Early Season Observations and Watch-Outs

HARD FREEZE, SEVERAL INCHES OF SNOW

Wow, what an exciting week for some of our Dairyland Seed agronomists! 

During the week of April 19, much of the Dairyland Seed marketing area received snow and freezing temperatures. Very few times have we had this much crop in the ground, a hard freeze and several inches of snow. Please note: as agronomists, what is interesting and useful to us may not be quite as fun for our clientele.

The good news is that our team believes most seeds and/or seedlings in the ground survived the cold temperatures and snow quite nicely. Many times, in post mortem examination of an agronomic situation, we find it’s simply a matter of timing. We feel this was the case here as well.

The early May event last year happened three weeks later when more corn and soybeans were emerged and exposed to the elements. Another stark contrast was soils temperatures. It seems very odd, but soils temperatures going into the April 2021 event had been warm. Let’s add on a nice blanket of insulating snow, and we kept crops fairly well protected. 

The other key was simply most seedlings were tucked nicely in the ground at this time safe from the cold temperatures. Please refer to last week’s article to review cold tolerances for corn and soybeans.  As you review the pictures below, note the integrity of the seedlings three days after the damage occurred. When assessing damage of this type, it is often best to wait several days before making a final determination of recovery and condition. We like to say “Let the plant tell us what it’s doing”. 

As in every crop year, we always have a little surprise and excitement. Let’s hope this was it for this crop season. Please be mindful of safety as we establish our 2021 crop.

SOYBEAN GERMINATION AND EARLY GROWTH REFRESHER

Soybeans, much like corn, need to imbibe (take in) water for the germination process to take place. The difference is that soybeans need to take in 50 percent of its weight in water to start this process compared to 30 percent for corn. Since soybeans are about two-thirds the weight of corn, the actual amount of water needed to germinate is very similar.

• Germination is impacted by both moisture and temperature.
• Germination is driven by hormonal systems within the seed. (This process is not well understood, but is being studied.)
• Once germination starts, the Cotyledons (the two halves of the soybean seed also known as the seed leaves) begin to swell. The Radicle, or Primary Root emerges from the seed and Gravitropism or Geotropism (cells within the plant responding to Gravity) take over and the Radicle starts to grow down.
• As cell division continues, the Radicle lengthens. As this is taking place, the Hypocotyl (which is the small section of the stem between the Cotyledon and the Radicle) begins to stretch out and grow toward the soil surface.

• As the Hypocotyl elongates, the Cotyledons are oriented downward and are, in effect, “pulled” upward by elongating Hypocotyl. (Think of a pebble in a sling shot.)
• Lateral roots begin growing from the Radicle shortly before the Hypocotyl pulls the Cotyledons through the soil surface.
• It takes approximately 100-125 Growing Degree Units (GDU’s) after planting for the neck, or curved portion of the Hypocotyl above the Cotyledons, to emerge from the soil surface. As it continues its growth upward, the Cotyledons are pulled through the soil surface.
• Once the Cotyledons emerge above the soil line, this is known as the VE stage, or emergence stage, they stretch up, open up and enlarge.
• Shortly after the Cotyledons emerge from the stem, the Hypocotyl will cease to grow but the Epicotyl (stem and subsequent leaves) continues to grow from a point above the Cotyledons.
• As the Epicotyl grows, the Unifoliate leaves emerge, one on each side of the stem. We are now in the VC stage. This is the last node with two leaves. All subsequent nodes will have Trifoliate or three leaves.

• As the stem continues to grow, the first Trifoliate emerges. We are now at the V1 growth stage.

EARLY SEASON PEST ROUNDUP

While planting is arguably the most important event of the growing season for creating yield, we have to quickly shift focus to protecting yield. Now is the time to anticipate where you may need to pay special attention to any insect pressure.

Black Cutworm

The Midwest experienced a modest moth flight in mid-April this year, with recent numbers being suppressed by low temperatures. While flight numbers will likely peak in May, the eggs laid in the first round are very tolerant to cold temperatures and should be hatching this week. Living for about a month, these larvae could feed on newly emerging corn in the coming weeks. Watch weedy, high residue or cover crop areas first. Soil applied insecticides and foliar insecticides offer good control. For the latter, be sure to scout corn for 2 to 5 percent plant cutting (depending on the age of the larvae population) before deciding to treat.

All of Dairyland Seed’s Qrome®, AcreMax®, AcreMax® Xtreme and SmartStax® corn hybrids offer Bt control of black cutworm. Just remember that an insect must feed on plant tissue for the Bt to work. Therefore, cutworms can still do some damage to newly emerged corn, but the protein will prevent most “down the row” feeding.

True Armyworm

True armyworm (TAW) migrations are more difficult to time each spring and tend to be localized. Issues can arise at nearly any corn stage, so monitoring the various trapping networks is key to picking up on this pest. So far 2021 has been quiet, but it’s still very early. TAWs are defoliators that favor grassy areas. Watch field edges and cereal crops closely for early indicators. In corn, treatment requires 25 percent of plants to have two larvae or 75 percent of plants to have one larva. A limited number of Bt traits offer control of TAW.

Bean Leaf Beetle

Bean Leaf Beetles (BLB) are likely the most widespread early season soybean pest (seed corn maggot and slugs might give them a run for their money!). BLB show up in two generations each year; the first one being associated with overwintering beetles. Watch for them a little closer if you experienced good snow cover this past winter. BLBs look very similar to corn rootworm beetles, but can be identified with a black triangular mark just behind the head. Three beetles per plant at the unifoliate growth stage or earlier may warrant treatment, as does 30 percent defoliation from the V1-V7 growth stages.

Alfalfa Weevil

The Dairyland Seed agronomy team has observed larvae in northern Indiana about 10 days ago. Southern portions of Michigan, Wisconsin, and Minnesota should be reaching the heat unit threshold that initiates the larvae hatch this week.

Primarily a pest of first crop alfalfa, the alfalfa weevil is a pale green larva with a black head that can reduce tonnage and quality from our crop. Control weevils when 40 percent of first crop plants show signs of feeding (not to be confused with 40 percent defoliation). If harvest is more than 10 days out, spray with insecticide. If the normal cutting schedule puts harvest at less than 10 days, go cut immediately to save an application. Watch the regrowth of second crop closely.