VOLUME 22, NO. 11                                                                                                                                                                              July 17, 2008

GRAND FORKS COUNTY PLOT TOUR:

We will be having our variety plot tour on July 21, 2008 starting at 4:30 pm on the Chuck Nelson farm.  The Nelson farm is located 7 miles south of Grand Forks on Highway 81 (between I-29 and Highway 81 north of the Thompson exit).  The events will include our small grain variety plot, soybean variety plot, and corn plot tours.  Breeders from Westbred and representatives from Agripro will be on hand to visit about their small grain varieties.  Sam Markell, NDSU Extension plant pathologist, will give a disease update.  NDSU corn breeder, Marcelo Carena, will take us through his corn variety plot.  The evening will conclude with dinner sponsored by Farm Credit Services.  For additional information contact the Grand Forks County Extension office at 701-780-8229.

EARLY APPEARANCE OF SUNFLOWER RUST IS A CAUSE FOR CONCERN IN NORTH DAKOTA

After a recent conversation with Dr. Sam Markell, NDSU Extension Plant Pathologist, on sunflower rust, I thought I would include his article on the disease in this newsletter:

Sunflower rust is a disease that is capable of causing significant yield loss to sunflowers. Sunflower rust appears most years in North Dakota, but isn�t usually observed until late July or early August. However, the presence of sunflower rust in North Dakota was recently brought to my attention by crop consultant Mike Hutter (Renville County) and the disease has since been observed in other counties throughout the state.

Symptoms: Rust will often appear initially on the lower leaves and spread upward as new leaves are produced. The disease produces small (approximately1/16 inch) dusty cinnamon-brown pustules full of brown spores. Brushing your thumb across rust pustules will leave a dusty brown streak on it.  Rust can also infect the stems, bracts and head.

Disease Cycle: Once pustules are observed, they each are capable of producing many more spores and many cycles of infection. These spores can be dispersed long distances by wind, which may rapidly spread the disease to other fields. Spores need a minimum of 2-3 hours of free water (either dew or rainfall) to germinate, but 6-10 hours of free moisture will produce higher levels of germination and infection. Optimal temperature for infection ranges from 60-75 F, but can occur between 39 and 86 F. At temperatures above 90 F, rust spores do not germinate on sunflowers. Once infection occurs, temperature is the only environmental factor that will determine how fast the disease progresses.  During cool conditions (65 F day/55 F night) it may take up to 14 days for new pustules to form, but at warm conditions (85 F /75 F) new pustules can form in as few as 8 days. Thus, warm temperatures will often speed disease development.

Fungicides: We have almost no fungicide data from early rust epidemics, simply because they are rare. However, after conversations with colleagues in other sunflower growing states and provinces, I would recommend being aggressive controlling this disease. We have a long growing season in front of us, the disease is well-known to cause yield and quality losses, and the price of sunflowers is high enough to justify managing the disease. I think it is important to scout your fields weekly for the disease.  In fields where rust is not found, be happy and scout again next week.  In fields where rust is found, you likely need to consider a fungicide application this season. Currently, Headline and Quadris are labeled for rust control. If rust is absent or present at very low levels, it may be prudent to wait until the upper leaves have emerged. However, if severity on the lower leaves is higher (3-5% or more average for all leaves) and favorable conditions for disease exist (prolonged dew and relatively warm days), a fungicide application to arrest the development of the disease may be warranted. In this case, a follow-up application could be necessary later, depending on severity and plant growth stage. Headline is labeled at 6 � 12 oz/A and Quadris has a North Dakota Section 2(ee) label at 6 - 7 oz/A, but both disease control and residual will be better if a higher rate of either product is applied (9 oz/A or more for Headline). Remember to read the label, follow directions, and pay attention to the PHI.  In some fields, a threshold model for rust control developed by researchers in Israel in the mid 1990�s may be useful, with some modifications. The model is based on fungicide timings around flowering, so it may be relevant in some areas. The research group found that yield loss was limited if a fungicide application was made when the upper four leaves had an average pustule coverage of 3%.  They also found that at 27 days after flowering, a fungicide application no longer benefitted the crop, since the seed filling period was largely finished. However, two things about this study suggest to me that we might want to be more aggressive than this. First, this data was based on an application of a triazole fungicide (Folicur, which is not labeled on sunflower), which has been shown to have more curative activity than strobilurins (Headline and Quadris) on rusts of other crops (strobilurins should be viewed more as a protectant for sunflower rust). Thus, an application before the 3% severity threshold is reached is critical when using the strobilurins, and I would strongly encourage the use of a higher application rate. Second, we should expect our climate to be more conducive to disease development; further suggesting that an application before the 3% severity threshold is reached would be prudent. If rust is in your area and you are considering a preventative application, I would recommend waiting until early flowering. That way you protect the upper leaves for a prolonged period of time, removing much of the window for new infections to cause damage.

GET READY TO SCOUT FOR BANDED SUNFLOWER MOTH

Banded sunflower moth is just starting to emerge in our area.  Fields should be monitored for adult moths and eggs when sunflowers are in the R3 (immature bud elongated 0.5 to 2.0 cm above the nearest leaf) stage.

Description: The adult has a dark band across the buff or yellowish-tan forewings. The wingspan is about 0.5 inch. Early instars larvae are off-white; late instars larvae are pinkish to red with a brown head capsule. Larvae will be about 0.4 to 0.5 inch at maturity.

Damage: Newly hatched larvae move from the bracts (where they feed initially) to the florets of the sunflower head and enter open florets to feed. During later stages, the larvae tunnel through the bases of the florets into the seeds and consume the contents. Each larva may destroy 5 to 7 seeds.  Silken webbing on the face of the head at maturity indicates the presence of larvae within the head.

Control: The economic threshold level has changed with the current high market value. When monitoring for adults during daylight hours, one banded moth per 100 plants is a reasonable threshold given the high 2008 sunflower market prices. For egg counts, the threshold level in 2008 is about 2-3 eggs per six bracts. Chemicals should be applied from the late bud stage (R4) to early bloom (R5.1).  Border spraying can be an option. Spraying in early morning or late evening is preferred to minimize the impact of pollinators. Some common control mistakes include: not scouting; waiting too long to spray; and perimeter spraying only and not scouting the interior of the field.

GRASSHOPPERS IN THE INCREASE

It�s important to remember that grasshoppers can affect any crop in the region.  We have had several conditions this growing season that have been favorable to a potential grasshopper outbreak: 

� Cool and wet early spring prevented premature grasshopper hatch and insured an adequate food supply.

� Warm and dry late spring promoted uniform hatching time and good weather conditions for feeding.

� Hot summer with adequate rainfall in some areas of North Dakota have provided good food supply and low incidence of diseases.  Thresholds are different depending on whether you�re scouting for adults or nymphs or from the field margin or inside the field.  Numbers in this table are based on grasshopper/square yard.

	Nymph		Adult
Rating	Margin	Field	Margin	Field
Light	25-35	15-23	10-20	3-7
Threatening	50-75	30-45	21-40	8-14
Severe	100-150	60-90	41-80	15-28
Very Severe	200+	120	80+	28+