MOOSE JAW, Sask. – A project designed to develop an early warning system for ascochyta blight in chickpeas didn’t do the trick in the first year of a three-year trial.
However, the sentinel plant trap-line project will be refined for 2008 as researchers continue to look for ways to control ascochyta.
Penny Pearse, Saskatchewan Agriculture’s plant disease specialist, told pulse growers at a workshop that pre-grown, susceptible chickpea plants were placed in fields near Swift Current, Sask., and Hodgeville, Sask., to determine when spores were first released.
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The idea was that the sentinels would be infected first, trapping spores and allowing producers to determine when to apply fungicide.
The sentinels were CDC Xena, a variety known to have a poor ascochyta blight rating.
The plants were in pots and wire cages to prevent gopher damage. The cages contained four plants each and were placed in three locations: chickpea residue; one metre from residue and 10 metres from residue.
Beginning May 18, batches of the sentinel plants were placed outside in the cages every few days until June 21. Each set remained in the cage for three or four days and was then removed for three days of incubation in a humidity chamber to encourage infection.
The plants were then placed in a growth chamber for two more days to encourage symptom development.
“We learned the trap plants did develop lesions … about one week sooner than the commercial crop,” Pearse said of the findings from the 11 batches of plants.
However, that wasn’t early enough to make a difference in terms of fungicide application timing.
The May 22 plants, or second batch, developed lesions but they weren’t observed until June 5. By then, commercial crops were also infected.
This year, she said, the sentinel plants will go out one to two weeks earlier than 2007. Improved incubation techniques should result in an earlier confirmation of the fungus, she added.
The experiment also found that the spores first infected the plants growing directly in the chickpea residue.
However, this difference was visible only until May 25. After that, the sentinel plants located further away from the residue were just as likely to develop lesions as those in the residue.
Pearse said that suggests spores blown by the wind cause infection as much as those splashed by rain.
Weather data recorded by electronic weather stations at two of the four sites showed rainfall and high humidity were critical for disease development. Temperature had less impact.
Pearse said ascochyta blight developed early in sentinel plants and commercial fields, which emphasizes the importance of spraying at or around the seven-node stage and certainly during the first two weeks of June.
