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Vol. 19, No. 2, June 24, 2004 In
this Issue
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Beware of needles |
Six samples collected from corn were recently submitted to MSU Diagnostic Services. Corn needle nematodes, Longidorus breviannulatus, were recovered from five of the samples at extremely high population densities. For example, in one sample, 156 needle nematodes were recovered in 100 cm3 of soil. The damage threshold for this nematode on corn is 5/100cm3 soil. These results were somewhat surprising, because it is often difficult to detect corn needle nematodes during the summer. The corn needle nematode is the most serious nematode parasite of corn in Michigan. Feeding by these nematodes can result in yield losses of 50 bu/A or more. Typically, needle nematode-infected plants are severely stunted and often chlorotic (yellow). The symptoms may develop very early in the growing season, and these infected plants will remain stunted for the rest of the year. The most notable primary symptoms of needle nematode feeding are swollen root tips that often become necrotic (brown). According to Steve Gower, Weed Science Diagnostician at MSU, injury from dinitroaniline-type herbicides, such as pendimethalin (Prowl), trifluralin (Treflan), and ethafluralin (Curbit), will produce "club-shaped" root hairs on corn. However, in the cases of herbicide injury, the root tips are usually not brown because the herbicides prevent cells from dividing properly, whereas, nematodes will kill the cells. Corn roots fed on by needle nematodes also usually have somewhat of a "bottle-brush" appearance where after primary roots are killed many secondary or lateral roots emanate from behind the killed root tips. Needle nematodes prefer sandy, cool, moist soils. They are usually not found in sites where soils contain less than 70 percent sand. Needle nematodes are typically only found near the soil surface during the spring and fall when soils are usually cool and moist. They will migrate to depths of 24 to 36 inches during the summer months to survive periods of adverse conditions. However, May was an unusually wet month in Michigan and soils have stayed moist in June. Therefore, apparently, needle nematodes have remained in root zones longer this year than usual. If they feed, severe symptoms may develop. As with other plant-parasitic nematodes, the only way to diagnose problems and to assess nematode population densities, is to collect soil and plant samples and submit them to a nematode lab for analyses. Unfortunately, if needle nematodes are detected, there are virtually no control options for the growing season other than trying to keep plants fertilized and watered as optimally as possible. If you suspect you may have a corn needle nematode problem, samples should be collected as soon as possible. Needle nematode problems often go undetected due to the behavior of these organisms to migrate deep into the soil. Diagnosis and subsequent management of these pathogens is imperative to avoid losses in the future. If corn needle nematodes are detected within samples, crop rotations to non-host crops such as alfalfa, dry beans, soybeans, or sugar beets will be recommended. For field crops, rotation is the only viable economic option for management of these very important corn pathogens. |
Fomesafen carryover to corn |
A corn sample submitted to the lab this week had symptoms indicative of fomesafen (Flexstar/Reflex) carryover. Corn injury was worst on sandy, elevated knolls and slopes in the field. Fomesafen injury to corn will result in midrib and subvein clearing, which appears as a "stripping" of the leaves. The tissue between the veins will not yellow; this is symptomatic of nutritional deficiencies. More severe fomesafen injury results in improper unfurling to a "buggy whipping" of the leaves. The midrib can also be weakened and collapsed. Fomesafen is often used for postemergence control of late emerging broadleaf weeds in soybeans and dry beans. Fomesafen carries a 10-month rotation restriction to corn. Late applications of fomesafen followed by fairly early corn planting the next season can result in nearing this restriction. Studies have shown that fomesafen is broken down in the soil more quickly under anaerobic (oxygen deficient) conditions. Anaerobic conditions result after a rainfall event in which water infiltration forces out oxygen in the pore spaces of the soil. In a season of drought or low precipitation, fomesafen may not be fully degraded and has the potential to carryover in sandy or even very well drained soils. Corn injury is first noticed on sandy hills and knolls because these areas can only hold moisture for a short period of time. |
Wheat scab (Fusarium Head Blight) in Michigan in 2004 |
Wheat scab symptoms are widespread and severe from Southern Montcalm County running south and east to Monroe County. Wheat fields within this area have been surveyed, samples collected, and disease incidence runs from 20 to 100 percent of the heads infected. Disease severity, the percent of the head infected, has increased significantly in the past week. The thumb and the western part of Michigan have not been surveyed. Reports from counties in these areas suggest low numbers of infected plants, with an occasional field having severe infection. However, fields in Southeast Michigan with low levels of visible scab symptoms last week (that is the number of infected heads) had significantly increased numbers of heads with symptoms this week. The thumb especially should be watched carefully for developing scab symptoms over the next seven to ten days. |
Wheat harvest considerations |
Michigan farmers who have winter wheat should immediately scout fields for head scab and evaluate fields for disease problems and potential harvest timing. The heavy and sustained rains of May and June have created some tremendous disease pressures in some varieties. If farmers are finding lots of white heads with a pinkish coloration, they should plan to turn up the combine fan speed to blow these light kernels out the back of the combine as these kernels may well be diseased. Farmers want to be sure to deliver high quality wheat, as there may be some quality problems in our area of Ohio, Indiana, and Michigan. Farmers should also plan to begin wheat harvest earlier than normal, starting harvest when wheat is 16 to 17 percent moisture. Waiting till wheat is completely dry before beginning harvest may result in a lighter test weight, especially if rain interrupts harvest and wheat has to dry down again. If there are diseased kernels present, some fields may get a double whammy of less test weight and a dockage for quality. Farmers should immediately check with their commercial elevator about delivering wheat at higher than normal moisture and inquiring about quality premiums and quality dockage. Ideally, a farmer should use on-farm storage to screen and dry wheat, at low temperatures, to obtain maximum quality. Wheat harvested "early" should be dried to 14 percent. |
Wheat pre-harvest field meeting |
A pre-harvest field meeting will be held at the Michigan State University Extension Wheat Variety Trial located in Lenawee County. This meeting will be held on Tuesday, June 29 at 7:00 PM. Dr. Rick Ward, MSU Wheat Breeder, will be the featured speaker. There are 81 red and white wheat varieties in the trial this year. This meeting is open to all area farmers and is free of charge. The Monroe and Lenawee County MSU Extension offices will provide refreshments. The plot is located on Hoagland Road, just north of Holloway Road, north of Deerfield, Michigan. For more information or a map to the plot, contact Ned Birkey of the Monroe County Extension office at 734-240-3170. |
West Nile Virus wall charts available |
All field crop growers should post the new MSU West Nile Virus wall charts (22" x 34") in their business where their employees can read them. They emphasize the precautions workers and businesses
need to take to reduce their risk of contracting West Nile Virus.
The two wall charts are available in English and in Spanish and
each sells for $1.00 a copy. Order copies from your local MSU Extension
office. Or they can be ordered from the online MSU website for Extension
Publications at: The wall charts are: Extension Bulletin E-2916: What You Should Know About West Nile Virus In Michigan Extension Bulletin E-2916SP: Lo Que Usted Debe
Saber Sobre El Virus Del Nilo En Michigan |
Regional reports |
1 - Southeast |
Commodity reports Soybeans are growing slowly and tend to be slightly chlorotic. Farmers attribute off color and slow growth to wet soil conditions. Many farmers are reluctantly driving across fields to apply herbicides. Their regrets are related to wet spots, some of which have standing water. Weeds are approaching eight inches, so farmers feel they can wait no longer. Wheat is still a few weeks away from harvest. Farmers have commented on off color heads. Our hopes are that the wheat survey being conducted by Dr. Hart will help determine the degree to which bleached colors should be attributed to scab infections. Alfalfa is under heavy leafhopper pressure. Farmers known for focusing on hay quality have begun applying insecticides to protect second cutting. |
2 - Southwest |
Weather Commodity reports The wheat crop has reached maturity in many areas of Southwest Michigan, and wheat fields are beginning to turn in earnest across the lower portions of the region. Fusarium can be found in most fields to some degree, but should still be able to be cleaned up at harvest because most affected kernels are shriveled and small. The earliest planted corn is probably at the 10 to 12 collar stage (chest height). The latest planted corn is still below 6 inches in height. Sidedressing of nitrogen is continuing on later planted corn. The earlier planted corn is either in the rapid elongation stage of growth or getting there fast. This period of time can leave corn susceptible to green snap if plants are subjected to high winds during the period two weeks before tassleing. Some ECB larvae can be found in fields, but the number of larvae in most fields has been well below threshold. Seed corn is about as variable as commercial corn. Some of the crop has recently emerged. Wet areas of fields continue to look somewhat haggard, but warmer weather last week helped to move the crop forward. Earlier planted seed corn is growing pretty well. Some fields are being treated to for European corn borer larvae. Larvae have been extremely small, first to second instar larvae are being found. Damage being found is primarily windowpane leaf feeding. Potatoes continue to look good for the most part. There have been some flooded out areas of fields, as with every other crop in the area, but the crop seems to have tolerated the wet conditions very well on balance. Most of the pesticide applications have been fungicides at this point. Planting of soybeans has finally wrapped up in Southwest Michigan, and it is most certainly the latest planting dates for this crop that I have ever seen. The good news is that the later planted beans are emerging rapidly. Some of the beans planted in the May 20 window are showing signs of problems from the heavy rainfall, including reduced stands from washing, crusting, and some seedling diseases. On the insect front, I have not seen soybean aphids in our area at this point, but we are watching field for the first signs of winged aphids. You can find potato leafhoppers at low levels, so don't confuse one lime green colored small insect for another. I suspect we are very close to the emergence of Japanese beetle adults in Southwest Michigan. For more current pest information in Southwest Michigan, visit the St. Joseph County Ag Web Page at: http://web1.msue.msu.edu/stjoseph/anr/anr.htm |
3 - West Central |
Weather Commodity reports Symptoms of
head scab are abundant in many wheat fields. Armyworms have
declined in numbers, but fields should still be monitored. Rye
is turning. The condition of the oat and barley crops
has gone down hill over the past four weeks. The excessive rain
and standing water has caused a variety or problems with these spring-seeded
small grains, in particular nitrogen loss. Corn ranges from V6 down to in the seed is still in the bag. Much of the corn
crop is V3 to V4. Condition of the crop is highly variable. A multitude
of problems have been observed causing corn plants to look yellow,
red, and in some cases, progressing to brown (dead). Many of these
cases are relate to excessive soil moisture. Soybean planting continues to progress and will soon end. Condition of the crop is somewhat similar to corn in variability and slow growth. Dry bean planting is at 30 to 40 percent complete. Emergence has been slow. |
4 - Central |
Weather Commodity reports The soybeans are similar to corn in that there is extreme variability in stands and growth stage. Early planted fields that were drilled are beginning to canopy while some fields are just emerging. Many fields were planted in less than ideal conditions and weed control will be challenging. Wheat has several challenges. I guess you could say that we have a dog from every town in most fields. The armyworm is in nearly every field, but feeding varies from very light to complete defoliation. We are seeing lots of septoria and glume blotch. We also are seeing fields with scab and it may be a little early to tell the level of infection in the central region. Many growers are reporting smaller than normal heads on the wheat crop this year. Alfalfa harvest is about 75 percent complete. The farmers who chop their first cutting are done and the regrowth is 6 to 8 inches tall. We are seeing many fields over threshold for potato leafhoppers, and the fields are being treated. The farmers who are trying to bale are struggling to get three to four days back-to-back to get hay dry. We have seen armyworms in grass hay and pastures. Again, scouting fields will be important this year. Drybeans are being planted as field conditions allow. We have fields in that are in the unifoliate stage to fields that still will be planted. There is concern that the calendar is running out. Sugar beets are filling the rows with good stands. Scout fields for diseases |
5 - Thumb |
Weather Commodity reports Many water damaged sugar beet fields continue to struggle to get more growth and get weeds under control. The other extreme is a few very good looking fields at or near row closure with very active leaf growth. Bacterial leafspot has been found in isolated areas. In corn, sidedress nitrogen application is getting wrapped up in most areas. Early planted corn is looking good where water did not damage it. Later planted corn is also picking up its pace with fast growth and moisture. Armyworms can be found in light populations near borders of wheat fields or grassy areas, but most have not reached threshold levels. Random bleached heads from head scab can be found in most wheat fields. It appears to be pretty limited in most areas. The level of vomitoxin that may be found in the grain is unknown at this time. A reliable system of estimating vomitoxin levels in grain by assessing field conditions has not been found yet. Many soybean fields are finally turning green from the bare soil that we have been looking at for two months this spring. Emergence looks good. Crop growth may be a little slow due to cool temperatures and limited sunlight. Emergence of dry beans also looks good in most areas. Some growers had concerns where heavy rain fell just after planting but moist surface helped emergence. |
6 - Northern Lower Peninsula |
Weather Most wheat fields are headed and are flowering this week, again about 10 days behind normal. No major signs of mildew or scab yet. Soybeans are anywhere from not emerged to the 3 leave stage. Some fields have had some germination or emergence problems, mostly on fields planted just before some of the heavier rains. Dry beans are emerging fast with the warmer soils. A lot of fields were planted 7 to 10 days later than most would like but have popped out of the ground fast and look good so far. First cutting alfalfa is finished for some and just starting for others. Most fields that are over two to three years old really have been overtaken with grasses this year. Oats have been looking very yellow with shallow roots. They are very spotty with yellow and green areas. Potatoes are having a hard time with all the rains. There are lots of washouts and some emergence problems due to heavy rains. Some fields have 5 to 30 percent loss due to rains. Aphids and Colorado potato beetle are present. |
Weather news |
The spate of storms and showers will clear today in most parts of the state; rain is still a possibility for parts of the Upper Peninsula Friday (June 25). High temperatures will climb from 65 to 75°F to the high 70s and low 80s by the middle of next week. Low temperatures in the 50s are forecast. Current forecasts call for dry weather for most of the state over the weekend and through midweek. The 6-10 day outlook, covering June 28-July 2, calls for below-normal temperatures and precipitation. The 8-14 day outlook for June 30-July 6 predicts normal temperatures and above-normal precipitation. |