NDSU Crop and Pest Report

Plant Science


ISSUE 9  June 27, 2002

 

OILSEED SUNFLOWER DEVELOPMENT

Sunflower growth and development responds to heat units similar to corn and several other crops. The base temperature of 44EF is used to determine Growing Degree Days (GDD). GDD formula = [(daily maximum temperature + daily minimum temperature)/2] - 44 degrees F.

In the table below research data was collected at the Carrington Research and Extension Center over a number of years on sunflower stage development and heat units.

Oil sunflower development by days and growing degree day (GDD) units, 1994-95, Carrington Research Extension Center*

Sunflower
stage

Average days and GDD units increase from previous stage

Average days and GDD units accumulated from planting

 

days

units

days

units

VE

10

167

10

167

V4

10

182

20

349

V8

8

196

28

545

V12

6

145

34

690

V16

5

82

38

772

V20

6

99

44

871

R1

2

49

46

919

R2

15

333

61

1252

R3

6

142

67

1394

R4

4

99

71

1492

R5.1

3

54

73

1546

R5.5

4

77

77

1623

R6

8

158

84

1780

R7

12

272

96

2052

R8

9

159

104

2211

R9

15

259

119

2470

Planted on May 25 in 1994 and May 23 in 1995. Growing Degree Days were averaged over 5 hybrids each year and 5 plants per hybrid per plot were observed.

GDD units/data for 2002 can be found on NDSUís Extension site under Ag weather (NDAWN). Just click on the applications section and then to "Degree Days".

Dr. Duane R. Berglund
NDSU - Extension Agronomist
dberglun@ndsuext.nodak.edu

 

DRY BEANS: GROWTH AND MATURITY

Two basic plant types are found in dry edible bean, determinate (bush) or indeterminate (vining or trailing). Cultivars may be classified according to plant types. For example, navy beans may be either of the bush or vining types. In the determinate type, stem elongation ceases when the terminal flower racemes of the main stem or lateral branches have developed. On indeterminate types, flowering and pod filling will continue simultaneously or alternately as long as temperature and moisture permits growth to occur.

The question of dry edible bean maturity has been debated for many years. Compared to many other plants, the dry edible bean is orderly in its growth and development. There are two basic stages of growth: The vegetative and the reproductive. Growth at any point in the vegetative stage can be determined and defined by counting the number of nodes on the main stem. The reproductive stage begins when the first flower opens and is described and characterized by observing pod development and seed fill within the developed pod. Both vegetative and reproductive stages can further be separated into two periods for a total of four major growth periods in the life of a bean plant. They are:

1. Germination and stand establishment (V1 to V2)

2. Rapid vegetative growth (V3 to V8)

3. Flowering and pod development (R1 to R4)

4. Pod fill and maturation (R5 to R9)

The time required for the two growth periods of germination and stand establishment and flowering and pod development under the same growing conditions is the same for all varieties. Differences in maturity of varieties are experienced during the two periods of rapid vegetative growth and pod fill and maturation. The way it works is that late maturing varieties will require a longer period of time to pass through the rapid vegetative growth period than will early maturing varieties. This increase in time results in increased vegetative growth, capable of producing and filling pods over an extended period of time.

This sounds simple and straight forward and leads one to wonder why two people can come up with a different maturity value for the same bean variety. The reason seems to be that maturity for a given variety may be extended during one or more of the growth periods.

The developing bean will respond to many factors including planting in cool and/or wet soils, planting

in dry soils, insufficient soil moisture, excessive soil moisture high temperatures during flowering which delays pod set, or low temperatures during maturation. Maturity of a variety may also be extended by preplant herbicide injury, excess of or lack of certain plant nutrients, low plant stands, beans following alfalfa in a rotation, or damage from hail. Some of these factors can be controlled, others cannot. It's important to consider these factors, however, when comparing differing maturity dates for a bean variety. One of the above factors will usually be responsible for the difference.

Dr. Duane R. Berglund
NDSU - Extension Agronomist
dberglun@ndsuext.nodak.edu

 

APPROACHING CRUCIAL SMALL GRAIN STAGES

Small grain crops around North Dakota are approaching critical development stages. While developmental covers a wide range of stages much of the crop, particularly the early planted portion, is in the boot and early stages of flowering.

Two problems, scab (fusarium head blight) and wheat midge, become problems during heading and flowering. From heading to flowering is when wheat is susceptible to the wheat midge. Once flowering is complete wheat midge no longer attack the developing heads. Wheat midge is not a problem on barley. Flowering is also when wheat is most susceptible to scab infection. Barley flowers in the boot and is most susceptible to scab once heading occurs.

Monitoring heading in barley and wheat is extremely critical for effective control of either pest. The time required for both wheat and barley to go from mid boot to head emergence can range from three to five days. Obviously environmental conditions have a large impact on the developmental rate. Warm sunny days favor rapid development.

Growing degree days (GDD) can be used to predict when heading will occur . Both wheat and barley will require about 140 GDD to go from mid boot to heading. Wheat will require about 270 GDD to go from mid boot to completion of flowering. The NDSU NDAWN system ( http://ndawn.ndsu.nodak.edu/applications.html ), "click on Degree Days" and input location provides GDD for several regions around the state.

Even though the past several weeks have been quite cool early planted crops are developing rapidly. Development rate of barley at Fargo and Prosper this year has exceeded rates predicted using a GDD model.

The important point is, if you plan on controlling wheat midge or scab with a pesticide application, timing application with development is crucial to success. Knowing the stage of a crop now and when it will head or flower is useful when planning for the pesticide application.

Control of scab with a fungicide depends on correct timing of the application. The optimum time for fungicide application on wheat is at 25% flowering and after heading is complete in barley. Fungicides only provide protection against scab on tissue that receive a direct application. Even though fungicides like Tilt and Folicur are systemic they do not move throughout the plant but remain in a localized area near the site of absorption. Applications before heading is complete in both wheat and barley will compromise control of scab.

Dr. Duane R. Berglund
NDSU - Extension Agronomist
dberglun@ndsuext.nodak.edu


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