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PLANT SCIENCE INTEGRATED PEST MANAGEMENT IN WINTER CANOLA Introduction Integrated pest management or IPM uses all the tools available for controlling pests. The goal of using IPM is to achieve effective management of pests by using all of the tools that are available in the safest manner possible and in a way that enhances the economic viability of the farm. This includes chemical, cultural, mechanical and biological tools. It means not exclusively relying on one technique (e.g., using herbicides exclusively for weed control or tillage exclusively for disease control). The challenge for growers is to tie them all together for a complete program that maximizes the effectiveness of their pest management. Most of any canola IPM program takes place in the timeframe before seeding canola. One estimate of the resources needed for IPM shows that about 70% of the work comes in the seasons leading up to the seeding year. This is because the IPM approach requires forward planning, good knowledge of pest life cycles and is less oriented toward quick fixes. Canola is a management-responsive crop. Weather certainly plays a role in canola yields, but management makes the difference between average and above average yields. Canola should not be planted in the fall and ignored until harvest in June. Effective canola production requires hands-on involvement with the crop. Weed Management Weed management is a key component of any winter canola production system. In the southern Great Plains, winter canola is commonly grown in rotation with wheat, sorghum, and corn. Winter canola has difficulty competing with established weeds at emergence. Planting winter canola into a weed-free seedbed is essential. Weed control before seeding can be obtained with tillage, herbicides, or a combination of both methods. If planting winter canola after wheat, it is critical to control volunteer 1 cereals and cool-season winter annual grasses, but attention must be given to previous herbicide applications. Once plants are established, winter canola suppresses and out-competes most annual weeds if good management practices are followed. Spring weeds become a problem when canola stands are poor and areas of the field are left open. The most common mistake with canola weed control is waiting too long in the fall to control weeds. If volunteer wheat or grassy weeds are present, a herbicide should be applied by 4 to 6 weeks after seeding. Waiting for additional rain to germinate more weeds is usually a serious mistake. Winter canola varieties with the Roundup Ready (glyphosate tolerance) trait are currently available in the Great Plains region that have been developed for seeding in the fall and harvesting the following spring/summer. Roundup Ready winter canola varieties contain in-plant tolerance to Roundup agricultural herbicides, enabling growers to apply Roundup agricultural herbicides over the top of winter canola anytime from emergence throughout pre-bolting. Do not apply any herbicides once canola has entered the flowering growth stage. This system provides nonselective control of winter annual grasses and broadleaf weeds. The introduction of the Roundup Ready trait into winter canola varieties assures growers of unsurpassed weed control, crop safety and maximum yield potential. Roundup Ready winter canola will offer growers an important option as a rotational crop in traditional monoculture winter wheat production areas. Introducing crop rotation is an important factor in reducing pest cycles, including weed and disease problems Apply 1 to 1.5 pints of glyphosate per acre to Roundup-Ready canola from emergence through the 6-leaf stage of growth. Common weed pests to canola in the southern Great Plains include henbit, common chickweed, cheat grass, rescue grass, Japanese brome, jointed goatgrass, Italian rye, wild oat, volunteer wheat, several various mustards, flixweed, field pennycress and shepherdspurse. Canola is very sensitive to SU (Sulfonylurea) herbicides typically used in wheat production; therefore, all equipment must be thoroughly cleaned. Herbicides currently labeled for weed control in winter canola include Treflan, Stinger Select, Assure II, and Roundup Ultra Max II on Roundup Ready winter canola varieties. Diseases Diseases can attack canola at any stage of development. They can be soil borne, seed borne, or airborne. Only a few major diseases are likely to be of concern in the southern Great Plains. The occurrence of major diseases in the Great Plains is low, but will likely increase as winter canola acres increase. These include blackleg, Sclerotinia stem rot, powdery mildew, Alternaria black 2 spot, and aster yellows. Currently labeled fungicides include Abound, Curalan, Ronilan, Quadris, Endura, M-Pede, and Trilogy. Blackleg The blackleg fungus, Leptosphaeria maculans, is common worldwide and infects canola and related crops. Blackleg is the most serious threat to canola production. There are both mild and aggressive strains of the fungus. The blackleg fungus survives in infected seed, stubble, and on certain weeds. Long-distance spread of the disease occurs when over-summering spores, known as ascospores, are released from infested stubble. Ascospores can travel on air currents for many miles. On newly infected plants, a second spore type called conidia, are released from small, black, pimple-like structures known as pycnidia and are responsible for infecting neighboring plants and seed pods. Blackleg is introduced into new areas with infected seed. Infections from the mild strain usually occur much later in the season than those from the aggressive strain. Shallow white to gray lesions will form on the leaf or stem, but stems are usually not girdled. Only a few pycnidia are formed. In contrast, the aggressivee strain can infect early and produce leaf spots as well as stem lesions. Leaf spots are round to irregular in shape and are usually tan to buff in color with many pycnidia present. Stem infections are usually first observed as inconspicuous bluish lesions at a petiole scar near the soil line. Later, these lesions develop into an elongated, light brown sunken area with a purplish or black margin. The most important management method to control blackleg is excluding it from an area. This is accomplished by planting only disease-free, certified seed that has been treated with a fungicide that is effective against blackleg. Several see treatment products are registered for control of blackleg. Sclerotinia Stem Rot Sclerotinia stem rot is caused by the fungus Sclerotinia sclerotiorum. It is a serious problem in many areas throughout the world and is present in the Great Plains. Sclerotinia, also known as white mold, is most severe when warm wet conditions occur during the flowering period. A wide range of field crop hosts exists including dry beans, sunflowers, and soybeans. , 3 The first noticeable symptom of Sclerotinia stem rot is the presence of prematurely ripened plants. Under high moisture conditions, a white moldy growth may develop on the surface of stems and pods. Stems become bleached and tend to shred. Hard black structures known as sclerotia appear in or on he stems near the soil line as well as on infected pods. Sclerotia fall to the ground at harvest or when the stems break from lodging. During the spring, sclerotic near the soil surface germinate to produce small golf-tee shaped structures known as apothecia. Apothecia release ascopores during wet weather and periods of heavy dew. Spores are carried on air currents and infect flower petals. Infected petals fall on leaves or stems, which in turn become sites for the fungus to invade the plant. Symptoms of stem rot appear approximately 10-14 days after infection. Sclerotia remain dormant in the soil or 8 or more years and can be brought near the surface by cultivation. To reduce the incidence of conditions favorable for Sclerotinia infection, use lower plant densities to facilitate air movement, light infiltration, and drying. Alternaria Black Spot The fungal disease known as Alternaria black spot is widespread and is worse in wet years when seed yields can be significantly reduced by pods splitting or early death of the plants. All aboveground parts of the plant are susceptible. Black, brown, or gray spots on the leaves, stems, and pods are the most common symptoms. Often the spots are surrounded by a light green or yellow halo. Alternaria survives in infested crop residue, on infested seed, and on some alternative weed hosts. Infested seed either rots in the soil or produces infected seedlings. Wind-blown spores germinate, penetrate plant tissues, and cause lesions within a few days. These lesions produce more spores, which cause new infections on the same or neighboring plants. Downy Mildew The downy mildew fungus, Peronospora parasitica, causes yellow, irregular patches on upper leaf surfaces, giving the leaf a stippled appearance. Undersides of the leaves exhibit yellow patches with a white, granular 4 appearance. Sparse webs of fungal growth occasionally occur on stems and pods. Little damage is caused by spring infection, but occurrence of the disease on the fall reduces winter survival. Losses from this disease are rare to the Great Plains. Powdery Mildew The powdery mildew fungus, Erysiphe curciferarum, causes a white, dusty growth on aboveground plant parts. The disease is favored by moderate temperature, high humidity, excessive nitrogen fertilization, and excessive canopy density. In some production areas, powdery mildew results in serious yield losses. Aster Yellows Aster yellows is caused by a phytoplasm (a bacteria-like, plant pathogenic micro-organism). This organism has a wide host range and infects about 300 species of pants. Plants infected with aster yellows fail to set pods, producing bluegreen, sterile, hollow bladders in place of normal pods. Infected plants remain in a vegetative state during the entire growing season and remain greener and taller than uninfected plants at harvest. Aster yellows is spread from plant to plant by the aster leafhopper in the fall or spring. Aster yellows is common throughout the southern Great Plains. Insects Several insect species can damage winter canola. Because winter canola production in the region has been limited, these pests have not posed a large threat or problem. Starting in November and continuing through harvest, scouting should be done on the field to identify insect infestations. Canola pests can cause problems throughout the entire growing season. Some insects reduce yields by defoliating plants or attacking buds or seedpods. Other insects carry plant pathogens such as yellow asters. Some insects exist on canola and mustards only, whereas some are found in other cole crops and still others have an even wider host range. Labeled insecticides include Helix (seed treatment), Capture, Warrior T, Confirm, methyl and ethyl parathion as well as several others. Chemical pesticides should not be used as a substitute for good agronomic practices or as “preventative insurance” because it is rarely economically or environmentally justifiable. Some canola pest problems can be avoided by following good cultural practices planting at an optimal date and providing proper fertilization and weed control. 5 If spraying of insect pests is necessary, select insecticides carefully and consider options that would protect pollinating insects as well as predatory insects. Cultural practices such as crop rotation, killing volunteer canola, spraying ditches and fencerows for wild mustard, and incorporating plant residue into the soil are important means of insect control. As the number of acres of canola increases in the region, insect problems will likely increase, but so will the availability of management options. Insects causing serious problems in the southern Great Plains over the past 10 years include flea beetles, cabbage seedpod weevils, cabbage worms, alfalfa looper, diamond moth larvae, and aphids. Flea Beetles Generally, flea beetles are less of a problem with later plantings of winter canola. Flea beetles attack the cotyledons at emergence and the first true leaves of the seedlings producing pits or shot holes in leaves. Plants withstand 50 percent damage to the cotyledons without suffering any loss of yield potential. Overwintering flea beetles attack canola in the spring, but foliage is abundant and potential damage needs to be severe for treatment to be economical. Aphids Aphids have become the most important insect pest of canola in the southern Great Plains. The turnip and green peach aphids have been frequently observed to colonize fields during fall growth, survive mild winters, and increase to damaging levels during the early spring. Green peach and turnip aphids feed on the underside of canola leaves. Cabbage aphids colonize the terminal buds late in the season. Predatory and parasitic insects such as Ladybugs, contribute to aphid population control. During and following mild winters, aphid populations are sometimes high enough to cause significant stand decline and reduce seed production. The frequency of fall aphids and their potential for damage clearly suggest that a seed treatment should be considered as an important preventative management approach. Scouting is the best method to ensure effectiveness of seed treatments during the fall and determining if 6 treatment is necessary on emerging spring infestations. If populations are high from January through March, an insecticide treatment may be necessary. It is important to note that canola can recover from aphid infestations following timely insecticide applications. During flowering, cabbage aphids reproduce on the stalk inside the cluster of flower buds making it difficult for ladybugs to penetrate this cluster and eat aphids. Pushing the flower cluster open with your fingers is often necessary to find these aphids. Damage to flower buds and flowers prevents pod set and can reduce yields severely. Cabbage aphids can reproduce and spread quickly so it is important to scout your fields for these aphids several times during flowering. For every aphid per plant, 0.5 pound of seed yield is lost. Before flowering begins, canola can handle large numbers of aphids before a costly insecticide is justified. It is important to delay insecticide use until aphids approach economic levels. Diamondback Moth Larvae Diamondback moth larvae may cause serious problems in the southern Great Plains. Scouting canola fields for diamondback moth larvae should begin following emergence. In the fall, diamondback moth larvae and aphids arrive earlier if a seed treatment was not used. Diamondback moth larvae often attack larger canola that was seeded early. Diamondback moth larvae will overwinter and feed in the crown of canola plants. If infestations in the crown are high, they can be very destructive and stand loss may occur before spring. Larval infestations of the crown can easily be mistaken for winter kill. To scout for the larvae, pull up a few plants and tap the crowns on a piece of white paper. Root Maggots Root maggots can be a problem on canola during cold, wet growing seasons. Plants infestedd with maggots may easily lodge, have feeding damage inside the stem at the soil level, and are often infected with secondary fungi. 7 Cabbage Worms and Alfalfa Loopers Cabbage worms and alfalfa loopers defoliate canola plants in the spring and summer. Damage is usually minor and yield loss is minimal if the plants are healthy and growing vigorously. False Chinch Bugs False chinch bugs can occur in large numbers during mild, dry winters. Research shows that severe damage can occur if false chinch bugs infest racemes during bloom and early pod fill. It is suggested that fields should be treated if five to 10 false chinch bugs occur on flowering racemes, and if 10 to 20 false chinch bugs occur on racemes during early pod set. Fall infestations of false chinch bugs could cause stand losses. False chinch bugs are common in ripe fields of canola, but damage rarely occurs. Summary Using an integrated approach to managing weeds, diseases, and insects in canola needs to make sense from a financial standpoint as well as an environmental point of view. Although many of these pests have not posed a serious problem for canola producers in the region, as canola acres begin to increase it will be the responsibility of all growers to keep the problems under control. The first step is knowing what to look for, knowing the management options, and making knowledgeable decisions. Together, southern Great Plains canola producers can grow high quality, pest free winter canola. References Great Plains Canola Production Handbook, Kansas State University, March 2009 www.canola .okstate.edu/index.htm greatplainscanola.com/ www.canola-council.org/ www.uscanola.com/ www.northerncanola.com/ 8 SUGGESTED STUDENT ACTIVITIES FILL IN THE BLANK: Complete the following statements. Scouting Tools Insecticides Spraying Management Mechanical Disease Pesticides Chemical Identification 1. Integrated pest management uses all ____________ available for controlling pests. 2. The goal of using IPM is to achieve effective _______________ of pests by using all tools available in the safest manner possible. 3. IPM includes using chemical, cultural, _____________, and biological tools. 4. _____________ can attack winter canola at any stage of development. 5. _____________ should be done on winter canola fields to identify insect infestations. TRUE/FALSE: Circle the “T” if the statement is true or “F” if the statement is false. If false, correct the statement to make it true. T F 6. Weed management is not a key component of any winter canola production system. T F 7. Winter canola easily competes with established weeds at emergence. T F 8. Field history of previous herbicide use is not important. T F 9. Once established, winter canola suppresses and out-competes most annual weeds. T F 10. The most common mistake with canola weed control is waiting too long in the fall to control weeds. 9 MULTIPLE CHOICE: Write the letter corresponding to the correct answer in the blank provided. _____ 11. Which of the following is not a weed affecting winter canola? a) b) c) d) Wild Oats Henbit Duck Weed Volunteer Wheat _____ 12. Which of the following does not cause damage to canola plants? a) b) c) d) Lady bug Cabbage Worm Aphids Flea Beetle _____ 13. Which of the following insects causes damage to the buds during flowering? a) b) c) d) Turnip Aphids Flea Beetle Cabbage Aphids Alfalfa Looper _____ 14. The first noticeable symptom of Sclerotinia stem rot is the presence of a) b) c) d) Seed production Prematurely Ripened Plants Black Leaf Spots Golf-Tee Shaped Structures _____ 15. Canola is very sensitive to ________________ herbicides typically used in wheat production. a) b) c) d) Sulfonylurea Roundup Ready Generic Select 10 _____ 16. Do not apply any herbicide once canola has entered the __________ growing stage. a) b) c) d) _____ 17. Ripening Rosette Seeding Flowering Insects reduce yields in canola by a) b) c) d) Defoliation Attacking Flower Buds Carrying Plant Pathogens All of the Above _____18. ____________ is the most serious threat to canola production. a) Root Rot b) Blackleg c) Aster Yellows d) Downy Mildew _____ 19. _____________will overwinter and feed in the crown of canola plants. a) b) c) d) False Chinch Bugs Aphids Diamondback Moth Larvae Flea Beetles _____ 20. For every aphid per plant, ____ pound of seed yield is lost. a) b) c) d) 0.5 1.0 0.25 1.5 SHORT ANSWER/LISTING: Answer the following question or statement in the space provided. A local first time canola grower has noticed problems with some of the plants in each of his three winter canola fields. He knows that you have been learning about canola in your agricultural classes and has decided to hire you to help find out what is wrong with his crop. Use the following scenarios to determine what pest or pests are causing the grower problems in each field. 11 21. Field 1-The grower informs you that the field is in the flowering stage. He also mentions that the weather has been unusually warm and wet for this time of year. At first you notice a white moldy growth on the surface of the stems. Near the soil line on the stems of several plants in the area you notice hard black structures you think may be sclerotia. Upon further inspection you notice some prematurely ripened plants. 22. Field 2- The grower informs you that this canola was seeded earlier than the rest. After walking through the field you notice several shot holes in the leaves. You notice that the crowns appear to be damaged from winterkill. Given that this winter was rather harsh it makes sense. However, you decide to pull up a few plants and tap the crowns onto a white sheet of paper. After a few taps you notice that several worm like insects have fallen on the paper. 23. Field 3-Shallow white to grey lesions have formed on the leaves and stems of a few plants. You notice a few black-pimple like structures. As you scan the field you notice another potential problem. It appears that some foliage damage has occurred on some the neighboring plants. You decide to take a closer look at the underside of the leaves and locate groups of tiny insects feeding on the underside of the leaves. 12 ADVANCED ACTIVITIES 1. Have the students create their own sweep net to use out in the canola field. Supplies: 1 Pillow Case 2 Wire Hangers Duct Tape 1 piece of wood about 3 feet long for the handle Scissors for cutting the pillow case Step 1: Turn your 2 wire hangers into similar circles. Then tape them together in several places, leaving the open end opened. Step 2: Now cut two holes on either side of the seam where there are two layers of pillow. Then put the wire through the pillow. Straighten out the ends sticking out for the handle. Step 3: Now heavily tape the four wire pieces hanging out of the pillow to your handle. Make sure its sturdy because it’s used to sweep through high grasses, alfalfa, clover, and canola. 2. Create an insect collection. Collect and identify insects common to canola and your area. List the insects you collect as pests or beneficial insects. Combine all individual collections to create a large classroom display. 3. Interview winter canola farmers in your area and develop a winter canola IPM journal. Include the techniques they use to control pests, any success stories or barriers they have encountered, and any other valuable information. Share your stories with the class. 4. Photograph or collect pictures of the different pests (weed, disease, and insect) you encounter while out in the field. Create a collage of your findings. Develop an IPM program for the local participating farmer. 13 SUGGESTED STUDENT ACTIVITIES (KEY) FILL IN THE BLANK: 1. 2. 3. 4. 5. TOOLS MANAGEMENT MECHANICAL DISEASE SCOUTING TRUE/FALSE 6. T 7. F-HAS DIFFICULTY COMPETING 8. F-IS VERY IMPORTANT 9. T 10. T MULTIPLE CHOICE 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. C A C B A D D B C A SHORT ANSWER/LISTING 21. SCLEROTINIA STEM ROT 22. DIAMONDBACK MOTH LARVAE 23. BLACKLEG; TURNIP APHIDS 14 15