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Integrated Pest Management (Part 2)

Discussion in 'General Gardening' started by w_r_ranch, Mar 27, 2014.

  1. w_r_ranch

    w_r_ranch Master Gardener Moderator

    South Central Texas
    Planting Zone:
    Let's talk a little about the 4 steps that form the foundation of an IPM program that we touched on yesterday:

    Set Action Threshold

    We know insect-free gardens do not exist. As gardeners, we should use the least amount of pesticides needed to control insects without jeopardizing the integrity of our fruit or vegetable crop. When we see insects in the garden, we need to decide on a level of damage that we are willing to 'live with' prior to applying insecticides. So when do we decide it is time to manage 'a 'pest'??? There are various criteria used to answer this question. If the pest is life-threatening to the plant, mere presence may dictate management action. However, mere presence does not always dictate action. For example, many deciduous trees can take up to 25% defoliation before plant health is seriously impaired, unless they are otherwise stressed.

    In agriculture, pest managers often use 'economic threshold' (population level at which serious damage or yield losses occur) to signal that action must be taken. This threshold is not 'set in stone'... each individual gardener has to decide the level of 'acceptable loses' for themselves. As an example, lets say a person has 6 tomato plants & half of his plants are being destroyed, that would be an unacceptable loss... while another person has 100 plants & 3 are destroyed, that would be an acceptable loss. Here are a few more thing to ponder on this subject:

    Before insecticides are sprayed in the garden, we first look at where the damage is occurring. For example, if all insect damage is located on the foliage and the fruit is the portion of the plant we are going to eat, we probably won’t apply an insecticide at all. An excellent example of this is flea beetle damage to eggplants. The flea beetles feed on the leaves, leaving small holes, but they do not damage the eggplant itself. Therefore, we would not spray.

    Another example of foliage damage is leaf miner on citrus trees. Unless the damage to the foliage is so intense that it actually interferes with photosynthesis (causing more than 25% leaf drop) we will not use an insecticide. Leaf miners can move into the fruit causing a cosmetic damage to the outside of the fruit but the inside is still edible. Leaf miner damage to trees in most cases is so little, insecticidal usage is not warranted.

    On the other hand, if the insect was damaging the foliage of plants such as mustard greens, cabbage or lettuce, we would need to establish a level of tolerance at which we would spray insecticide, since the insect is damaging the edible portion of the plant.

    If the insect is damaging the fruit of the plant, such as stink bugs on tomatoes, we would need to develop a level of tolerance (economic threshold) before resorting to chemical spray.

    Monitor & Identify Pests
    As stated yesterday, Not all insects, weeds, and other living organisms require control. Many organisms are innocuous & some are even beneficial. IPM programs work to monitor for pests & identify them accurately, so that appropriate control decisions can be made in conjunction with action thresholds. This monitoring & identification removes the possibility that pesticides will be used when they are not really needed or that the wrong kind/form of pesticide will be used.

    There are many methods of monitoring. The key ones are plant examination, pheromone traps, sticky colored traps & pitfall traps. Monitoring can be as simple as timely close observations (walking through you garden with a magnifying lens). Observing aphid buildup or disease symptoms & signs on susceptible plants might require repeated examinations. Weather can also be instrumental in determining when to monitor. Early season warming can trigger early emergence of pests & earlier damage. Monitoring is critical to the success of an IPM effort.

    Before recommending any type of treatment, particularly a pesticide, it is essential to identify the problem correctly. If a pest population is causing a problem, then it should be identified (to species if possible) so that information about it can be researched. The key to planning a control program that works is knowing the life cycle of the pest & the conditions that favor its development.

    When learning about the pest helps to:
    • Know what to look for & where to look to keep an eye on the problem
    • Apply controls at the right time & place (its life cycle) to be most effective .
    • Plan an effective prevention/control program

    When pest problems are identified based on plant damage, careful identification is essential because similar looking damage can have different causes. For example, curled leaves from a virus disease look much like damage caused by sucking insects. Spraying an insecticide would be useless if the plant symptoms were caused by a disease. Also, damage caused by nutrient deficiencies or poor growing conditions may be mistaken for signs that pests are present.

    Identification is also important when gardeners have caught an insect they associate with plant damage. Often it turns out to be to a beneficial species that was feeding on the pests that caused the damage, such as assassin bugs. Identify Pests By:
    • Comparing specimens with pictures in reference books or on the internet
    • Recognizing characteristics of damage or of the excrement & castings left by pests
    • Consulting experts for assistance (state/County Extension Offices)
    The long-term goal of managing any pest problem should be prevention. This includes:
    • Planting pest/disease resistant plant varieties
    • Using barriers to keep pests out (if feasible)
    • Floating row covers
    • Sanitation
    • Removing food and water sources & eliminating garden debris used nesting and over-wintering sites.
    • Checking new plants (before buying) to make sure they are not diseased or infested with insects.
    • Picking up & destroying early dropped fruits, which are often infested by insects & fungus.
    • Cultural practices that ensure healthy plants
    • Select plants that are adapted to the conditions where they are to grow (soil type & drainage, shade or sun, exposure to wind or salt spray).
    • Use proper watering, fertilizing & soil amendments.
    • Changes to the environment to make it less hospitable to pests.
    Ideally, controls are only called for where preventive measures have not been sufficient. Generally, controls for home & garden pests fit into four main types:
    1. Physical Controls
    2. Mechanical Controls
    3. Biological Controls
    4. Chemical Controls
    These controls may be used separately or in combination for greater effectiveness. When deciding which controls to choose, consider those that are:
    • Least hazardous to human health
    • Least toxic to other non-target organisms (for example, pets, fish, and beneficial insects)
    • Least damaging to the environment
    • Most likely to provide a long-term solution
    • Most likely to be used correctly by the gardener
    • Most cost-effective in the long run to the customer

    Physical Controls include mulches, sticky insect traps & rat/mice traps, as well as using hoeing or hand pulling to control weeds. Sticky traps for insects can be used both as a monitoring tool and as a physical control. It is possible to control whiteflies if enough yellow sticky traps are placed among the plants.

    Mechanical Controls are machines or equipment used to control pests. These include vacuum cleaners, ultra-violet light traps & cultivators for weeds like line trimmers/weed-wackers.

    Biological Controls are the use of living organisms that are the natural enemies of pests to control pest populations. Many of these natural enemies are beneficial insects and mites such as ladybugs, praying mantis & nematodes. Even micro-organisms, such as beneficial soil fungi & bacteria.

    Chemical Controls include any insecticide, herbicide & fungicide are any substances that are used to kill, control, repel or manage insects, rodents, fungi, weeds or other living things that are considered to be pests. They vary greatly in their toxicity & the way they work (more on this later).

    When pesticides are necessary in a pest management program, the gardener use the most appropriate pesticide & method of application. They should only be considered after careful assessment indicates their use is required. 'Preferred' pesticides are those that:
    • Present the least short and long-term health risk to humans.
    • Have the lowest environmental impact, due to the short residual effects and/or their specificity to target pests.
    RLwhaler, Mike and whistech like this.
  2. Rahab222

    Rahab222 Well-Known Member

    Planting Zone:
    You give really good information. So, in determining whether or not to treat whatever is eating holes in my potato plant's leaves - since the potatoes are beneath the ground and the damage is to the leaves, should I even bother to treat whatever is munching holes in my potato plants leaves or just not worry about it since the spuds are beneath the ground? There are also holes on my peppers. Photos posted below. Thanks!

    PotHole.jpg PepperHole.jpg
  3. w_r_ranch

    w_r_ranch Master Gardener Moderator

    South Central Texas
    Planting Zone:
    I would inspect the undersides of the leaves to see if there are any insects present or any egg cases (use a magnifying glass if necessary). If so, post a good picture so it can be identified. Thus far, you don't have significant damage that would threaten the health of the plant, but keep a close eye on it.

    If I had to guess, it sounds as though your potatoes have Colorado potato beetles. This beetle has a rounded light yellowish shell marked with black stripes. The adult Colorado potato beetle is resistant to most chemical controls (it's better to prevent infestations by using appropriate physical & cultural practices), however the Colorado potato beetle larvae can be killed by using a product containing Bt (Bacillus thuringiensis). Spray Bt when the larvae (caterpillar stage) are just starting to develop. Google Bt to learn more.

    You must understand a pest's life-cycle to control it. Learn about the life-cycle of the Colorado potato beetle here.

  4. whistech

    whistech Well-Known Member

    Spring, Texas
    Planting Zone:
    Mr. Ranch, thank you for sharing your knowledge with us.
    w_r_ranch likes this.
  5. majorcatfish

    majorcatfish Well-Known Member

    north carolina
    Planting Zone:
    Colorado potato beetle is a very destructive bug.....
  6. Rahab222

    Rahab222 Well-Known Member

    Planting Zone:
    W. R. Ranch;

    Thanks again for the information. I really like this board because I get quick, clear, concise answers to my questions. I was away from the house today so I couldn't work in the garden, but I did pull in and get me some treatment methods suggested on this board for my current pest issues. I think I'll dig around in the potato leaves before I hill everything again and see if I see anything that looks like the picture of the Colo. Potato Beetle you posted. So far, only the leaves in one of my three potato boxes have these holes. This box is quite a distance from the other two boxes. I think I'll take your suggestion to monitor the situation for a few days before treating these with anything to see how much damage they do.
    w_r_ranch likes this.
  7. DonaKen

    DonaKen Member

    Planting Zone:
    Good stuff.....yes that's the #x!% culprit...thanks for the info and link.

    w_r_ranch likes this.

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