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Manitoba Agriculture, Food and Rural Initiatives

Manitoba Insect Update

August 10, 2009                   

Compiled by: John Gavloski, Entomologist, Manitoba Agriculture, Food and Rural Initiatives, Crops Knowledge Centre,
Phone: 204-745-5668; Fax: 204-745-5690

To report observations of insect activity or control that may be of interest or importance to others in Manitoba, please send messages to the above contact addresses.

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Summary

Aphid levels continue to be high in some cereal fields, and Lygus bugs are a concern in some sunflower fields.

Recent Insect Concerns and Observations

Aphids in cereals: High population of aphids continue to be noticed on some cereal crops. In addition to high levels previously reported in the eastern and central regions of Manitoba, high populations have also recently been reported in the Parklands area south of Riding Mountain National Park. The economic threshold for aphids in cereal crops is 12-15 per stem prior to the soft dough stage. Once cereal crops reach the soft dough stage aphid control is no longer likely to be economical.

Diamondback moth in Canola: The Minnesota Canola Council has reported that “in northern Minnesota, recent moth monitoring trap counts were extremely high, with localized numbers of larvae exceeding action thresholds.” So far we have not had economical populations of diamondback moths in Manitoba. However, canola growers and agronomists scouting canola may want to check levels in fields, particularly in areas close to the Minnesota border.

Caution when preparing bins for harvest. Prior to harvest it is recommended that bins that will receive this year’s crop be as clean as possible and any grain residues be removed. Ideally, residues of old grain should also be removed from equipment used to move grain, such as combines, trucks and augers. Populations of grain feeding insects that have started in these areas can easily be transferred to bins. Remember that bins which are to store oilseed crops such as canola, flax and sunflowers should not be treated with malathion prior to storing these crops. Residues may be absorbed into these crops, with one of the implications being trade restrictions.

Surveys and Forecasts

Monitoring Insects in Sunflowers: Pheromone-baited traps are being used to monitor the emergence and levels of banded sunflower moth adults, and determine whether sunflower moth has moved into Manitoba. So far, numbers have not been high. In the same fields as the pheromone-baited traps are in, we have been looking for red sunflower seed weevils, and so far have not been able to find any. The following table is the cumulative counts after 6 weeks of trapping (with the exception that data from the Kaleida and Treherne traps was not collected last week because of recent insecticide applications):
 

Location

Banded Sunflower

Moth

Sunflower Moth

Sunflower

Seed Weevils

Altona

113

2

0

Kalieda

6

3

0

Treherne

119

2

0

Waskada

171

1

0

Winnipeg

47

0

0

Souris

203

0

0

Last year, with just one trap for each of the moths set up in the Carman area, we had a cumulative count of 753 banded sunflower moths by August 8th. So by comparison numbers seem low this year. Counts for banded sunflower moth continue to increase weekly, however, so we may not be at peak flight yet.

 
  Adult of banded sunflower moth

 

Lygus bugs, continue to be the only seed feeding insects found in concerning numbers in some sunflower fields. As mentioned in last weeks update, there are plant bugs other than lygus bugs being found on sunflowers, some of which are being confused for lygus bugs. Unfortunately, we currently know little about these other species of plant bugs on sunflowers.

While scouting sunflowers, you may notice the occasional head has a small dark spot amongst the disk petals, and when you peel back the petals to investigate there is a small pupa, such as in the photo below

Sunflower Seed Maggot Pupa

This is the pupa of a species of sunflower maggot sometimes called the sunflower seed maggot (Neotephritis finalis). A few of the young flowers may be damaged, but overall the damage from this species is thought to be minor.