Whole Manual - Michigan State University: Integrated Pest ...

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Pathogen type: bacterium (Xanthomonas campestris pv. campestris) Disease symptoms: Infected seedlings turn yellow and die. Symptoms on older plants include yellow, wedgeshaped areas at the leaf margins. The affected areas expand toward the center of the leaf, turn brown, and die. The veins become discolored at the leaf margins and the discoloration extends toward the base of the plant. The head is stunted, and symptoms are frequently more severe on one side of the head. Environmental conditions favoring disease: The optimum temperature for disease development is 80 to 86 degrees F, and either rain or persistent dew is required. The bacteria overwinter on and in seed and debris from diseased plants left in the field. They spread by splashing water, on wind blown leaves, or by handling infected plants. CLUBROOT ALTERNARIA LEAF SPOT Clubroot causes wilting (top) and enlarged plant roots (bottom). Alternaria can also cause head rot in cabbage. Pathogen type: fungus (Alternaria spp.) Disease symptoms: Spots with dark, concentric circles form on lower leaves. In moist weather, a dusty fungal growth occurs on the spots. Environmental conditions favoring disease: Disease development is favored by cool, wet weather. The fungus overwinters in seed and diseased crop residues. Pathogen type: fungus (Plasmodiophora brassicae) Disease symptoms: Infected plants yellow and wilt. The roots are enlarged and “clubbed.” Young plants can be killed; mature plants will not produce a marketable crop. Environmental conditions favoring disease: Clubroot thrives in cool, wet soils. This soilborne fungus can remain viable indefinitely in the soil. DOWNY MILDEW Plants infected with downy mildew can have a white, fuzzy appearance. Vegetable Crop <strong>Pest</strong> Management 65 Chapter 7
Pathogen type: fungus (Peronospora parasitica) Disease symptoms: Downy mildew begins as small, yellow spots on the leaves, which later turn brown. White fungal growth appears on the lower leaf surface during periods of moist weather. Environmental conditions favoring disease: Downy mildew is worse in cool, wet weather in spring and fall. Plants infected with downy mildew are often more susceptible to secondary pathogens, such as soft rot bacteria. The fungus overwinters on seed and in cruciferous weeds (for example, Shepherd’s purse and mustard). CORN SMUT Control strategies for diseases of cole crops: ■ Plant disease-free or certified seed and transplants. ■ Avoid dipping transplants in water before planting to reduce the spread of disease. ■ Practice at least a three-year crop rotation out of cole crops for most diseases. ■ Plant disease-resistant cultivars. ■ Maintain good weed control. DISEASES OF CORN COMMON RUST Ear of corn infected with corn smut. Pathogen type: fungus (Ustilago zeae) Disease symptoms: Galls are formed on aboveground young growing parts of the plant, typically the ear, tassel, leaves, and stalk. The young galls have a greenish white covering, which turns silver-gray with age. Mature galls are full of black, powdery fungal spores that disperse into the air when the gall ruptures. Blisters on corn leaf infected with common rust. Pathogen type: fungus (Puccinia sorghi) Disease symptoms: Oval or elongated, brick-red blisters appear on the leaf surfaces, husks, leaf sheaths, and stalks. Severe infections result in leaf death. Killing the leaves of young plants reduces plant vigor and yield. Environmental conditions favoring disease: The fungal spores are wind dispersed every year, usually late in the season. Rust develops under cool temperatures (60 to 73 degrees F) and high humidity and bright days. Control strategies: Planting resistant hybrids is the best way to control rust. Fungicides are used, especially in seed corn. Environmental conditions favoring disease: Corn smut is most prevalent under dry conditions and temperatures of 78 to 94 degrees F and on stressed plants. Fungal spores overwinter in the soil and prefer high levels of soil nitrogen. Control strategies: ■ The best management strategy is to plant corn hybrids that have some level of resistance. ■ Rotating crops and burying crop residue may be helpful. Chapter 7 66 Vegetable Crop <strong>Pest</strong> Management
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Vegetable Crop Pest Management A Gu
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Acknowledgements We would like to e
Page 5 and 6:
General Vegetable Insect Pests . .
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vi Vegetable Crop Pest Management
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accurately written records of field
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Ladybird beetle adults and larvae c
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Phytotoxicity—when a pesticide da
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19. How are tolerance and pesticide
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Always: ■ Select pesticides label
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■ Select the least hazardous pest
Page 21 and 22: C 2 H A P TER Review Questions Chap
Page 23 and 24: 16 Vegetable Crop Pest Management
Page 25 and 26: Hydraulic Sprayers Water is most of
Page 27 and 28: Nozzles Nozzles are important to co
Page 31 and 32: 24. Granular applicators are design
Page 33 and 34: will not double the flow rate - you
Page 35 and 36: 6. The average output of the nozzle
Page 39 and 40: 32 Vegetable Crop Pest Management
Page 41 and 42: stages. Larvae and adults are often
Page 43 and 44: down into the crown and eventually
Page 45 and 46: INSECT PESTS OF CUCURBITS (CUCUMBER
Page 47 and 48: CABBAGE LOOPER (Trichoplusia ni) Ca
Page 49 and 50: Damage: First-generation European c
Page 51 and 52: ■ Natural enemies such as ground
Page 53 and 54: educed yields. They feed on a wide
Page 55 and 56: C 5 H A P TER Write the answers to
Page 57 and 58: Chapter 5 50 Vegetable Crop Pest Ma
Page 59 and 60: BIENNIAL Biennials complete their g
Page 61 and 62: Advantages of preemergence applicat
Page 63 and 64: 9. Which of the following is true o
Page 65 and 66: BACTERIA Bacteria are very small, m
Page 67 and 68: DISEASE MANAGEMENT Options for dise
Page 69 and 70: Outbreaks occur first as isolated p
Page 71: FUSARIUM YELLOWS Environmental cond
Page 75 and 76: MOSAIC VIRUSES POWDERY MILDEW Cucum
Page 77 and 78: DOWNY MILDEW SMUT Severe downy mild
Page 79 and 80: humidity. The disease is more likel
Page 81 and 82: BLACK SCURF/STEM CANKER DISEASES OF
Page 83 and 84: ■ Remove or destroy crop residue
Page 87 and 88: 26-29. Match the following cucurbit
Page 89 and 90: PLANT-PARASITIC NEMATODES Plant-par
Page 91 and 92: depending on age. Males are worm-li
Page 93 and 94: Needle nematode feeding can result
Page 95 and 96: 7. Which female nematodes, of those
Page 97 and 98: Chapter 4 Calibration (1) Calibrati
Page 99 and 100: APPENDIX C GLOSSARY ABDOMINAL PROLE
Page 101 and 102: DERMAL TOXICITY—The ability of a
Page 103 and 104: MESOTHORAX—The second segment of
Page 105 and 106: STOMACH POISON—A pesticide that m
Page 107 and 108: Notes 100
Page 109: MICHIGAN STATE U N I V E R S I T Y
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Whole Manual - Michigan State University: Integrated Pest ...

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