North Dakota State University
NDSU Extension Service

North Dakota Pesticide Quarterly

Volume 15, No. 1 -- January 1997


IPM
Integrated Pest Management (IPM) -- NDSU's Annual Report
Sugar Sprays -- Encourage Beneficials

Insect Management
Furadan Cr-10 for Use on Canola
Pests in Grocery Stores

Disease Management
Application Equipment and Timing of White Mold Fungicides
Dry Bean Rust
Sugarbeet Cercospora Resistance and Tolerance to Fungicides

Weed Management
Special Weed Control and Herbicide Use Issues from Midwest States in 1996
Onion-leaf Corn
Pursuit Carryover in some Midwest States
Sterile "Ergot" Wheat
CRP Breakout
Herbicide Resistance
Application Issues
Special Weeds -- Caused by the Pattern of Herbicide Use or the "System"
Diagnostic Laboratory Discussion

In This Issue
Coordinator's Comments
Pesticide Perceptions
Law
Equipment
Safety
Training



IPM


Integrated Pest Management (IPM) -- NDSU's Annual Report

Each year NDSU submits an annual IPM report to the IPM Program Leader, USDA, Washington, DC.

A few of the examples included in this year's report are:

(Submitted by: Dr. Marcia McMullen, NDSU Extension Plant Pathologist/IPM Coordinator)




Sugar Sprays -- Encourage Beneficials

Can spraying sucrose (table sugar) solutions on plants increase populations of natural enemies? Two recent studies -- one in Honduras on corn and another in Colorado on alfalfa howed increase numbers of predators in these crops with sugar sprays. There are also several commercially available food spray supplements designed to increase predators and parasites. Some of these are primarily sugar; others are based on yeast, and contain more protein.

Use a rate of 14-20 pounds of sugar dissolved in 10-20 gallons of water per acre, or for smaller areas, use 150g (1/3 pound) sugar in a liter of water. Spray half of the plots with the sugar solution, the other half with plain water. In corn, sprays should be applied relatively early (in whorl state) to allow enough time for beneficial insects to build up before pest populations increase.

Count the number of predators on 10 plants per plot just before treatment and continue at weekly intervals after spraying. Yellow stick traps can also be used to measure levels of lady beetles and lacewings.

(Source: MBCN, Univ of Neb. June, 1996)




Insect Management


Furadan Cr-10 for Use on Canola

EPA has approved the use of Furadan CR-10 on canola for one more year. Use will be limited to existing seed treated with Furadan CR-10 and existing stocks of product left over from the 1996 growing season. These will be allowed for use during the 1997 growing season. All new product labels and treated seeds must carry the following statement, "Do not use on Canola after September 30, 1997."

(Submitted by Phillip A. Glogoza, NDSU Extension Entomologist)




Pests in Grocery Stores

Grocers have varied opinions towards pest management and PCOs. Their attitudes to IPM, perceptions of pest occurrence and distribution within packaged foods in grocery stores were documented recently in a study conducted in Oklahoma, Arkansas and Texas.

Grocers were also asked about the role of PCO's within grocery stores. In 85 percent of grocery stores surveyed, a pest control company handled the pest management; 14 percent of grocers did their own pest control and one percent used no pest control. The majority have a monthly contract, with an average service call of every 31 days.

The majority of grocers (307) felt there were no insect pests problems in their stores. Thirteen grocers believed there were problems, and one was unsure. Sanitation and insecticides were most-used management practices, with IPM practices such as stock rotation, traps, baits, temperature control and screens, followed with limited usage. (See table 1).

Table 1. IPM practices used by 
grocers in Oklahoma, Texas and 
Arkansas in 1995.
-----------------------------------
IPM Practice	OK	AZ	TX
-----------------------------------
	        Percent of Grocers
Traps		30	50	49
Screens	 	 7	29	 5
Temperature	14	29	17
Insecticides	68	86	 8
Stock rotation	25	82	70
Sanitation	26	92	90
-----------------------------------

Grocers rated the back storage and trash areas as the trouble spots for insects, with areas such as pet foods, flour and cereals being less of a problem. They felt overall, however, that there were no real problems in the store. The most highly reported insects in grocery stores were cockroaches, flies, weevils and ants (See table 2).

Table 2. Perceived insect problems 
and insects recovered in pitfall traps.
-------------------------------------
Managers	Recovered
-------------------------------------
Cockroaches	Indianmeal Moth
Files		Merchant Grant Beetle
Weevils		Drugstore Beetle
Ants
-------------------------------------

Grocers perceive insects as coming into the store from outside, the warehouse or the delivery truck. Grocers also stated they were somewhat concerned about pesticides used in the store, but believe customers are not concerned. This is an interesting contrast to other Oklahoma State University (OSU), Stillwater, Okla., studies, that show grocers feel consumers are very concerned about pesticide residues on fresh produce.

These studies indicate a need for education and training in IPM practices, and better communication between PCOs and grocers. One interesting observation was that grocers depended on PCOs to find the insects and PCOs depended on grocers to find the insects. This indicates a serious lack of communication, and a tendency to "pass the buck." IPM requires communication and cooperation between the PCO and the grocer if it is to work. Without communication, training and cooperation, pest populations go unmanaged, grocers receive customer complaints and PCOs lose accounts.

(Source: Ento. Dept; Okla State University; PC July, 1996)





Disease Management


Application Equipment and Timing of White Mold Fungicides

In October 1995 I reported on duPont-sponsored trials using different types of ground application equipment to apply Benlate for white mold control. The best white mold control in 1994 and 1995 was obtained with a Willmar Spray Air (air assist unit) and a high pressure unit (Brittonya) with drop nozzles between the rows. Low pressure sprays with drop nozzles and high pressure broadcast sprays also provided white mold control, but were less effective than the best treatments.

Additional trials were conducted in 1996. The ground application trials showed variable results and are not reported here.

DuPont sponsored an aerial application trial using Benlate to control white mold in RS 101 pinto beans planted on 30" rows. Benlate was applied on July 22 at 20% bloom with a turbine Air Tractor, using 2 lb/A in 5, 7½ and 10 gpa. I made white mold counts on August 15. Fifteen assessments of white mold incidence were made in each treatment, with assessments 50 paces apart. There were 22 observations (11 for each of two rows over 10 feet of row). There were highly significant differences between treatments. Results are shown in the following table.

---------------------------------
	      White Mold 
Treatment     Incidence	   Yield
---------------------------------
		 (%)	   (lb/A)
10 gpa		57.9	    3962
Untreated	84.9	    3010
7 gpa		50.6	    3978
5 gpa		71.2	    3672
---------------------------------

White mold pressure was very high in this trial. Many growers would feel that the control obtained was inadequate. Perhaps a more accurate and honest term would be "white mold suppression" rather than "white mold control." The data indicate that even though disease counts were disappointingly high, there was a highly economic yield response from the use of fungicide. The results also indicate that good white mold suppression is possible using aerial application, although the exact level of suppression cannot be compared with good ground application since ground equipment was not included in these trials. Previous data had left this point in doubt. The data also suggest that high gallonage application, 7½-10 gpa, may be more effective than 5 gpa. Results of other trials, also applied by air, also suggest that good suppression may be obtained, especially using high gallonage aerial application.

AtoChem sponsored two timing trials with Topsin M, both applied by air. Topsin M was applied at 1½ lb/A at early bloom, early bloom + 4 days, and early bloom + 10 days. Schooner navy beans, planted on 30 inch rows, were sprayed on July 18 using an Ag Cat and 7 gpa. Envoy navy beans, planted on 22 inch rows, were sprayed on July 24 using an Ag Cat and 5 gpa. I made white mold counts on the Schooner navy beans on August 12 and on the Envoy navy beans on August 15 using the methods described above. The white mold counts from both trials were highly significant, with all treatments significantly less than the untreated check. Yields were inversely related to white mold incidence. The data on white mold incidence (WM) and yield (lb/A) are shown in the next two tables.

------------------------------
Treatment	% WM	Yield
------------------------------
Schooner
  10% bloom	 18.2    1894
  10% +4 days	 14.2    2094
  10% + 10 days	  7.3    2231
  untreated	 32.4    1580

Envoy
  10% bloom	 42.2	 1849
  10% + 3 days	 40.0	 1769
  10% + 10 days	 59.7	 1269
  untreated	 77.6	 1295
------------------------------

When white mold pressure was relatively low, as in the Schooner trial, the best white mold suppression was obtained by spraying at 10% bloom + 10 days. When white mold pressure was high, as in the Envoy trial, the best white mold suppression was obtained by spraying earlier, at 10% bloom or 10% bloom + 3 days. Yields were inversely related to white mold incidence in both trials.

Although these data appear contradictory, laboratory trials by Dr. Jim Venette, NDSU legume pathologist, indicate that when white mold spore concentrations are low, the time for white mold development is inversely related to the spore concentration falling on each blossom -- the more spores on the blossom, the shorter the time required for infection. When spore concentrations are above a certain threshold, however, additional increases in spores on the blossom do not further reduce the time for white mold infection. These data suggest that when white mold pressure is low, a delayed application may be more effective; but when white mold pressure is high, an early application may be more effective. Thus, the apparently conflicting field results may be related to different levels of disease pressure in the two trials.




Dry Bean Rust

Bean rust was controlled adequately in most fields in 1996, but there were some surprises: some navy varieties developed higher levels of rust than would be expected based on their past rust reactions. In addition, California Early kidney, which should have shown good resistance, showed a susceptible reaction in north central Minnesota, and supposedly resistant pole beans showed a susceptible reaction in Jim Venette's back yard garden in Fargo. Jim Venette is determining the rust races on nearly 40 samples taken last summer. As of this writing we do not know what the current race picture is, but feel certain that there were more races present in 1996 than in previous years. Until we know more, do not assume that any variety is resistant if you are seeing moderate to rapid rust development.

Perhaps we will have more information by spring or early summer. I will try to keep you informed.




Sugarbeet Cercospora Resistance and Tolerance to Fungicides

In the January 1996 issue of this Quarterly, I reported on the development of tolerance to the tin fungicide Super Tin and on the development of resistance to the benzimidazole fungicides Benlate and Topsin M. When the Cercospora fungus is cultured in the laboratory on 5 ppm of benzimidazole fungicide, a resistant strain will grow as if there were no fungicide present, but a sensitive strain will not grow at all. When the fungus is cultured on 0.2 or 1 ppm of Super Tin, a tolerant strain will grow, but produce reduced growth, whereas a sensitive strain will not grow at all. Benzimidazole resistance apparently is controlled by a single gene and is an "all or nothing" response, with resistant strains growing normally on quite high concentrations of the fungicide. On the other hand, tin tolerance apparently is controlled by a number of genes and is an incremental response, with the fungus gradually becoming tolerant to increasing levels of tin.

Resistance to the benzimidazole fungicides is a common phenomenon in many fungi, and resistance can develop with alarming rapidity. Benzimidazole resistance has been widespread in southern Minnesota since 1981 when benzimidazole-based disease control programs failed suddenly. Prior to 1996 there had been scattered reports of benzimidazole resistance in the Red River Valley. Tin tolerance, reported some years ago in Europe, was first observed and confirmed by USDA sugarbeet pathologist Dr. Bill Bugbee in 1994. Tolerant strains were found that autumn in a few fields in southern Minnesota and the southern Red River Valley.

In 1995 Bill Bugbee conducted a survey of tin tolerance and benzimidazole resistance in the seven factory districts of southern Minnesota and the Red River Valley. Benzimidazole resistance was common in the Renville (southern Minnesota) and Wahpeton factory districts, but rare in the other five factory districts farther north. Tin tolerance was present in most samples at Renville, two thirds of the samples at Wahpeton, 15% of the samples at Moorhead and rare north of Moorhead.

In 1996 USDA Sugarbeets conducted another survey. Benzimidazole resistance was present in two thirds of samples at Renville, over half of samples at Wahpeton, three quarters of samples at Moorhead and one third of samples at Crookston. These data represent an increase in resistance at Wahpeton and dramatic increases at Moorhead and Crookston. Tolerance to 1 ppm of Super Tin continued at high levels at Renville, and had risen to 90% of samples at Wahpeton, 60% of samples at Moorhead, over one third of samples at Crookston and 16% of samples at Drayton. Percent of samples tolerant to 0.2 ppm of Super Tin was equal to the percent tolerant to 1 ppm at Renville and Wahpeton, but was greater than the percent tolerant to 1 ppm at locations farther north; it was 80% at Moorhead, 70% at Crookston, 58% at East Grand Forks and 42% at Drayton. Some tolerant samples also were found at Hillsboro.

Data from replicated experimental plots at Wahpeton indicated low levels of tin tolerance and benzimidazole resistance in the unsprayed plots and in plots sprayed four times with mancozeb. Levels of tin tolerance were intermediate in plots sprayed three times with Pro Tex, a tin-mancozeb prepack mix. Levels of tin tolerance were high in plots sprayed with Super Tin, Topsin M or a tank mix of Super Tin and Topsin M. Levels of benzimidazole resistance were high only in the plots sprayed with Topsin M or the tank mix of Super Tin plus Topsin M. These data indicate that a tank mix of mancozeb with Super Tin may help to retard the development of tin tolerance, but that a tank mix of Topsin M with Super Tin may not retard the development of tin tolerance or benzimidazole resistance. This is contrary to what was expected. The data as well as performance data from other trials suggests that a tank mix of benzimidazole and mancozeb may be less liable to result in sudden performance failure than a tank mix of benzimidazole and Super Tin.

Based on the data, we should expect levels of tin tolerance and benzimidazole resistance to be higher in 1997 than in 1996 and that Cercospora management will require tank mixing of fungicides in most areas. For the most part, these would be tank mixes of Super Tin with another fungicide. The data further indicate that the best tolerance management strategy would be to use mancozeb in rotation with tin-mancozeb tank mixes. Extreme caution will be required if the benzimidazole fungicides are used at all. Guidelines on tolerance and resistance management strategies will be developed (hopefully by consensus) for the 1997 Sugarbeet Production Guide, also known as the pocket guide. See the next issue of the North Dakota Pesticide Quarterly for details on the management strategy for 1997.





Weed Management


Special Weed Control and Herbicide Use Issues from Midwest States in 1996

Exceed Carryover to Soybean
Exceed is labeled for postemergence grass and broadleaf weed control in corn. Exceed is a prepackaged mixture of two long residual sulfonylurea herbicides: Beacon and Peak. Exceed was used extensively throughout the midwest in 1995. In 1996 soybean were planted as a follow crop and several states reported soybean injury due to Exceed residue. Research conducted on Exceed prior to registration indicated safety to soybean planted the year following application. The issue received high exposure due to the wide geographic region where the occurrence was documented. Soybean fields in Minnesota, South Dakota, Nebraska, and Iowa were confirmed with soybean damage due to Exceed carryover.

Factors that seem to contribute to Exceed carryover were application to soil with pH above 7.0, late applications, dry conditions after application, and possibly herbicide stacking from other long residual herbicides of the same mode of action (ALS inhibitors).

Injury symptoms on soybean were described as normal sulfonylurea herbicide symptoms on susceptible species: soybean internode compression, dark veins, and interveinal chlorosis of upper leaves which may mimic and exaggerate iron chlorosis.

Solutions recommended were to not grow soybeans on fields suspect for carryover, soil dilution from plowing may help only to a limited degree, and plant sulfonylurea tolerant soybean (STS) soybean varieties, except that there may be a limited supply and few varieties for the northern soybean area. Using STS soybean does not provide safety for other long residual sulfonylurea herbicides. For example, STS soybean are injured by Ally residue. To determine residues low enough to escape soybean injury alfalfa should be used as a bioassay plant species. If alfalfa is planted and exhibits no injury symptoms then soybean will be safe to grow.

As a result of Exceed carryover the label may be changed to restricting geographic regions, restructure rates, require minimum amount of rainfall after application, restrict application based on previous ALS herbicide use, and further restrict application based on soil pH.

This information is important to North Dakota growers because Exceed is not be used in North Dakota. High soil pH, dry conditions, and other sensitive crops planted in rotation following corn makes Exceed use high risk of carryover to severely restrict crop rotation for many years following application.




Onion-leaf Corn

Onion-leaf corn or corn with fused leaves occurred throughout the midwest. Determining factors responsible for symptoms were difficult but thought to be caused by ALS herbicide + Banvel interaction, adjuvant use with ALS + Banvel, environmental extremes (stressed conditions), and varietal response. Symptoms seemed to occur more with Basis than Accent. It is thought that applications made during the 12th node (12th leaf initiation) stage has greater risk of this injury even though symptoms are not expressed until later. This may show the need to use a planned herbicide program with soil and postemergence herbicide applications together or to make an early postemergence followed by another postemergence application rather than make one postemergence application late after most all weeds have germinated.




Pursuit Carryover in Some Midwest States

Some states reported that 10 to 20% more samples were sent in for analysis as compared to other years. Symptoms on corn were stunting, enhancement of iron chlorosis, exaggerated by tankmixes with other ALS herbicides, making late applications.




Sterile "Ergot" Wheat

South Dakota and one report in North Dakota reported a few cases of normal looking wheat fields but when harvesting began the yield was 3 bu/A and 2 bu of the total was ergot. Reason for occurrence could not be identified.




CRP Breakout

Several states have documented that warm season grasses are harder to kill than cool season grasses. Quackgrass and several cultivars of wheat grass can be controlled from spring applications of Roundup. However, bromegrasses may need three applications prior to crop planting (summer, fall, and spring) to achieve satisfactory control.




Herbicide Resistance

Minnesota has reported possible green foxtail resistance to Accent herbicide, but that biotype was controlled by Pursuit in tests.

Iowa reported possible foxtail resistance to certain ACCase herbicides. Further tests will be performed to document this observation.




Application Issues

Roundup drift will continue to receive more attention as more Roundup Ready Soybean are grown. No difference in drift between Roundup and Ultra Roundup were observed. However, more drift is occurring as evidenced by the rise in insurance claims by 200 to 300%. Commercial applicators will charge more per acre for Roundup applications or they may not spray at all to avoid crop injury to other neighboring crops. A common situation might be a burndown application prior to planting soybean when corn is emerged). Factors that can determine extent of Roundup drift are wind speed, pressure, humidity, and gallons per acre applied.




Special Weeds--Caused by the Pattern of Herbicide Use or the "System"

Waterhemp -- emerges later than other pigweed species. Dual, Lasso and other chloroacetamide herbicides may initially provide 80 to 90% control but herbicides are degraded prior to crop canopy. Prowl, Treflan, and Sonalan gives less control than chloroacetamide herbicide despite a longer residual activity. Waterhemp appears to be shade tolerant and can has a growth rate of at least 12 inches per week. It can be more of a problem tire tracks and draws in the field. Iowa has found that early records show a higher population of waterhemp in 1920 than redroot pigweed.

Woolly Cupgrass -- approximately 80% emergence occurs in the first flush. Accent does not control the grass as when first released (possible biotype shift to a more tolerant type in the population). SR (sethoxydim resistant) corn and Lightning herbicide in IMI corn can be used to successfully control woolly cupgrass. Harness and Surpass appears to provide the highest amount of control of chloroacetamide herbicides. A new herbicide called Balance to be released for use in corn in 1997 has provided fair to good control. Successful control strategies should include sequential herbicide applications or tankmix combinations such as Accent + Harness/Surpass + Banvel (moisture is required for adequate control with cultivation.

Biennial Wormwood -- serious problem, especially in wet areas of no-till fields where no burndown herbicide was used. Often confused with common ragweed. It can emerge in fall and spring exhibiting very fast growth in open canopy crops. Recommendations for control include use of 2,4-D ester in fall or Sencor at 2 to 4 oz for spring burndown for no-till soybean. The amount of control from Roundup is not known. All postemergence herbicides labeled in soybean do not control biennial wormwood. Stinger and Curtail provide excellent control.

Kochia -- 2 qt/A of Basagran provides good to excellent control and is safer to soybean than the severe burn from Cobra or Steller.




Diagnostic Laboratory Discussion

Many universities have good diagnostic labs, some have only limited services available, and some universities do not have a lab. Some questions that should be considered is, "Do diagnostic labs fit the teaching and information transfer objective or is it just a source to support a particular party in litigation for crop injury or herbicide nonperformance? Should plant ID and crop herbicide symptomology be a service that the Extension Service should provide? Is it EDUCATIONAL? What is the function or mission of a diagnostic lab -- to generate funds to support the plant diagnostician?

With the continual reduction in extension funds and resources and losing positions due to down sizing, a serious commitment will need to be made to a diagnostic lab for its continuation.

(Submitted by: Richard K. Zollinger, Extension Weed Specialist)




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[ In This Issue / Coordinator's Comments ]
[ Pesticide Perceptions / Law ]
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