By Willie Kirk... Recent weather conditions have been favorable for Fusarium head blight (FHB), or scab. The FHB models have been predicting low risk, and this may well be true but where local, persistent and heavy rain has occurred, growers may be advised to apply an appropriate fungicide immediately.

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By Diane Brown-Rytlewski... Wheat has begun to flower in fields in the southern-most portions of the state bordering Indiana and Ohio.

Elsewhere, wheat ranges from second node in the north to the boot stage or heading. Most of the wheat is likely to flower this week. Once wheat begins to flower, it enters the critical stage for fusarium head blight infection.

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By Diane Brown-Rytlewski... The current risk for fusarium head blight in Michigan is low. We have still seen very little foliar disease, but now is the time to scout fields with susceptible varieties. There was heavy rainfall in the St. Joseph County area last week, which may have brought in the leaf rust that is now showing up on the flag leaves of some varieties in that area.

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By Diane Brown-Rytlewski... The heavy rains we have had created favorable conditions for the fungus that causes SDS, Fusarium virguliforme. With the clock ticking and unfavorable conditions for planting in many fields, it’s unlikely that any plantings you’re doing now would be considered early, but there are still some important considerations.

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By Diane Brown-Rytlewski... Plant pathology colleagues at CornellUniversity have shared research they have been conducting on brown root rot (Phoma sclerotioides), a disease that occurs on alfalfa in northern climates. Although this disease has not yet been reported in Michigan, it was recently confirmed in southern Ontario and Wisconsin. It is also found throughout New York, Vermont, New Hampshire, Maine, in the Northern Plains’ states and western Canada.

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Willie Kirk, Ralph Fogg, Corey Guza, Linda Hanson and Steve Poindexter...The Cercospora spraying season has started for those of you that are in the high-risk areas and have either B1643N or ACH 827 varieties. The weather has been suitable for Cercospora development so you need to be ready to spray. The forecast for the next week is also suitable for development of Cercospora leaf spot, so growers in lower risk areas should also be prepared to make a fungicide application. Many fields are too wet to enter, but will need to be sprayed as soon as you can enter them.

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Willie Kirk, Christie Sprague, Steve Poindexter, Linda Hanson, Corey Guza and Ralph Fogg...Recent weather conditions may have been suitable for the development of Rhizoctonia crown and root rot and possibly damping-off. Quadris can be applied early in the sugar beet growing season for control of Rhizoctonia damping-off and Rhizoctonia crown and root rot caused by Rhizoctonia solani anastomoses groups (AG) 4 and 2-2, respectively.

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Diane Brown-Rytlewski...Symptoms of net blotch (Pyrenophora teres) appeared in a campus research plot and a grower’s field of winter barley in Ingham County this week. The foliage had numerous small dark green to light brown spots, and some larger parallel brown stripes and blotches with yellow halos. (see photo) Wheat is not affected by net blotch.

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Diane Brown-Rytlewski...Last fall, an epidemic of Stewart’s disease occurred with foliar symptoms showing up on many field corn varieties in numerous locations across the state (figure 1). Stewart’s disease is caused by the bacterium, Pantoea stewartii, and transmitted to corn by the corn flea beetle when it feeds on foliage and deposits its bacteria-laden feces in the feeding wounds. The flea beetle overwinters as an adult in ground litter and harbors the bacterium in its gut.

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Diane Brown-Rytlewski...Although drought conditions aren’t especially conducive to the development of root diseases on soybean, there is one notable exception – Charcoal rot (Macrophomina phaseolina). (view photos) Although this disease organism survives in the soil and in crop residue from year to year, it develops when there is a high level of the pathogen in the soil, and plants are stressed by weather that is hot and dry. Recent rainfall and cooler temperatures should help to reduce plant stress, but plants damaged by this disease are likely to have already suffered some loss of yield.

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Diane Brown-Rytlewski...There have been a couple of reports in Michigan of wheat with a red or yellow discoloration beginning at the flag leaf tip and progressing toward the base of the leaf. There is no stunting of the heads and minimal stunting of the plants. These leaf discoloration symptoms, along with stunted heads, stunted plants and flag leaves remaining in an upright position, are classic symptoms of barley yellow dwarf virus, an aphid transmitted virus.

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Diane Brown-Rytlewski...Powdery mildew is the only wheat foliar disease showing up with any regularity this season, and the amounts of it are quite variable. On susceptible or highly susceptible varieties, there is a substantial amount of mildew. With rain and humid weather along with cooler temperatures forecast for the next few days, conditions may be favorable for powdery mildew to come up out of the lower canopy where the temperatures have been cooler and more humid and climb up on the flag leaves and heads.

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Diane Brown-Rytlewski...Powdery mildew is beginning to show up on wheat in Michigan. Wheat is currently at Feekes 5 around Isabella County, and at Feekes 6-7 (first to second node) for most other parts of the state. It is not uncommon to see powdery mildew low in the canopy, early in the season. Current temperatures are in the favorable range (around 59-72°F) for this disease. Often, mildew stays low in the canopy and does not cause significant loss to yield.

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Diane Brown-Rytlewski, Willie Kirk and Martin Nagelkirk...Fusarium head blight (FHB), commonly called head scab, is caused by several species of fungi in the genus Fusarium. It causes premature bleaching of spikelets and infected spikelets may be sterile. Grain from infected heads may be chalky white to pink, shriveled and light in weight. FHB is capable of causing a loss of grain yield, but the most significant financial losses result from the mycotoxin deoxynivalenol (DON or vomitoxin), which the fungus produces within infected kernels.

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Diane Brown-Rytlewski, Willie Kirk and Martin Nagelkirk...The most important leaf diseases of wheat in Michigan include powdery mildew, Stagonospora leaf and glume blotch, Septoria leaf blotch, and leaf rust. Depending on conditions, a serious level of any one of these fungal diseases can cause a significant yield loss. Part 1 of this article on wheat foliar diseases covers powdery mildew, Septoria leaf blotch, and Stagonospora leaf and glume blotch.

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Diane Brown-Rytlewski, Beth Bishop and Tracy Aichele...Growers of sweet corn and seed corn are well acquainted with Stewart’s disease (Stewart’s wilt), a bacterial disease transmitted to corn in spring by corn flea beetles carrying the disease feeding on emerging corn seedlings. Corn flea beetles survive over winter in grassy areas, in soil and plant debris, and become active in the spring once temperatures warm to around 65-70ºF

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Willie Kirk, Diane Brown-Rytlewski, Jan Byrne, Beth Bishop and Chris DiFonzo...Stewart’s disease of corn has been reported in several field corn fields in Saginaw and Allegan counties so far this summer. The disease has also been confirmed in Clinton and Gratiot. So far we do not how extensive this disease is in Michigan.

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Martin Nagelkirk and Diane Brown-Rytlewski...A Section 18 special exemption allows the use of Folicur® fungicide again this year to combat fusarium head blight (FHB) of wheat. One application of Folicur at the rate of 4 ounces per acre may be applied up through early flowering (Feekes 10.51). Folicur may be applied with ground equipment or aircraft. Applications are not allowed within 30 days of harvest.

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