Module 3 - Insect Pests I

Lady bug larvae dining on aphids. Image Source: Benimoto.

ANNOUNCEMENTS

INTRODUCTION
For many years horticulture students studying pest management would learn pest identification and control, usually synthetic chemical control. However, over the past decades things have begun to change and integrated pest management principles (some of which have been known for centuries) are becoming the focus of such courses.

This week you have a rather large reading assignment, but don't despair. I don't want you to memorize all these pests. Instead I want you to notice how different life cycles, climate, plant species distribution, and management practices impact plant damage and economic loss. You will have a chance to choose a pest during this weeks assignment and focus on the detail.

After this week's assignment and next's, you should develop a good feel for how Integrated Pest Management Practices not only help stop economic losses in horticulture, but reduce cost and protect the environment.

Beyond environmental protection these practices also maximize the ability of the local ecological resources to maintain and repair damage. For example, a broad spectrum pesticide will control aphids on succulent herbaceous plant materials, but will also kill beneficial organisms such as lady bug larvae and adults that can help with biological control. The successful horticulturalist will target control measures to reduce pest problems while maintaining beneficial populations.

In most cases invertebrate (insects, mites, snails, and slugs) pests damage horticultural crops by feeding on them. The pests are after the energy that plants are able to produce directly using the sun's energy. In addition to energy, plants are also good sources of nutrients for pests. You should also remember from last week that in many cases plants can tolerate quite a bit of damage from pests and what we seek to due as pest managers is keep that damage below the economic threshold using integrated pest management.

Brown Lacewing. An example of a beneficial insect that when in its larval stage is a great bio-control for aphids and other pests. Image Source: kidcadaver

LEARNING OBJECTIVES

• Explain the relative proportion of invertebrates that are pests, innocuous visitors, and beneficials
• Differentiate between different types of damage produced by insects
• Discuss differences in insect life cycles
• Explain the concept of economic threshold
• Discuss the importance of monitoring insect populations and diagnosing problems
• Compare and contrast the different management practices for insect pests
• List examples of natural enemies of insect pests
  

TERMS TO KNOW

• chewing mouthparts, sucking/piercing mouthparts
• invertebrate, vertebrate
• life cycle, complete metamorphosis, incomplete metamorphosis
• larva, caterpillar, chrysalis, adult
• egg, nymph, adult
• branch beating, sticky traps, sticky cards, pheromone traps, pitfall traps
• time counts, honeydew monitoring, frass dropping, degree-day monitoring
• Biological Control, importation, conservation, enhancement, augmentation
• pesticide types, acetaldehyde, botanical, carbamate, chlorinated hydrocarbon, contact
• insect growth regulator, inorganic, microbial, organophosphate, pyrethroid
  

READING AND MULTIMEDIA ASSIGNMENTS

• Chapter 4. Insects, Mites, and Snails and Slugs. pages 49-196. Focus on pages 49-71.
  
• Familiarize yourself with the Biological Control Information Center (NC State)
• International Concern. Watch YouTube video on Red Palm Weevil.
• International News Story. Watch YouTube video on Spiraling Whitefly
  
• Potential BioControl of Aphid. Watch YouTube video on Aphidius, an aphid endoparasitoid
• EXTRA: General Introduction to Systems Thinking. This is the wave of the future.
  

STUDY QUESTIONS (Answer all questions in complete sentences.

1. Compare the damage symptoms caused by insects with chewing mouthparts (ex. Tobacco Hornworm) with symptoms caused by an insect with sucking piercing mouthparts (ex. aphid). (5 pts)
   
   
2. What is the reward for an insect consuming a plant? Eating the plant takes energy and time what does the pest get out of it? (5 pts)
   
   
3. Compare and contrast complete metamorphosis and incomplete metamorphosis life cycles in insect pests. Provide two economically important pest examples for each type of life cycle. (10 pts)
   
   
4. Briefly describe 5 different types of insect monitoring methods. List at least one specific insect species that is monitored with each type. (10 pts)
   
   
5. Pest Degree Days can be an important tool to measure insect population growth. Go to the University of Illinois Warm Pest Degree Day Web tool. Choose 45.5 for the Bean Leaf Beetle and using the web-based tool determine the current degree day total and how many generations the insect has had this summer. Describe the steps you went through to determine your answer (5 pts).
   
   
6. Describe what can happen when a method is applied to control target Pest A and kills the natural enemies of Pest B (not currently a problem). A good place to start is figure 4-3 in the textbook. Has this method of control been a problem in the past (10 pts).
   
   
7. You run a landscape maintenance company. Why might the whitefly and psyllid management practice in Figure 4-5 0f your text require you to educate your clients before implementing. (10 pts).
   
   
8. Explain how a parasitic wasp can be used to control aphids. Describe the life cycle of the wasp and aphid and how the interaction of the two leads to population control of each species. (10 pts).
   
   
9. Briefly describe 5 natural insect predators and at least one pest each can help control (5 pts).
   
   
10. What are some types of pesticides that may only be available to professionally licensed applicators? List 5 different classes of pesticides. (5 pts)
    
    
11. Explain in detail how the Bacillus thuringiensis toxin can control Lepidopteran pests. (5 pts)
    
    
12. Discussion: Bt is commonly used by organic growers as a form of pest control. The gene that encodes production of the toxin is one of the most common Genetic Modifications made to crop plants for pest protection (Ex. Bt-corn). Why would organic growers voice concern over the tool they use for pest control being used in GMO crops. Hint: This one may require a little research on your part. (20 pts).
    

EXTRA CREDIT
In greenhouse pest control you will see both yellow and blue sticky cards used for insect monitoring? What pest does the blue sticky card target? (+2)

Two thousand Galerucella beetles released into Cutler Park, as part of the Purple Loosestrife Biocontrol Project. We will cover weed control in a later chapter. Image Source and Description: urtica