June 30, 2008

OBSERVATIONS FROM LAST WEEK

This past week not a lot new has come into the office. However I did have one unconfirmed report of leaf rust on wheat in the Ollie area, so you may want to be on the lookout for rust as you scout fields this week. If you have any questions on anything you see happening in the field please give me a call.

NDSU ANNUAL FIELD DAYS THIS SUMMER

June 26 Central Grasslands Research Ext.Center, Streeter

July 8 Hettinger Research Extension Center, Streeter

July 9 Dickinson Research Extension Center, Dickinson

July 10 Williston Research Extension Center, Williston

July 14 Agronomy Seed Farm, Casselton

July 15 Carrington Research Ext. Center, Carrington

July 16 North Central Research Extension Center, Minot

July 17 Langdon Research Extension Center, Langdon

July 23 Turf Field Day, NDSU campus, Fargo

July 29 Oaks Irrigation Research Site, Oaks

Aug.2 Horticulture Research Field Day, Absaraka

For these and other events this summer (including Pulse Crop Tours, Canola Days, etc…), visit http://www.ag.ndsu.edu/research/fielddaydates2008.htm or contact your local county agent or Research Extension Center. Hope to see you this summer!

RECENT FIELD OBSERVATIONS OF INSECT PESTS

Janet J. Knodel

Extension Entomologist

janet.knodel@ndsu.edu

Sunflower - Sunflower Beetle: Adult sunflower beetles are emerged, however, no economical populations have been reported. The economic threshold is 1 to 2 adults per seedling on seedlings. Please refer to the NDSU Bulletin E-824 for more information: http://www.ag.ndsu.edu/pubs/plantsci/pests/e824.htm

Small Grains - Cereal Aphids: Low numbers of cereal aphids are being reported throughout the state (see IPM map).

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)

AVOID FLAG LEAF APPLICATIONS OF INSECTICIDE FOR CONTROL OF WHEAT STEM MAGGOT

Janet J. Knodel

Extension Entomologist

janet.knodel@ndsu.edu

Preliminary research indicates that insecticides applied at the flag leaf stage were NOT as effective in reducing the number of white heads caused by wheat stem maggot when compared to insecticides applied at the 4- leaf crop stage (see table). Warrior insecticide reduced the number of white heads caused by the wheat stem maggot when applied at to 4-leaf wheat. However; the number of white heads per plot was not significantly different from the untreated plot when Warrior was applied later in the growing season. Wheat yield was the greatest where Warrior was applied with a fungicide (Quilt or Tilt) for leaf disease control at the 4-leaf stage. Although later season applications of fungicide also increased wheat yield, it did not show the same level of increase as the 4- leaf application applied with an insecticide (Warrior). NDSU Ext. Entomology recommends ‘NOT to add an insecticide’ at flag leaf for control of wheat stem maggots or when no economic levels of insect pests are present in field.

Clearfield HRSW was seeded May 24, 2007, at 1.1 million seeds/A. Source: D. Markle, NCREC, Minot, ND

STILL EARLY IN SEASON FOR COLLECTING LEAFY SPURGE FLEA BEETLES

Janet J. Knodel

Extension Entomologist

janet.knodel@ndsu.edu

There have been several questions about how many degree days are required for collecting leafy spurge flea beetles. The accumulated growing degree days (AGDD) for sunflower (base of 44 F) can be used as a guide to determine when to begin scouting for adult flea beetles. Begin scouting for adult flea beetles when the AGDD approaches 1,000. Likewise, the flea beetle population and egg laying by females begins to decline when the AGDD reaches 1,600 or more. Collect flea beetles between 1,200 and the 1,600 AGDD.

With the cool spring temperatures, most of North Dakota is still below 1,000 AGDD (see sunflower AGDD map), except for the far southeastern region. The GDDs for sunflower are about 200 GDDs behind the five-year average. Use the sunflower degree days/growth stage application in NDAWN and enter "2008-03-01" for planting date and select "degree day" for map type.

http://ndawn.ndsu.nodak.edu/sunflowergdd-form.html

CORN DEVELOPMENT AND STAGING

Joel Ransom

NDSU Extension Agronomist - Cereal Crops

joel.ransom@ndsu.edu

The first seven weeks of the corn growing season, at least for most of the state, have not been kind to the corn crop. The cool weather earlier in the spring slowed emergence, exacerbated the challenge of establishing a uniform stand, and slowed root development. This coupled with the excessive moisture in the eastern part of the state has delayed corn development (at least a full leaf behind normal) and resulted in the plants generally looking weak and yellow. The dry and warm weather over the weekend have improved the appearance of the corn crop marginally and crop growth is starting to accelerate. We are still at least 100 GDD behind normal and much further behind last year – most fields were knee high by this time last year and waist-high by July 4th.

GROWTH STAGING CORN

Joel Ransom

NDSU Extension Agronomist - Cereal Crops

joel.ransom@ndsu.edu

A few management practices, such as the application of certain herbicides, are growth stage dependant.

Therefore, being able to properly identify the growth stage of your corn crop is important to ensuring that management practices are applied at the appropriate time. The leaf collar method of growth staging corn is the method most often used in recommendations related to the timing of herbicides. When growth staging your crop you should begin by obtaining a representative sample of plants from the field or part of the field of interest. Ten plants should be selected at random. If emergence has been uniform, you can probably get by with fewer plants. Remove any soil attached to the plants so that you are able to observe the roots and crown. The number of leaves defines the vegetative stages of corn (i.e. V1 equals the 1st leaf stage). Counting leaves in corn is straight forward as the process is not usually encumbered with tillers and leaves on tillers as is the case in small grains. However, care must be taken to ensure that the earliest leaves are included when counting leaf numbers. The first leaf is small and often dies and is torn from the plant during early plant development. The first leaf has a blunt tip (see photo). Look for sheath remnants at the crown of the plant if you suspect that the first leaf (or second for that matter) is missing. Count only those leaves that have a collar. Do not exclude leaves that have been damaged by hail or frost. The total number of leaves that a plant will developed is more or less fixed for a given hybrid; additional new leaves will not replace leaves that are stripped from the plant. In order to determine the growth stage of older plants that have lost their lower leaves, uproot the plant and split the stem with a knife through the root ball. At the very base of the stem, identify the first visible internode. Internodes are the white area between the more yellow bands of the nodes. The first obviously visible internode should about 2 to 3/4 inch in length. The node directly above this internode will be the fifth node, and the leaf arising from this node will be the 5th leaf. Find that leaf and continuing counting leaves from that point

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RELATIONSHIP BETWEEN GDD AND LEAF NUMBERS

Joel Ransom

NDSU Extension Agronomist - Cereal Crops

joel.ransom@ndsu.edu

There is an excellent relationship between corn growing degree days (GDDs) and leaf appearance in most environments. Corn GDDs are calculated using a base temperature of 50 degrees F (average temperature for the day minus 50) and therefore, differ from small grain growing degrees days which use a base of 32 degrees.

GDDs for both corn and small grains for locations near your farm can be obtained using NDAWN (http://ndawn.ndsu.nodak.edu/corndd form.html). Corn requires about 120 GDDs to emerge. Researchers from other states have found that it takes about 80-85 GDDs to produce a new leaf through the 10 leaf stage. Data from the last two years in ND would suggest that new leaves appear after about 70 GDDs (see Figure 1). Based on these data, corn planted on May 1st in Fargo this year should now have about 6 leafs (542 GDD accumulated minus 120 GDD for emergence = 422, 422/70 GDD per leaf = 6 leaves). This number corresponds fairly well with what can be observed in plots near the NDSU campus.