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| Field Crop Advisory Team Alert newsletter | |||||||
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| Vol. 23, No. 15, August 7, 2008 |
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| In this issue Update: Western bean cutworm Soybean aphid - I’m not kidding! Spider mites showing Update on Michigan 2008 corn grain yield potential Common rust on corn Soybean disease update-soybean rust, white mold and root rots Soybean sentinel plot update Regional reports Weather news Next issue August 21 |
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| Update: Western bean cutworm Western bean cutworm flight is petering out across the state. Figure 1 shows the total moth catch per county as of August 1, as well as the number of traps per county in parenthesis (n). The timing and number of moths caught in western Michigan confirm we now have a resident, overwintering population of western bean cutworm. The traps also confirm the movement across the entire state to the Canadian border. Furthermore, egg-laying was confirmed in fields in the western part of the state in July. Many fields in the northwest were over threshold for egg masses (30 percent infestation confirmed by me in Oceana, and similar levels reported in Benzie, Grand Traverse, Leelanau, Missaukee and other northwest counties) and thousands of acres have been sprayed in that area. Eggs were found in southern Michigan as well, by Bruce MacKellar (St. Joseph MSUE), but were not over threshold. I have not yet had reports of eggs or larvae in dry beans, but I have found that scouting beans to find caterpillars is difficult, even on plants that I infested. |
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| Scouting for eggs and larvae needed to begin when moths were detected, concentrating particularly on the weeks of peak catch. This was the last two weeks of July in most areas. Moths prefer to lay eggs in fields close to tasselling; this was very evident in the fields I visited in Oceana County. Differences in growth stage (thus attractiveness of fields for egg laying) explains some of the wide variability in the number of egg masses from field to field. Thus scouting was critical to determining which fields were infested. By this time, eggs have hatched. Insecticide applications must be timed close to egg hatch and when small larvae are exposed on the tassel and leaf surface. We are past this window at most locations. The threshold for treatment is five percent of plants with egg masses or small larvae. Many bulletins and the MSU Insect Guide E-1582 give a threshold of eight percent. However, in discussions this winter with entomologist Tom Hunt from the University of Nebraska, I reduced the threshold this summer to five percent (five of 100 plants with eggs or larvae). More critical than which insecticide to spray was proper timing to kill exposed caterpillars, and we are again likely past the spray window, even if a field is infested. For those of you who planted a Bt hybrid, Herculex corn for European corn borer does kill western bean cutworm, although the control is not 100 percent control, and the refuge is still susceptible. Yieldgard-type corn does not kill western bean cutworm. Expect discussion of western bean cutworm at the 2008 - 2009 winter meetings, including presentations of whatever plot-data we can generate in the state.
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| Soybean aphid - I’m not kidding! You all know I love aphids, and that I can talk endlessly about them. But I really wasn’t kidding the last few weeks when I reminded you to watch fields for my favorite pest. Populations per plant in most of my field plots remained low throughout July, but the percent of infested plants was high, and has increased steadily - nearly 100 percent in some trials last week. Within the last several weeks, aphid populations increased in southern Minnesota, producing winged migrants that have been caught in the Midwest aphid suction trap network. We definitely had an aphid flight into Michigan last week, perhaps from the infestation in Minnesota. On July 31, I found winged aphids with babies on plants on campus. By the following day, Friday, August 1, we were finding tiny aphid babies on most of the plants in an MSU efficacy trial. This means even if you didn’t have aphids, you probably have them now. Furthermore,Bruce MacKellar in southwest Michigan, reports a few fields over threshold in southwest Michigan, with a high enough population to produce winged migrants. These fields are in the infamous “K-deficient” belt that in the stretches across several counties. Potassium deficiency is a well-documented soybean aphid risk factor. Target such fields for scouting immediately to catch any infestations heading over threshold. The soybean aphid threshold remains at 250 per plant, until plants are in the later R-stages (R5 and beyond). Should you spray at a lower threshold because of high crop prices? No. The aphid threshold was developed taking into consideration a range of crop prices and input costs. Even given higher returns, lowering the threshold doesn’t make good biological sense. We have never detected yield differences in treated and untreated plots when fewer aphids are present. And at lower aphid numbers, there still appears to be a battle going on between the aphids and predators. Pulling the trigger early wipes out the predators, so the aphids certainly win. Should you spray at a lower threshold because of the additional impact of defoliators, such as bean leaf beetles and Japanese beetles? No. The threshold was developed using data from plots in eight states over three years, including plots in Michigan. We did not keep bean leaf beetles or Japanese beetles out of these plots during the studies, they were there right along side the aphids. The yield from untreated plots in the study included the impact of both aphid sucking and beetle defoliation. The yields in treated plots included the impact of killing both aphids and beetles. Thus the soybean aphid threshold already includes the impact of defoliating pests, because we didn’t exclude them. What about ignoring the threshold altogether and spraying an insurance application? Bad idea. Killing beneficial insects can actually flare, or increase, an aphid population that was otherwise under control. Insurance applications may also flare spider mite (see accompanying article), which are making an appearance this week. Insurance applications also smoke honey bees, which have taken a beating in the last several years. See the August 4 edition of the Ohio State CORN newsletter for a cautionary article by my colleague Ron Hammond, “Spraying Insecticides on Soybeans and Honey Bees”. |
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| Spider mites showing Spider mite infestations are starting in some fields. Hot, dry weather favors this pest. A rating system helps to decide if treatment is needed. That rating system with images is available at http://www.ipm.msu.edu/cat08field/pdf/8-07mitescouting.pdf Mites move into fields from the edge, often by passive airborne movement. Damage may be noticed first near an obstacle, such as a tree-line or power pole, that disrupts wind near the edge of the field. Mites feed with a piercing mouthpart, inserting it directly into plant cells and sucking out the contents. This type of feeding not only injures or kills plant cells, but results in water loss through the feeding wounds. Mite feeding leaves behind tiny yellow dots or specks on the leaves. As mite numbers and feeding increase, the yellowing becomes more apparent across the leaf surface. Cells are disrupted, water is lost, and plant tissue begins to die. Under severe infestation, leaves turn brown and eventually drop off the plant. Mites are best seen with a hand lens, especially by shaking plant foliage over a white piece of paper. A heavy mite infestation, however, is fairly obvious to the naked eye, with leaf speckling and yellowing, obvious numbers of mites on the undersides of leaves, plus webbing. Treatment options insecticides with the OPs chlorpyrifos or dimethoate (Lorsban, Dimethoate, Cobalt) or bifenthrin (Capture, Hero). Unfortunately, if you treat spider mites, populations can resurge due to: Egg hatch: Mites lay eggs on the plant surface. Insecticides kill adults and nymphs, but do not kill eggs. Since Dimethoate and Lorsban have short residual, newly hatched nymphs survive and repopulate the plants. Rebound or flaring: Insecticides kill beneficial insects, but 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 for mites as well as soybean aphid. Resistance: Spider mites can become 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, as populations can crash quickly. 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. |
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| Update on Michigan 2008 corn grain yield potential Corn grain yield determination involves the continuous interaction of genetic, climatic, soil, plant pest, and nutrient factors present for a specific growing season. Michigan has a wide range of soil types and in most years, a high degree of variability in rainfall and pest patterns. This variability in weather and production potential makes forecasting state-wide yields a difficult proposition at best. However, from an individual farm crop management standpoint, it is helpful to characterize the most critical stages of development in the life of a corn plant with respect to determining final grain yield. The following are four critical stages in the development of a corn plant that are fundamental to determining corn grain yield and a quick assessment of how the state has progressed through each stage. The first of these four critical corn yield determination stages is emergence. Corn does not have the ability to compensate for poor stands as well as other crops such as soybean. Establishing a uniform, optimum population stand is the first step in developing corn grain yield potential. Studies on the genetic evolution of corn indicate that modern hybrids tolerate field stress associated with higher plant populations better than their earlier genetic predecessors. Growers should continually evaluate the carrying capacity of their fields by putting in a few strip trials to determine the optimum plant population for each field. Keep in mind that as corn genetics continue to evolve, you will likely need to continually adjust your planting population upward to find that optimum plant population for each field. In general, much of the state had good to excellent conditions for corn emergence in 2008, and plant stands are correspondingly good to excellent. The second critical growth stage is when the plant determines the number of kernel rows and the number of potential kernels (ovules) per row. This is primarily determined during the rapid phase of corn vegetative growth, which generally occurs in early to mid July in Michigan. The number of kernel rows per ear is heavily influenced by genetics and is generally determined by growth stage V12, which corresponds to the 12 leaf collar stage. The number of potential kernels per row is being determined at V12 and is usually completed a week to 10 days prior to silking (V17). The number of potential kernels per row is strongly influenced by field conditions. Managing corn to reduce environmental, pest, moisture and nutrient stress during this time will maximize the potential number of harvestable kernels. This stage, along with the pollination stage described below, determines the “sink” which the corn leaf canopy will work to fill with photosynthetically derived starch. Follow a plan to ensure adequate nutrient levels and minimize stress from pests such as weeds and insects during this critical period to establish the potential for high yield. Most areas of the state came through this second important yield determining stage of development in very good shape due to the timely rains we received throughout the early 2008 growing season. The third critical stage is pollination. Successful pollination is required to convert potential kernel numbers to actual developing kernels. Pollination occurs when a pollen grain is shed from the tassel, lands on an emerged silk, grows down the length of the silk, and successfully fertilizes the ovule. It generally takes two to three days for all the silks on an ear to be exposed and pollinated. Pollen shed generally occurs in the late mornings and early evenings and the pollen shed period typically lasts from one to two weeks. From a management perspective, there is not a lot that can be done to ensure good pollination, since it is highly dependent upon the weather. Droughty conditions can de-synchronize pollen shed and silk emergence and also can desiccate silks and pollen grains. This results in barren ears or in short ears with barren tips. Insect pests such as adult corn rootworm beetles can feed on emerging silks and reduce pollination and therefore should be scouted during silk emergence. Finally, because the tassel and all leaves are completely exposed, the plant is especially vulnerable to hail damage at this stage. Most of the corn in the state has now completed the pollination stage of development. Consistent with the previous yield determining factors, over all, the state fared quite well during the 2008 pollination period. To assess pollination on your own farm, remove the husk from developing ears and vigorously shake. Silks on successfully pollinated kernels will drop off and silks emerging from nonpollinated ovules will stay fast. Corn grain is sold by the pound and the final critical growth stage for determining yield is the grain fill or kernel development period. The grain fill period which begins at pollination and ends at kernel black-layer formation generally takes from 60 to 70 days (855 to 1200 GDD) for Michigan conditions depending upon climate, planting date, and hybrid relative maturity. The size and weight of harvested kernels are determined at this time and under adverse conditions kernel number can also be reduced. Ideal conditions for the grain fill period include: plenty of soil moisture; warm days; cool nights; and low humidity. Stress on the corn plant during the grain fill period can affect final yield by reducing either of these factors. Although field and machinery conditions can still influence final harvestable yield, the corn plant has physiologically completed its work once kernel black-layer has occurred. Regarding pests, one particular insect pest to watch out for during the 2008 grain fill is the western bean cutworm (see the July 24, 2008 Field CAT Alert for more on this subject by Chris Difonzo). This pest can invade developing ears causing significant damage. Diseases to scout in the 2008 grain fill period include stalk rots. Early reports noted higher than usual anthracnose levels which could lead to isolated areas of high stalk rot incidence. To date, the 2008 Michigan corn growing season has progressed through the first three stages of corn yield determination in very good shape, especially when contrasted with the rest of the Midwest. If adequate moisture and heat units are obtained, and insects and disease are kept in check, the stage is set for excellent 2008 state-wide yields. |
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| Common rust on corn This year, there have been higher than usual amounts of common corn rust showing up, as weather conditions were conducive for the disease early on. The fungus spreads by airborne spores traveling on wind currents and storms from the South, and does not overwinter in Michigan. Common rust rarely causes economical loss in field corn, as most hybrids have adequate resistance. Unless there are other foliar diseases present, such as gray leaf spot or northern corn leaf blight, it isn’t usually an economic proposition to apply a foliar fungicide. Seed corn inbreds may be much more susceptible to rust and are commonly treated with a fungicide to control rust and other foliar right around tasselling. If a fungicide is to be used, it’s important to make the application early before the disease has a chance to become established. Once the pustules begin to produce the reddish-orange spores (called uredospores), repeating cycles of infection can take place, spreading the disease. New infections can occur about every seven to 14 days. A single application of fungicide is best made at tasselling, which has passed except for a few of the seed corn inbreds. Most corn is now in the grain fill period, which is beyond the optimum time for fungicide application. |
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| Soybean disease update-soybean rust, white mold and root rots
Rust So far, soybean rust hasn’t spread very quickly this year in part due to unfavorable weather conditions down south. Soybean rust has been confirmed on soybean in several southern states, including Texas, Alabama and Florida. Since the first of this year, soybean rust has been reported in two counties in Alabama; one county in Georgia, 16 counties in Florida; three counties in Louisiana; one county in Mississippi, and four counties in Texas, mainly on kudzu. Rust was also reported in three states in Mexico on jicama and soybean, but these have been destroyed or are no longer active. However, the effect of recent hurricane activity on the spread of soybean rust may soon be detected as scouting activities continue. Rainfall traps monitored by the USDA Cereal Rust Lab have recently shown an increase in frequency and detection of rust spores, although the three rust spore trap locations in Michigan have shown no detection of spores as of August 1. White mold Conditions in parts of Michigan are favorable for white mold (Sclerotinia sclerotiorum), especially in irrigated fields, or fields with lush growth and dense canopies, and it is beginning to show up. We’ve had cool morning and evening temperatures and high humidity, which provide a favorable environment for the disease to develop particularly as plants are flowering. Even if it has been hot during other hours of the day, remember that temperatures in the crop canopy may be considerably cooler than air temperatures. Hopefully, you won’t be seeing white mold if you planted partially resistant varieties, which should be the first line of defense in managing this disease. An in-state source with ratings for white mold resistance, including partially resistant varieties can be found at the MSU Soybean Variety Trials website: http://www.css.msu.edu/varietytrials/soybean/whitemold.htm White mold symptoms first appear as wilting and dying upper leaves, with dead leaves staying attached to the stems. Infections take place through blossoms and develop at the stem nodes as water-soaked lesions. Cottony tufts of white mycelium appear on stems and other infected parts. Later on, stems look bleached, papery or shredded. Black pieces of dormant mycelium (sclerotia) that look like rat droppings appear loosely attached to stems, in stem pith and sometimes in pods. Cropping practices that promote a dense, lush canopy including narrow rows, high planting rates (more than 200,000 plants/acre), irrigation and high soil fertility, contribute to an environment that favors white mold. Once the disease is present, there isn’t much that can be done to treat it in soybeans. There aren’t many fungicides registered for controlling white mold in soybeans, canopy penetration and coverage are major issues and currently registered products have limited efficacy. Soybeans’ extended bloom period and tendency to rebloom on the lower stem, creating new infection sites for the fungus, makes control with a single fungicide application difficult. Although fungicides are rarely used to control white mold in soybeans, they are used in dry beans. Achieving good control of white mold in dry beans is still a challenge, but there are more fungicides with greater efficacy to choose from, and reblooming low on the stem isn’t an issue to confound the effectiveness of treatments. Page 95 of the extension bulletin E-1582 Insect, Nematode and Disease Control in Michigan Field Crops lists products registered for use on dry beans. Most of the strategy for managing white mold is based on using good management practices. These include rotation to non-hosts such as corn, sugar beets, alfalfa or small grains for two to three years to reduce the number of sclerotia in the soil, and controlling broadleaf weeds during the non-host crop rotation (many broadleaf weeds are hosts for this disease). During years when soybeans are planted, in addition to selecting varieties with partial resistance, having lower planting rates and wider row widths that promote air circulation and rapid drying of plants and soil surface create a less favorable environment for the white mold fungus. Seed used should be clean and free of sclerotia and can be treated with one of several seed treatment fungicides labeled for white mold if it is present on the seed. Irrigation should be limited to what is needed for optimum plant growth. Root rots Some soybean fields are just not growing well this year, with stunted plants, yellow foliage, and bare patches evident in fields. Some of this can be attributed to earlier weather conditions, but Rhizoctonia root rot, phytophthora root rot and fusarium root rots are appearing in some fields. Symptoms of Rhizoctonia usually appear as the weather becomes warm and plants become drought stressed, although infection occurs under wet conditions. Soil temperatures between 77°F - 84°F, wet soils, and high organic matter provide favorable conditions for development of the pathogen. Seedling stem discoloration by Rhizoctonia is usually limited to the outer (cortex) layer of the main root and hypocotyls (portion of the stem below the first leaves). Infected stems have a reddish brown color and do not become mushy; they remain firm and dry. On older plants, the reddish brown discoloration of the main stem tend to stay below the soil line and may develop into sunken lesions and girdle the stem. Management options for this disease are limited. Soybean varieties differ in their susceptibility to Rhizoctonia seedling and root rot, but none are resistant. Crop rotation is of limited value because so many crop species are hosts for Rhizoctonia. At planting time, using high quality seed will help, and several seed treatments are labeled to control damping-off caused by Rhizoctonia. Phytophthora can develop any time from plant emergence to early maturity, but is most often seen shortly after emergence and during early flowering. Young plants turn yellow, collapse, and die, leaving gaps in row plantings. Foliage of older plants wilts and turns yellow starting at the bottom of the plant and moving up. Dead leaves may remain attached. A chocolate-brown discoloration of the lower stem starts near the soil line, and spreads upward. Root systems are rotted. Conditions favoring the disease include poorly-drained or saturated soils, and soil compaction, phytophthora prefers soil temperatures that are above 80°F. A primary strategy for managing phytophthora is to plant soybean varieties that are tolerant. Look for soybean varieties with specific resistance genes Rps 1c or Rps 1k and good partial resistance/field resistance to all races of phytophthora. Rotate with a non-legume crop for at least two years. Improve soil drainage, avoid working or driving on wet soil, and tillage practices that contribute to soil compaction. At planting time, seed treatments labeled for phytopthtora can be used for fields with a history of the disease. Several species of fusarium cause seed and seedling rots and root rots, including F. solani, complex, F. graminearum, F. oxysporum complex and others. Isolates within some species of fusarium may vary widely in their level of pathogenicity, ranging from saprophytes, to those that cause increasing amounts of root rot. Seedlings may not be killed outright, but may be severely stunted. Although infection can take place early, symptoms may not be noticeable until early flowering. Fusarium root rot often is found in wet, poorly drained areas of the field such as low spots. Infected plants may have poor root systems and poor nodulation with reddish brown or dark brown lesions on lateral roots and taproots. Plants may appear stunted or unthrifty, and there can be a yellowing of the leaves with the veins remaining green for a short time. The leaves eventually turn completely yellow, die from the edges inward and fall from the petioles. The foliar symptoms are different from those caused by sudden death syndrome (fusarium virguliforme), where veins remain green. Fusarium root rot may be observed in association with stressed plants, such as in drought conditions or with herbicide damage. The root rot predisposes plants to damage from other stresses. High populations of the pathogen in the soil, however, may result in disease development under good growing conditions. The pathogen may interact with other pathogens such as rhizoctonia or the soybean cyst nematode to cause disease. Disease severity may be greater in plants showing iron chlorosis There is no known resistance to fusarium. Resting spores can remain in soils for extended periods of time. Conditions that delay germination and emergence such as cold, wet or compacted soils favor fusarium seedling blight and root rot. To reduce losses from fusarium seedling blight and root rot, plant good-quality seed with a good germination rate under good seedbed conditions, and minimize or avoid stresses that delay germination and emergence. Several fungicidal seed treatments are labeled to control fusarium damping-off. Seed treatments have not consistently reduced SDS. |
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| Soybean sentinel plot update This summer the weather in Michigan, especially June, could be described as a “cornucopia” of climatic changes. Above all the changes, we experienced unseasonably rainy days and chilly nights, which have resulted in a delayed development of many plants, vegetables, and crops, including soybeans. As the month of July rolled in, we finally had warmer temperatures. In spite of Michigan’s weather roller coaster, many plant pathogens continued their life cycle and made it into our crops, and soybean was no exception. As of August 5, we have received samples of soybean leaves from Michigan’s sentinel plots, and a number of samples are being processed and diagnosed, but no soybean rust has been detected. Septoria brown spot, bacterial blight and bacterial pustule make up the majority of diseases diagnosed from sentinel plot samples so far. |
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| 2 -- Southwest Bruce MacKellar Weather Recent dry conditions have begun to take a toll on the non-irrigated crops in the southwest region. Most of the rainfall that has occurred this summer has been associated with thunderstorms, which have been highly variable in coverage and intensity. Berrien County seems to have been able to catch some precipitation from recent thunderstorms that have dropped down into Indiana. Thunderstorm activity on the evening of August 6 produced rainfall east of US-131 at 0.22 – 0.33 of an inch. Crop report Commercial corn is in early grain fill. We have seen some severe damage on some dryland fields due to drought stress. The lower plant canopy has fired up to the ear leaf in a few fields, but most fields have gone through a period of some moisture stress over the last two weeks. There continues to be elevated levels of common rust in both commercial corn and seed corn, but the drier conditions have seemed to reduce the spread of this disease on the plants. We rarely treat commercial corn for common rust. Regional university field crop pathologists suggest that treatment of rust with fungicides (in high pressure years) should occur when the first pustules are found on the lower leaves to help keep the disease from spreading up the plant. In general, we have seen less silk clipping activity from western corn rootworms and Japanese beetles than normal in St. Joseph County. Crop water usage in dry, hot conditions is still near the maximum for the season, with evapotranspiration rates ranging from 0.25 – 0.28 inches per day. The water usage curve for corn will begin to decline over the next two weeks. Seed corn de-tasseling and male row destruction are moving beyond the 50 percent mark. We continue to see common rust, some northern corn leaf blight, and some gray leaf spot on susceptible inbreds. We also have seen some fields that have had bacterial stalk rots associated with irrigation from surface water resources. The water sources of the infected fields I have seen this year have been ponds, but we can also see the disease coming from river and streams. The organism usually responsible for this disease is Erwinia chrysanthemi. The bacteria can thrive in water, and generally infect the plant when water collects at the base of the leaves. The bacteria then move into the plant through the stomates, and cause damage to the vascular tissue. The plants often show browning of the leaves with a distinctive odor coming from the infected plants. Our most advanced soybean fields are at R3 – R4 (pods developing at the upper nodes of the plant). We are entering the most critical period for plant water usage in the soybean crop, which tends to peak as the soybeans begin to size. Drought stress can be critical during this stage, because the plant will often abort flowers and pods on the upper nodes, and will soon lose the ability to set new flowers and pods at the plant reaches maturity. Crop water removal for vigorous soybean stands will increase to the 0.23 – 0.26 inches per day over the next two weeks for advanced fields. Soybeans are beginning to show the various effects of environmental stresses that we have seen through this growing season. We have a wide variety of circular patterns of decline going on in many fields right now. The areas where water stood early in the season are generally devoid of plants. We also are seeing effects of root rots in some of these fields. In other fields, you can find plant stress in pockets where high soybean cyst nematode populations exist, even where cyst resistant varieties have been planted. This is especially evident in non-irrigated fields. In some of these pockets, sudden death syndrome can be found. Soybean aphid numbers are on the increase, with a few fields in Centreville approaching the 250 aphids per plant level. We are also seeing spider mites in pockets of fields. Look for yellowing and bronzing, especially in fields adjacent to gravel roads where dust has been prevalent this summer. Most alfalfa producers have been able to harvest second or third cutting over the last two weeks, depending upon when the first harvest occurred. Potato leaf hopper numbers continue to be very high, and some fields have hopper burn where they were not protected. Keep in mind that regrowth alfalfa is much more susceptible to damage than larger plants, so continue to monitor these fields to prevent yield losses.
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| 3 -- West Central Fred Springborn Weather Dry, could sum up the weather in a single word. Rains have been scattered and have been light. Most areas that have received rain have only seen a tenth of an inch or two inches at best. High temperatures have been in the upper 70s to low 80s. Crop report Alfalfa harvest continues with relatively slow regrowth. Potato leafhoppers are present in many fields at relatively low levels. Wheat harvest is complete with generally good yields and test weights reported. Oat harvest is under way. Corn pollination is complete in most fields. Dryland fields are quite variable due to soil moisture, corn on the lighter soils is under stress. European corn borer trap counts remain quite low. Western bean cutworm trap catches have been low. Soybeans are flowering and setting pods. Plants are generally short and many fields could use a good soaking rain shower. Dry beans are setting and filling pods. Dry weather is a concern especially for those fields that are suffering from root rot. |
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| 4 -- Central Paul Gross Weather There were some scattered showers over the region in the past two weeks. The amounts were very small ranging from a trace to a couple of tenths. We are at the point in the growing season that regular rains are needed. Many crops on lighter soils are showing moisture stress and if adequate amounts of rain do not occur soon, we will begin to lose yield. The temperatures have been somewhat forgiving as we have not had extreme heat. Crop report The corn crop has completed pollination and is looking pretty good at this point. Rain will be needed soon if the current yield potential is to be achieved. We are not seeing any insect or disease problems at this time. There is evidence of nitrogen deficiencies with the yellowing of the tips of lower leaves in some fields. Soybeans are filling the pods and rain will be critical at this time in the growing season. It is pretty easy to find soybean aphids on nearly all fields. At this time aphid levels are well below threshold so continue to scout fields on a regular basis. There are also low numbers of grasshoppers in many fields. Disease pressure is low. Wheat harvest is now complete. Most farmers are reporting very good yields and quality. Some indicated their yields were the best they ever had. Farmers are reminded that this is a good opportunity to manage any problem perennial weeds in these fields as well as manage the volunteer wheat. Oat and barley harvest is nearly complete. Yields are being reported and are very good. Harvest of third and second cutting alfalfa is well under way, depending on the farmers’ cutting schedule. We have found potato leafhoppers by the pound in nearly every field. Some fields that have not been cut are showing signs of “hopper burn” coupled with lack of moisture; yield will be poor on these fields. Scout fields for this pest. Dry beans are progressing but are in need of rain. Fields are being treated for leafhoppers. Sugar beets are looking very good. |
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| 5 -- Thumb Bob Battel Weather |
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| Weather news Jeff Andresen Agricultural Meteorology Geography During the past one to two weeks, a broad upper air ridge has persisted across much of the central United States, resulting in oppressive heat across sections of the southern and central Great Plains and generally drier than normal conditions across much of the Upper Great Lakes region. That general pattern is expected to continue for much of the next week, but with a shift of the ridge axis westward into the Rockies. That shift should in turn lead to the development of a troughing feature across the Great Lakes and a period of cooler and drier than normal weather. In the short term, cooling temperatures aloft and a series of weak upper air disturbances will lead to the chance for scattered showers and a few thundershowers Thursday, August 7 and Friday, especially in eastern sections of the state. Given limited low level moisture, however, rainfall amounts and areal coverage are expected to be limited with most totals remaining in the 0.10-0.25-inch range or less where rain falls. Cool and mostly dry weather is expected for the upcoming weekend (a few stray showers will be possible). Temperatures Thursday through Sunday will fall back from recent levels to highs ranging from near 70°F north to 80°F south, with lows from the low 50s north to near 60°F south. A weather system approaching from the west will bring the next chance for significant rainfall by next Monday or Tuesday. In the medium range period, forecast guidance suggests a general continuation of the upper air pattern mentioned above. Both National Weather Service 6 ‑ 10 day, covering August 12 - 16, and 8 ‑14 day, covering August 14 - 20, outlooks call for below normal mean temperatures state- and region-wide. Precipitation totals are forecast to remain at below normal levels during the 6 - 10 day time frame and range from below normal levels in western sections of Upper Michigan to near normal levels across the remainder of the state during the 8 - 14 day period. New long lead outlooks Latest long lead forecast guidance suggests that the El Niño Southern Oscillation (ENSO) index will remain near neutral for the next several months into early 2009 at least. Thus, while some impacts of the recent past La Niña event may persist for another month or two (including increased chances for hurricane activity in the northwestern Atlantic Basin), ENSO is expected to have little or no influence in the outlook for the next several months. The latest NOAA Long Lead outlook for August calls for mean temperatures in Michigan to remain in the climatology scenario with near equal odds of below, near, and above normal values. The outlook for rainfall suggests above normal totals across some western sections of the state, with near the equal odds scenario elsewhere. Further ahead, the outlook for the three-month August through October period calls for increased odds of above normal mean temperatures statewide. Precipitation totals for this frame are forecast to remain in the climatology/equal odds scenario. |
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