and other environmental protection regulations.

The spent brewer’s yeast is a microbial protein from the fungus Saccharomyces cervisiae. It has been turned into a few marketable products. One use is in compost. Spent yeast also has been tried with mixed success as an ingredient of animal feed and food spreads for humans.

In a study published in October in the Journal of Economic Entomology, a team of scientists in China, led by Pumo Cai of the Fujian Agriculture and Forestry University, shows that protein bait derived from spent brewer’s yeast is much more attractive than traditional baits used on the spotted-winged drosophila. This fly is a major pest of soft-skinned fruits such as cherry, strawberry, blackberry and blueberry.

Long a pest in its native Asia, the spotted-winged drosophila has cost US growers hundreds of millions of dollars since it was first seen in 2008. Finding an attractant that specifically targets the fly for monitoring populations and luring it to insecticides is complicated by its exceptionally broad diet. Most attractants draw large numbers of other insects as well as the spotted-winged drosophila. Use of yeast as an attractant makes sense because studies have shown that protein is essential to egg development in the group of flies to which the spotted-winged drosophila belongs.

The Chinese researchers compared brewer’s yeast protein bait with ACV and SVW baits and found it was by far the most attractive. The yeast protein not only attracted more flies but also drew in flies of both sexes and over a wide age span. Potentially, say the scientists, the bait could be used to remove reproductively immature female flies from the field before they start to mate and lay eggs in crops.


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Of course this is the same system used to control Tephritid fruit flies in Australia, SE Asia and for a while in Fiji. This is protein (yeast extract) spot spraying which is so effective, being highly attractive to female Tephritids. I am carrying over the Mauri yeast extract (sourced from Queensland) to Cambodia to demonstrate its use in fruiting vegetables, especially control of Melon fruit fly in bitter gourd and chilly crops. Only problem is resurrecting a local producer in SE Asia. Malaysia and Vietnam both previously had production units. I note there is a new unit in Fiji (at Koronivia RS). Spot spraying Yeast extract (from brewing beer) is such an environmentally friendly.

Control method for Tephritids in so many fruit crops, a classic IPM tool with no pesticide residues on fruit (you just spot spray on leaves or branches Or roosting sites). 

So not new technology, just a new target pest?
Graham Walker 

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