Number 272 November 19, 2010

Transcription

1 Number 272 November 19, Early-season plant growth of canola this fall 1 2. Wheat conditions in western Kansas 5 3. Red Flag Warning in Central Plains 7 4. Comparative Vegetation Condition Report: November Most recent K-State Agronomy webinar Early-season plant growth of canola this fall A fall canola field tour was held November 10 and 11, starting near Marquette and ending south of Kiowa. Overall, the canola appeared healthy and was not stressed by the dry conditions that Kansas has experienced so far this fall. Plant growth was very favorable at all six locations. By mid-november, the plants had developed a large crown and the kind of extensive root system needed to store carbohydrates used during the winter months. As temperatures continue to drop over the next couple months, keep the following points in mind. Winter hardening Canola is very tolerant to freeze damage when 3 to 4 true leaves are growing rapidly. Winter survival is increased when 6 to 8 leaves are fully formed and the plants are 8 to 10 inches tall. Smaller plants can survive the winter; however, much will depend upon winter temperatures, snow cover, and available soil moisture. Plants that are larger than 10 inches tend to use the majority of soil moisture and nutrients available in the fall and are more prone to winterkill. This is likely due to an elevated, exposed crown. Temperatures recently dropped below 30 degrees F across the area and the plants are beginning to show signs of physical change. At this point in time, canola is beginning to winter harden. As a result of colder temperatures and shorter day length, plant growth slows and many visible physical changes take place. Several days of near-freezing temperatures set off a chain of plant gene activities to produce or degrade proteins to protect cells. Plants produce smaller cells having a higher concentration of soluble substances that are more resistant to frost. Developed leaves will discolor to white, brown, purple, or red and then die. However, as long as the crown remains green and firm and does not die, the plant will resume rapid growth in the spring. 1

2 Insect pests Unlike wheat and other cereal grains, whose growing point is protected beneath the soil during early development, the growing point of canola is above the soil after emergence. Thus, canola is more susceptible than cereals to environmental hazards. Canola is especially vulnerable to chewing insects because plants will die if the aboveground portion is completely eaten. Common insect pests at early establishment include grasshoppers, turnip and green peach aphids, and diamondback moth larvae. Grasshoppers are the most common pest at emergence and tend to infest field edges more than the centers. If pressure is high, grasshoppers can quickly devour canola plants on field edges. The most commonly identified insect pest in the rosette stage is diamondback moth larvae. Scouting for the larvae should begin following emergence. Freshly hatched larvae are light green with a green head and become darker with time. The larvae have four instars of development and are ½ inch long when fully grown, and all life stages may be found in the field at one time. Diamondback moth larvae on leaf underside. Photos by Mike Stamm, K-State and OSU Canola Breeder. Depending on temperature, the larvae can complete one full life cycle in about 32 days. The caterpillar will pupate in a loose, silken cocoon attached to the plant. When disturbed, the larvae will thrash aggressively and drop on a silk strand. The larvae are the most damaging stage and begin with leaf feeding. As the larvae grow, they chew small windowpanes on leaves. Eventually they will chew entire leaves leaving only the veins. 2

3 Excessive diamondback moth larvae feeding in winter canola. Notice only the veins remaining on some leaves. Also, as temperatures get colder, the larvae will move to the crown. The larvae are more protected here and freezing temperatures will not necessarily kill them. If the infestation is high enough and feeding continues in the crown, plants can be killed. In the spring, plants that appear to have been lost to winter temperatures may in fact have been lost to larval feeding. The emergence of malformed leaves in the fall may be an indication that larvae are present. Spraying with a labeled pyrethroid insecticide and using a ground rig with plenty of water will control these insects in the crown. Applications are effective even as temperatures cool in the fall. The best preventive measure is to scout for diamondback moth larvae when holes are observed in developing leaves. Plants should be pulled from a 1-square foot area. Beat the collected plants into a white bucket or piece of paper and count the larvae. Take counts in at least 5 locations to get an average number of larvae per square foot. Unfortunately, economic thresholds for the region have not been developed for diamondback moth larvae feeding at the rosette stage. However, if populations exceed larvae per square foot, then an insecticide application should be strongly considered. Weed pressure Canola has difficulty competing with established weeds at emergence; however, once established, canola outcompetes most winter annual weed species. The best form of weed control is a fully developed canola canopy. Roundup Ready varieties can be sprayed from emergence to canopy closure in the fall and prior to bolting in the spring for non-selective control of grassy and broadleaf weeds. Grass control products can be sprayed from emergence to before bolting to control volunteer cereals and other grassy weed species in all canola varieties. 3

4 Nutrient deficiency and ph Nitrogen deficiency likely will appear in the fall if no nitrogen is applied prior to planting. Deficient plants will be stunted with yellowing of the lower, older leaves. Research at K-State has shown that canola has better winter survival when 40 to 80 lbs of nitrogen per acre is applied prior to planting. The onset of cold temperatures often brings out observable nutrient deficiencies if inadequate fertility exists. Canola field suffering from poor fall fertility. Notice the green patches where fertility is adequate. Plants lacking proper nitrogen, phosphorous, or sulfur fertility will appear intensely purple, red, or yellow; severely stunted; and suffer leaf loss. A closer look at the plants from the field in the photo above reveals discoloration, stunting, and leaf loss. Window panes also indicate diamondback moth larvae feeding. 4

5 Remember that natural purpling and reddening occur as a result of colder temperatures this time of year. If adequate fertilizer was applied and soil tests were taken, then one can be more confident that the discoloration is due to cold weather. If one didn t soil sample and shorted fertilizer or didn t apply fertilizer at all, then inadequate fertility is more likely to be the issue. The most reliable way to tell if you have fertility issues is with soil and leaf tissue sampling. Low-pH symptoms in canola will be seen in the fall as crinkled, cupped, or strapped leaves. Micronutrient deficiencies are more likely in high-ph soils because most micronutrients are less available to plants at high ph. For more information about canola seedling establishment, consult the Great Plains Canola Production Handbook, MF-2734: -- Mike Stamm, Canola Breeder, K-State and Oklahoma State University mjstamm@ksu.edu -- Kraig Roozeboom, Cropping Systems and Crop Production Specialist kraig@ksu.edu 2. Wheat conditions in western Kansas In areas west of U.S. Hwy 283, many wheat fields are thin or poorly developed. There are some fields in relatively good condition, especially where wheat was planted on fallow ground. But most of the better looking wheat is in areas east of Hwy 283. The photos below were taken on Nov. 15 in Lane County, and show fields with poor stands and poor plant development. If this area receives some rain yet this fall, the wheat would still have time to develop a better root system and withstand winter stresses better. In its current condition, this field is going to be susceptible to blowing this winter and next spring. 5

6 This field in Lane County has a very poor wheat stand due to dry conditions, and will be susceptible to blowing this winter and next spring if it remains dry. Photos by Jim Shroyer, K-State Research and Extension. The root system of the plants in the field above is poorly developed, making those plants that have emerged susceptible to stress. -- Jim Shroyer, Extension Agronomy State Leader jshroyer@ksu.edu 6

7 3. Red Flag Warning in Central Plains Something relatively new and different appears likely to be a frequent feature in central High Plains weather forecasts this winter: a Red Flag Warning. A Red Flag Warning is a step above the Extreme category on the old Range Fire Danger index. And, for the first time in a number of years, Kansas appears to be primed to hear it during wintertime, too. The National Weather Service now reports overall U.S. wildfire conditions, rather than separating the risks for forests and grasslands. Figure 1. NWS warnings for November 19, 2010, including Red Flag warnings in New Mexico and Florida. What warrants a Red Flag varies from area to area. In general, the criteria are a dangerous mix of wind, low relative humidity, moderate to warm temperatures (usually), and available fuel. No matter the location, however, a Red Flag always means the same: Fire-promoting conditions have reached or will soon be at the critical level. The danger is real, and it s high. Any spark could create a devastating fire with explosive growth potential. Unfortunately, Kansas is leaving a dry fall and moving into our normally drier winter months. Added to that, the state has a much bigger supply of natural fuels, due to beneficial rains over the last two years. Also, most producers are now leaving stubble on harvested fields to conserve soil and moisture. A number of landowners are no longer burning pastures as often as recommended. As a result, trashy shrubs and trees are rapidly become part of the state s burnable mix. To see the Kansas drought data, forecasts and fire-weather links, see: -- Mary Knapp, State Climatologist mknapp@ksu.edu (Adapted from a story by Kathleen Ward, Communications, kward@ksu.edu) 4. Comparative Vegetation Condition Report: November 2 14 K-State s Ecology and Agriculture Spatial Analysis Laboratory (EASAL) produces weekly Vegetation Condition Report maps. These maps can be a valuable tool for making crop selection and marketing decisions. 7

8 The maps below show the current vegetation conditions in Kansas, the Corn Belt, and the continental U.S: Map 1. The Vegetation Condition Report for Kansas for November 2 14, from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows clearly the region of moderate drought in west central Kansas. Moisture this week would not be reflected in this map, although the snow from November 13 can be seen in parts of northeast Kansas, particularly in Washington, Marshall, and northern Pottawatomie counties. 8

9 Map 2. Compared to last year at this time, this year s Vegetation Condition Report for November 2 14, from K- State s Ecology and Agriculture Spatial Analysis Laboratory shows the impact of the milder-than-normal weather this season. This has allowed longer period of vegetative production. Note also the area of southeast Kansas were production this year is behind last year. This region corresponds to an area that shows as abnormally dry on the latest Drought Monitor. 9

10 Map 3. The Vegetation Condition Report for the Corn Belt for November 2 14, from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows much of the region is dormant for the year. The exceptions are the southwestern corner of Missouri and the eastern portions of Ohio. Parts of Minnesota, Wisconsin, northwestern Iowa, western Nebraska, and western Montana show signs of snow and cloud cover from the November 13 storm. 10

11 Map 4. The Vegetation Condition Report for the U.S. for November 2 14, from K-State s Ecology and Agriculture Spatial Analysis Laboratory shows the beginning snowpack in the northern Rockies and Intermountain West. Some snow is also apparent in upstate New York, Vermont, and Maine. The small white area in the Texas Panhandle is due to cloud cover during this period, not snow. -- Mary Knapp, State Climatologist mknapp@ksu.edu -- Kevin Price, Agronomy and Geography, Remote Sensing, Natural Resources, GIS kpprice@ksu.edu -- Nan An, Graduate Research Assistant, Ecology & Agriculture Spatial Analysis Laboratory (EASAL) nanan@ksu.edu 5. Most recent K-State Agronomy webinar K-State Agronomy offers a regular series of webinars on various topics throughout the year. These webinars are free and available to the public. The most recent webinar: Title: Weed Control in Wheat Presenter: Dallas Peterson, Weed Management Specialist 11

12 Description: An overview of potential broadleaf and grassy weeds in wheat, the impact of weeds on wheat production, and control options. Link: -- Brian Olson, Northwest Area Crops and Soils Specialist (Note to readers: There will be no Agronomy e-update next week due to the Thanksgiving holiday and short work week. Steve Watson, Agronomy e-update Editor) These e-updates are a regular weekly item from K-State Extension Agronomy and Steve Watson, Agronomy e- Update Editor. All of the Research and Extension faculty in Agronomy will be involved as sources from time to time. If you have any questions or suggestions for topics you'd like to have us address in this weekly update, contact Steve Watson, swatson@ksu.edu, or Jim Shroyer, Research and Extension Crop Production Specialist and State Extension Agronomy Leader jshroyer@ksu.edu 12