Vol. 18, No. 13, July 24, 2003

In this Issue
Rootworm damage severe in some locations
MSU Diagnostic Services fees and sampling methods
Use of mosquito trapping devices to control mosquitoes on the homefront
Is your favorite tree an ash tree?
Regional reports
Weather news

Rootworm damage severe in some locations

Christina DiFonzo, Entomology

In northern Ohio and Indiana, rootworm damage has been reported since early July. Over the last several weeks, reports of rootworm damage are now coming in from southern Michigan. In continuous (non-rotated) corn, insecticides used at planting in April may not have lasted long enough to protect roots from feeding in May and June. In other cases, heavy rain may have moved insecticide from the root zone, or the environmental conditions may have led to a faster break down of insecticide. The problems have been exacerbated by the storms that caught the southern edge of Michigan, bringing high winds that cause lodging.

In first-year (rotated) corn, I visited fields with severe root damage in the southern part of Berrien County, just north of the Indiana border. Portions of these fields are severely goose-necked and on the ground. The majority of roots we examined from the field have at least one full node of roots pruned; many plants have two or three nodes - essentially no roots at all. Again, recent storms have contributed to the damage.

Thus far, reports of economic damage from the so-called variant rootworm in rotated corn have only been made and confirmed from a limited area of Berrien County. However, we know from sticky trapping in soybean (and digging roots the following year) that we find evidence of the variant as far north as St. Johns. In fact, this summer we see root feeding in every field we have sampled on the MSU campus. This feeding consists of light root scarring, and is not at a level yet that would have needed an insecticide application. However, it does appear that the problem with rootworms in rotated corn is moving further north into Michigan.

The bottom line is that now is the time to look at fields. In central and northern Michigan, check fields to determine insecticide performance. In southern Michigan, check both continuous and rotated corn for lodging and root damage. The producer who owns one of the rotated fields in Berrien County commented, "The field looked good from the road, until I walked into it."

MSU Diagnostic Services fees and sampling methods

MSU Diagnostic Services assists a wide variety of people experiencing problems with plants and pests. There are many things that cause plant problems. The laboratory specializes in problems caused by arthropods (insects, mites, ticks, ect.), pathogens (fungi, bacteria, viruses), nematodes, weeds and herbicides.

You can submit samples by either mailing them or dropping off samples at the facility in person. For a nominal fee, the sample will be analyzed. Following are some suggestions on how to submit a sample and contact information. For more information on Diagnostic Services and submitting samples, visit the website at: http://www.cips.msu.edu/diagnostics/

Diagnostic Services general contact information
101 Center for Integrated Plant Systems (CIPS)

East Lansing, MI 48824

Ph. 517-355-4536

Fax 517-353-1781

Diagnostic Services staff
Howard Russell, insect / arthropod diagnostician

116 CIPS, 517-353-9386, bugman@msu.edu

Fred Warner, nematode diagnostician

117 CIPS, 517-432-1333, fwnemalb@msu.edu

Jan Byrne, plant pathology diagnostician

114 CIPS, 517-355-3504, byrnejm@msu.edu

Steve Gower, weed science diagnostician

113 CIPS, 517-432-9693, sgower@msu.edu

Angie Miller, nematode diagnostician

115 CIPS, 517-355-3504, millerA3@msu.edu

Jackie Smith, diagnostic technician

109D CIPS, 517-432-0988, smithjac@msu.edu

Soil & Plant Nutrient Laboratory Staff
Jon Dahl, laboratory manager

A81 Plant & Soil Sciences Building

Ph. 517-355-0211

Administration
George Bird, coordinator

517-353-3890, bird@msue.msu.edu.

Darryl Warncke, supervisor, Soil & Plant Nutrient Lab

517-355-0210, warncke@msu.edu

Tips for sample submission
Accurate diagnosis depends on the rapid receipt of fresh and representative samples along with pertinent information relating to the problem and client objectives. Diagnostic Services submittal forms are available at Diagnostic Services, your local Extension office or can be downloaded from the website at: http://www.cips.msu.edu/diagnostics/services/form.html

Plant samples
Herbaceous plants: Send whole plants, including roots and soil. Roots and soil should be in a plastic bag to prevent soil from touching foliage. For more information on how to submit whole plants, see Jan's graphic guide on the website at: http://www.cips.msu.edu/diagnostics/profiles/tipsforsamplesubmission.htm

Tree decline / wilt: Send 6 to 12 branch sections 1/2 inch to 1 inch diameter and 8 inches long. Branches should be taken from live areas of tree with symptoms, not from completely dead branches. Seal branches in plastic to retain moisture.          

Seedlings: Leave plants in plug sheets or trays if possible, send a minimum of 12 seedlings.

Leaf spot and fruit rot: Send several affected samples representing the early and moderate stages of the symptom progression.

Homeowner turfgrass: Include a 4"x 4"x3" square of turf from the margin of the diseased area so that healthy and diseased turf is included. An intact layer of soil should be included. Wrap sample in newspaper and pack in a box for shipment. Include detailed description of cultural practices. Professional turf samples should be sent to Dr. Joe Vargas' lab, 517-353-9082.

Insects/arthropod samples
 Precise identification of insects or other arthropods requires specimens to be undamaged upon arrival to the laboratory. It is very important to kill and ship the specimens in a manner that will not damage delicate structures that facilitate their identification. Killing and shipping specimens in a small, leak-proof vial filled with rubbing alcohol is usually best. Peeling a squashed bug from a flyswatter or from the bottom of your shoe and putting it in an envelope for mailing is not recommended. Dried and unprotected insects are easily crumbled during mail processing. Attaching the specimen to scotch tape is not recommended.

Moths / butterflies: Wing coloration is the most important characteristic in identifying these insects and precautions need to be taken to reduce the loss of the tiny scales that give moths and butterflies their distinctive wing patterns. Place them in the freezer for half an hour to kill them and then gently pack them in a small box or vial with tissue paper.

Ants: Specimens should only include worker ants (i.e. those without wings.) It is very difficult and in many cases, impossible to identify winged ants. Please submit these in alcohol.

Other adult and hard-bodied specimens: Submit in alcohol.

Larvae (caterpillar, grub, maggot, etc.): Whenever possible, soft-bodied larvae should be lightly boiled for a few minutes before placing them in alcohol. Boiling helps prevent the specimens from shriveling and becoming discolored, however, this only works if the larvae are alive when dropped into boiling water.

Nematode samples
Refer to MSU Extension Bulletin E-2199, Detecting and Avoiding Nematode Problems. Always store nematode samples in plastic bags or other containers that retain moisture. Submit a pint to a quart of soil.

Problem diagnosis: Collect soil and roots (or foliage) from the margins of diseased areas. Submit samples of diseased plants and apparently healthy ones.

Problem avoidance: Collect soil and roots (if available) by walking a zig-zag or w-shaped pattern. The more sub-samples (soil, cores, probes, etc.) collected, the "better" the sample.

Soil and plant nutrient samples
Mail or deliver to: A-81 Plant & Soil Science Building (PSSB) or drop off at Diagnostic Services, 101 Center for Integrated Plant Systems.

Use of mosquito trapping devices to control mosquitoes on the homefront

Mike Kaufman
Entomology

Editor's note: Many residents in Michigan are interested in factual information about West Nile virus and mosquito control. Dr. Mike Kaufman is one of the scientists at MSU working in this area. We are sharing this information of general interest with our CAT Alert readers.

With the onset of mosquito season and the ongoing concern about West Nile virus, Michigan residents have been deluged with a variety of mosquito "control" products. The manufacturers invariably claim that these products offer effective control for large areas and allow the safe, comfortable enjoyment of one's backyard, garden, or deck. Prominent among the advertisements this year are those for propane-driven adult mosquito traps that essentially attempt to mimic the cues given off by large mammals. These devices convert propane from typical gas grill-sized tanks into heat and carbon dioxide - two primary mosquito attractants. Attracted mosquitoes are then sucked into a trap and die. Some of the devices supplement the CO₂ with octenol, another general attractant, and others use CO₂ released from gas cylinders. The devices are relatively expensive, $200 to more than $1000, and represent a non-trivial investment for the homeowner along with the need to replenish propane, octenol, and CO₂ cylinders.

Are these devices useful? Studies have shown that they do trap mosquitoes. Most evaluations have been conducted in large, screened-in rooms where a known number of mosquitoes are released and the percent trapped are evaluated. Some of the devices trapped over 70 percent of the mosquitoes in 24 hours. Field trials have also shown that the devices also capture many mosquitoes of various species. However, there is little evidence that they effectively reduce mosquito populations in the half acre to one acre area coverage claimed. As with most insect traps, it is possible that more mosquitoes would be drawn into one's backyard from surrounding areas, effectively nullifying the effect and purpose of the traps.

The effectiveness of these devices would depend upon placement (upwind) of the desired protection area, use of the device for several days prior to persons' use of the area, etc. It is also noteworthy that the effectiveness of the devices varies for different species of mosquito. The Culex species involved in West Nile virus transmission are not necessarily trapped with high efficiencies in these units.

We cannot yet recommend these devices for mosquito control. Although they show promise, it is unlikely they will achieve the blanket control often claimed. On the plus side, they are certainly better options than devices based upon electric fields, sound generators (one claims to mimic the sound of dragonflies to scare mosquitoes away), or the ubiquitous "bug-zappers." The former (electric or acoustic) are simply ineffective and the latter is almost completely useless in reducing mosquito populations and likely kills proportionately more beneficial insects. Another product that claims to lure mosquitoes into traps by simulating the sound and patterns of a mammal's heartbeat, is not based on our current understanding of how mosquitoes locate hosts. (i.e., There is no evidence that mosquitoes use heartbeat sounds to find an appropriate blood meal.)

Unfortunately, there is no single method that will allow the mosquito-free use of the outdoor areas on one's property. If the homeowner eliminates the standing water breeding sites of mosquitoes, some relief would be obtained. There are also several larvicide options that are extremely safe for humans and pets, and are "environmentally friendly" for instances where removal of breeding sites is illegal or impractical. These include formulations of Bacillus thuringiensis and Bacillus sphaericus, and the insect growth regulating hormone analog, methoprene. However, many mosquitoes can originate from remote breeding sites and where mosquito-borne disease is present, one may also have to deal with small but infected adult populations. Control of adults is best achieved through fog and spray application of insecticides that have some residual effects (e.g., malathion and synthetic pyrethroids). Application can be targeted to adult resting areas in vegetation surrounding lawns, tree foliage, etc. Adulticiding should be considered a "last resort" option because of the chances for over-application and because the insecticides do not specifically target mosquitoes.

Even with the exercise of the above control measures, one cannot eliminate the risk of diseases such as West Nile virus entirely. We also recommend that when engaging in outdoors activities when mosquitoes are active that individuals use proven repellents. The most effective of these are formulations that contain DEET. Other repellents (e.g., botanical oil-based) may be effective for shorter periods of time, so if they are your choice, be prepared to re-apply frequently. The use of citronella candles may offer some very limited and temporary protection in small areas, but is considered inadequate for disease risk reduction. (In one study the use of regular candles had nearly the same weak repellency effect as a citronella candle). The use of marigolds as a mosquito barrier is an even less effective option than citronella based products.

Is your favorite tree an ash tree?

A new MSU Extension bulletin, Distinguishing Ash from other Common Trees has been created to serve as a tool to help homeowners and property managers in areas affected by the emerald ash borer learn to identify whether or not they have ash trees on their properties. The bulletin, number E-2892 can be obtained from local county Extension offices, from the Michigan State University Bulletin Office for $.50 per copy, or on the Internet as a pdf at: http://www.ipm.msu.edu/pdf/E2892Ash.pdf

The new bulletin features black and white line drawings and photos of ash and trees commonly confused with ash, such as boxelder, mountainash, elm, black walnut and hickory. It uses a simple identification key with definitions of characteristics such as alternate and opposite branching and simple and compound leaves to provide the essential characteristics needed to identify the tree. The publication has been created by MSU IPM Program's Diane Brown-Rytlewski and Rebecca Thompson.

Regional reports

1 - Southeast

Ned Birkey

Weather
Weather has been great for tourists and parades because of moderate temperatures! The rains have been very timely this month for corn and soybeans. Fortunately we have missed most of the severe storms, winds and excessive rainfall. A low of 50 degrees this past Saturday (July 19) has the rumors going about an early frost. The moderate air temperatures have still been high enough to keep growing degree days near normal.

Commodity reports
Alfalfa is mostly finished with the second cutting. Potato leafhoppers were severe in that stand, so the harvest was very timely to prevent further damage.

Corn is tasseling in many fields. Timely rains, but without the storms have kept plants upright and very green. European corn borer traps show very little activity as we are between generations. Yield potential looks very good, but it is a long time until the crop is safely in the bin.

Soybeans are very short and are now flowering. I doubt we get record yields, but plants will still continue to grow and produce pods. Soybean cyst nematodes, spider mites and leafhoppers are in fields, though timely rains have minimized their impact. I have not seen any soybean aphids. With the rains, I think we will have some white mold and late season weed control problems.

Wheat harvest was mostly finished before the recent rains and will finish yet this week. Yields are excellent with 90 to 116 bushels confirmed. With better prices, farmers are generally pleased with this crop this year. No reported problems with vomitoxin, though central Ohio reported high levels.

Miscellaneous
This has been almost as good of summer weather as we had in 1998 when we had record yields. The rumors have started of an early fall however. In 1998, we did not have a killing frost till November 3. Unfortunately, corn and soybean prices are very low so farmers will need to work on their pricing alternatives skills. It appears as if farmers will be getting a counter cyclical payment for corn and soybeans as well as the direct payment.

2 - Southwest

Mike Staton

Weather
Cooler than normal temperatures prevailed over the past week. Thunderstorms continued to move though the area delivering 0.5 to 5.0 inches of rain.

Commodity reports
Early planted corn is tasseling. Tassel emergence is uneven in most fields. Corn rootworm larvae have severely pruned roots in some first year cornfields in Berrien County. Larvae have stopped feeding, and we found our first adult beetles on July 17. Check your cornfields now for signs of corn rootworm feeding as these will be the areas most likely to lodge and create problems at harvest. Also, check for rootworm beetles feeding on the ear silks during pollination.

Early-planted soybeans are beginning to set pods. Soybean aphids are easily found. Giant ragweed and common lambsquarters are escaping glyphosate treatments. Manganese deficiency symptoms are still visible on dark-colored soils. Monitor soybean fields adjacent to cornfields for adult western corn rootworms

Heavy rains have delayed wheat harvest. Most of the wheat is still standing well. Isolated fields are severely lodged. Yields are excellent and no vomitoxin problems have been reported.

Second cutting of alfalfa is nearly completed. Potato leafhoppers are causing severe damage in untreated fields. Monitor fields closely and treat as needed. Pay close attention to the pre-harvest interval listed on the product label.

3 - West Central

Fred Springborn

Weather
Looking back over the month of July we have seen a quite a bit of variation in our weather. The month started out hot and quite dry through July 7 with high temperatures in the upper 80's to low 90's and turned relatively cool and moist later with high temperatures in the upper 70's and low 80's. Rainfall in Montcalm County has been quite variable. Much of the county has adequate soil moisture for crop growth. In a storm event on July 13, an area of approximately 20 square miles north of the city of Greenville received 3 to 4 inches of rain and hail that produced significant crop damage

Commodity reports
Second cutting alfalfa harvest is nearly complete, rain delays are an issue. Insect pressure is heavy in many fields with potato leafhopper being the primary pest.

Oat heads are filling, and a few fields have turned. Wheat for the most part is in fair to good condition; some fields have lodged after storms passed through. In Newago County, one field was nearly destroyed by black sooty mold. Harvest has begun on a very limited basis.

Corn growth stages vary from V10 to tassel emergence. This crop continues to improve in condition over all; there is still a great deal of variation within fields. While this may be excellent weather for pollination (cool and moist), this crop is behind normal in maturity. European corn borer numbers caught in pheromone traps have declined to darn near nothing.

Soybean growth stages vary. Many are producing blossoms. Plant height is very short. Dry beans are progressing well overall. Fields need to be monitored closely for potato leafhopper. Many fields are producing blossoms.

4 - Central

Paul Gross

Weather
The region has received adequate rain over the past two weeks. The amounts have varied greatly but for the most part soil moisture is very good as we enter a period of high water use by the crops. There were some areas that report some hail. Cooler than normal temperatures have slowed crop progress but this may be beneficial as the corn begins to pollinate.

Commodity reports
Corn is just beginning to pollinate. Most fields look very good and the yield potential is very good at this time. There have been no serious disease or insect problems at this time. Fields should be scouted for corn borer and corn rootworm damage.

The soybean crop is flowering and some of the early-planted fields have set some pods on the lower nodes. At this time, yield potential looks good, however the crops seem to be rather short. We've had some reports of high numbers of grasshoppers in a few fields. We are seeing the soybean aphid in almost every field but at low numbers. Fields should be scouted for these pests.

Wheat harvest is well under way in the southern part of the region. Yields have been good in most cases. The northern part of the region will begin harvest as soon as conditions improve. The harvest season will be long this year because of some of the very late plantings.

Harvest of second cutting alfalfa is nearly complete. Yield and quality have been very good. Leafhopper populations have been very high. Fields should be scouted for this pest on a regular basis.

Sugar beets are doing very well.

Dry beans are progressing nicely. Some areas have been receiving more rain than is really needed, so we are seeing some root rots in areas of fields. Leafhopper populations are very high.

5 - Thumb

Mark Seamon

Weather
Variable weather of high temperatures, low temperatures, rainfall and sunshine seems to be just what most crops really like. Crop conditions are generally good with isolated trouble areas.

Commodity reports
The potato leafhopper populations continue to feed on alfalfa while cutting of some fields is delayed due to rain. Visual symptoms of leafhopper feeding appear in most fields.

Cercospera leafspot can be found scattered throughout the sugar beet growing areas. It is showing up in high-risk areas first such as early-planted fields, susceptible varieties and traditional geographic areas prone to this disease. Overall this crop looks very good.

Tassel emergence in corn is occurring in many fields. Some of this is spotty through the field due to uneven crop development. Pollination conditions are very good now with moderate temperatures and adequate soil moisture. I hope a bunch of corn can get pollinated before this weather changes again.

Wheat harvest has begun but is delayed by rainfall. About 10 percent of the crop was harvested last weekend, and most growers are ready to go now when conditions allow. Vomitoxin levels have been very low in tested loads of wheat. Yield and test weight are very good in early harvested fields, but we need to get more harvested before knowing if this is wide spread.

Soybeans are flowering now. These first blossoms should have the potential to produce many multiple bean pods with very good growing conditions. Soybean aphids are being found in many fields, especially in Saginaw County. Some fields that have reached the treatment threshold of 250 to 300 aphids per plant have been sprayed. Many fields have populations of 50 to 100 aphids per plant and are being watched carefully.

The potato leafhoppers are also feeding on dry beans. Most growers are actively spraying for these insects but some damage occurred before spraying. This crop is also flowering and developing well except for areas that received heavy rainfall that caused ponding or continued saturation. Some root disease is showing up in these areas that may limit yield.

6 - Northern Lower Peninsula

Dave Glenn

Weather
Great weather the past week has helped move crops along. Some very scattered rain has fallen in some areas but only a few tenths. Most fields are dry and potato growers are starting irrigators back up again. Most rain that has been forecast has missed the area.

Commodity reports
Wheat is trying to dry down but is still a couple weeks away from harvest. Most fields look pretty good yet. The thin, winter-injured stands have filled in nicely, but will still yield less than average. There are a lot of blank heads and parts of heads with little or no seed in them that will fool some into thinking they may have higher yields. I anticipate a 40 to 50 bushel yield average.

Soybeans are flowering. They look very good, with plenty of heat finally and the moisture has been timed just right so far. A rain in the next few days will help a lot. No soybean aphids have been detected so far.

Corn has popped up nicely also. Some early corn is now in tassel. Most corn looks as good as it has in many years, staying plenty green and healthy growth.

Alfalfa is slow in regrowth. Second cutting has begun, but tonnage is down again, as it was in first cutting. Potato leafhoppers are around and some fields have been sprayed. There will be less hay overall with some dairy producers looking for stumpage already.

Dry beans are flowering and looking excellent. Most stands are excellent and have great potential for high yields.

Miscellaneous
Grasshoppers have been a problem in some areas and sprays have been applied in those cases. Oats and barley are looking excellent with heading complete and dry down about to begin. Potatoes are doing very well with the more moderate temperature this year. Rain has been adequate, but we could use more in the next week or so.

Weather news

Jeff Andresen
Agricultural Meteorology
Geography

A large upper air trough more typical of October than July was centered over the Great Lakes and New England regions Thursday morning (July 24). This trough will slowly move eastward during the next 48 hours, only to be replaced by another (weaker) troughing feature by the middle of next week.

In the short term, look for fair, dry weather Thursday and Friday with a slow warming trend. The next chance for significant precipitation will be overnight Friday/Saturday in northern sections of the state and Saturday and Sunday across the south in response to a cool front moving from north to south across the state. Given ample moisture ahead of the front and relatively slow movement, some heavy rainfall totals are possible. Drier conditions are expected by late Sunday continuing into early next week. Temperatures will slowly warm from highs in the 70's on Thursday to the low or mid 80's by Friday. Similarly, lows will warm from the 50's Friday morning to the 60's by Saturday. Overall, temperatures and daily growing degree day totals will continue to remain at below normal levels for much of the upcoming week.

In the medium-range time frame, the NOAA 6-10 day outlook for July 29 through August 2 calls for the return of upper air troughing across eastern North America. Both temperatures and precipitation in Michigan are forecast to remain at below normal levels.

For the 8-14 day time frame (covering July 31 through August 6), the outlook assumes the troughing pattern will persist with a continuation of near to below normal temperatures and precipitation. Given good agreement between the forecast tools and continuity with previous outlooks, forecaster confidence in this outlook is considered higher than usual for the season.