Month: July 2023

Soybean Postemergence Weed Control – Grasses

After planting, the second biggest challenge we face is timely weed control.  If you haven’t already made a postemergence application, it might be time to check your fields.  Most beans (and weeds) are at stage that might warrant an application.

Table 15 below from the 2023 OSU Weed Control Guide compares the relative effectiveness of herbicides on individual weeds. Ratings indicate the level of control of weeds present at the time of application, and are based on labeled rate and weed size or growth stage.

Click on table to enlarge

Field Observations Thru July 7

Alfalfa

Recent weather has delayed 2nd cutting in many fields.  Potato leafhoppers are very active.  Continue to monitor, where damage is increasing, cut as soon as weather permits.

Click here for alfalfa insect scouting calendar

Click here for more information on Potato Leafhopper

Corn

Plenty of moisture and some welcome warm weather – What a difference a week makes!

Warmer weather has slowed slug activity and the rapid corn growth is helping these plants escape (outgrow) this damage.

Our corn growth varies greatly throughout the county.  Most of the county is between V6 and V12. However, there are some fields at V12 and beyond.

V10 to V11 – The corn plant begins a steady and rapid increase in nutrient and dry-matter accumulation. The time between the appearance of new leaves is shortened, with a new leaf appearing every two to three days.  Demand for soil nutrients and water are relatively high to meet the needs of the increased growth rate. Moisture and nutrient deficiencies at this stage will influence the growth and development of the ears markedly. Fertilizer, especially phosphorus and potassium, is needed near the roots, which do not move appreciable distances in most soils. Dry soils also may make needed nutrients less available.

I have received a few questions about postemergence herbicide applications.  Click the links below for OSU Postemergence Herbicide Ratings.

Table 5. Postemergence Herbicides in Corn – Grasses

Table 6. Postemergence Herbicides in Corn – Broadleaves

Soybeans

Ok, many soybean fields just don’t look good, especially for this time of year.  While scouting your bean fields, check for seedling diseases and water-logged roots.

Warmer weather has slowed slug activity however beans are still growing slowly and may not be able to outgrow the feeding yet – Continue to monitor your bean fields for slug feeding.

Click here for slug information

Our Soybean  growth varies throughout the county.  Most of the county is between V3 and V6. However, there are some fields at and approaching R1.

V3 through V6 – The third trifoliolate (V3) stage takes place when three trifoliolates are unrolled. In case of damage to the growing point, axillary buds permit the plants to compensate for yield or final productivity.  The unrolling of six trifoliolates indicates the V6 stage. The root system continues to grow, even expanding across a 30-inch row spacing.  The V growth stages continue as long as a plant continues to produce trifoliolates. Determinate soybean plants complete most of their vegetative growth when flowering begins. Indeterminate plants produce trifoliolates until the beginning of the seed formation stage (late reproductive period).

Wheat

When, When, When will the wheat be ready??  Wheat harvest is just getting started.  A little sunshine and continued warm weather would certainly speed up the process.

Planning on planting beans after wheat? 

Click here for the Double Crop Soybean Production Guidelines from Dr. Laura Lindsey.

Click here to view herbicide restrictions prior to planting.  Table 23 from the Ohio Weed Control guide lists these restrictions.

Misc. – Something you don’t see everyday.

I can honestly say that I have never seen one of these before! Click on the picture to see the video. If you know what it is, put your answer in the comment section.  Be sure to check back next week for the answer!

County Rainfall Update

 

Pest of the week – Japanese Beetle

Japanese Beetles

Identification:

Adult: Adults are 5/16 inches long and have metallic green bodies with bronze forewings (elytra) and clubbed antennae. The forewings do not completely cover the end of the abdomen, and there are six white tufts of hair on each side of the abdomen. Males have large spikes on the front tibia while females will have spoon-like paddles.

Lifecycle:

Larvae (grubs) feed on roots of many hosts, and overwinter. Adults emerge mid-summer and feed on hundreds of hosts, including soybeans. Adults may persist into fall. Eggs laid in the soil in July-Sept.
1 generation per year

Damage:

Injury to corn: Although Japanese beetle adults can feed on the leaves of corn plants, the main concern is silk clipping. Silk clipping may interfere with pollination and lead to reduced seed set. Additionally, adults may feed on exposed kernels, but this injury is less concerning than silk clipping. Drought stress can exacerbate the effect of silk clipping by Japanese beetles. Silk clipping usually only causes reduced pollination when a majority of corn plants have silks clipped back to less than ½ inches.

Injury to soybeans: In soybeans, Japanese beetle is part of the complex of defoliating insects. Japanese beetles cause skeletonization, which is characteristic of this species because adults feed on the leaf tissue but leave all veins intact. Aggregations of Japanese beetle adults on soybean plants can cause heavy defoliation in a particular area, but beetles are usually only feeding in the upper canopy and on a few trifoliates.

Scouting:

Corn: Obtain a representative sample of silk clipping in corn by assessing silk clipping for five random plants in five locations of the field. It is especially important to scout for silk clipping during the first five days of silking.

Soybean: Scouting for Japanese beetle in soybean involves estimating percent defoliation across the entire field and throughout the entire plant canopy. Management decisions are often made for the entire complex of defoliating insects in soybean (caterpillars, beetles, grasshoppers) since it is often difficult to distinguish between types of defoliation. Use the scouting plan in Figure 2 to estimate field-wide defoliation. Remember it is important to scout the entire field because defoliation may be concentrated at field edges, and it is important to scout the entire canopy because Japanese beetle exhibits top-down feeding behavior. Make sure that defoliating pests are still present in the field before making an insecticide application by visually looking for pests or using a sweep net.

Economic Threshold:

Corn: Foliage feeding in corn is almost never economic, though economic damage from silk clipping is possible (though rare).  A foliar insecticide is warranted if three conditions are met:

  1. Three or more beetles are present per ear;
  2. Silks have been clipped to less than ½ inch; AND
  3. Pollination is less than 50% complete.

Because adults are highly mobile, remember to continue scouting until pollination is complete. Adults can continue to reinfest fields even after an insecticide application.

Soybeans: While the damage might look startling, it is very rare that this reaches economic levels from Japanese beetle.  A rescue treatment is advised when defoliation levels reach 30% in pre-bloom stages, and 20% in bloom to pod fill.  These defoliation levels apply to the plant as a whole, not just certain leaves, and can also be used for general defoliation from more than one kind of leaf-feeding insect in soybean.

Control Options: Many insecticides are labeled for Japanese beetle grubs and adults and are very effective. However, Japanese beetle adults are highly mobile and may reinfest fields even after an insecticide application.

Corn Insect Control Table

Soybean Insect Control Table

Soybean defoliation guide:

 

Weed of the week – Common Pokeweed

Common Pokeweed (AKA – Pokeberry)

Family:  Pokeweed Family

Life cycle: Perennial

Description: A large, 3 to 10 ft tall, perennial weed with thick, reddish-purple branched stems and dark purple to black berries. All parts of the plant are poisonous to cattle, horses, swine, and humans, especially the roots.

Seedlings: Cotyledons 7-33 mm long, 6-11 mm wide, egg-shaped but pointed at the apex. Stems below the cotyledons (hypocotyls) are without hairs, succulent, and often purple-tinged. Young leaves alternate, egg-shaped but pointed at the apex, and without hairs. Cotyledons and young leaves are pale green in color, with reddish tinted petioles.

Roots: Large, white tap root up to 6 inches in diameter.

 

 

Stem: Branch from the root crown at the base of the plant, erect, large, smooth, purple-tinged.

Leaves: Alternate, 3 1/2-12 inches long, 1-4 inches wide, egg-shaped, petiolated, without hairs, and are smaller in size toward the top of the plant.

Flower: Individual flowers small (6 mm wide) with 5 white to pink-tinged sepals.

Fruit: A berry, 7-12 mm, green when immature, dark-purple to black when mature. Contain a dark red juice.

 

Special identifying characteristics: Large, tree-like plant with egg-shaped leaves, purple-tinged stems and dark purple berries.

Pokeweed Control in Corn and Soybeans

 

Hot summer temps increase risk of heat illness

Source:  Dee Jepsen, OSU Extension

Farmers, producers, and anyone who works outdoors should beware: When the weather is warmer, you’re at a higher risk for heat illness, which can come on suddenly with many people unaware they’re in danger.

Even experienced workers are vulnerable to heat-related illness, said Dee Jepsen, state leader, Ohio State University Extension Agricultural Safety and Health Program. OSU Extension is the outreach arm of The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES).

One reason is that, often, some are unwilling to admit that heat affects them. Or they don’t recognize the symptoms.

In fact, almost half of heat-related deaths occur on a worker’s first day on the job. According to the Occupational Safety and Health Administration, over 70% of heat-related deaths occur during a worker’s first week.

“There seems to be a stigma associated with being affected by heat illness,” Jepsen said. “Some of the typical responses from some as to why they’re unwilling to acknowledge the risk of heat illness include, ‘I don’t need a break,’ ‘I need to prove I can work hard,’ or I don’t usually need to drink a lot of water.”

Signs of heat illness can include headache; nausea; weakness; dizziness; heavy sweating or hot, dry skin; elevated body temperature; thirst; and decreased urine output. Signs of a potential medical emergency include abnormal thinking or behavior, slurred speech, seizures, or loss of consciousness.

Steps to prevent heat illness include drinking water every 20 minutes; taking breaks in shady or cool locations; wearing a wide-brimmed hat and light-colored, loose-fitting breathable clothes; and monitoring oneself and others for signs of heat illness.

“Some tips to help lessen the potential for heat illness in agricultural workers include increasing general ventilation in barns and outdoor structures or installing cooling fans and misters under tents during outdoor field work and vegetable crop activities,” Jepsen said. “Other strategies include reducing manual labor, increasing the use of mechanized systems, and taking frequent breaks during peak heat hours.

Dry Weather Effects on Corn at Early Growth Stages

This past weekends’ rain certainly helped alleviate moisture concerns throughout Knox County.  What impacts will the early dry weather we experienced in parts of Knox County have on potential corn yield?  The following information from Chad Lee at the University of Kentucky suggest the earlier dry weather may have minimal impacts as long as Mother Nature cooperates through the rest of the growing season.

The dry weather across the state is putting stress on the corn crop. The lack of water to corn before the V12 growth stage usually results in minimal yield losses if adequate water occurs at V12 and beyond. Most of the corn in Kentucky ranges from just planted to about V9 as of June 5, 2023.

While yield losses might be minimal, some other issues can or will occur with a lack of water. Each of these scenarios assumes that the water stress lasts for about two weeks and plants will recover on the other side.

  1. Leaf rolling: The corn leaves will roll during the heat of the day to try to conserve as much water as possible. When this leaf rolling occurs, the plant conducts less photosynthesis, causing it to produce less biomass during drought stress.

  2. Potassium Deficiency: Potassium deficiency is a common indicator of drought stress on young corn plants. Plant tissue samples were taken on V3 to V6 corn last week, and this week likely will show K deficiency, and that K deficiency may be from the drought and nothing else. The corn plant needs water to take up K, so adding more potassium will have no effect on the corn crop if the crop does not have water.

  3. Other Nutrient Deficiencies: Water is needed for corn to take up several nutrients, not just potassium. Potassium might be the most obvious, but a tissue test will reveal several others as being deficient as well. A soaking rain is the best remedy for these transient deficiencies.

  4. Compaction Becomes Evident: Both seed furrow sidewall compaction and subsurface tillage compaction become more obvious in dry soils. If corn in a single row or a section of the field shows twisting and curling before other corn, compaction could be a problem. “Vertical tillage” implements and discs often cause soil compaction at the depth they are set. In dry soils, these compacted areas become impossible for roots to break through. Both sidewall compaction and subsurface compaction stunt roots. Those stunted roots cannot take up as many nutrients resulting in stunted corn plants. Timely rains are about the only in-season remedy for these soils. With the dry weather in the forecast right now, rains might be too late to help.  

  5. “Floppy” corn syndrome. (Someone needs to write a “Floppy Corn” song to the tune of Adam Sandler’s Sloppy Joe chorus in “Lunch Lady Land.”) The dry weather and hot temperatures can cause all roots from one or more nodes to desiccate or dry out and die. A strong wind at this point will knock the plants over. Corn plants from about V2 to V3 will be most susceptible this week. Corn plants in shallow placement are more susceptible. Soaking rains to allow new root growth before any strong winds occur is the best remedy. For more on Floppy corn, see this article.  As for that song: “Floppy corn, flop-floppy corn…” It’s in your head now, isn’t it?   

  6. Loss of Row Number or Kernel Number: Once corn reaches V6 growth stage, the dominant ear and tassel formation start. However, water stress starts affecting row number and kernel number closer to the V12 growth stage. At the V6 growth stage, the corn plants have switched to the nodal root system. This is the final stage before exponential growth. A lack of water from V7 to about V12 could reduce the total biomass of the stem and leaves. A lack of water around V12 will reduce kernel rows and then kernel numbers per row on the ears.

  7. Less Disease Risk: So, we are looking for a positive aspect with this one. A lack of water means foliar disease pressure is extremely low right now. We should not be applying fungicides to V5 or V6 corn anyhow. We certainly do not need fungicides in a drought. Kiersten Wise will have more on this issue.

  8. A Lack of Residual Herbicide Activity: Most soil residual herbicides need rainfall to activate. Scout fields to identify which weeds are escaping and plan to spray once a rain event occurs. The weeds are not growing well now, either. They need the rain event to be receptive to the herbicides. When applying the herbicides, be sure to use the full adjuvant types and rates recommended on the labels. Travis Legleiter will have more on this issue.

  9. Watch the Roots this Week: Soils usually dry from the surface downward. This movement of water can affect root development. The V9 corn should have well-developed roots that are deeper into the soil. While the V9 corn demands more water than V2 corn, the V9 roots are more likely to interact with plant available water longer than the V2 corn this week. Emerging corn (VE) and V1 corn demands very little water (less than 0.1 inches per day), and most soils still have enough for those plants at the start of this week. Corn at the V2 to V3 growth stage this week may be at soil depths without water and could lose nodal roots to the lack of water.  

  10. Nitrogen On Dry Soils: Volatilization losses are the greatest risk for N losses in dry weather. Urea fertilizers on the soil surface will be actively volatilizing within 72 hours (about 3 days) after application. Urea treated with an adequate rate of NBPT (the active ingredient in Agrotain and other products) will not begin volatilization for about 7 to 14 days. Urea treated with adequate rates of Duromide plus NBPT (the active ingredients in Anvol) will not volatilize for about 14 to 21 days. If possible, sidedress with liquid urea ammonium nitrate (either 28% or 32% UAN). Only half of the UAN product is urea, making volatilization a smaller risk. The liquid form will soak into the soil, further reducing volatilization losses. Injecting the UAN into the soil would be preferred where possible. Whether injected or applied to the surface, the UAN will not move far until water re-enters the soil profile. Corn will not take up the N, either, until water is available, so getting the N right next to the corn plant may not be as important. Spray booms with StreamJet (or similar style) nozzles in between each row will apply some of the N closes to the plant. Avoid applying any of the nitrogen directly to the corn plants. If applied this week, direct contact of N fertilizer with corn leaves will burn the corn leaves. Usually, this burn is cosmetic and does not affect plant health and yield. But, the corn crop is stressed already, and leaf rolling is limiting photosynthesis. There is no need to add additional stress with leaf burn. If dry urea is the only option available, then apply it. If other options are available, pursue those. Edwin Ritchey and John Grove have more on this topic.

The weather forecast this week provides low chances of rain. More corn in more fields will roll this week. Some of it will look bad. But all of it still has a chance to make good to excellent yields. We will all be monitoring the crop closely and will provide updates in the coming weeks.