Manitoba Agriculture, Food and Rural Initiatives
Manitoba Insect and Disease Update
June 6, 2011
| Compiled by:
|
John Gavloski, Entomologist, Manitoba Agriculture, Food and Rural Initiatives Phone: (204) 745-5668; Fax: (204) 745-5690 Holly Derksen, Plant Pathologist, Manitoba Agriculture, Food and Rural Initiatives Phone: (204) 750-4248; Fax: (204) 745-5690 |
To report observations on insects or plant pathogens that may be of interest or importance to farmers and agronomists in Manitoba, please send messages to the above contact address.
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Recent Insect and Plant Pathogen Activity
Canola
Flea beetles: Flea beetles are active but the relatively cool weather has reduced the amount of feeding. We are at that time of the spring where we are seeing fewer striped flea beetles (Phyllotreta striolata), as the emerged adults start to die, and a greater proportion of the population being crucifer flea beetles (Phyllotreta cruciferae).
The crucifer flea beetle population can still be quite large in early- and mid-June, and will do more feeding on warm, calm days. If canola was seeded prior to mid-May, insecticides in the seed treatment may start becoming less effective against flea beetles soon. If these fields are not yet at the stage where plants have 3 or 4 true leaves expanded, fields should be monitored for flea beetle feeding. Minor feeding to leaves and cotyledons is normal, as the flea beetles need to ingest the seed treatment to be killed. But if the seed treatment has become less effective, higher levels of feeding can occur.
In the photo below, the 2 flea beetles at the top are striped flea beetles and the flea beetle below is a crucifer flea beetle. The photo also shows the feeding pits caused by flea beetles.
Surveys and Forecasts
Diamondback moth monitoring: Diamondback moth (Plutella xylostella) was first reported this year in a trap near Carman during the week of May 2-8, then more generally during the week of May 9-15th. Numbers in the traps have been relatively low so far. So the moths did arrive early, but it appears just in low numbers. Out of 54 traps reporting diamondback moth counts in Manitoba so far in 2011, 31 of the traps are reporting 0 moths as cumulative counts. Higher risks of economic damage from diamondback moth occur when they arrive in higher levels early in the season, and weather and natural enemies fail to prevent the populations from growing as diamondback moth go through their generations. When this happens the population of later generations can be high enough to cause economic damage to crops. The Central and Eastern areas of Manitoba have the highest trap catches so far, and although we do not have data that enables us to correlate adult catches in pheromone-baited traps and larval numbers, the counts so far in Manitoba do not suggest a high risk.
Table 1. Week of first reporting of diamondback moth in pheromone-baited traps in Manitoba in 2011:
Date |
Location(s) |
May 2-8 |
Carman |
May 9-15 |
Carman, Oakville, Haywood, St. Claude, Culross, Beausejour, Thalberg, Boissevain |
Table 2. Highest cumulative trap counts for diamondback moth in Manitoba as of June 6, 2011
Location |
Cumulative Trap count |
Carman |
33 |
St. Joseph |
28 |
Thalberg |
18 |
Beausejour |
16 |
Culross |
16 |
The full data set for adult counts of diamondback moth can be viewed at: https://www.gov.mb.ca/agriculture/crops/insects/db/pdf/2011diamondbackdata.pdf
Bertha armyworm monitoring: For those setting up traps to monitor adult moths of bertha armyworm, this week or next week would be appropriate timing for setting up these traps. Protocols for setting up the traps can be found at: https://www.gov.mb.ca/agriculture/crops/insects/fad59s00.html
