In this issue
§ Watch for cutworms
§
Honey bee colony collapse disorder
§ Crop rotation and replant considerations with herbicides
§ Soybean root diseases and wet soils
§ White grubs
and corn stand reductions
§ Early
season irrigation
§
2007 MSU Weed Tour
§
Regional reports
§
Weather
Christina DiFonzo
Entomology
Black cutworms are “right-on-time” this year. Trap catches to the south of Michigan have been high (to see what is happening to the south of us, visit the Chat’n Chew cafe web site which links to newsletters from Illinois, Indiana, and Ohio http://www.agry.purdue.edu/ext/corn/cafe/.)
Adult black cutworm moths migrate into
Effective weed control avoids or reduces black cutworm infestations. Controlling low lying, densely growing weeds such as chickweed, deadnettle and mustards reduces the areas for moths to lay eggs. If weeds or a cover crop can be killed a week or two before crop emergence, most cutworm larvae will starve. Over the last few years, there have been spotty cutworm infestations in corn, soybeans and sugar beets, perhaps because of earlier planting or changes in production practices to no-till. Also, with the use of herbicide-resistant crops, fields may be weedier early in the season before glyphosate is applied.
Scout for cutworms at seedling emergence. Look for wilted or cut plants, and dig around the base of nearby seedlings to find the larvae. If you can’t find cutworms near a damaged plant, move down the row to the next apparently undamaged plant. Larvae feed at night and hide during the day, so the best time to look for larvae is in the early morning.
A general threshold is 5 percent or more of plants showing cutworm damage. Rescue (foliar) insecticide treatments are the preferred way to manage cutworm because few fields will have a significant problem. Insecticides are most effective if sprayed in the evening when the cutworms are active. In crops like corn, beans and alfalfa, pyrethroids such as Ambush, Baythroid, Mustang, Pounce, and Warrior are particularly effective against cutworms (check labels for specific crop registrations and rates). For sugarbeets, options include Asana, Declare and Lorsban. As usual, be careful when adding an insecticide to a micro-rate herbicide application for beets.
Honey bee colony collapse
disorder
Zachary Huang, Entomology Department
Modified for the Field Crops CAT Alert by Christina DiFonzo
If you have been listening to the radio or reading papers the last few weeks, chances are that you have already heard about the alarming honey bee die-offs around the country. The phenomenon is officially named “colony collapse disorder” (CCD). This disorder has the media all excited because it is large in scale (25 states are affected), came in quick (colonies that were fine in August-September collapsed around October-November), and hit people hard (many beekeepers with hundreds to thousands of colonies are losing 50-90 percent of their hives). The worst of it all, we do not yet know what causes it.
The symptom seems to be that bees simply disappear. Initially, people called it the disappearing disease (or fall dwindle disease). A colony with 40,000 bees in the fall, apparently healthy with lots of honey and pollen, suddenly has no or few bees left. Very few dead bees are found inside the hive or near the entrance. Strangely, wax moths, small hive beetles, robbing bees and other pests are slow to move into such newly abandoned colonies – taking two to three weeks rather than moving immediately into defenseless colonies.
There are several possible causes for hive deaths, several
of them natural. One is tracheal mites (Acarapis
woodi), which first were found in
Unfortunately, all these factors (mites, disease and
pesticides) are unlikely to be the causes of CCD. Scientists from
Field crops producers do not have to worry about pollination fees because corn, soybean and small grain crops are not bee-pollinated. However, bees visit field crops, especially alfalfa and soybean fields, to work flowers. The majority of insecticides used to control weevil and potato leafhopper in alfalfa, and soybean aphid in soybean, are highly toxic to bees. Given the recent reduction in hives, anything you can do to protect bees is important for the food supply. Here are some bee-protection tips:
§ Cut alfalfa before 10 percent bloom (bees are attracted to fields in bloom).
§ Note honey warning labels on insecticides used on alfalfa.
§ Notify bee keepers in your area when you treat. They may be able to restrict bee movement.
§ Spray
in the evening when bees are not foraging.
Christy Sprague
Crop & Soil Sciences
Crop rotation and replant restrictions for herbicides are extremely important to follow prior to planting. One of the desired characteristics of an herbicide can often be residual activity for weed control. However, this characteristic can also cause some headaches if the rotation restrictions are not followed. Herbicides need sufficient time to dissipate or breakdown prior to planting crops that are more susceptible to that herbicide. For example, 1 pt/A of 2,4-D ester can be an extremely valuable tool for burndown applications prior to planting soybeans. However, for this application to be safe to soybeans, 2,4-D ester needs to be applied seven days prior to planting soybeans. The restriction or days to planting is longer for higher rates of 2,4-D ester and even different formulations (amine formulations) of 2,4-D. The restriction is 15 days between an application of 1 pt/A of 2,4-D amine and soybean planting and is as much as 30 days if the application rate is higher than 1 pt/A.
There are several factors that influence the dissipation of an herbicide in the soil. These factors include: the herbicide’s ability to persist in the soil, the amount of rainfall or soil moisture available for degradation, soil temperature and soil pH. Although these factors all influence herbicide persistence, certain factors are more important than others for specific herbicide chemistries.
First of all, it is always important to know what products were applied in the field, how long these products persist and what rotational crops are sensitive to soil residues. Different herbicides persist in the soil different lengths of time. It is important to know when a product was applied to determine the time the product has been available for degradation. For example, the atrazine label indicates that soybeans can be planted the following year, if applications were made before June 10 of the previous year. This rotational restriction was made to ensure that there was sufficient time for atrazine to degrade between application and soybean planting the following year.
Other factors to consider include the amount of
precipitation received following application and soil temperatures. Dry soil
conditions generally reduce the rate of herbicide degradation. Soil moisture is
extremely important, especially during the first two to four weeks after
application. If rainfall and soil moisture are not sufficient, dissipation of
the herbicide will most likely be reduced, ultimately increasing the potential
problem for the following crop. Additionally, lack of soil moisture can result
in increased herbicide adsorption to soil particles and organic matter,
reducing herbicide availability for degradation. Soil temperature also plays an
important role in herbicide degradation. Colder soil temperatures can decrease
herbicide degradation. That is why certain herbicides are not used in
Soil pH affects the persistence and degradation of many herbicides. In particular, high soil pH (above 7.0) reduces the dissipation of atrazine and simazine. Also, dissipation of chlorimuron-containing products (Classic, Canopy, Canopy EX, and Synchrony XP) is reduced if the soil pH is greater than 7.0, increasing the likelihood of persistence. Clomazone (Command) dissipation is reduced by soil pH levels less than or equal to 5.9, increasing the chances of carryover to corn the following year.
To avoid problems due to herbicide carryover, it is always important to follow the crop rotation restrictions that are found on the herbicide label. Additionally, this information can be found and is summarized in Table 12 of the 2007 Weed Control Guide for Field Crops. If you are still concerned about the potential for carryover, field or greenhouse bioassays can be conducted to help determine potential carryover problems. These bioassays are generally inexpensive and will help estimate the potential for rotational crop injury from herbicide residues.
Diane Brown-Rytlewski
Plant Pathology
Recent heavy rainfalls have delayed soybean planting, and put more pressure on growers to plant when conditions are less than ideal, but it’s a good idea to consider the effect of planting into wet soils on soybean seeds from a perspective of seed and seedling diseases.
During wet years, fields of newly-planted soybeans and soybean seedlings can be subject to significant losses from root-decaying fungi such as Pythium, Phytophthora, Rhizoctonia and Fusarium.
Although each pathogen has an ideal temperature range for
germination of spores and development of disease, one thing they all have in
common is a liking for wet soils. Soils may be soggy due to poor drainage
resulting from heavy clay, or compaction, or saturated from heavy rainfall.
Soils may remain wet for extended periods of time, especially in low areas of
fields where water collects. Fields that are under no-till or reduced tillage,
tend to stay wet longer and warm up more slowly than fields under conventional
tillage.
Pythium spp. are common soil-borne pathogens that can infect seeds, seedlings and roots of soybeans at cool soil temperatures (40-59oF). Pythium can cause delayed emergence and poor stands, resulting in significant plant losses. Pythium belongs to a class of fungi called oomycetes, whose dead spots on roots where infection is mild, to dead root tips and loss of the taproot. Severely infected seedlings are stunted, chlorotic and may die. Symptoms caused by another oomycete, Phytophthora sojae, are similar. P. sojae is most severe in flooded or poorly drained soils, but its development is favored by warmer soil temperatures (68-77°F). A row of dead plants may occur in a low area or in patches in the field. Plants pull up easily from the ground, because there are almost no roots attached.
Rhizoctonia root and stem rot also tends to occur in patches, and is more common on seedlings and young plants. A reddish-brown lesion develops on the root and may extend upward to the stem. Plants look chlorotic due to lack of roots, but the chlorosis is sometimes mistaken for nitrogen deficiency. Wet soils, high organic matter and temperatures of 77 to 84°F are optimum for development of the disease, although symptoms become much more visible when plants are under drought stress later in the season.
Several species of Fusarium cause root rots that produce sunken, light to dark brown lesions and loss of lateral roots. The damage may go undetected during scouting, and the disease may only be evident when a loss of yield is noted. In a limited survey of soybean root and stem disease in Michigan last year, the most commonly isolated fungus from field samples collected was F. oxysporum, but we have not yet determined how significant a role it may be playing in affecting soybean yield.
Regardless of the disease, good drainage is important for management. Take what measures you can to improve drainage. If your field has a history of seedling disease, fungicidal seed treatments may be helpful. Consult the field crops guide for a list of seed treatments and the fungi they are labeled to control. A few seed treatments are labeled for Phytophthora, but look carefully at the label for the rate to use. Use Phytophthora- resistant varieties if this disease has been a problem in the past. Try to delay planting into wet fields until planting conditions improve.
White grubs and corn stand reductions
We have had at least one instance this spring in
While many areas in the state have had high populations of
European chafer in the past, areas in
Grub damage often tends to be patchy. European chafer damage is
often found in sandier parts of fields. Delayed emergence can also increase
damage, especially from annual grubs. There is no rescue treatment for grubs in
field crops. Corn planted into grub-infested fields should be treated with a
soil insecticide to protect plants until grub feeding stops before pupation, or
until sufficient root mass is developed to withstand damage. Poncho seed
treatment has also worked well under low to moderate grub pressure.
There is no threshold for determining when it is important to control grubs in corn. However, a history of grub damage in an area, plus seeing large numbers of grubs during field preparation, is a good indicator to use a soil insecticide to protect your crops from these pests.
Reference: Some of the information in this article is extracted from articles by Entomologist Christina DiFonzo.
Early season irrigation
Lyndon Kelley
Extension Educator Purdue/MSU
How to achieve the most agronomical and economical start from irrigation during planting season is important. Achieving the maximum uniform germination and emergence can be assured through proper early season water management. Irrigating fields prior to or just after planting, can keep the planter moving and still meet the “plant into moisture” requirement.
Irrigation water applied at ½ to ¾ inch will wet dry soil down to six inches to replace water loss to tillage. An inch of irrigation will often be needed in a field that has not received rainfall since the cover crop was destroyed. Monitoring newly emerged crops that were “irrigated up” is essential. It is important to water enough to keep roots growing down into the moisture. Most year rainfall is plentiful enough to replenish water lost to tillage or cover crop, but a dry layer six inches to eight inches down can greatly hinder crops development, and needs to be replenished by rain or irrigation.
Early season irrigation can be both the cause and solution to soil crusting and emergence problems. Depending on soil type, crop residue, and irrigation application equipment early season irrigation can create some soil crusting accelerated by rapid surface drying. Small applications of water 0.2 to 0.3 of an inch may help to allow emergence of seed through the crust.
Many herbicide options can be assisted by a timely rain or irrigation. Applications of 0.3 to 0.5 of an inch of water will move activated herbicides if rainfall does not occur within two days after herbicide application. Irrigating in herbicides can also create the problem of different levels of weed control between the dry corners and the irrigated portion of the field. Timely and directed scouting for weeds in dry corners will be needed later in the season.
Early season irrigation can be more accurately scheduled from monitoring soil moisture in the root zone rather than checkbook irrigation scheduling system for newly emerged crops. Later in the season, checkbook irrigation scheduling will show its advantages over scheduling by soil moisture in the root zone alone. To learn more about checkbook irrigation scheduling click on the following link: http://www.msue.msu.edu/portal/default.cfm?pageset_id=28706&page_id=361029&msue_portal_id=25643 and see the irrigation scheduling tool fact sheet.
For more information on irrigating, contact Lyndon Kelley, Extension Educator Purdue/MSU, Irrigation at 269/467-5511.
Christy Sprague,
Crop and Soil Sciences
The 2007 Weed Tour will be held on the
Ned Birkey
The weather has been unsettled with hot, stormy and then cool weather. Farmers were just getting back into the fields, when another violent thunderstorm hit the area on Tuesday, May 15. Some farmers received another inch of rain with high winds. Our area has the chance of a light frost forecast for early Friday morning.
Alfalfa weevils are continuing to feed. We are not at the bloom stage yet, and I have not seen any fields cut yet. Grasses in mixed hay fields have headed out, however.
Corn that is planted is mostly emerged, and stands appear uniform, except where there is standing water. Some fields have lots of volunteer wheat and may be attractive to cutworms and armyworms.
Soybean planting will start or resume when fields dry out. I still have not seen any emerged fields.
Wheat varies from Feekes’ growth stage 6 to 8. Some fields are weedy with winter annuals, annual grasses and annual broadleaf weeds. Most fields are at Feekes’ stage 8 and do not have much disease. I have seen powdery mildew and Septoria leaf blotch, though neither was at threshold level. I have not seen any aphids in the fields that I was in this past week.
Miscellaneous
Farmers are starting to get anxious about the potential yield loss of (unplanted) late-planted corn using a May 20 date as that after which yields diminish.
Bruce MacKellar
Weather
Favorable conditions over the
weekend and Monday, May 14, allowed planting to continue in the southwest
region. Severe thunderstorms provided some much needed rainfall, but caused
widespread damage to many areas in the region, particularly the
Schoolcraft/Vicksburg areas of Kalamazoo County and the Three Rivers area of
St. Joseph. Rainfall totals were relatively light from this fast moving system,
and field work will progress again shortly.
Commercial corn planting is getting close to complete in the Southwest portion of the region. Early planted fields range in development from V3 to V1. Fields are beginning to show some signs of annual grasses and broadleaves at this point. Some fields that were planted a little later have received very little rainfall, since preemergence weed control programs were applied. There remains very little incidence of insect feeding in the fields I have scouted, but some flea beetle feeding can be found. Black cutworms could still be a threat, especially on fields where cover was removed later in the season.
Seed corn planting has been moving forward. Early planted fields have emerged, and are growing rapidly. We have been irrigating some seed fields early in the week to provide for even emergence and to activate soil applied herbicides. Fields that had cover crops later in the season may be more at risk for black cutworm or potentially armyworm injury, depending upon moth flight and egg laying activities. We have seen virtually no evidence of feeding from these insects at this point, but damage can be localized.
Soybean planting jumped into high gear last week. Many of the early planted beans have emerged, and are at the unifoliate leaf stage. There has been little, if no insect damage in the fields that I have walked through at this point. For the most part, stands look very good at this point.
Alfalfa weevil continues to be the major pest story in the region. (view image) Fields continue to be over threshold levels, with many fields having been treated. Weather permitting, we will be moving towards the harvest of first cutting shortly. We have reached the 750 GDD Base 41 F 1 cutting harvest window this week at many locations in the Southwest Region. Threshold before the first cutting, treat when 40 percent of stems damaged, plus live larvae present. After first cutting, treat when 25 percent or more of new tips damaged, or six to eight larvae per square foot of re-growth. See MSU Extension Bulletin E-1582, Insect and Disease Control in Field Crops for 2007, or click here to see the alfalfa section of E-1582 for 2007 for recommendations.
Wheat is growing
rapidly. Advanced fields are in the boot stage. Some producers have been
irrigating wheat on the lighter soils. There was some armyworm moth activity
down in the
Fred Springborn
Roger Peacock
Minimum soil temperatures as recorded at the MSU Experiment Farm in Entrican, are well into the 50s as of today Thursday, May 17. Light rain showers again this week have given farmers a midweek break in planting. Totals received on Tuesday and Wednesday were generally in the 0.25 to 0.5 inch range.
Wheat is in Feeke’s growth stage 8 in most fields and 7 in others. A couple of fields were observed this week that had late applications of 28 percent UAN solution. The foliage, including the tip of the flag leaf and the next leaf below, was showing symptoms of moderate to severe injury. This is a reminder of how timely and appropriate application is important. Few disease problems have been reported or observed at this time. Powdery mildew is present at low levels.
Corn planting has
made rapid progress with 70-80 percent of the crop planted in Montcalm and 50
percent in
Soybean planting is progressing with 30 percent of the crop in the ground with a few fields emerged.
Alfalfa growth is up to 18-21 inches, associated
grasses even more. Orchardgrass is headed out. Alfalfa weevil damage is present,
but below threshold. GDD 41 are above 600, the cooler temperature forecasted
will slow things a little. Some cutting will start next week. New seedings are
completed with some emerged.
Paul Gross
Weather over the past week has been pretty much a mixed bag. After drying out from the rains last Wednesday, May 9, planting resumed across the region. Most farmers were able to plant in conditions that most described as marginal. Light rains on Tuesday evening and Wednesday brought about 0.2 to 0.5 inch of moisture. There were a few reports of light hail on the northern portions of the region. Soil temperatures have fallen below 60ºF with the cooler temperatures. Planted crops have been emerging in a timely fashion.
The corn crop is over 90 percent planted at this point. If we can get three to four good days, we should be able to complete planting. The early planted fields are emerging in a timely fashion. The largest corn is one collar, but most is just emerging. The frost on Monday did not seem to harm any of the emerged corn. There are concerns cooler temperatures Friday and frost could be a problem. Preemergence herbicide applications are being made.
Soybeans are about 30 percent planted, and early planted fields are sprouting, but no emergence at this time. Burn down herbicide applications are being made. Growers should not wait in applying the burn downs because of potential yield loss. Planting will occur as field conditions allow.
The wheat crop is in Feeke’s 7-8. Most fields look good and are progressing normally. There are still a few nitrogen applications being made. There has been light powdery mildew pressure in some fields, but low in the plant. Continue to scout the wheat crop for foliar diseases.
The alfalfa crop is 12-16 inches tall and the PEAQ stick readings are 30-32 NDF. We are seeing alfalfa weevil feeding in several fields. Harvest is expected to begin late next week if the weather patterns continue. New alfalfa seedings are doing well.
Sugar beets are emerging with no serious problems at this time.
Mark Seamon
Most of the Thumb area received about one inch of rain this week. This schedule of two days of field work followed by four days of rain and cool temperatures is getting a little old.
A few sugar beets are still emerging through moist soil with most stands being good. Some micro rate applications have been delayed due to rain. Weed size is becoming a concern.
Watch for seedling disease with high soil moisture levels.
The wheat crop looks good in most areas. Marginal fields are not improving very quickly. Average growth stage is around the Feekes 7 with a range of 6 to 8. Some powdery mildew can be found. Cool temperatures are slowing development.
Corn planting has made some progress in the past week, which gets this area to about 85 percent planted. Planting conditions were mostly good with some growers pushing soil conditions due to the calendar. Emergence looks good in earlier planted fields. Some soil crusting can be found, which is reducing stands.
Soybean planting has started nicely with about 25 percent of the crop planted. A few fields have emerged, but most have not.
Jeff
Andresen
Agricultural Meteorology
Geography
A Canadian-origin area of high pressure will hold across the
Great Lakes region Thursday, May 17 and Friday, bringing a continuation of
cooler than normal temperatures across
During the day Friday, fair, dry and warmer weather is
expected. Another frontal boundary will approach the state from the north
Saturday, bringing the chance for light rain or showers, beginning in northern
sections of the state overnight Friday, spreading southward across the
In the medium range time frame, forecast guidance is
suggesting a relatively flat, west to east upper air pattern during the 6-10
day period with the gradual formation a troughing feature across eastern