Regional reports on Michigan field crops – July 28, 2011
MSU Extension educators’ pest and field crop updates for Michigan.
This week’s regional reports:
- Southeast Michigan – Ned Birkey
- Southwest Michigan – Bruce Mackellar
- West Central Michigan – Fred Springborn
- Central Michigan – Paul Gross
Weather has been hot and dry for much of July, with 17 days at 90 degrees or higher this month alone. So far we have had about 25 days at 90-plus temperatures this season.
Alfalfa second cutting is finishing up. The hot temperatures have moderated the potato leafhoppers. The first and second cuttings are both of high quality and good quantity. The new growth will struggle to grow until we get some rain.
Corn growth ranges from tasseling and pollination and other fields with plants just at the V9 stage. Corn plants will be shorter than normal as the plant compensates for the late start, with a shorter internode between leaves. Corn plants at ear set time can use 0.25 to 0.5 inches of water per day, so the next couple of weeks will be a critical time for yield determination. European corn borer numbers are at zero, corn earworm numbers are increasing, though at low levels, and western bean cutworm numbers this week were lower in Monroe County but higher in Washtenaw County. The counts are still low compared to other areas of Michigan and the Midwest. For some reason, corn rootworms can be found in the corn where you would expect them, and not in the soybeans.
Soybeans are at the R2 full bloom stage, even though plants are short. No soybean aphids were found in samples pulled this week. Phytophthora and Rhizoctonia root rots, sudden death syndrome, potassium deficiency and some herbicide injury have been observed. Root rot diseases will continue to spread and those plants will likely die before maturity. One farmer has “John Deere” soybeans – patches of bright-yellow soybeans – which is soybean cyst nematodes and potassium deficiency. The yellow, unbaited sticky traps did not catch any variant western corn rootworms in Monroe, Wayne or Washtenaw counties this week. I have not seen any spider mites, though they should be present in field margins of extremely dry fields.
Wheat harvest finished with generally above average yields and excellent test weight. High test weight is important to companies like Chelsea Milling (Jiffy Mix) and the Nabisco Flour Mill in Toledo, Ohio to help make high quality flour for uniform baking of products.
Heat has been the story over the last couple of weeks in southwest Michigan. Excessive heat warnings, coupled with thunderstorm rainfall, provided an incredible boost to crop development. However, not all areas benefited from the heat. Variable thunderstorm rainfall totals left some areas both hot and dry, which was a bad combination as much of the areas corn crop moved into pollination. The quiet passage of a cold front brought a return to seasonable temperatures and humidity. And finally, an approaching warm air mass provided tremendous amounts of rainfall (8-plus inches in some areas) on July 27-28. Southwest Michigan tended to escape the heaviest rainfall totals from this storm, with 1- to 2-inch totals common. The latest rainfall impacted many areas in south and central Michigan, ending the prolonged drought in some of these areas.
Temperatures and growing degree days
A quick look around the region shows that we are at 1399 - 1597 GDD’s Base 50 since May 1, depending upon the proximity to Lake Michigan, with an average of 1515 for the 12 Enviro-weather stations in the southwestern portion of the region. This has moved us above the long term average GDD accumulation in the Region of 1427 (about three to four hot summer days). The average GDD accumulation Base 50 in the region for the next five days is 20.4 and the following five days is 20.2. The 6-10 and 8-14 day outlooks have southwest Michigan solidly remaining in the above normal temperature zone.
Rainfall totals since July 14 range between 1.54 inches in Benton Harbor, Mich., and 3.98 inches in South Haven, Mich. The average precipitation total for the 12 Enviro-weather stations during this period was 2.76 inches. Both the 6-10 and 8-14 day outlooks have southwest Michigan in the somewhat above normal precipitation range.
Alfalfa harvest has been pretty much on schedule in most of the region. There has been enough dry days and heat to allow for harvest operations between the showers. Potato leafhopper numbers remain high. Remember, alfalfa regrowth thresholds for treatment are pretty low – two potato leafhoppers per sweep, 1 to 3 inch alfalfa. Even on more mature alfalfa, it is important to watch for signs of leafhopper feeding injury. Read MSU Extension Bulletin E-1582 for MSU field crops entomologist Chris DiFonzo’s recommendations for potato leaf hopper control.
As of today (July 28), the majority of the corn planted by May 15 has either pollinated or is currently in the process of it. Corn planted in early June is beginning to set tassels here. The warm conditions have greatly benefited the growth of the later planted corn. Western bean cutworm moth flight has been on an increase and may have reached peak at about 20 to 25 moths being caught per night in a few locations. The average moth catch in Van Buren County has been around 8 to 10 moths per night. Egg masses have been a bit harder to track. Egg masses in fields I have scouted ranged between 0 and 2 percent. The cumulative threshold for treatment is 5 percent of the plants with egg masses. For more information on western bean cutworms, read Difonzo and Fred Springborn’s article on Western bean cutworm update for July 25, 2011. Western corn rootworm beetles activity has increased a bunch this year compared to recent years.
We are also catching a lot of Asiatic garden beetle adults in our western bean cutworm traps. Asiatic garden beetle white grubs can cause damage the following spring when female beetles lay their eggs in soybean, potato and alfalfa fields. There are signs of root feeding in a lot of rotated and non-rotated fields. We might want to be on the lookout for gray leaf spot in corn fields. The disease really likes hot and wet weather, which we have had a lot of in the region. I have also seen signs of leaf rust and northern corn leaf blight in fields I have walked.
Soil water removal in corn fields is probably above normal this year in southwest Michigan due to the large plant heights.
Seed corn de-tasseling is in full swing right now. Watch for silk clipping insects (western corn rootworms and Japanese beetles) that are active in fields in the region. Watch closely for the development of corn leaf diseases, particularly gray leaf spot in seed fields. Both rust and northern corn leaf blight are also active. Purdue University field crops pathologist Kiersten Wise has developed a series of excellent fact sheets that discuss gray leaf spot,northern corn leaf blight and leaf rust.
Most soybean fields are heading into early pod fill. In general, the crop looks good. We have some defoliation going on with Japanese beetles, but the vegetative growth on these plants has been impressive on fields where water has been adequate. We do have some areas where the plants have been stunted because of drought stress in those areas missed by rainfall. In these areas, we need to keep an eye out for spider mite activity. Spider mites often get a foothold in dry and dusty areas in fields. Wet and humid conditions usually provide a boost to pathogenic fungi, which can quickly crash populations of spider mites and soybean aphids. Speaking of soybean aphids, it is hard to find them in fields.
In areas where moisture has been good, we have very dense canopy growth in fields. This has set the stage for white mold development. The unusually high temperatures have probably helped to suppress the incidence of white mold, but cool and wet conditions may make for a significant infection period. We have begun to see white mold in irrigated fields in southwest Michigan. We are also beginning to see evidence of sudden death syndrome in several irrigated fields in southwest Michigan, and it is important to know what to look for when scouting for sudden death syndrome.
Sudden death syndrome in a soybean field in 2010.
Welcomed rainfall last night (July 27) and this morning has brought many dry land crops back from wilting in the Montcalm area and has given irrigators a few days off. High temperatures have been in the mid-80s this week and the mid -90s during the week of July 18.
Much of the corn crop is pollinating or just past pollination this week. There is a significant portion, however, that was planted in early June that is still whorl stage V10- V12. Western bean cutworm pheromone traps have been catching significant numbers of moths throughout the west central region (See the trap catch map at the MSU Field Crops Entomology website.). Western bean cutworm egg mass counts in several of my plots have been at or above threshold 5 to 8 percent, while other plots and many fields have missed the infestation due to timing of tassel emergence. Egg masses have been hatching in as little as four days last week in the high temperatures. If scouting was done on a seven-day schedule, egg masses may have been missed.
Japanese beetles are present in many corn fields in low numbers. European corn borer and corn earworm pheromone traps continue to catch very low numbers of moths.
Dry beans are right at the start of the spray window for western bean cutworm. From research conducted in 2009 and 2010, it is better to be a little late than too early when applying insecticides to control this pest. Some fields may not be attractive for egg mass deposits due to small canopies and stressed plants. Another factor that may lessen the western bean cutworm pressure on dry beans is late planted corn that is prevalent in some areas of the west central region. If there is attractive pre-tassel corn near dry beans, it should help absorb some of the egg mass load.
Western bean cutworm moth resting during the day in a dry bean canopy.
Soybean aphids are present but in very low numbers. Until last night’s rain, many fields had been showing the effects of being drought stressed. Japanese beetles are present and feeding, but causing damage well below the 25 percent defoliation threshold.
Japanese beetle feeding injury on soybeans.
Just in time, rains fell across the region July 28. Rainfall totals range from 1 inch in the northern parts of the region to over 3 inches in the south. While the rain will benefit most crops, some corn fields on sandy soils have suffered too much drought stress and will not recover, resulting in significant yield loss. Growing degree day totals are near normal and with predictions of warmer weather it is expected we will be a little ahead of normal in the next two weeks.
The corn crop varies widely across the region and is based on planting date and soil type. The early planted corn on heavy soils is pollinating, and with the recent rain, has excellent yield potential. The later planted fields on heavy soils are just beginning to tassel and will need a good fall to mature. The corn planted on sandy soils is drought stressed and yield has been lost. Western bean cutworm moth trap catches were at high levels last week. Scout corn fields for egg masses and monitor this pest.
The soybean crop struggled early-on, but is looking much better and will benefit from the recent rains. The crop ranges from just flowering to the growth stage R2. There are no reports of problems at this time. Fields should be scouted for soybean aphids and spider mites.
Harvest of third cutting alfalfa is just getting under way for farmers on aggressive cutting schedules. Some are just wrapping up second cutting. Most are reporting very good yields and quality. New seeds are being cut for the first time. Scout fields for potato leafhoppers.
Wheat harvest is just wrapping up. Most all are reporting very good yields and quality. It will be important to manage weeds in these fields. Farmers should consider planting a cover crop in these fields for weed suppression, nitrogen scavenging and improving organic matter.
Dry beans are flowering with pod set just around the corner. It is advised to scout these fields regularly for western bean cutworm. Trap catches have been high and the early planted dry bean fields will be attractive for the female moths to lay eggs. Fields should also be scouted for leafhoppers.
Oat and barley harvest should begin next week. Both crops look very good with yields expected to be good.
Sugarbeets have been a real challenge this year. Fields are beginning to even out and just filling the rows in later planted fields. The crop will benefit from the recent rains.