August 9, 2007
In this issue
§ Aphids increase
§ Spider mite control
§ Western bean cutworm distribution maps available
§ Do I have enough soil moisture to make a crop?
§ Soybean disease update and fungicide use
§ 2007 soybean yield contest
§ Development of drought conditions in Michigan
§ Drought online resource now available
§ Regional reports
§ Weather
Next issue August 23
Christina DiFonzo, Entomology
Quick take home messages
§
Aphid numbers have increased in the eastern
§ If you haven't already, check fields for aphids, especially late-planted and potassium deficient fields. Even a quick walk into the field will alert you to a problem.
§ Think coverage, coverage and COVERAGE.
Aphid numbers in many locations in the eastern Great Lakes
area have come up, including locations in
Michelle Roy, an entomologist with the Province, reports
that 90 percent of the acres in southwestern
Christina DiFonzo, Entomology
Unfortunately, with the dry conditions mites are more common than aphids. Many are spraying in the southern tier of counties, and I’ve had a bunch of reports of mite populations returning after treatment. Several things may be happening:
§ Egg hatch: Mites lay eggs on the plant surface. (The eggs are quite large and easily seen with a hand lens. Here is a picture: http://extension.missouri.edu/explore/images/ipm1025art18.jpg
§ Insecticides kill adults and nymphs, but do not kill eggs. Since Dimethoate and Lorsban have short residual, the newly hatched nymphs survive and repopulate the plants.
§ Rebound or flaring of mites: Insecticides kill beneficial insects, but likely don’t kill 100 percent of the mites. The mites reproduce in the absence of predators, potentially leading to a rapid increase, or flaring, of the population. This is one of the reasons we recommend scouting and spraying only when mites have reached a threshold, avoiding insurance applications of insecticide.
§ Resistance: Spider mites are notorious for becoming resistant to insecticides. This problem increases with the number of applications. This is another reason we recommend scouting and spraying only when mites have reached a threshold.
If you do plan to treat, check fields before you spray to make sure mites are still present. We have had rain this week, plus the mornings have been “dewy.” Rain itself reduces plant stress and replaces water lost to pest feeding. But more importantly, high humidity is critical for promoting the growth of fungi that naturally infest and kill mites. Humidity must be elevated for an extended time, 48 hours or more, before naturally occurring fungi are active. Mite populations can crash in a matter of days once fungal pathogens become active.
Christina DiFonzo, Entomology
Trap captures for 2007 are now posted on the western bean
cutworm monitoring site at
http://www.ent.iastate.edu/trap/westernbeancutworm/.
There is a map of trap locations by county, plus several maps showing cumulative
captures over time.
This season moths were trapped in six counties in Southern
and Central
Why the concern? Western bean cutworm has moved rapidly
cross the
I will coordinate trapping of moths again in 2008, and would
like to expand the numbers of counties in
For the future, here are several free western bean cutworm references on-line:
§ Picture of a WBC larva: http://www.ent.iastate.edu/imagegal/lepidoptera/wbcutworm/40wbcutworm.html
§ “Don’t confuse western bean cutworm with other moths.” Shows pictures of common moths that can be confused with western bean cutworm. http://www.ent.iastate.edu/trap/westernbeancutworm/files/wbc_id.pdf
§ “Identification of western bean cutworm and similar species.” This slide set shows distinguishing characters of larvae attacking corn http://ipcm.wisc.edu/Portals/0/Blog/Files/19/236/3_Look_alikes.pdf
Kurt Thelen
Crop and Soil Sciences
The dry conditions of the 2007 growing season to date have many wondering if they have enough soil moisture to finish out their corn and soybean crops. A few simple calculations can give us a pretty good idea whether or not we have a chance of making it to the finish line.
For starters, we know that a 150 to 200 bushel corn crop or 50 to 60 bushel soybean crop require approximately 20 to 24 inches of water. By adding up our seasonal rainfall and estimating the amount of water stored in our soil profile, we can get a pretty good idea if we have adequate moisture available to reach our yield goal.
For example, my field consists of a Blount loam soil. By checking a USDA Soil Survey or by looking up the USDA, Natural Resource Conservation Service web-based Soil Survey at: http://websoilsurvey.nrcs.usda.gov and following the prompts, I can get a good estimate of my soils water holding capacity. In my particular case with a Blount loam soil, the water holding capacity is listed as: 0.17 cm per cm in the top 36 inches of soil. The cm per cm unit is actually a straight percentage so:
36 inches x 0.17 percent = 6.12 inches of available soil water in the upper 3 feet of soil assuming I start at field capacity in the spring.
The next step is to add in the amount of rainfall received since planting. If you don’t record this information for yourself, you can use precipitation data recorded at the “Michigan Automated Weather Network” (MAWN) station nearest your field which can be accessed at: http://enviroweather.msu.edu/home.asp. Checking the MAWN website, I find that I have received only 6 inches of rainfall in my vicinity since planting. Assuming that I began the season with my soil moisture at or near field capacity, I calculate:
6 inches of rainfall received + 6.12 inches stored soil water = 12.12 total inches of available water.
This leaves me a water deficit of 8 to 12 inches short of the precipitation levels needed to meet my yield goal. What are the chances I’ll get another 8 to 12 inches of rain while my crops can still benefit from it? By using 30-year average rainfall data I can get a pretty good idea. Thirty-year average precipitation levels are available at: http://climate.geo.msu.edu/. The 30-year average August rainfall in my area is about 3.8 inches. If August precipitation levels are near average, my total crop available precipitation would then be just short of 16 inches (12.12 inches +3.8 inches) which is still considerably short of the 20 to 24 inches desired. The 30-year average data also show that I could expect another 3.8 inches in September, but most of that would likely be too late for the corn plant to benefit in terms of grain yield. Therefore, it appears that 2007 precipitation levels will likely limit my corn and soybean grain yields below my targeted yield goals.
Of course these calculations should be considered “ballpark estimates” as actual soils vary considerably in terms of water holding capacity. Additionally, crop rooting depth will vary based on soil structure, crop genetics, nutrient status, and early season water levels.
Diane Brown-Rytlewski
Plant Pathology
Many areas of
Growers have had to face serious issues with drought, spider
mites, bean leaf beetles, Japanese beetles and other problems. With all these
other challenges, at least foliar diseases have not been a problem in soybeans.
Soybean rust has stayed out of
Using any kind of pesticide in the absence of a specific
pest runs strictly against the principles of integrated pest management. One of
the consequences always thought of is the risk of resistance developing from
repeated fungicide use. We don’t always think about
other unintended results of applying fungicides, such as “…the suppression of native fungi that naturally keep
insect populations in check. There is already some evidence that indiscriminate
use of fungicides in soybean has resulted in increased insect/mite activity in
some states.” Not a particularly good idea to further suppress beneficial
fungi, especially if you are already experiencing spider mite or insect
flare-ups in your fields. Another unintended consequence “…could be stricter
future pesticide laws and regulations.” (The
Integrated Crop Management Newsletter,
Growers who are thinking about making a fungicide application for “plant health” benefits should be aware that there is no magical formula to predict a significant economic return. Although a positive yield effect may take place, it may not. There isn’t enough information to determine in advance which fields/situations will respond with an economic yield increase and which ones won’t.
Ned M. Birkey, EANRA
2006 was the first soybean yield contest in
The contest is a “fun” way to encourage farmers to get
higher yields of their soybeans because they will be recognized for this by
their peers and the soybean industry in
This contest is based similar to the National Corn Grower contest. There will not be a re-checking of yields in this case and there are other differences. Entry forms are now being mailed to farmers and are available to farmers through the Monroe County Extension Office. Farmers with interest can contact Ned Birkey at 734-240-3170 or Mike Staton at 269-657-7745. Entry forms and a $25 per entry fee must be postmarked by August 18 and mailed to the Monroe County Extension office.
Jeff Andresen
Agricultural Meteorology
Geography
Scattered showers and thunderstorms brought some much needed
rainfall to a few locations across
As an example of the gradual depletion of soil moisture,
volumetric soil moisture at a 10-inch depth under grass taken from the MAWN
automated weather station at
With this season facing drought conditions, a new online
resource offering helpful tips and information has been established. Please
visit http://www.ipm.msu.edu/drought2007.htm.
Topics include: general drought and crop information, effects on corn and
forages. This site will be updated as articles come in from the Field Crop Area
of Expertise Team and CAT Alert authors.
–Andrea Buchholz, asst. editor.
Ned Birkey
The weather
has turned around with up to eight inches of rain, primarily near the state
line area, since two weeks ago. Everyone has had some rainfall, and areas near
Alfalfa hay is in very short supply, with small
square bales of hay being shipped to
Corn is pollinated and in the blister to milk stage. The rains of the past two weeks have benefited everyone who has corn as we are in the all important kernel fill stage. Even with the rain, it has come too late to benefit some three-foot tall fields. One local chemical company has been spraying corn for gray leaf spot. It is surprising to see how green many cornfields are. I think improved genetics is responsible for drought resistance as it is unusual to see lots of lower leaves firing anymore.
Soybeans are still growing, flowering and podding. Soybean aphids can be found, though not at threshold levels. Spider mites are the main problem, though recent rains will help soybeans compensate. You can find as many potato leafhoppers in soybean fields as aphids. Japanese beetles are plentiful and are still feeding, though I have not seen any fields near the 25 percent leaf loss threshold. Some fields are showing severe brown spot and bacterial pustule. One local company sprayed over 600 acres with Stratego and “bug juice” this past week. One farmer was worried about Asian soybean rust. Another farmer had a soybean field sprayed, as he did not want any more insects feeding on “his beans.” He was talked into using a foliar fertilizer applied at the same time. The company spray “jockey” refused the farmer’s request to leave a check strip on untreated soybeans.
Wheat ground is being mowed and the straw baled as
wheat straw is fetching up to $5.00 per bale in northeast
Farmers here are being taken advantage of by some people who are selling pesticides and saying that yields will increase up to 30 bushels per acre, even though fields are not at threshold for spraying of insects or diseases. Hay looks to be in very short supply this winter as our crop supply is down this year and hay is already being shipped to other areas.
Fred Springborn
Rain showers two weeks ago were more limited than what was
first thought. One to two inches of rain did fall across much of
Corn is variable.
Irrigated corn is progressing well with many fields in the dough stage and
excellent yield potential. Dryland corn is variable from very poor to better
than what might be expected with such little rain fall. Pollination of this
crop is complete with variable success. European corn borer trap catches are
very low with most traps catching one to two moths. Corn earworm trap catches
have picked up again this week with an average of five moths per trap. No
western bean cutworm has been detected this year in
Irrigated dry beans are in very good condition where there is adequate moisture. Dryland beans are suffering from drought stress, most fields are flowering and setting pods. Where soils were allowed to dry out before planting, stands are poor. Weed control has also been fair to poor in many dryland bean fields.
Soybean fields are setting and filling pods. Plant size is below normal. Low numbers of soybean aphid have been observed. Spider mites are present in many fields, some above threshold. Potato leafhopper, bean leaf beetle, grasshopper and other minor pest are also present.
Alfalfa second and third cuttings are continuing. Yields are very low, it is estimated that the hay crop will be no better than 60 percent of normal (40 percent loss). There is slow spotty re-growth due to dry weather and leafhopper damage in some fields.
Pastures in
Sugarbeets are doing well by and large. Even irrigated beets have shown moisture stress on several days when temperatures were high and humidity was low.
Dan
Rossman
Weather
Small amounts of rain were not enough to make much of a difference. Some areas have been missed by rain altogether. The extreme dry and hot conditions are a very serious situation over the region.
Crop report
The corn crop is firing up from the bottom. Some fields have been chopped for silage already. Yield loss will be substantial.
Soybeans have had very little growth in the last two weeks. Spider mites are easily seen along field margins. Aphids are now present and increasing in numbers. Most are still well below threshold, but need to be scouted closely. Grubs are killing soybeans on sandy ground in a few pockets in the area. Pod set appears to be very light.
The oat crop is harvested. Yield and test weight is lower than normal.
Alfalfa has had nearly no re-growth over the last few weeks. Hay is in short supply.
Dry beans are in bloom or setting pods. Leafhoppers and dry weather are taking their toll on this crop.
Mark Seamon
To be consistent with almost all rainfall this summer, the showers on Monday, August 6 helped some areas and left others wanting much more. Rainfall amounts ranged from more than 2 inches to a couple of tenths of an inch.
Alfalfa re-growth is slow and providing very short second and third cuttings.
Beets are taking advantage of the rain where it fell. Cercospera leafspot is the biggest topic in sugar beets now. Disease Severity Values from the Beet Cast system are variable across the beet growing area. Leafspot symptoms have been limited, but the recent rainfall has caused a lot of leaf wetness. Be sure to check specific data for a site near you. This can be found at www.MichiganBeets.com Sugar beet cyst nematode feeding can be seen in many fields.
Corn has pollinated pretty well in most areas. Drought has limited pollination in some places and has caused some kernel abortion after pollination in other areas. Fields in dry areas with lighter soils or variable soils are showing a lot of firing of lower leaves with some plants nearly dead.
The soybean crop is also struggling with the dry conditions with very slow growth. Bean leaf beetles are feeding in most fields with those slow growing fields showing defoliation up to 20 percent. Soybean aphids are still present in most fields, but variable within fields and between fields. A few reports of fields with aphids over the 250 per plant threshold have been sprayed, but most are well below threshold.
Dry beans have been affected by the drought conditions as they blossom with poor pollination and pod set. Longer maturity and later planted beans may benefit from the rainfall this week.
Jeff
Andresen
Agricultural Meteorology
Geography
Showers and thunderstorms brought more rainfall to many
areas across southern
At this point, best chances for precipitation will be across
southern sections of the
In the medium range time frame, both 6-10 day and 8-14 day
outlooks, covering August 14-18 and August 16-22, call for a continuation
of above normal temperatures state- and region-wide. Precipitation totals
during the 6-10 day time frame are forecast to range from below normal levels
in southern Lower Michigan to above normal over the
