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IPM and Biological Control

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Integrated Pest Management

Components of an IPM and biological control program

Getting started in Bio Control

Implementing biological control - some questions to ask

Benefits of Biological Control

Strategies of Introducing Bio Control Agents

Method of releasing biocontrol agents

Some difficulties encountered with Biological Control

Pest and Beneficial Sampling Sheets

Monitoring is the cornerstone of IPM. A well designed monitoring routine can provide a wealth of information useful in the current and future seasons.

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Advantages of IPM 

The advantages of IPM are:

  • slower development of resistance to pesticides 
  • reduced risk to spray operators 
  • reduced chemical contamination of food and the environment 
  • reduced dependence on chemicals; hence IPM is a step towards sustainable agriculture. 

Disadvantages of IPM 

The disadvantage of IPM is that it is more complex than control by chemicals alone. It requires a greater understanding of the interactions between pests and beneficials, as well as the effects of chemicals.Adoption of IPM

For practical purposes, IPM programs can develop through three stages.

STAGE 1

  • improved cultural and hygiene practices
  • monitoring of pest to reduce pesticide use and achieve better timing of pesticide application

STAGE 2

  • as for stage 1, plus
  • monitoring that also includes beneficial species
  • selection of chemicals which are less hazardous to beneficials
  • spot spraying and targeted spraying
  • selective control of pests with the use of products such as pheromones, Nuclearpolyhedrosis virus, Bacillus thuringiensis, insect growth regulators and baits  

STAGE 3

  • as for stage 1 and 2, plus
  • environmental modification to encourage beneficials
  • release of mass-reared beneficials

Some crops or situations may be unsuited to Stage 3, but will benefit from Stage 1.

Stage 3, the highest level of commitment, means investing time and money into encouraging biological agents.

A decision to use broad spectrum pesticides in a Stage 3 IPM program cannot be taken lightly, as this may undo the work of the previous months or even years.

The main components and tools of a biological control focused IPM program

Natural enemies

Predators

Locally occurring

and

commercially mass reared

Parasitoids

Pathogens - locally occuring pathogens

and commercial products

Commercial products include:

Bacillus thuringinesis or B.t. products,
e.g. Dipel®, Novosol®, Biobit®, Xentari®.Nuclearpolyhedrosis Virus (NPV)
e.g. Gemstar®, Vivus®.

"Soft" selective insecticides

Strategically applied selective insecticides

e.g. Avatar®/Steward®, Success®, Pirimor®, Mimic®, Insegar®, Neem products etc.

Oil and soap sprays

e.g. D-C-Tron®, Natrasoap®

Other tools

Pheromone mating disruption

e.g. for codling moth, oriental fruit moth, lightbrown apple moth.e.g. Isomate® products

Baiting and trapping

e.g. yeast baits for Qld fruit fly, sticky traps

Getting Started with the biological control component of IPM

The stages outlined above provide a framework for the adoption of IPM. The points below need to be considered to implement Stage 3:

  • Seek specialist advice from suppliers of BCA's and consider employing an IPM crop monitoring specialist*.
  • Monitor crops regularly and learn to identify your pests and beneficials while doing so.
  • Determine what level of pest you can tolerate.
  • Replace broad spectrum sprays with biological or more selective insecticides if available.
  • Identify any local BCA's that are likely to assist you - these can be very sugnificant.
  • Determine which mass produced BCA's are suitable for your pests, crop and district.
  • Determine the best times for introducing natural enemies.
  • Ensure chemical residues have had time to disperse before introducing BCA's.
  • Identify other practices which will assist establishment of BCA's. e.g. wind breaks.
  • If appropriate, reorganise plantings and location of plantings to facilitate use of BCA's.
  • Experiment with part of the crop or one planting.

*Many of the suppliers of bicontrol agents also provide commercial monitoring services.

IPM and Biological Control

IPM systems consist of numerous elements with monitoring usually described as the "cornerstone of IPM". Biological controls, cultural practices, nutrition and irrigation management are all important elements.

The degree to which biological control agents (BCA's) can be utilised will vary from crop to crop and from area to area and will depend on the answers to a series of questions. For example:

  • Are there effective natural enemies for the major pests of this crop?
  • Effective natural controls exist for some pests but not others.
  • Are these mass reared for introduction or do they enter the crop from local populations?
  • This will influence management practices. eg. conservation of refuges or alternative crops.
  • What crops or types of vegetation are adjacent to the target crop?
  • Some crops act as refuges for natural enemies while others can harbour unwanted pests.
  • Is the crop being grown under "organic" or "conventional" classification?
  • If the crop is "organic" this can provide added incentive to use biocontrol methods
  • While a crop does not have to be grown organically to make use of biocontrol methods.
  • Are there "soft" chemical options for use in conjunction with natural enemies?
  • Soft options are available for some pests and not others.
  • Is the crop life span and environment suitable for natural enemies?
  • It can be difficult to establish BCA's in short lived crops.
  • Are certain plant life stages suitable for natural enemies and others not?
  • BCA's may be most appropriate at a particular stage of the growing cycle.

A crop consultant versed in biological control options will help you answer these questions so that an appropriate program will evolve. Each farm and crop has unique characteristics which need to be catered for in developing a program and responding to events as the season progresses.

In addition to these questions are those related to cost and practicality and the degree of difficulty controlling key pests with chemical means alone. Do not assume that it is more expensive to use biological control methods.

Strategies for releasing biocontrol agents

BCA's can be used in various ways. These methods are usually divided up into the follow categories:

Inoculative release: One or two releases early in pest infestation to control pest gradually. e.g. predatory mites in strawberries, Trichogramma in outdoor crops, lacewing in field and greenhouse crops.

Regular or dribble release method: Regular small release during likely problem periods, used like preventative fungicides. e.g. P. persimilis is nursery crops, Encarsia in green house crops.

Inundative releases: Repeated high rate releases during periods of pressure for quick knock down. e.g. Cryptolaemus beetles, Trichogramma in green house crops, P. persimilis for dosing hot spots of TSM.

Combination of above methods: e.g. initial high release rate for quick knock down followed by regular targeted small releases.

Methods of releasing biocontrol agents

Biocontrol agents are released using a wide range of methods.

  • Some are placed in the crop as adults (aphytis wasps),
  • some as pupae in moth eggs (trichogramma).
  • Some use a card or capsule system (trichogramma, encarsia)
  • Some in sachels with food (cucumeris, montdorensis)
  • some are spread loose or in a carrier (persimilis in vermiculite, lacewing eggs and larvae in chaff).

Talk to your supplier about the best strategy and release methods for your crop and situation.

Benefits of using Biological Control

Numerous benefits arise from utilising natural enemies. Some are obvious while others are more hidden and difficult to quantify:

BCA's assist in control of some important pests which have developed high levels of tolerance to chemical products - e.g. twospotted mites, Heliothis, cabbage moth.

In combination with soft options, BCA's help to prolong the useful life of the remaining effective chemicals - less pests are subjected to the chemical and pests that escape the chemical have a good chance of being eaten by a BCA.

Some BCA's are mass produced. Reductions in chemical inputs necessary for mass release of BCA's also enables movement of local beneficials into the crop. Some of these can be very significant in there own right.

Natural enemies can enable control of pests in crops sensitive to chemicals.

Reduce problems with withholding and worker re-entry periods.

Minimise chemical residues in the end product and the environment generally.

Difficulties encountered moving to IPM

Practices and routines need to be modified and new information absorbed by the practitioners. The following are some areas that are likely to be important:

Regular monitoring is necessary to identify pest outbreaks and their location within a crop. It may take time to develop suitable procedures and routines.

"Soft" controls for some pests are available but not for others. If unavailable, spot spraying with broad spectrum products may be more appropriate than widespread spraying.

Some damage from pests may need to be tolerated. Some pests may be required to support a useful population of the natural enemy.

Good timing is necessary when introducing natural enemies - not too early, not too late. For example: You may need to target moth flights, or detect early signs of a pest etc.

Need to get natural enemies established quickly. If introducing mass reared BCA's, introduce appropriate numbers to facilitate quick establishment.

Deciding when to or not to spray can be difficult. If soft options are available for the pest in question this is not such an issue.

Providing a suitable environment. Very hot dry conditions are not conducive to some BCA's. Adjustments may need to made to favour BCA's, e.g. shade, windbreaks, overhead watering.

Having an expectation that one cannot spray chemicals at all is incorrect and may result in failure of the IPM system. BCA's usually recover from occasional sprays of moderately toxic products and can remain at useful levels.

Pest and Beneficial Sampling Sheets

Crop specific sampling sheets are useful and provide an easy to collate method of transferring and recording information. For an advanced IPM program the score sheet should include the major natural enemies as well as pests.

The presence/absence method is sufficient for secondary pests or natural enemies. This can be elaborated to include a score, say from 1 to 4 to quickly rate the severity of the infestation.

This information can of course be recorded on portable digital devices for uploading or emailing to clients and/or home base computers.

Heliothis egg on tomato leaf. The presence of moth eggs is not enough to trigger a spray decision - there are a number of mortality factors which can prevent the egg producing a larva - unviability, parasitism, predation, pathogens, weather conditions...

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Monitoring for twospotted mite in strawberries. A good 10x hand lens is required for "bug checking".

Encarsia - whitefly parasitoid - release card

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Trichogramma wasp release capsule in sweet corn

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Monitoring involves learning to tell a pest from a beneficial. In this case Persimilis (left) is a predator of twospotted mite(centre). While the large egg on the right is a Persimilis egg and the smaller that of TSM.

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"Black" macadamia nutborer egg parasitised by a Trichogramma wasp showing wasp escape holes. Eggs that are parasitised go "black" about 5 days after they are parasitied. Monitoring that includes an assessment of parasitism rates can save a lot of time and spraying.

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In citrus, being able to assess the level of parasitism of red scale by Aphytis is an integral part of the monitoring process. Image shows aphytis pupa exposed by removing the scale cover. The pupa forms after the larva has consumed the scale insect An adult aphytis wasp will emerge from each pupa.

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Cucumeris release satchel in glasshouse cucumbers

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Persimilis released on bean leaves

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Example of a monitoring record sheet that includes Pests and Beneficials and an assessment of moth egg parasitism.

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Whitefly nymphs parasitised by Encarsia go black within 2 weeks of being parasitised - faster in hot conditions. The adult wasp will emerge from the black scale by chewing an escape hole.

Integrated Pest Management

Integrated Pest Management (IPM) is a strategy which encourages the reduction of pesticide use by employing a variety of pest control options in harmonious combination to contain or manage pests below their economic injury levels. These options include:

IPM aims to maximise the use of biological control. Other control measures, especially chemicals, must play a supportive, rather than a disruptive role. 

Chemicals should not be used on a 'calendar' basis but strictly when needed as defined by systematic pest monitoring. Selective rather than broad-spectrum chemicals should take preference. 

The aim is to produce high-quality marketable produce at minimal cost by intelligently using the various control options to manage pests. 

©Denis Crawford/Graphic Science