,

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

 

Respond
Have a follow-up question?

SOYBEANS – TIME FOR THE SPRING CHECKUP!!

Now that many soybean crops are getting to where the crop has fully emerged (usually about three to four weeks after planting) it really is time for those crops to get their spring checkup. It’s the time for growers and agronomist to get their hoops or tape measures and do a plant stand assessment.  The spring checkup is the field visit that will give you the greatest opportunity to protect your profit.

Why is the spring checkup so important?            

  • It’s when you learn the most about what costs the most – Seed can make up half the direct cost of growing soybeans. The spring checkup allows you to see how good of a job of seeding you did. Are you hitting your desired plants per acre target? The spring checkup gives you the chance to do stand counts. And it is an opportunity to inspect seedling health.
  • It’s when you evaluate the major yield driver – If you are counting the plants anyways you have a chance to dig some of them up. Nitrogen is the yield driver because high yielding soybeans need a lot of Nitrogen (N); approximately 6 lbs per acre for every bushel harvested. The spring checkup is your chance to check nodulation.
  • It’s when you are battling the greatest yield threat – Soybeans are not competitive with weeds when small and research has clearly show that early weed control protects the greatest amount of yield. The spring checkup is your chance to assess weed populations and target post emergent applications. And don’t forget to reassess weed control after spraying as well.
  • It’s when you might be deciding to play catch up – If you couldn’t roll your soybeans right after planting, you may be considering post emergent rolling. Rolling at the right crop growth stage is important for minimizing plant damage. Ideally, you are aiming to roll at the first trifoliate. The spring checkup lets you get a handle on crop growth stage.
  • It’s when you might see a disturbing change – A few weeks after planting is when we might start to see yellowing in soybeans. A generalized yellowing of soybean plants may mean that they have exhausted their cotyledon based N supply and are now starting to nodulate and fix N. Soybeans need to starve for N a bit to get the message to start N fixation. The spring checkup lets you ensure that nodulation is proceeding or interveinal leaf yellowing may mean that your soybeans are starting to experience Iron Deficiency Chlorosis (IDC). The severity of IDC varies from year to year and is depending on weather, soil properties and variety genetics. The spring checkup is your start on monitoring this condition in your fields and determining severity.

For a comprehensive but easy to watch explanation of the ways a spring checkup of soybean crops will protect your profit, check out our latest Manitoba Agriculture YouTube feature at: Soybeans – Time for the Spring Checkup.

Submitted by Dennis Lange (IDS – Pulses, Altona) and Terry Buss (FPES – Pulses, Beausejour), Manitoba Agriculture

Respond
Have a follow-up question?

Dry soils and soybean tolerance for starter fertilizer

Most farmers and agronomists should be very aware of the extensive Manitoba research that applied phosphorus fertilizer does not increase soybean yield.  However, phosphorus replenishment of soil with P is important.

Some farmers may still will wish to add some starter fertilizer with soybeans, since in this study (Phosphorus Fertilization Beneficial Management Practices for Soybeans in Manitoba), the seed placement of phosphorus only reduced stands significantly in 7 of 28 sites (1 in 4 cases).  Before growers jump to the conclusion that soybeans tolerate high rates of fertilizer with the seed, let’s review these cases:

  • In almost all cases, soybeans were seeded in moist to wetter soils – as soon as soils were fit to allow traffic.  Row spacing ranged from 7-12” with knife or disk openers.
  • The 7 cases of stand damage highlighted the risk factors:
    • 3/7 = disk openers with row spacings of 12” (so low seedbed utilization)
    • 3/7 = sandy soils (less water holding capacity and buffering)
    • 1/7 = dry seedbed (higher risk)

Our traditional safe seedplaced fertilizer guideline for soybeans is no fertilizer for rows wider than 15”, and up to 10 lb P2O5/ac when seeded in narrower rows.  These limits may even be too high when soils are drying as at present.  We do not expect any advantage to this seedplaced P, so the safest option is to avoid any with the seed.

Again – a review of risk factors for seedplaced P:

  • Soil moisture:  dry = riskier
  • Sol texture: sandy = riskier
  • Seed opener:  narrow or disk = riskier
  • Row spacing: wider = riskier
  • Fertilizer rate: more = riskier

These factors are all considered in the  Seed Placed Fertilizer Decision Aid posted at https://www.ipni.net/toolbox

Submitted by:  John Heard, Crop Nutrition Specialist, Manitoba Agriculture

Follow Manitoba Agriculture on:
Twitter: @MBGovAg
YouTube: www.youtube.com/ManitobaAgriculture

 

Respond
Have a follow-up question?
,

Historically, what has been seeding progress prior to May 1st?

Some producers have started their 2016 seeding operations, with spring wheat being seeded and from what I’ve heard a few acres of corn as well.  With some seeding done, I’ve been asked the question: “What has been seeding progress prior to May 1st in Manitoba in recent years?”.

Producers who participate in AgriInsurance provides seeding date information to Manitoba Agricultural Services Corporation (MASC).  This dataset provides us a historical perspective of when seeding has taken place in the past.

In Table 1, cumulative seeding progress prior to May 1st for six crop types is provided.  A five year (2010-2014) average cumulative seeding progress is noted, along with what was seeded prior to May 1st in 2015. Please note that data is for final insured crop in the ground.

Table 1:  Seeding progress in Manitoba prior to May 1st.

Historical Planting Progress prior to May 1st

Data Source:  Manitoba Agricultural Services Corporation (MASC)

What the table doesn’t show is the wide range of seeding progress prior to May 1st over the past few years.  If we look at seeding progress for red spring wheat in Manitoba, we’ve seen less than 1% of acres seeded prior to May 1st (2009, 2011, 2013 and 2014) but as many as 65% of acres (2010) planted in April.

Look for future updates to historical seeding progress as we enter May!

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, Manitoba Agriculture

Follow Manitoba Agriculture on Twitter (@MBGovAg) to receive updates on seeding progress through the weekly Manitoba Crop Report.
The weekly crop report is also available at Manitoba Crop Report.

 

Respond
Have a follow-up question?
,

Effect of Temperatures, and Natural Enemies, on Soybean Aphids

Effect of temperature on soybean aphids: As with other insects, soybean aphids have a temperature range where development is optimum, with development being slower below and above the optimum range. For soybean aphid the temperature for optimum growth is around 27C. At lower temperatures development will be slower. At the other extreme, in experiments where soybean aphids were kept at high temperatures, nymphs did not complete development at 35C and died within 11 days (J. Econ. Entomol. 2004: 854-861).
Soybean aphid consumption by natural enemies: High levels of natural enemies have been reported by some monitoring levels of soybean aphid. Predaceous insects are the easiest natural enemies to recognize; levels of parasitism and insect pathogens are not often as obvious but with training can be estimated as well. Lady beetles, lacewings, and larvae of hover flies are some of the common and easily recognizable predators in soybean fields. When checking soybean fields, consider whether the aphid populations are increasing or decreasing, and the level of natural enemies present.
Common species of lady beetle that may be noted in soybean fields include the sevenspotted lady beetle and the multicoloured asian lady beetle (Figure 1).
asian-lady-beetle-larva

Figure 1. Larva of multicoloured asian lady beetle

A study looking at predation rates by these two species of lady beetles on soybean aphids found that for sevenspotted lady beetle third instar larvae could each consume up to 105 aphids per day, adult females could each consume up to 115 soybean aphids per day, and each adult male up to 78 aphids per day when soybean aphids are high. (Environmental Entomology: 2009. 708-714). For multicoloured asian lady beetle, third instar larvae could each consume up to 112 aphids per day, adult females could each consume up to 95 soybean aphids per day, and each adult male up to 53 aphids per day when soybean aphids are high.
Some have been sending in photos of hover fly larvae, which may be found in many crops where aphids are present, wondering what they are. Although the adults, which are good bee mimics, are easy to recognize, the larvae may not be as well known. Note that hover fly larvae (Figure 2) are legless, and narrow towards the head. There are different species that can vary in colour, often brown or green.
hover-fly-larvae-on-soybean-leaf

Figure 2. Larvae of 2 species of hover flies and soybean aphids

The above information was submitted by John Gavloski, MAFRD Entomologist.  It is available in this week’s issue of the Manitoba Insect and Disease Update which is posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2015-08-17.html

Respond
Have a follow-up question?
,

Soybean Aphids & Importance of Economic Thresholds

Soybean aphids have been showing up in many fields, but so far populations have stayed below the economic thresholds. A few things to note regarding economic thresholds for soybean aphid:

  • The economic threshold for aphids in soybeans is 250 aphids per plant, and the population is increasing, and the plants are in the R1 (beginning bloom) to R5 (beginning seed) growth stages.
  • The reason that “and the population is increasing” is part of the threshold is because the actual economic injury level, where control costs will equal yield loss, is actually about 670 aphids per plant. The economic threshold, where control is suggested, has been set much lower than 670 to allow time for the spray to be applied before increasing populations could potentially reached 670 per plant. The population doubling time for soybean aphids can be as low as about 7 days if they are not being regulated well by natural enemies or weather.
  • Aphid populations do not always continue to increase. So we can not assume that because a certain number is present this week that even more will be present the next week. Populations can plateau or start decreasing due to natural enemies or weather conditions or events.
  • The above-mentioned economic threshold is based on the average of multiple plants selected from throughout the field and not just hotspots or field borders. Avoid making treatment decisions based on field borders. Small aphid hotspots often collapse from predation, parasitism or emigration.
  • When the value of the soybean crop is high, it is a mistake to try to lower the economic threshold below 250 per plant and the population increasing. There is already a large gap between the economic injury level and the economic threshold that is suggested. But what also needs to be considered is that the damage boundary, which is the lowest insect pressure where any yield loss can be detected, is well above the 250 economic threshold that used. So it would be illogical to try to reduce a threshold which is already below a level where yield loss can not be detected. Although economic injury levels (where control cost = yield loss) do change with commodity prices, damage boundaries do not. And given that aphid populations do not increase in linear fashions, there would be no advantage, and potential costs, to spraying at levels below the suggested economic threshold for soybean aphids. The research publication where the economic thresholds for soybean aphids are presented states “setting an economic threshold at lower aphid densities increases the risk to producers by treating an aphid population that is growing too slowly to exceed the economic injury level in 7 days, eliminates generalist predators, and exposes a large portion of the soybean aphid population to selection by insecticides, which could lead to development of insecticide resistance (Journal of Economic Entomology. 2007: 1258-1267). So to summarize, monitor fields and use the suggested economic thresholds.
  • When aphid levels are high, exact counts are not possible and would consume too much time. Estimates after a quick examination of the plant will be sufficient. Note in figure 1 below the soybean aphids, and the white shed skins from aphids that have molted. Avoid including the shed skins in your counts.
Soybean Aphids on Soybeans

Figure 1. Soybean aphids and shed skins.

The above information was submitted by John Gavloski, MAFRD Entomologist.  It is available in this week’s issue of the Manitoba Insect and Disease Update which is posted at: http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-update-2015-08-04.html

Respond
Have a follow-up question?

Historical Seeding in Progress in Manitoba – First Week of May

Producers who participate in AgriInsurance provides seeding date information to Manitoba Agricultural Services Corporation (MASC).  This dataset provides us a historical perspective of when seeding has taken place in the past.  Seeding date data information is broken down into a week:month format, i.e. 1:05 is Week 1 in the 5th Month (May).  So 2:05 is Week 2 in May, and so on.

Each week is then categorized dependent on the day of the week in which the month starts.  So if Week 1 starts on a Sunday, there will be 7 days of seeding captured in Week 1.  However, if Week 1 starts on Friday (like we have in 2015), there are 9 days captured in Week 1.  Confused yet?  Essentially, each year will have a different number of days captured in each weekly timeframe, varying from 5 days up to 12 days.  However, the data still provides good reference points to seeding progress in Manitoba.

In Table 1, cumulative seeding progress to the end of Week 1 in May for six crop types is provided.  The last five year (2009-2013) average cumulative seeding progress is noted, along with what was seeded in the same timeframe in 2014.   Please note that data is for final insured crop in the ground.

Table 1:  Seeding progress (%) in Manitoba by end of Week 1 in May (1:05).

End of Week 1 May Seeding Progress

Based on the May 11th Manitoba Crop Report, overall seeding progress is estimated at 55% complete.  There isn’t a provincial breakdown provided of seeding progress by crop type, but in looking at each region, seeding of spring cereals is ahead of the 5-year average of 2009-2013, and well ahead of 2014!

Submitted by: Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD 

Respond
Have a follow-up question?

Yields Respectable in 2014 Despite a Challenging Year

Manitoba Agricultural Services Corporation (MASC) has released an early version of the 2014 yield report with 99.8% of the Harvest Production Reports (HPRs) keyed in.  The table below summarizes the 2014 average yield by crop type based on the harvested acres, as well as comparisons to 2013 and a 5-year average (2009 to 2013).

2014 yields

In February 2015, MASC will release their annual Yield Manitoba publication and update their Manitoba Management Plus Program (MMPP) website (http://www.mmpp.com/mmpp.nsf/mmpp_index.html) where further information on yields and acres by variety will be released.  Additionally, the data will be more complete in February as all HPR’s will be keyed in.

Submitted by:  Pam de Rocquigny, Anastasia Kubinec & Dennis Lange, Crop Specialist with MAFRD

Special Thanks to Doug Wilcox, MASC, for providing the 2014 data!

Respond
Have a follow-up question?

My winter wheat has been fertilized with nitrogen, but is so thin it is going to be sprayed out and seeded to soybeans. Will the extra nitrogen harm the soybeans?

Answer provided by John Heard, MAFRD Crop Nutrition Specialist

Our initial experiences of soybeans and high nitrogen soils in Manitoba were negative. High soil N tends to inhibit nodulation while at the same time this nitrogen tends to grow slightly larger vegetative plants. However after flowering that nitrogen is often insufficient to provide full yield and protein potential for the crop. So we adopted a thumb rule that if soils had more than 60-75 lb nitrate-N/acre, producers should consider growing a crop other than soybeans.   The other crops should benefit more from the N than the soybeans, which would still take up the nitrogen but may not express full yield and protein. Nitrogen was also seen to trigger iron deficiency chlorosis in soybeans grown in wetter, high lime soils.

But more recently farmers and agronomists have observed that soybeans may perform well on some high N soils. This may be because soybeans have been grown more often and a native reserve of rhizobium exists in many of these cropped soils. With industry partners (AGVISE Labs and ToneAg Consulting) we made observations at 13 field demonstrations in 2013 where high soil N levels were simulated with N application (Heard et al, 2013). Our observations were:

  • Nitrogen at 50-100 lb N/ac reduced nodulation at all sites, but most severely at the virgin or first time soybean sites. Nodule numbers were still generally sufficient on those fields with a previous history of soybeans (Figure 1).
  • Few sites were harvested for yield, but nitrogen affect was more severe on the first year soybeans (reduced yield or lower protein).

Figure 1: Average rhizobium nodules per root from 13 demonstrations in 2013.

Picture1

So if one needs to replant soybeans on a field already fertilized with nitrogen consider:

  • Whether well nodulated soybeans have been grown in the past.
  • Treating fields with a history of soybeans as virgin fields by applying full rate of inoculant
  • Even if fields have high N in the spring, soybeans will largely deplete those reserves during the season

One may still wish to avoid planting soybeans if it is a virgin field or if there is risk of iron deficiency chlorosis.

There was no advantage to supplementing properly nodulated soybeans with additional nitrogen at these sites. In US studies, additional nitrogen appears warranted “sometimes” when yields are very high (>65 bu/ac) or when nodulation failures occur due to acid soil, drought or other adverse weather conditions.

References:

Heard, J., J. Lee and R. Tone. 2013. Nitrogen and soybeans: Friends, foes or just wasted fertility? Manitoba Agropnomists Conference 2013.

http://www.umanitoba.ca/faculties/afs/agronomists_conf/media/2013_Heard_N_on_soybeans_friend_foe_or_waste_Dec_3_final.pdf

 

Respond
Have a follow-up question?

Update to Historical Seeding Progress in Manitoba

Another week has passed and seeding progress was made in some areas of Manitoba, while some producers wait for warmer and drier conditions.  Hopefully many producers are able to make good seeding progress while the sun shines over the next few days.

Last week I provided an update “What is ‘normal’ seeding progress for this time of year?”  http://cropchatter.com/what-is-normal-seeding-progress-for-this-time-of-year/.  That information covered up to end of Week 1 in May.

In Table 2 below, cumulative seeding progress to the end of Week 2 in May for six crop types is provided.  The last five year (2008-2012) average cumulative seeding progress is noted, along with what was seeded in the same timeframe in 2013. (In 2013, Week 2 ended on May 18th).   Please note that data is for final insured crop in the ground.

Table 2:  Historical seeding progress in Manitoba by end of Week 2 in May (2:05).

Crop Cumulative 5 yr Cumulative 2013 (%)
(2008-2012) (%)
Red Spring Wheat 65 54
Barley 58 38
Oats 56 36
Argentine Canola 36 22
Grain Corn 62 79
Soybeans 22 28

Good luck to everyone with their seeding operations and keep safe!

Submitted by:  Pam de Rocquigny, MAFRD Provincial Cereal Crops Specialist

Respond
Have a follow-up question?