Traill County Ag Alert Newsletter

Traill County Ag Alert Newsletter

June 12, 2008

RAINFALL & GROWING DEGREE DAYS (GDD)

Location Mayville Hillsboro Galesburg

Corn GDD 356 367 364

Compared to 2007 -135 -134 -119

Wheat GDD 892 898 912

Compared to 2007 -234 -241 -199

Rainfall since June 1 2.5 inch 3.39 inch 3.22 inch

COOL WEATHER FURTHER DELAYS CORN DEVELOPMENT
We are six weeks into the corn growing season and the lag in corn development is a concern. GDDs typically accumulate at the rate of 13 per day in early June. We are currently about six to seven calendar days behind normal corn development. This means that corn is 1.0 to 1.5 leaves behind normal (about 85 GDDs are required for each new leaf). It is still early in the season and there is certainly potential for crops to catch up if temperatures during the remainder of the season are above normal.

NDSU CROP MANAGEMENT FIELD SCHOOL AT CARRINGTON
Crop management field school will be offered Thursday, June 19, from 9 a.m. to 4:30 p.m. at the NDSU Carrington Research Extension Center. For further details and preregistration information, contact the Carrington Center at (701) 652-2951 or go to http://www.ag.ndsu.nodak.edu/carringt/. A completed preregistration form and $50 fee is requested by June 16 ($75 after June 16).

GET READY TO SCOUT FOR CEREAL APHIDS
Cereal aphids have been reported in South Dakota on winter wheat. These aphids will be migrating into North Dakota. The greenbug, English grain aphid and bird cherry oat aphid are the principal species that cause problems in North Dakota small grains. These aphids transmit the disease barley yellow dwarf virus. When aphid populations are high, the disease can spread quickly through small grain fields. At greatest risk are later-planted fields, which attract aphids that are moving from more mature fields.

Greenbug - pale green with dark stripe down back.

Bird Cherry Oat Aphid - olive green, brownish patch at bases of cornicles.

English Grain Aphid - bright green with long black cornicles.

(For wheat, field scouting should begin at stem elongation and continue up to the heading stage.)

Thresholds for Small Grain Aphids: English Grain, Bird Cherry Oat, Greenbug
To protect small grains from yield loss due to aphid feeding, three different treatment thresholds are available:

- 85% of stems with at least one aphid present prior to complete heading.
- 12-15 aphids per stem prior to complete heading
- 100 aphid days prior to complete heading (=0.6 bu/acre yield loss)

If you averaged 10 aphids per stem and had 12 days to reach heading, you would have 120 aphid days (10 aphids x 12 days). This is above the 100 aphid day threshold and an insecticide should be applied to prevent yield loss. On the other hand, if you averaged only one aphid per stem and had 12 days to reach heading, you would only have 12 aphid days (1 aphid x 12 days). Thus, no control action would be necessary.

Susceptible Crop Growth Stage:
Crop growth stage also affects its susceptibility to aphids. Vegetative to boot stages are the most susceptible stages to aphid feeding and subsequent yield loss. By heading, only kernel weight is affected. After flowering, small grains are less susceptible and producers are discouraged from spraying.

Natural Controls: Lady beetles, aphid lions, syrphid fly, and parasitic wasps play a major role in reducing aphid populations. When natural enemies are present in large numbers, and the crop is well developed, farmers are discouraged from spraying fields.

SUGARBEET ROOT MAGGOT
Degree-day (DD) accumulations for development of sugarbeet root maggot (SBRM) populations this year are running about 7-10 days behind normal. This, combined with frequent events of windy, rainy weather during the past several days, has resulted in very little SBRM fly activity thus far.

A rapid increase in fly activity could occur if warm, dry, and low-wind conditions develop in the next week or so. Peak fly activity usually occurs shortly after the accumulation of 600 DD. Hillsboro is at 846 DD but the conditions have not been conducive to fly activity. It is important to note that warm weather (around 80 F), and calm to low-wind conditions are most conducive to fly activity. Flies will remain relatively inactive in cool, rainy, or windy conditions.

Fly emergence and movement into beet fields can be accelerated quickly following a major increase in air temperatures. Growers in high-risk areas for SBRM infestation should consider applying a postemergence insecticide, especially if a low or moderate rate of an at plant soil insecticide was applied. Postemergence liquid insecticides should be applied within 3 days of the expected peak (before peak is best). This will provide control of both adults and larvae.

For more guidance on postemergence control strategies, consult the “Insect Control” section of the 2008 Sugarbeet Production Guide or the “Sugarbeet Insects” section of 2008 Field Crop Insect Management Recommendations. Online versions of these publications are located at: www.sbreb.org/Production/production.htm and www.ext.nodak.edu/extpubs/plantsci/pests/e1143w1.htm

WET FIELD CONDITIONS
We went from being dry to wet in the last few days. The respiration of plant roots, soil micro-organisms and fauna leads to rapid exhaustion of soil oxygen. Whenever the plant faces prolonged (>3–4 days) excess soil moisture conditions, the plant roots suffer extreme oxygen stress. The extent of damage due to excess moisture stress varies between crops and also depends on the developmental stage of the crop. Just emerging plants are more susceptible than established plants. Dry beans are very susceptible to excess moisture. Corn is susceptible to excess moisture stress during the early seedling to tasseling stage. Soybeans have been somewhat tolerant to short periods of excess moisture.

When the soil is just dry enough to go into the field the potential for compaction is greatest. Low pressure tires, large flotation tires, or dual wheels may help reduce surface compaction. However, any machinery traffic on a waterlogged field will cause subsoil compaction – the heavier the load, the greater the impact. Compacted soil reduces root growth and the movement of water and air through the soil. Once the soil is compacted it is difficult to get it back in good shape. Prevention of compaction is easier than trying to manage compact soils.

SUGARBEET – LOOKOUT FOR DISEASES
Rhizoctonia solani can infect sugarbeet at all growth stages and results in wilting and death of plants. The fungus causes infection when soil moisture range from somewhat dry to wet and soil temperatures above 68ºF. The fungus typically causes damping-off, and crown and root rot of sugarbeet. Damping-off occurs at the seedling stage when the fungus infects the hypocotyls resulting in rapid collapse of seedlings before soil emergence or postemergence. Crown and root rot infection occurs in older plants when the pathogen infects the petioles or the roots. Characteristic symptoms of Rhizoctonia include sudden wilting of leaves, and petioles of outer leaves are blackened at the point of attachment to the crown. When the crown rot infection extends to the roots, it causes root rot. Crown and root rots, separately or collectively, are the most damaging phase of the disease and reduces yield significantly. The disease may also produce dry rot cankers on the root surface.

When cultivating, avoid throwing soil into the crowns of plants to help reduce infection. The use of the fungicides Quadris® or Proline® at the 4 to 6 leaf stage or when the soil temperature at the four inch depth is about 65ºF will also help to control Rhizoctonia crown and root rot.

RUST DISEASES OF WHEAT
Three rust diseases have the ability to infect wheat in North Dakota. Leaf rust currently is the most important of the three, but stem rust has been problematic in the past, and stripe rust may appear in cool summers. The publication (PP-1361) Wheat Leaf Rust, includes information on the three major wheat rusts with symptoms, life cycle, and management discussed. This publication is available at: www.ag.ndsu.edu/pubs/plantsci/smgrains/pp1361.pdf

RECENT RAINS BRING INCREASED DISEASE RISK
Recent rains have increased the potential for leaf and head diseases of small grains. The NDSU small grains disease forecasting site indicates 7 out of the last 8 days have been favorable to infection of tan spot, and the Fusarium head blight (scab) risk has also increased. The Fusarium head blight risk should be of concern for producers with winter wheat, as many winter wheat fields are now in the heading stage.

EARLY SEASON FUNGICIDES FOR WHEAT AND BARLEY
Many producers have recently applied fungicides for early season disease control, often in a tank mix with herbicides. Some injury has occurred with these applications on the very succulent, thin leafed cuticle, wheat and barley. In previous years when this type of symptom was observed, the new growth generally looked good and we did not see yield reductions, but did see yield increases with these treatments. In 2003, NDSU did a number of fungicide + herbicide combination treatments and did not have any injury, a year in which we had a little warmer, sunnier June than we’ve had so far this year.

FUNGICIDE UPDATE
Growers contemplating using fungicides for scab control in the near future should be considering using either Folicur®, Orius®, Tilt®, Proline 3+3®, or Caramba®, as these products are triazoles with the best and safest activity against scab. In NDSU field tests, the Proline 3+3® or the Caramba® have consistently given the greatest scab and DON (vomitoxin) reductions. Bayer CropScience just announced the registration of Prosaro® fungicide, a pre-mix of prothioconazole and tebuconazole (the same active ingredients of Proline® and Folicur®). Although Prosaro® just got registered in wheat and barley, Bayer will continue to market the Proline 3+3 (prothiconazole + tebuconazole, not premixed) program for the 2008 growing season, and Bayer says they will transition to Prosaro® in 2009. Prosaro® is labeled for wheat and barley for multiple leaf and stem diseases, as well as suppression of Fusarium head blight (scab). The use rate will be from 6.5 to 8.2 fl oz/acre, with two applications per season possible, but not to exceed 8.2 fl oz.

SIDE-DRESSING CORN
Side-dress for corn should be made anytime that the applicator can practically be in the field. When corn is small, there is potential for covering up the plants with soil, so applications are usually made between 5-leaf and 10-leaf corn. Corn higher than this may require a liquid applicator equipped with drop hoses and orifices to dribble 28% between the rows on the soil surface and hope for rain.

Do not broadcast spray liquids, or broadcast spread dry fertilizer over the top of corn. The leaves of corn act like a funnel and you will burn the corn plants badly if this is done. Last year a few novices did this and I think they won’t do it again.

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Traill County Extension Office

P.O. Box 730

Hillsboro, ND 58045

701-636-5665 or toll-free1-877-843-6383