Recent insect problems seem to trace back to good overwintering conditions in combination with slow emergence. Problems include the following.

Alfalfa weevil in alfalfa
Weevil defoliation remains a big issue, especially in central Michigan. Wet weather prevented foliar insecticide applications in many cases, thus weevils were able to thrive in these fields. For the most part, cutting is the management strategy of choice at this point, then be sure to watch regrowth for weevil numbers and damage. Extension educators in central Michigan report that larvae are still quite small, and these certainly can survive cutting and reinfest new growth. Threshold after cutting: 6 to 8 larvae per square foot of stubble or 25% of new tips damaged.

Bean leaf beetle in soybean
There have been several reports of this pest in Central Michigan and in Ontario. Bean leaf beetles overwinter as adults. The beetles feed in alfalfa early in the season, then move to early-planted (first emerging) soybean fields after first-cutting. It is the adults that cause damage by defoliating young plants, leaving small round holes between the leaf veins. Young soybeans can tolerate considerable amount of injury (25 to 30% defoliation) without loss of yield. Although feeding injury may be common, I have not heard of a field actually infested to this extent.

Cereal leaf beetle in wheat
This is another pest that overwinters as an adult. Adults lay eggs early in the spring, and larvae feed in May into early June. The adults are very distinctive, metallic beetles with a blue-black head and body and red legs and thorax. The larvae are equally distinctive – they are yellowish, hump-backed blobs (the legs may not be very obvious) that resemble slugs. They are often covered with darkish fecal material, a ploy to ward off predators (What, after all, wants to feed on a waste-covered blob?). Larvae feed on the leaf surface, giving plants and fields a “frosted” appearance. Damage from cereal leaf beetle larvae has been reported on wheat in central Michigan. Threshold: 3 or more larvae per plant on small plants, 1 or more per flag leaf on larger plants.

Flea beetle
Flea beetle feeding was reported on field corn in central Michigan. Mild winters favor survival of flea beetles, which overwinter as adults. Adult beetles feed (scrape) on the upper leaf surface, leaving white streaks and scratches. This is not likely to cause problems in field corn, but flea beetle feeding can transmit the bacteria that cause the disease Stewart’s Wilt to sweet and seed corn.

Potato leafhopper
Potato leafhopper was reported in southern Michigan this week. Leafhopper can be easily managed with insecticides if fields are scouted and treated in a timely fashion. In re-growth, the threshold is 0.2 PLH per sweep (20 PLH per 100 sweeps). In taller alfalfa, the thresholds increase to 0.5 PLH per sweep in 3-8 inch fields, and 1 per sweep in 8-12 inch fields.

Other potential problems
Soybean aphid. Winged aphids were found on May 25 on buckthorn near MSU, but as of this date (June 1), no aphids have been found on soybean.

Millipedes. In the past under cool, wet conditions we have reports of millipede damage, (for example along rivers in Saginaw County). Extension educators in Ontario reported the same injury. This year, I haven’t seen this problem, but the Purdue Pest & Crop Newsletter (May 26) reports this odd problem in Indiana. Millipedes are normally beneficial, feeding on decaying plant material. But under unusual conditions they can damage seeds and emerging plants. This is the same situation we’ve seen with springtails in sugar beet and other crops over the last few years. Millipedes are distinguished from other long, brown insects in the soil by having four legs on every body segment.

Slugs. Ron Hammond at Ohio State University notes that juvenile slugs are present in northern Ohio (see May 25 C.O.R.N. Newsletter). Slugs feed on cotyledons, stems and leaves of emerging plants. Cool, wet conditions favor slug populations. No- and reduced-till fields with residue are at greater risk for slug feeding, especially if plants are emerging and growing slowly as we’ve seen in the last few weeks.

Newsletters in other states. Purdue’s Chat-n-Chew Café web site is a one-stop-shop for the crop newsletters in the region, including the Field Crop CAT Alert: http://www.agry.purdue.edu/ext/corn/cafe/

Field sampling supplies. Great Lakes IPM, a homegrown Michigan company in Vestaburg, has sweep nets, hand lenses, trap supplies, and other items you need to sample for insects in field crops. Visit http://www.greatlakesipm.com/ or call 1-800-235-0285.

Want to sharpen your diagnostic skills and stay on top of the latest information in production agriculture? If so, we have the perfect opportunity for you. We would like to invite you to attend the fourth annual MSU Crop Diagnostic School. This event is scheduled for July 21 at the MSU Plant Pathology Research Center on the south side of the MSU campus. This event is open to all who are actively involved in production agriculture (growers, agri-business reps, Extension educators, and agency personnel).

Participants will have the opportunity to hone their field decision-making and problem-solving skills as they interact with MSU Extension specialists in small groups while participating in hands-on field activities.

• Nutrient deficiencies and nitrogen management
• Corn Root Health; Soybean Pest Issues
• Cover Crops
• Herbicide Carryover Issues in Field Crops.

Approval is pending for RUP credits and 6.0 continuing education units for certified crop advisors (CCA).

The $125 registration fee is due July 12. Participation is limited to the first 150 paid registrations. For more information contact any MSU Extension office or call 517-355-0271, ext. 1112 or e-mail misiak@msu.edu. A brochure with the registration form is enclosed in this issue and can be found at: http://www.ipm.msu.edu/cat06field/pdf/diagnosticschool06.pdf

Early season weed competition may be one of the biggest contributors to unseen yield losses in corn and soybean. Appropriately timing postemergence herbicide applications is critical to preserving crop yields. Several studies have shown that delaying postemergence weed control strategies can substantially reduce crop yield. This has become more of a concern with the large number of Roundup Ready corn and soybean acres that rely on postemergence applications of glyphosate for weed control. We are not saying that postemergence herbicide application timings are not important in non-Roundup Ready corn and soybean; but herbicides generally used in these crops are most effective on small weeds. Therefore, growers growing non-Roundup Ready crops are probably already making postemergence herbicide applications early. If they are not, it is important to also follow the below outlined guidelines for postemergence herbicide applications.

In Roundup Ready corn and soybeans, there is the temptation to delay postemergence glyphosate applications until all of the weeds have emerged. Delaying these applications can rob corn and soybean of their maximum yield potential. As mentioned before, research throughout the Midwest and Canada has shown the importance of early season weed control. For example, research conducted in Ontario has shown that delaying herbicide applications more than four weeks after soybean emergence can reduce soybean yield ~0.75 bushel/acre/day. In corn herbicide applications delayed more than three weeks after corn emergence reduced corn yield ~0.5 bushel/acre/day.

Over a four year period, MSU conducted research to study the effect of glyphosate application timing and row spacing on corn and soybean yield loss from weed competition. This data is summarized in the fact sheet Weed Competition in Roundup Ready Soybeans and Corn. This research showed that in at least one of the years that this research was conducted, if weeds were allowed to reach 6-inches in height before control, yield was reduced narrow row soybean and 30-inch row corn. Depending on when this yield loss occurred, soybean yield was reduced from 2.5 to 5.5 bushel/acre/day and corn yield was reduced between 1.3 and 5.3 bushel/acre/day. This starts to add up when you consider the economics. Considering these crop loss estimates, delaying herbicide applications 3 days would cost you anywhere from $9.13 to $37.21/acre in corn ($2.34 new crop corn) and $41.25 to $90.75/acre in soybean ($5.50 new crop soybean). Waiting to make postemergence herbicide applications can cost you money. Therefore, it is important to follow the recommendations below to avoid yield losses due to early season weed competition.

Recommendations

Weeds should be controlled in:

• 15-inch row corn before weeds exceed 2-inches.
• 30-inch row corn before weeds exceed 4-inches.
• 7.5 and 15-inch row soybean before weeds exceed 4-inches.
• 30-inch row soybean before weeds exceed 6-inches.

According to the Penn State model, risk is high to moderate along the western edge of the state. Hot, humid weather over the last few days has accelerated flowering. In addition to estimating risk based on the seven days of weather prior to flowering, the Penn State model provides risk estimates based on weather forecasts. Clicking on the 24 or 48 icon in the upper left corner of the screen will bring up estimates of infection risk 24 hours out and 48 hours out. Both of these show increasing areas of the state moving into the moderate risk category.

In many parts of the state, wheat is either flowering now, or about to flower within the next couple of days. In the central area (around Montcalm County), the earliest wheat is beginning to flower, while the latest wheat is just emerging from the boot. There is still about another five to seven days to go before wheat flowers in the northern part of the Thumb area (Huron County). This area, as well as many other parts of the state has experienced showers and high humidity, along with favorable temperatures for scab infection. Fog has kept wheat from drying off until late morning. If similar weather continues over the next few days, growers in areas experiencing these conditions should consider an application of fungicide to protect their wheat. Growers also need to take into account the variety’s level of susceptibility to scab, and the yield potential of the field to determine whether an application of fungicide is economical. Michigan has a Section 18 label for application of Folicur through Feeke’s growth stage 10.51 (beginning of flowering). By the time half the florets on a head have flowered (on 50% or more of the heads in the field), wheat has reached Feeke’s growth stage 10.52 and is beyond the period of Section 18 labeling.

As we mentioned in earlier Field Crop CAT Alerts, we are evaluating both the Penn State model and the DONcast model (Ontario) in research plots this year. The Penn State model predicts the risk of an epidemic with severity (average percentage of wheat head area that is blighted) of 10% or greater. In our research plots, the Penn State model indicated low risk in the campus and Ingham County locations, moderate risk in the Sanilac County location and moderate risk at the Bean and Beet Farm plot. The DONcast model looks at the chance of 1ppm or more of DON (deoxynivalenol, vomitoxin) at harvest based on weather at heading. The DONcast model for the same locations predicted greater than 1ppm DON at all locations. We are collecting data from several growers’ field as well. We will keep you posted on what we find.

Leaf rust (Puccinia recondita f.s. tritici) was found in several wheat fields near Holland, Michigan this week. (see photos) When rust severity is high, as it was in these locations, one of the most noticeable symptoms for anyone walking the field is that their hands or clothing become covered with a powdery orange dust from the spores. There can be substantial differences among wheat varieties in their levels of resistance to leaf rust. Fields in the vicinity planted with other varieties did not show any symptoms of the disease. Leaf rust has not been found to any great extent in Michigan for several years, and so far, has not been reported from any other locations.

It is possible for leaf rust to overwinter during a mild winter such as we experienced this past year. The leaf rust fungus needs living leaf tissue to survive. It does not survive in the soil or in crop residue. It can move to volunteer wheat in the summer after harvest, and travel to newly planted wheat in the fall. In locations where it has overwintered, it is most severe on the bottom leaves. Usually, rust travels to Michigan on storms from the Gulf Coast area. When it blows in from distant locations, it will be most severe on upper leaves. Rust typically occurs uniformly across a field. During favorable weather conditions, rust seems to explode, as spores are produced and create additional infections in the field. Infection can take place in as little as four hours under favorable conditions. Rust development during spring is favored by daytime temperatures between 60° and 75° F, and light rain or dew. Heavy rain tends to wash spores off the leaves. Dispersal of spores to upper leaves and between fields is favored by dry, windy conditions. Rust infections can be spread by human activity and equipment that has been in infected fields. Practice good sanitation by power washing equipment that has come into contact with the spores before using it in a clean field. Similarly, avoid wearing clothing contaminated with spores into clean fields.

Regional reports
1 -- Southeast
Ned Birkey

Weather
It has been hot and humid for almost the entire past week. Memorial Day tied the record at 92 degrees in Detroit and 93 degrees in Toledo. Toledo says we had the sixth wettest May on record with about 6.5 inches of rain. We have had wildly scattered and locally heavy showers and even some hail this past week. One part of Monroe County may get as much as one inch of rain while another part of the county does not get any rain.

Commodity reports
Alfalfa still has not been cut for most fields and has alfalfa weevil. Should you spray or not with harvest imminent? I have not seen any potato leafhoppers, nor had any farmers report any, though I would be very surprised if they did not come into Monroe County this past weekend.

Corn has tripled in size this past week, is nice and green, and is generally at the five-leaf stage. A few fields could approach the “idealistic” knee high by the fourth of June. Some corn is still being replanted. Sidedressing is going on full speed ahead. Soils are finally dry enough for soil nitrate testing. I think post emerge weed control will be more important this year depending upon the individual situation. Weeds seem to have had a head start all year.

Soybean planting resumed this week though some fields still have water standing and cannot be completely planted. We finally planted the soybean cyst nematode plot on May 30. Even in the plot field the top couple of inches of soil was dry, but the beneath that, the soil was very wet. There are no aphids and minimal weed problems, but rust is forecast to get to Ohio this summer, so farmers in southeast Michigan will need to have their sprayers ready. Adjusting the spray boom height and sufficient spray pressure will be two key factors.

Wheat is in the middle to end of flowering with all the diseases present. High temperatures and humidity, plus some rain, have been conducive for diseases on the flag leaf. Although the yield potential is very good, the weather in June will be very important. I think wheat harvest will begin ahead of normal – around July 4.

2 -- Southwest
Bruce MacKellar

Weather
Hot weather returned to the region over the Memorial Day holiday weekend with high temperatures in the mid-90s and heat indexes around 100. The improvement in growing conditions kicked plant growth into high gear. Wind conditions were somewhat higher than we would like to see for perfect spraying conditions, but morning and evening opportunities were available on nearly every day. Thunderstorms returned to the area on the evening of Memorial Day with Berrien County receiving severe weather after 5:00 PM. Severe weather was prevalent in the area on Tuesday with several areas receiving severe thunderstorms and flooding rainfall. High totals in isolated areas were in the 4 to 5 inch range, especially in western Calhoun County in the Battle Creek area with widespread areas receiving 1.25 to 1.5 inches or more.

Commodity reports
The color of commercial corn in southwest Michigan made an amazing turn around with the sunny and hot conditions. The earliest planted corn has 5 to 6 leaf collars. Some fields have had rescue post emergence sprays to clean up weed escapes. Corn stands generally look good, but there are some fields that have had replant areas. Cutworms, sandhill cranes and flea beetle damage can be found in many fields, but are not causing widespread problems. We are approaching side dress nitrogen applications in many of the earlier planted fields. If you are in an area that received heavy rainfall and applied nitrogen up front, you may want to consider a PSNT test to see how much of the N applied may remain in the soil.

In seed corn, wet conditions for the extended period in May forced some fields to be replanted to help keep pollination at the right timing, but the acreage that had to be replanted was limited. Corn flea beetles can be found in some corn fields in the area. There are some fields with some grass weed escapes.

Early planted soybeans are developing the first tri-foliate, many later planted fields are now emerging. Bean leaf beetle feeding signs can be found, but not at threshold at this point. Many of the earlier planted fields have been emerged now for four weeks or so, and the weeds have been growing about as fast as the crop. Producers should keep an eye on the size of the weeds in their soybeans and treat before competition is a problem or the weeds get to the size where they are going to be hard to control. We will be starting to see glyphosate going on RR soybeans this week. Producers should also begin to start seeing cysts on early planted soybean fields that have extremely high levels of SCN in their fields. Look for uneven patterns of development in fields and try to make a note of areas affected for sampling later in the season. The St. Joseph County SCN Resistant – RR soybean trial featuring 17 varieties was planted early this week south of Mendon.

Alfalfa harvest was in high gear over the weekend. High temperatures made this operation brutal for those handling the crop by hand. Be sure to watch for alfalfa weevils in the early re-growth. Also, the warm southwest winds deposited the first potato leafhoppers across our areas. Watch you alfalfa re-growth carefully for this pest, because the early re-growth period is the most vulnerable to “hopper burn” injury. Cass County ANR Educator-CED Dan Rajzer reports that first cutting yields in his area have been off 20 to 30%, which may mean a localized shortage of hay later in the year.

A good portion of the wheat crop had flowered under fairly dry conditions. I think that the recent rainfall and warmer temperatures did the crop some good with heads filling out nicely on some of the fields that were looking tough earlier in the field.

The St. Joseph County IPM Breakfast Meetings are being held on June 7, June 21 and July 5 this year at the St. Joseph County MSU Extension office, 7:00 AM – 9:00 AM. Cost is $7, which includes a catered breakfast.

3 -- West Central
Fred Springborn

Weather
Summer weather dominated this week as air temperatures reached the 90s. Scattered rain showers on Tuesday deposited 0.75 inches in many places. Low soil temperatures have been in the upper 50 and 60s. We have quite adequate moisture with little direct damage from excessive water. Crop growth and development has been rapid.

Much of the wheat crop is heading. Flowering is complete in the most advanced fields, and most is flowering now. Head scab is the concern at this time. Fields flowering Monday and Tuesday were at significant risk of infection in much of the area. Powdery mildew is present at low levels low in the canopy. A few varieties have high levels of powdery mildew infection. Oats are growing rapidly with many fields jointing having 2 nodes above ground.

Alfalfa is 26 to 30 inches in height with alfalfa weevil feeding present in nearly all fields. Alfalfa weevil injury is variable ranging from well below threshold to well over threshold. GDD41 totals as of May 23, Entrican 789, Ionia 889, Fremont 799.

4 -- Central
Paul Gross

Weather
The region has areas that were hit hard with showers over the past week. The amounts range from a trace to four inches. For the most part, there was little fieldwork done. Some farmers were able to get some acres planted Sunday and Monday. Generally, fields are saturated, and it will take several days before field operations can continue. The very warm temperatures over the past week were very beneficial in getting color back into the corn crop and advancing soybeans, wheat, and alfalfa.

Soybeans have emerged and most stands are good. With questionable stands, growers are advised to make accurate stand counts to determine if there is adequate stand for optimum yield. There has been some replanting of early planted fields. There are reports of bean leaf beetles.

The wheat crop is in various stages. Some fields are flowering and others will be flowering in the next few days. Weather conditions are favorable for head scab and fungicide applications may benefit fields that have not yet flowered. We are seeing powdery mildew and septoria but in low levels low in the plant. There are reports of cereal leaf beetle in some areas. Scout fields for insect and disease.

Alfalfa is ready to cut. There are severe infestations of alfalfa weevil in many fields. Farmers are strongly advised to scout all fields and determine the level of infestation and cut as soon as the weather allows. Scout re-growth to determine if an insecticide application needs to be made.

The oat crop is progressing and some herbicide applications are being made. Some fields are very yellow, but should green up as conditions dry out.

5 -- Thumb
Mark Seamon

Weather
Three days of very warm temperatures over the Memorial Day weekend have helped to increase soil temperatures and get some slow growing crops moving again. But with these high temperatures, we also received spotty rainfall in amounts from a trace to more than four inches.

Some early planted sugar beet fields not pounded with rainfall in May look terrific. Other fields have stands of variable size due to delayed germination in some of the drier areas of the field. Weed size continues to be a concern where rain has prevented timely herbicide applications. Fungicide applications for Rhizoctonia control are being made where possible between herbicide applications.

The wheat crop continues to develop quickly with most fields well into flowering. Head scab control options for these fields are not available. Rainfall, humidity and free moisture on the heads are leading to favorable conditions for Fusarium (head scab) development and infection. Many white wheat growers applied Folicur over the weekend for protection. Septoria and powdery mildew are prevalent on the lower plant in many fields but upper leaves are pretty clean.

The corn crop has made good use of the warmer temperatures and drying of many soils to develop and grow quickly. The appearance of plant health improved dramatically in the past week. Post emerge weed control are becoming limited due to size of the corn crop. Utilization of presidedress nitrate sampling is strong with concerns about nitrogen cost and the loss of nitrogen form excessive rainfall.

Many growers have had a chance to finish up planting soybeans after the 10 days of being rained out of the field. Evaluations of stands where rainfall was heaviest and in lighter soil textures are being made. Some replants will occur as field conditions allow.

Field conditions have not allowed much progress with dry bean planting this past week. Most growers are not concerned about the planting timing since experience has shown very good crops planted in the first half of June.

The upper air ridging feature that brought hot and humid weather to Michigan during the Memorial Day weekend has moved off to the east of the region. This signals the beginning of a new upper air weather pattern that will lead to cooler, more seasonable temperatures during most of the week ahead. An upper air troughing feature is expected to form over the region by late Friday, which will bring relatively cold air aloft into the region and the chance for widely scattered showers or thundershowers Friday and Saturday, especially during the late afternoon and early evening hours. Sunday and Monday (June 4-5) are expected to remain fair and mostly dry. Temperatures during the next several days will slowly fall back to near normal levels. Highs Thursday will fall back to a range from the upper 60s far north to the upper 70s south and remain there Friday through Sunday. Low temperatures will fall to the mid-40s north to mid-50s south each day through Sunday. The next chance for significant rainfall will come Tuesday or Wednesday of next week as an area of low pressure and frontal system approaches from the west.

Medium‑range forecast guidance for at least the next one to two weeks is suggesting the formation of an upper air ridging pattern across the Great Plains region with more of a northwesterly component across the Great Lakes.

The NOAA 6-10 day outlook (covering June 6-10) calls for below normal temperatures statewide with precipitation totals expected to range from near normal across Upper Michigan to below normal over all of the Lower Peninsula. The 8-14 day outlook (covering June 8-14) calls for mean temperatures to moderate, ranging from below normal in extreme eastern sections of the state to near normal elsewhere. Precipitation totals during this time frame are forecast to remain at below normal levels statewide.