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Manitoba Insect & Disease Update – Issue 10: July 20, 2016

The Manitoba Insect and Disease Update is now posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-report-2016-07-20.html

Some highlights from the update:

Insects:

  • Pea aphid levels are still a concern in some pea fields, although many fields will be getting to the stage where management would no longer be economical.
  • Aphid levels have dropped in many cereal fields where previously levels had been increasing. High levels of natural enemies have been noted in some of these fields, and some intense rains may have also contributed.
  • In some areas of Central and Southwest Manitoba, greater than 90% of the wheat midge are expected to have emerged. In many areas of Manitoba about 50 to 90% of wheat midge are expected to have emerged. A reminder that wheat that has already produced anthers is no longer susceptible to feeding by wheat midge. Even if adults are still active in these more advanced fields, the larvae will not feed on the grain.
  • Egg masses of European corn corer are starting to be noted in some fields of corn. So far there are no reports of high levels, but now is the time to be checking fields for the egg masses.
european-corn-borer-egg-masses

Figure 1. Egg masses of European corn borer.

Plant Pathogens:

  • Some infections of blackleg in canola and fusarium head blight in cereals have been reported.
  • A few cases of loose smut in barley were also reported.
  • Two positive identifications of Goss’s Wilt in corn were made. The positive identifications were made based on immunostrips and/or polymerase chain reaction (PCR) assays.

Submitted by: John Gavloski, Entomologist & Pratisara Bajracharya, Field Crop Pathologist, Manitoba Agriculture

Manitoba Agriculture website: www.manitoba.ca/agriculture
Manitoba Agriculture on Twitter: @MBGovAg
Manitoba Agriculture on YouTube: www.youtube.com/ManitobaAgriculture

 

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What are minimum germination temperatures?

Soil temperature is a useful gauge for timing when crops are seeded.  Table 1 shows the minimum germination temperatures for various crops.  These values should be regarded as approximate since germination depends on several factors.  If the soil is too cool, germination can be delayed which can result in uneven or inadequate seedling emergence.

How do I measure soil temperature?

Determine how deep you will be seeding. Then place your soil thermometer at that targetted depth. Take two measurements throughout the day: one in the morning (8am) and one in the early evening (8pm) . Average the two readings to determine the average soil temperature.

MAFRD recommends that you take readings for two to three days to establish a multiple day average, and reminds you to measure temperature in a number of locations in the field, to account for field variability.  Still not sure, see soil temperature data for various locations across Manitoba is available from MAFRI’s Ag-Weather Program:  http://tgs.gov.mb.ca/climate/SoilTemp.aspx.  This can be used as a guideline for an area, but in-field measurements are going to tell you what is actually going on in your field!

Table 1: Minimum Germination Temperatures for Various Crops

Crop Temperature (°C)
Wheat 4
Barley 3
Oats 5
Corn 10
Canola 5
Flax 9
Sunflower 6
Edible Beans 10
Peas 4
Soybeans 10

Sources: North Dakota StateUniversity Extension Service, Alberta Agriculture & Rural Development and Canola Council of Canada

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