June 14, 2007
In this issue
§ Check April-planted beans for soybean aphid now
§ Western bean cutworm trapping starts
§ Common
pokeweed an emerging issue in
§ Purple corn
§ Yellow and red tipped flag leaves in wheat
§ Potato disease extension bulletins
§ Regional reports
§ Weather
Christina DiFonzo, Entomology
As in 2005
When should small beans be sprayed? Heavy early-season
infestations are rare, so research is lacking in this area. The 250 threshold
was developed and tested in larger beans, so there is no good data to set a
threshold for small beans. The infested fields I saw had adequate moisture to
replace the aphid feeding (but in the last few days, they need rain), and the
plants aren't putting on flowers or other critical structures. They appear to
be able to tolerate 100 soybean aphid per plant, and maybe even 250. My lab, as
well as researchers in
Be aware there are risks to spraying so early. Aphid populations are likely to rebound or “flare.” Predators will be killed, and any surviving aphids will reproduce fast in the absence of the predators. In early-sprays, insecticides can be mixed with Roundup from the crop-injury standpoint. However, it is critical to get excellent coverage to achieve excellent kill. Otherwise, you are leaving aphids alive to reproduce in the absence of predators. Some suggest using half-rates of insecticide because the plants are small. I do not have data to show that reduced rates are effective on small beans. Using half-rates makes me a bit nervous, because again, the goal is the excellent aphid kill to reset the field to “0” to avoid flaring. Because of the problem with flaring, early-sprayed fields may end up needing to be sprayed three times instead of once or twice to achieve the same yield.
Spraying in
Links to get insect trapping information:
www.sbrusa.net - Aphid numbers
in soybean. Currently
http://www.ncpmc.org/traps/index.cfm: Northcentral Aphid Suction Trap Network. The web site now has 2007 trap catches. Simply click on the state or trap to see suction trap catches of soybean aphid.
Christina DiFonzo, Entomology
Trapping of western bean cutworm will begin at 20 locations
in
For more information, visit http://www.ent.iastate.edu/trap/westernbeancutworm/about: Western bean cutworm trapping – site will be active later in June.
Christy Sprague
Crop & Soil Science
Over the last week common pokeweed plants have become more
apparent in several
Common pokeweed is a deep-rooted perennial that reproduces from root buds and seeds. Aboveground shoots of this plant arise from the taproot and consist of diffusely branched, fleshy stems (resembling a small tree) that can reach heights of 6 to 8 feet under fertile conditions (view photo1). In older plants, the taproot can be up to 6 inches in diameter and can grow to depths of more than 12 inches (view photo 2). Common pokeweed fruit is produced in late summer as clusters of green berries that turn purple to black at maturity and contain a profuse amount of red juice (view photo 3). The green leaves, fleshy stem, and purple berries of common pokeweed can inhibit the harvesting process and lead to discounts at the elevator for high seed moisture and staining. Areas with heavy infestations of common pokeweed can compete and reduce yield in both corn and soybeans. Numerous bird species are known to feed on the berries and are capable of randomly dispersing pokeweed seeds over sizeable areas. In fact, many times new common pokeweed plants are found at the base of trees or along electrical and telephone wires. Seedlings can emerge from mid-spring through early summer. Within five to nine weeks after emergence, seedlings of common pokeweed develop a taproot that is capable of regrowth (becomes perennial). New plants from dispersed seeds are capable of becoming entrenched as their taproots develop.
Many plants that form taproots generally do not tolerate intensive tillage practices. Common pokeweed is generally not a problem in crop fields that are exposed to tillage. In fact, one of the most effective methods to control this weed is use of mechanical controls, such as moldboard plowing and disking. However, since reduced tillage has become a desirable practice for corn and soybean producers to help reduce soil erosion, decrease energy and crop production costs, and to save time during the planting season, alternative or chemical control methods are more desirable.
§ Common pokeweed establishment often begins in fence rows or under power lines (dispersal by birds); Monitor and control pokeweed in these areas to prevent spread.
§ Common pokeweed does not become a problem in fields with intensive tillage.
§ Tillage will control true seedlings within five to six weeks after emergence.
§ After pokeweed establishment, reduced tillage will only suppress common pokeweed.
Several herbicides with residual activity are effective at controlling seedling common pokeweed. However, common pokeweed is more difficult to control once it has developed its taproot and becomes perennial. Because of the variable size of common pokeweed populations in a field, application timing is critical. For in-crop applications, time herbicide applications when common pokeweed is at least 8 inches tall and preferably less than 12 inches tall. Effectiveness ratings for several herbicides for common pokeweed control are available in the accompanying tables. Refer to the herbicide labels for maximum crop height and stage application restrictions for individual herbicides.
Soybeans
|
Herbicide a,b |
Rate |
Effectiveness |
|
Raptor + |
5 fl oz |
Fair |
|
Classic + |
0.67 oz |
Poor-Fair |
|
FirstRate + |
0.3 oz |
Poor |
|
STS SOYBEAN ONLY |
|
|
|
Synchrony XP + COC + N |
0.75 oz |
Fair |
Corn
|
Herbicide a,b |
Rate |
Effectiveness |
|
Callisto + COC + N |
3 fl oz |
Good |
|
Distinct + |
4 fl oz |
Fair-Good |
|
Clarity |
0.5 pt |
Fair-Good |
|
Northstar + |
5 oz |
Fair-Good |
|
Beacon + COC or |
0.76 oz |
Fair |
|
2,4-D amine |
1 pt |
Poor |
Roundup
Ready Crops
|
Herbicide a,b |
Rate |
Effectiveness |
|
glyphosate + AMS |
0.75 lb a.e. |
Good |
|
fb. |
|
|
|
glyphosate + AMS |
0.75 lb a.e. |
|
|
(if needed) |
|
|
Noncrop/Fallow
(Fall) c
|
Herbicide a,b |
Rate |
Effectiveness |
|
|
|
|
|
Glyphosate + AMS |
1.5 lb a.e. |
Good-Excellent |
a Refer to herbicide label for maximum application heights and stages.
b
c Apply in late-September or early-October when common pokeweed is 8 to 24 inches tall, but before a frost.
Kurt Thelen
Crop & Soil Sciences
There have been a number of reports of purple-colored corn
seedlings this year. These symptoms are not unusual for
Restricted root growth resulting from compacted soil and smeared and compacted seed furrow side-walls can contribute to the buildup of sugars in the corn leaf. The abundant sunshine and accumulation of heat units the past week have resulted in the production of lots of sugars in the corn plant shoots. These sugars would normally be used for root and shoot growth, but when accumulated in the leaf, result in the production of anthocyanins, which give the leaf a purple color. If the purple color persists after field conditions normalize, the discoloring may be indicative of other root-related problems such as a severe compaction problem or phosphorus deficiency in the soil. In addition, some corn varieties are genetically predisposed to have inherently higher levels of anthocyanins. These varietal differences are readily apparent when viewing variety trial plots this time of year, however, they do not appear to affect final grain yield.
Growers in the sugar beet producing areas of the state often report an increased incidence of purple-colored corn following sugar beet. This phenomenon was investigated by Don Christenson at MSU in the mid 1990’s. The work did not find a correlation with sugar beet carry-over herbicides, soil P levels and did not appear to be an artifact of soil compaction. The results indicate there may be an association with the sugar beet residue and early season purpling of rotational corn. Nevertheless, the increased incidence and severity of purpling following sugar beet was not detrimental to corn yield.
The good news is that corn will generally overcome early season purpling. Continue to monitor nutrient levels, particularly nitrogen and identify severely compacted areas for remedial tillage in the fall. Above all, next year use patience and discretion in deciding when to resume field planting operations following rainfall.
Diane Brown-Rytlewski
Plant Pathology
There have been a couple of reports in
Barley yellow dwarf virus is transmitted by several different species of aphids, including oat bird-cherry, corn leaf and English grain aphids. The virus persists in volunteer grains or wild grasses. It is reintroduced to crops each year, sometimes from aphids that have migrated from great distances away on storms. The disease usually occurs in small patches or portions of rows, sometimes along field margins. Symptoms are most severe when infection takes place in the fall, less so when infection occurs in the spring. When temperatures are around 68°F, virus symptoms are visible in about two weeks. As temperatures warm, symptom expression takes longer, for example, four weeks at 77 °F. No symptom expression occurs at 86°F. Yield losses to barley yellow dwarf virus depend on the growth stage at the time of infection, cool weather conditions that favor disease development and the susceptibility of the variety.
There is little that can be done to save diseased plants and management should focus on preventing the disease. There are resistant oat varieties, but wheat has limited resistance to barley yellow dwarf virus. Check with your seed dealer for recommendations about resistant varieties. Avoid early planting to avoid exposure to aphids during early crop growth stages. Control volunteer wheat barley, oats and wild grasses. Although foliar insecticides are available to control aphids, their short residual life gives them limited usefulness in barley yellow dwarf virus management.
Phill Wharton
& Willie Kirk
Plant Pathology
Seven new high
resolution potato diseases extension bulletins are now available for purchase at
http://www.emdc.msue.msu.edu/ for
$1.50 each. The new group of publications includes the recent potato late
blight bulletin and bulletins on early blight, pink rot, Fusarium dry rot,
Rhizoctonia diseases, potato common scab, white mold and seed piece management.
For more information, call 517-353-6740. You can also download these bulletins
from this web page http://www.potatodiseases.org/extensionpubs.html
as PDF files from our late blight website.
Also at http://lateblight.org daily updates of potato
late blight risk are available for all the Michigan Automated Weather Network
sites in
Ned Birkey
Weather has turned hot and dry with no rain and none in the immediate forecast.
Alfalfa was cut with the favorable weather this past week. This should finish the alfalfa weevil feeding. Although hay was past prime quality, at least most fields did not get rained upon.
Corn is at the V8 growth stage with some fields showing drought stress. Fall soil compaction is clearly showing up on end rows and elsewhere in fields with highly variable corn height. Fields with good drainage and good stands are evident as are fields with compaction, drainage or stand problems. Now is a good time to evaluate planter performance. Sidedressing is finishing up and weed control is still an issue in some fields. European corn borer counts were down in all trap locations this week. Fireflies are out so corn rootworms should be also.
Soybeans are starting to take root and show more top growth. Most fields are at the V2 growth stage. Bean leaf beetle feeding continues, though no soybean aphids were found at the Lenawee location this week. Soybean aphid and rust plots will become established in Monroe and Washtenaw counties next week. Western bean cutworm and corn rootworm traps will also go up next week. Post weed control will soon become the main farm chore.
Wheat has finished flowering and is now at Feekes’ growth stage 11. The continued high temperatures near 90ºF will hasten ripening. I am cautiously optimistic about wheat yields.
The MSU Wheat Variety Trial location for southeast
Bruce MacKellar
There has been no rainfall over the week. Hot weather, with
daytime highs in the upper 80’s and nighttime temperatures in the upper 60’s to
lower 70’s have really pushed the crop development into high gear this last
week. In fact, the
Commercial corn
is the crop that continues to take advantage of the warm conditions. Early
planted corn is approaching waist high V9 to V10, with later planted corn
mostly in the V5-V6 range. Side-dress nitrogen applications are completed on
the earlier planted fields and continue to be applied rapidly on later planted
fields. The average evapotranspiration rate for the largest corn is between 0.1
and 0.12 inches per day at this point. Early development begins early in corn,
around the 6 leaf collar stage. Between V6 and V12, many of the factors that
determine the ear size, and kernal counts are being determined. By V12, corn is
beginning to become more susceptible to yield losses from drought and other
stresses. Severe stresses can impact yields by 10 percent or so at this stage. European
corn borer moth activity appears to be on the decline. You can find the
telltale marks on corn leaves that denote some early instar European corn borer
feeding on corn plants has begun, but the number of plants that show damage
appears to be minimal at this time. We anticipate that rootworm larval feeding
will be on the rise as the eggs should have hatched over the last week or so. With
the deposition of armyworm moths into portions of west
Seed corn planting is nearly complete. There has been a long planting window this year. Early planted seed corn continues to look good. There continues to be some fields where weed escapes can be found in seed corn, but most are being treated with post emergence applications and are improving. Irrigation has been applied to many of the later planted fields to improve conditions for germination and emergence. As with the commercial corn, we need to monitor fields for armyworm larval feeding because of the step up in moth deposition over the last week.
Early planted soybeans
are developing their third to fourth tri-foliate. Bean leaf beetle feeding
signs remain low. Herbicide application has been completed in many of the
earlier planted beans, with those planted in mid-May are receiving post
applications at this time. There continue to be low numbers of soybean aphids
in fields at this time. The treatment threshold is 250 aphids per plant,
perhaps less on small, later planted fields. We will likely begin to see
pockets where aphid numbers will begin to increase in numbers in southwest
Alfalfa harvest moved into high gear here this week, as the first really good extended forecast that has shown an extended dry period. Potato leafhoppers are prevalent. Watch your alfalfa re-growth carefully for this pest, because the early re-growth period is the most vulnerable to “hopper burn” injury. It does not take many leafhoppers to cause serious injury on 2-3 inch alfalfa.
While the temperatures have driven the grain filling period at a fast pace, wheat will probably have good yield potential in the region, especially where irrigation was used to provide supplemental water when needed. It appears that the number of heads affected by fusarium head blight will be limited this year despite some extened wet periods during flowering.
The St. Joseph County IPM Breakfast Meeting will be held on Wednesday June 20 at the St. Joseph County MSU Extension office, 7:00 AM-9:00 AM . Cost is $7, which includes a catered in breakfast. Our guest speaker next week will be Dr. Chris DiFonzo.
Fred Springborn
Roger Peacock
Warm and dry sums up the weather of the past week with perhaps an emphasis on dry. Irrigation systems are running across much of the county. High temperatures in the last week have ranged from the lower 80’s to the lower 90’s.
Wheat is well past flowering in all fields. A few fields have shown some symptoms of glume blotch. Oats are progressing well with few insect or disease problems at this time.
Corn growth ranges from V3 to V10. The majority are in the range of V5 to V8. We are still getting complaints of yellow, red and purple corn. Much of this is related to weather and some is due to other factors. European corn borer trap catches are down a bit this week with an average of five moths per trap at our Stanton and Trufant trap sites.
Soybean planting is virtually complete with most fields ranging from V1 to V4.
Dry bean planting is in full swing with 60 percent of the crop planted. Earlier planted beans have emerged.
Alfalfa harvest
is underway with nearly 75 percent of the crop harvested. Quality is going down
rapidly with over ripe grasses. On the plus side, there is rapid drying and
short cut to bale time. Potato leafhopper is active with both adults and nymphs
present. In
Volunteer potatoes continue to be an issue.
Paul Gross
The crops enjoyed the warm temperatures over the past week and responded with rapid growth. Crops are living off the rains of last week and will need a rain in the next week to continue to progress normally. It is evident where there were harvest problems last fall or where crops were planted in wet conditions, stands are variable and are showing drought stress in some areas of the fields. Generally crops are off to a good start this year.
The corn crop is growing rapidly with the warm weather. Stands are variable. Fields that are well drained and were planted when conditions were right are excellent. We are seeing some purple corn, but expect the crop to grow out of that condition. Field activities include herbicide and nitrogen applications. Rain would be welcomed.
The soybean crop is progressing normally. We have found soybean aphid in each of the central region counties, but in very low numbers. Fields should be scouted regularly for this pest as the population can explode virtually over night. Field activities include herbicide applications.
The wheat crop is done flowering, and the yield potential looks good. We are seeing the normal foliar diseases, but nothing serious at this time. The big question is will we have head scab as much of our wheat flowered during the two to three day wet period two weeks ago. Scout fields for armyworm as this pest usually shows up this time of year.
Alfalfa harvest should wrap up this week. The weather has been great for making hay. Yields vary with some reporting below average, while others report excellent yields. It appears that first cutting yields may be correlated with the fall harvest schedule. We are seeing leafhoppers at levels that need to be monitored.
The oat crop is heading and looks very good.
Sugarbeets are dong very well with some fields beginning to fill the row.
Drybean planting will wrap up this week. Early planted fields have emerged. Scout new growth for leafhoppers.
Mark Seamon
Warm and dry describe most of the past week throughout the Thumb area. This has helped to dry out the southern Thumb, but others areas are getting a little too dry.
Alfalfa to be baled has made good progress with first cutting this week.
Sugar beets continue to look good in most areas. Variable fields are improving but slowly. The most advanced fields in 28 or 30 inch rows are approaching row closure.
The wheat crop is beyond flowering. These high temperatures and dry soil conditions may reduce the grain fill period and affect yield potential.
Corn growth is active with the tallest corn about 24 inches tall and in the V6 growth stage. Sidedress nitrogen applications are being wrapped up in many areas. Leafrolling can be seen in many fields, especially fields with compaction from last fall or heavy rain this spring.
Most soybean fields have emerged with the most advanced fields at the V4 growth stage. Soybean aphids have arrived with varying populations from none to over 250 per plant. Bean leaf beetle feeding is easy to find. Cruiser seed treatment has been effective in control of the bean leaf beetles.
Farmers have made great progress planting over the past week with more than 90 percent of this crop planted. Emergence has been good.
Jeff
Andresen
Agricultural Meteorology
Geography
A strong upper air ridge and associated surface high
pressure across the central
An upper air trough and associated cool front are expected to move into the region by the middle of next week, which will likely be the next chance for significant/widespread precipitation. Time-wise, this weather feature should bring the chance for showers and thunderstorms in western sections of the state by Monday evening and across the east on Tuesday.
Following the movement of the troughing feature through the region next week, current medium range forecast guidance for the 6-10 day and 8-14 day time frames covering June 19-23 and June 21-27 respectively, suggests that the troughing pattern mentioned above will linger for much of the latter part of next week, resulting in a cooler and more unsettled weather pattern. Above normal precipitation totals are forecast for both time frames. Temperatures during the 6‑10 day period are forecast to remain at near normal levels, which during the 8-14 day period, temperatures are forecast to range from near normal in northeastern sections of the state to below normal in the southwest.