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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.

To be placed on an E-mail list so you will be notified immediately when new Manitoba Insect and Disease Updates are posted, please contact John Gavloski at the address or numbers listed above.


 

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.

flea beetles on canola

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