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U-of-L Professor finds Less Can be More When Dealing with Some Crop Pests

Aug 1, 2016 | 4:36 PM

LETHBRIDGE:   It might be expected that heavy insecticide use is the best way to keep insects at bay in agricultural crops. 

However, a U-of-L professor has found low levels of insecticide may be all that’s needed.

An insect that can spread the zebra chip pathogen in potatoes has been found in Alberta, but, Professor Dan Johnson recommends potato growers take no action other than field sampling.

Johnson co-ordinates the Canadian Potato Psyllid and Zebra Chip Monitoring Network and leads the Alberta research, because  Zebra chip caused millions of dollars in losses for potato farmers in New Zealand and the U-S. He speculates that warmer conditions and insect movements in air and on transported plants may be responsible for an expanded range for the insects.

The monitoring network is backed by DNA testing, conducted by Dr. Larry Kawchuk at the Lethbridge Research Centre. While Scott Meers, with Alberta Agriculture and Forestry, collaborates on field sampling and design of a management plan. The cross-Canada monitoring network is funded by Growing Forward 2 through Agriculture and Agri-Food Canada and Agri-Science clusters and the participation of groups like the Potato Growers of Alberta.

The potato psyllid is about the size of an aphid and feeds only on potato and tomato plants and some related wild plants, and can transmit bacteria that leads to zebra chip. Plants infected by the bacteria will experience reduced growth, quality and yield. Potato fields are tested for the presence of the psyllid by way of sticky yellow cards placed on stakes.

About 2,000 cards are tested per year at the U of L.  No psyllids were found in 2013 or 2014. While a very small number were detected in 2015 and 2016, none tested positive for the pathogen that causes zebra chip.

Johnson says the psyllid has likely been in Alberta in very low numbers for decades but none of the insects here have tested positive for bacteria that causes the zebra chip disease.

According to Johnson, the low level of insecticide use in Alberta potato fields allows natural enemies of the psyllid to exist.   He says it’s better to have strong natural controls for insects, as opposed to using insecticides. It’s also positive for farmers, as insecticide use is very expensive.