1 President’s Pen – Steve Hunn Hello to all members It is perhaps timely for an update in regards the progress for changes to the HSNO regulations. The development of the Health and Safety at Work (Hazardous Substances) Regulations has been a substantial piece of work with PMANZ making a submission. MBIE have previously informed us that the regulations would be made by December 2016 to come into effect in July 2017. They now anticipate that the regulations can be made by late March/early April 2017 at the earliest, to come into effect in early December 2017. PMANZ Council will continue to monitor these proposed changes and keep members informed as to the impact on Approved Handlers and associated training requirements. PMANZ is also planning to conduct further “specialised” training for members in 2017, sessions are likely to cover the above regulations and perhaps hands on sessions for use of thermal foggers, misters etc. So watch this space! For those trainee members completing the L3 qualification, the way that the Council administers the trainee membership requirements is being reviewed. As from next year you will start to receive emails from the council requesting an update on your training progress, this is to ensure that you and PMANZ are getting value regarding the free 2yr trainee membership and that you are receiving appropriate assistance and support that ensures you are able to complete the qualification. Do members ever receive calls in regards “recovering” bee swarms? If so and you’re not sure of what the process or procedure is, please consider contacting Grant Senior at Paramount Honey - mobile 021 440 161, or email: [email protected]They may be able to provide advice or even collect the swarm! That’s it for now, All the best to members and families for a Merry Christmas! Steve Bi-Monthly Newsletter December 2016 Volume 9 No. 6 P M A N Z PO Box 133215 Eastridge Auckland 1146 New Zealand Free phone: 0800 476 269 (0800 4PMANZ) Email: [email protected]Website: www.pmanz.nz PRESIDENT Steve Hunn [email protected]VICE-PRESIDENT Sandra Charlton [email protected]COUNCIL MEMBERS Peter Barry [email protected]Shane Byrne-King [email protected]Mike Collins [email protected]Mike Hermansson [email protected]Bill Paynter [email protected]Rowan Washer [email protected]IMMEDIATE PAST PRESIDENT Campbell Perrin [email protected]TREASURER Bill Wills [email protected]EXECUTIVE SECRETARY Denise Faulkner / Jo Wright [email protected]News from the World of Pest Management WHAT’S BUZZING? IN THIS ISSUE President’s Pen 1 From the Editor 3 Write it down 5 Detect.Inspect.Prevent. 8 News Bites 12 NEW ZEALAND NEWS Live Capture Traps 13 GE Pest Control 16 Technical Hints 19
Transcript
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President’s Pen – Steve Hunn Hello to all members
It is perhaps timely for an update in regards the progress for changes to the HSNO regulations. The development of the Health and Safety at Work (Hazardous Substances) Regulations has been a substantial piece of work with PMANZ making a submission. MBIE have previously informed us that the regulations would be made by December 2016 to come into effect in July 2017. They now anticipate that the regulations can be made by late March/early April 2017 at the earliest, to come into effect in early December 2017. PMANZ Council will continue to monitor these proposed changes and keep members informed as to the impact on Approved Handlers and associated training requirements. PMANZ is also planning to conduct further “specialised” training for members in 2017, sessions are likely to cover the above regulations and perhaps hands on sessions for use of thermal foggers, misters etc. So watch this space! For those trainee members completing the L3 qualification, the way that the Council administers the trainee membership requirements is being reviewed. As from next year you will start to receive emails from the council requesting an update on your training progress, this is to ensure that you and PMANZ are getting value regarding the free 2yr trainee membership and that you are receiving appropriate assistance and support that ensures you are able to complete the qualification. Do members ever receive calls in regards “recovering” bee swarms? If so and you’re not sure of what the process or procedure is, please consider contacting Grant Senior at Paramount Honey - mobile 021 440 161, or email: [email protected] They may be able to provide advice or even collect the swarm! That’s it for now, All the best to members and families for a Merry Christmas!
Steve
Bi-Monthly Newsletter December 2016 Volume 9 No. 6
P M A N Z PO Box 133215 Eastridge Auckland 1146 New Zealand Free phone: 0800 476 269 (0800 4PMANZ) Email: [email protected] Website: www.pmanz.nz
IN THIS ISSUE President’s Pen 1 From the Editor 3 Write it down 5 Detect.Inspect.Prevent. 8 News Bites 12 NEW ZEALAND NEWS Live Capture Traps 13 GE Pest Control 16 Technical Hints 19
“Bites, Itches and Stings: Medical Entomology for the Pest Manager”
Dr. Stephen L. Doggett, Director Medical Entomology, Westmead Hospital
“Mosquito Surveillance and implications for NZ and Islands”
Dr. Julia Kasper – NZ Biosecure Entomology Laboratory
“Identification and control of drain flies in commercial situations”
Dr. Paul Craddock - Operations Manager | Flybusters/Antiants
“Changes in Approach to Cockroach Control”
Peter Ambrose Brown - Syngenta
“Bed Bugs; Where to From Here?”
Dr. Stephen Doggett
“Wasps “ - < Subject Title still to be finalised>
Richard Toft - Entocol
“Bird Management – Large project opportunities in New Zealand”
Peter McCarthy – Pest IT Products, Training and Consulting
Full details will shortly be posted to the PMANZ website with registration form and accommodation links.
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From the Editor – Peter Barry
The festive season is once again upon us. It seems too fast. Maybe it’s my age catching up, or the world is just too busy with the constant improvements in technology and communication. It’s now very hard to avoid a steady stream of “blue-light” information from news Apps, Facebook, LinkedIn and Twitter, or for that matter any other App you choose to follow – it just becomes exhausting to keep up with all of it. No wonder time fly’s… The evolving implementation of the HASWA Act 2015 across the country and the hefty fines it imposes on the director means PCBU’s (companies) need to ensure that their pest managers are documenting their treatments and recommendations, and getting signatures from home owners. The BPCA has written a very useful piece about getting things written down, reprinted in this months’ newsletter for your information. Summer brings with it the usual dose of annoying fly activity – more so in some parts of the country than others. Wherever it is that you reside, the article on Fly Management provides good guidance for you and your clients to manage this filthy pest. The July announcement from government about the new, Predator Free New Zealand 2050 continues to invoke interesting discussion, this time around GE pest control. Read more about this and other interesting aspects under our New Zealand News. As mentioned earlier by Steve Hunn, and in spite of a costly and substantive submission from PMANZ through a Barrister in February 2016, it looks like the Approved Handler requirement for Urban Pest Management materials may fall away with the new Hazardous Substances Regulation. It would appear that only pesticides 6.1A and 6.1B will be restricted to an approved handler. Effectively, an Approved Handler as we know it for most UPM pesticides may be gone by December 2017. Indications in the cabinet paper suggestion all other substances including most of UPM pesticides will probably follow the Aussie model - Poisons Standard November 2016 which will have label restrictions and some sale conditions. So it will be interesting to see how this all pans out over the next year or so. Below is a link to the relevant cabinet document – see pages 70 to 75 https://www.legislation.gov.au/Details/F2016L01638 Quite what this will mean for our industry is difficult to say at this stage, but your council and other industry suppliers continue to watch and monitor it very carefully. We will keep you informed as we know more.
Fair Use Reporting
Articles provided in "What’s Buzzing" are drawn from a number of sources. The source of the material is quoted, either by author, publication and/or organization, in line with the practice of ‘Fair Use’ reporting of news or information to PMANZ members for their ongoing education. The information contained in this newsletter is for member information only, and does not necessarily reflect the official views or opinions of the PMANZ Council and/or its members.
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If it’s not written down, it didn’t happen!
Kevin Higgins form BPCA explains how recording written evidence can make the difference between a contract renewal and a date in court.
Professional pest control: Essential records
In the age of digital technology the importance of records can sometimes be overlooked. The BPCA office receives calls at least once per week from members of the public that have had some sort of pest control treatment but had not been given any paperwork, whether written or electronic. “Really?” I hear you say, “surely not!”
Just last week alone I took three calls from members of the public that were concerned because a pest controller had carried out a treatment but had left them with nothing in writing. Not only is this unprofessional, it’s also a risk to health and safety should anything have gone wrong, and may even be a breach of consumer legislation. The only time records are normally requested are when things either go ‘pear-shaped’ or there is an issue with the treatment, so quite often technicians are mistaken in thinking that they are not that critical.
But the old saying “if it’s not written down it didn’t happen” applies - your paperwork is the only evidence you have to state that the work has taken place.
If a complaint or incident arises following a treatment, usually the first request made by investigators is for a copy of the treatment records.
I often hear the statement “it was only a small job, so no need for any paperwork” - this could not be further from the truth. In fact, the small jobs are just as important as any other for so many reasons, and getting paid is high on that list. This is not about recommended contents of a site folder, or an ‘all singing, all dancing’ electronic system – it’s the very minimum that we recommend you leave with any client. Firstly let’s cover the report, either paper or electronic. As a minimum it needs to have the customer’s name and address details, your name and contact information, what you have done and what has been used (actives and trade names of the products you have used, even if they are non-toxic). When you read the report, remember that nine times out of ten the client does not understand pest control, so make sure that they comprehend what you have done, but also what needs to be done next, if anything. We highly recommended that you sign the report, date it and get the client to do the same. This will add protection should you face any complaints but it also demonstrates your level of professionalism. We also recommend that you leave the client with all of the required health and safety documentation. Again this can be paper copies, web links or email, but as a minimum we recommend at least the MSDS for any
products used. It will always be of benefit to leave a copy of your site-specific (JSA) risk assessment. This is something that should be done on site for every job, however small.
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Also include copies of safe systems of work and any specific training certificates for jobs that require qualifications. All of these demonstrate your commitment to health and safety and will also give the client assurance that you represent a professional company. I could give a much larger list of documents that should be left with a customer, and many of you will already leave more than I have recommended. However, this article was prompted by the fact that so many are leaving nothing. So, make sure you are covered and leave these items as a bare minimum – anything more will only benefit you and your client
Finding pests in the home or business can be very distressing, and that is when the public turn to professional pest controllers to solve their problems. It is essential that good practices, as well as legislative requirements, are carefully followed. If a complaint or incident arises following a treatment , usually the first request made by investigators is for a copy of the treatment records. Professional companies must ensure that there is a true and accurate record of the treatments provided, but you may be surprised to know that some companies do not complete any treatment records, written or electronic, and some companies offer very little information on their reports, making them almost useless. Editor’s Note: In light of the new stringent fines under HASWA Act 2015, PMANZ recommends a formal record i.e. service report and client recommendations be included in a retained internal record of the pest management plan and service delivered. You never know when you might need it.
A good pest management report should comprise:
▪ All of the site details: address, date and call type ▪ Reason for visit and visit type (one-off, contract, routine call-out, follow-up) ▪ Detail what has been done on the visit, not just “inspected all areas” ▪ Pest activity found and any actions taken ▪ Recommendations or precautions – it’s unusual to find nothing to recommend, but as a
minimum mention something like “good hygiene and housekeeping in place” ▪ Progress (or otherwise) of prior recommendations ▪ Detail risks assessed and describe how any potential incidents were avoided, e.g. changing a
formulation, using PPE or safe access equipment ▪ List products used – don’t just put the product name, also record the active ingredient and
quantity, and also list where the products were applied (a simple map may help) ▪ Confirmation that the job has been done ▪ Get names and signatures! It’s very important to prove you have been there and your
client has received the report. Ensure you print names too.
Detect. Inspect. Prevent. Little Moths Can Cause Big Stored Product Problems
Moths are one of the predominant stored product pests of both ingredients and finished products in the warehouse. Because they are able to fly from area to area, they can disperse their eggs fairly rapidly across an array of food, contaminating and damaging grains, cereals, pet foods, dried fruits, and even chocolates.
But while it is the adult moths that are most readily seen, it is the moth larvae that cause the most damage. “The larvae of these moths do considerable damage to stored product by eating the product and leaving behind their waste,” said McCloud Training Manager and Entomologist Anna Getchell, adding, “The economic damage caused by these pests is often greater than the food safety risks. Food they’ve infested is hard to sell, as the food is laced with webbing, faecal matter, and moultings;
resulting in recalls, returns, and rejection.”
USDA ARS/Scott Bauer
Indian Meal Moth (Plodia interpunctella). One of the most common of all stored product pests, it feeds on grain, nuts, dried fruits and processed foods. Groupings of up to 30 eggs are laid on the food surface, with the hatched larvae trailing webbing as they crawl and feed.
Similar in size and food preference to the Indian meal moth, it is most often found on nuts. Able to survive outdoors, it is most common in the western and southern states, but it can be transported anywhere in goods.
In addition, some larvae will consume stored food product such as bird seed, pet foods and candy bars, said Insects Limited Technical Director Alain VanRyckeghem, and a single infested package of product can be a source of larvae that then search out other food products to continue feeding or to pupate on or in the packaging. For example, a perfectly sealed package of baby formula may have no infestation, “but the presence of larvae on the container will cause consumer complaints, and rejection of the product,” he said.
“This is essentially collateral damage from another food product.”
While causing contamination of the food, the webbing that many of the moths spin is difficult to remove, has been known to clog food-conveying systems, and can lead to sanitation deficiencies, added Trece PCO Market Manager James Miller.
Keeping your food products safe from this moth damage and contamination involves a four-phase system of
monitoring, inspection, control, and prevention.
MONITORING
“Monitoring for stored food moths is designed to be an early warning system,” said VanRyckeghem. “The objective is to detect sudden rises in catch rates indicating a recent introduction of infested product, or a sanitation issue that has been overlooked.” As such, he said, detection of a couple moths early in the season can help prevent or reduce further outbreaks during the summer and fall.
Without the use of monitors, it can be difficult to know there is a problem until there are a number of adults flying around. Then that population can explode, resulting in further infestations that are more difficult to control.
Sex pheromone lures are the best monitoring tool for detecting stored-product moths, Miller said, as the monitoring systems also enable determination of population size, as well as verification of corrective actions taken in an IPM Program.
As explained by Getchell, the pheromone monitoring traps are sticky tent traps with a sex pheromone which attracts the adult males. Males believe the scent to be emitted by a female ready to mate, so they fly within the plume of the pheromone to find her, only to find that they’ve been tricked: there is no “her” and they are stuck to the glue of the sticky trap. These traps are effective in monitoring for moth presence because they can operate 24 hours a day, seven days a week, and can be placed in any environment, VanRyckeghem said. Placement can be in a grid system to detect recent invasions, or it can be targeted to monitor selected storage areas or help pinpoint an infestation.
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Andy Reago & Chrissy McClarren
Mediterranean Flour Moth (Ephestia kuehniella).
Common across the U.S., it feeds primarily on flour, grains, beans, and dried fruits. Like the Indian meal moth, eggs attached to the food surface and webbing spun by the larvae are key signs of infestation.
However, it is important that the traps not be thought of as a control method. “Far too often people consider pheromone monitoring systems as ‘mass-capture’ traps,” expecting that the traps will solve an infestation, he said. Because the traps attract only the adult male, training and education on the effective use of monitoring systems is crucial to a successful food IPM program. Additionally, Miller said, “Where you have stored product moths, you almost always have stored product beetles.”
INSPECTION
If moths are detected through monitoring, the next step is to conduct a thorough inspection to identify the species and determine the source. This should start with examination of the product nearest the monitors with the most activity, using a flashlight to search for signs that include active larvae, webbing, and food spills that could be attracting the moths.
As with all pests, the goal is to eliminate the problem at the source. “The moth adults will point us to the general direction of the infestation, but evidence from the juvenile stages will really
tell us if we’ve found the source,” Getchell said. Thus, the inspection should focus primarily on stored foods with emphasis on older or forgotten product and the shelving/packaging that the product is on or in.
Webbing, which is typically found in nooks and crannies of the product, packaging, or shelving is a clue that the source is nearby, and Indian meal or Mediterranean flour moth larvae may be seen crawling in the product, she added. Because Angoumois grain moths develop inside the kernel, the larvae are not visible, so the existence of exit holes in the kernels is evidence of an infestation of these moths.
CONTROL
“Detection of insect activity will require movement and segregation of the product for further action,” VanRyckeghem said. “This may include cleaning, disassembly, fumigation, or disposal.” Pallets with insect activity should be covered before being moved to reduce accidental dispersal to uninfested areas, and sanitation issues should be cleaned up and the waste discarded outdoors in an approved dumpster system.
CSIRO
Angoumois Grain Moth (Sitotroga cerealella). Found around the world in mild climates, the larvae feed inside kernels of corn and grain, causing significant damage before an infestation is detected. One sign of its presence is an unpleasant smell.
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PREVENTION
Once all infested product and moth life cycles are removed, steps should be taken to prevent re-infestation. These should include:
• Continued monitoring at the area of original activity and adjacent traps, with any further activity spurring repeated inspection.
• Keeping product sealed and protected in a clean environment at all stages from farm to fork. • Maintaining a clean and pest-free environment in the plant and ensuring all food is put into well-sealed
packaging. • Implementing a good sanitation and product rotation program to decrease the risk that moths pose to
stored product. • Rejecting infested materials at the receiving areas. This requires receivers to be knowledgeable about
webbing on boxes or bags, live and dead larvae in the stretch wrap, and live moths flying out of the trailer or off a pallet.
• Use of a pheromone trap in the truck trailer, placed by the vendor at the time of shipment, also can provide an early warning of moth activity in the trailer.
The source of most stored product pest moth infestations is incoming goods, Miller said, so a rigorous incoming goods inspection program, supplier inspection program, and use of monitors inside transport containers/trailers can enable you detect a potential problem before it gets in your plant. However, Miller added, some moths also will fly in from outdoors, so occasional exterior monitoring also should be considered. “Never overlook outside environmental activity of the Indian meal moth,” he said.
The author is Lisa Lupo - editor of QA magazine. She can be reached at [email protected]. Reprinted with permission from Quality Assurance & Food Safety (QA) magazine October/2016 Link to full article -
Ministry for Primary Industries staff have intercepted 4 Queensland fruit fly larvae at Wellington airport, stopping the dangerous pest from making a home in New Zealand.
The larvae were found earlier this month in an undeclared mandarin carried by an Australian passenger arriving from Melbourne. They have since been confirmed as Queensland fruit fly – regarded as one of the worst horticultural pests in the world.
"One of our quarantine officers detected the fruit when the passenger's bag went through an MPI biosecurity x-ray machine. Another officer discovered insect damage on the mandarin and pulled the skin off, finding the larvae nestled inside," says Andrew Spelman, MPI Border Clearance Manager, Central and South Region.
"Keeping fruit fly out of New Zealand is one of our highest priorities. The Wellington interception shows the value of MPI’s biosecurity x-ray technology, which has been upgraded over the past few years."
So far this year, MPI staff have made 11 fruit fly interceptions at the border.
MPI checks all produce seized from arriving passengers for signs of pests or diseases, says Mr Spelman. It also checks organic material disposed in MPI amnesty bins at airports and ports.
The Australian traveller received a $400 fine for failing to declare the mandarin.
Remote monitoring of live capture traps for vertebrates
MPI (Ministry for Primary Industries) has issue the following good practice guidance for remote monitoring of live capture traps for vertebrates. Guidelines for good practice The use of remote monitoring technology to provide inspection of live-capture traps for vertebrates is an emerging practice in New Zealand. These systems are expected to provide cost efficiencies and there is also scope for improved animal welfare outcomes through earlier attendance to trapped animals, when compared to manual inspection systems. These guidelines are intended to support developers and users of remote monitoring systems to adopt good practice and ensure animal welfare outcomes are improved (or at least not worse) in comparison to manual inspection. These guidelines in no way derogate from the Animal Welfare Act 1999 and, more specifically, nothing in these guidelines absolves users of live-capture traps from meeting their obligations under Section 36 of the Animal Welfare Act 1999 (see Appendix 1, but also check www.legislation.govt.nz for the most recent version of the Act).
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The following is considered good practice for the use of remote monitoring systems for live capture traps in New Zealand: These guidelines were developed in consultation with organisations involved in the use of remote monitoring systems
1. Fail-safe design Systems need to be fail-safe to ensure that captured animals do not go unnoticed. This means that any fault in the trigger sensor or communication network needs to be detected quickly and responded to with physical inspection of all traps affected by the fault. Any remote monitoring system should operate in such a way that each trap must confirm it has not been sprung (i.e. that it is assumed sprung unless the system communicates otherwise). If the un-sprung confirmation is compromised in any way, the system should communicate that it should be inspected. 2. Testing and record keeping Systems should be regularly tested for reliability. Records of test outcomes, animal catch times and animal clearance times should be kept for at least a year. These records should enable audit of actual trap clearance data against the requirements in section 36 of the Act. 3. Responsibility for systems A nominated individual should be identified and responsible for determining the status of all traps via the system and physically inspecting the traps as required. The system should allow for immediate escalation or delegation in the event of that individual being unable to carry out their duties for any reason. 4. Backup capacity Sufficient capacity for people to physically ‘check and clear’ all traps within the timeframes stipulated in Section 36 of the Animal Welfare Act 1999 must be available as a contingency in the event of a complete system failure or in the event that all traps capture animals. Appendix 1 36 Obligations relating to traps (1) A person who, for the purpose of capturing alive a mammal, bird, reptile, or amphibian, sets a trap or causes a trap to be set must inspect that trap, or cause a competent person to inspect that trap, within 12 hours after sunrise on each day the trap remains set, beginning on the day immediately after the day on which the trap is set. (2) A person who, for the purpose of capturing alive a mammal, bird, reptile, or amphibian, sets a trap or causes a trap to be set must— (a) remove, or cause to be removed, any live animal found in that trap; or (b) attend properly to the care of the animal or, without delay, kill the animal. (3) A person who, without reasonable excuse, fails to comply with subsection (1) commits an infringement offence. (4) A person who, without reasonable excuse, fails to comply with subsection (2) commits an offence and is liable on conviction,— (a) in the case of an individual, to a fine not exceeding $5,000; or
(b) in the case of a body corporate, to a fine not exceeding $25,000.
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Government weighs option of GE pest control The New Zealand Herald - by Isaac Davidson
Stoats could be eradicated from New Zealand by 2050. Photo / Patrick Garvey
The Government has been told it is likely to need a genetically engineered solution to reach its ambitious pest-free New Zealand goal and that it should expect some staunch opposition from the public.
New Zealand scientists have been tasked with coming up with a breakthrough by 2025 which is capable of eradicating an entire species of mammalian predator.
It is part of a larger goal to exterminate all rats, stoats and possums from New Zealand by 2050, which was announced by the National-led Government in July.
Papers released under the Official Information Act show that officials are concerned about both finding a scientific "silver bullet" and whether the breakthrough will be publicly acceptable.
Such an ambitious policy could require novel methods, including genetic solutions, the Department of Conservation said in a business case for the predator-free policy.
Scientists around the world are looking at a range of potential pest control methods which involve varying levels of genetic modification or engineering. One of the possible solutions is "editing" an animal's genes to instil infertility throughout an entire population.
In a Cabinet paper, ministers were warned that genetically-engineered pest control could be controversial in New Zealand.
"Any science breakthrough in predator control must be both effective in the field and broadly acceptable to the community," officials said.
"Some iwi may be sensitive to issues where genetic solutions are involved. Such proposals may attract adverse comment from some iwi and other community sectors concerned with scientific work related to genetics."
Conservation Minister Maggie Barry said genetics was the "next frontier" for pest control.
She expected some backlash, but she did not believe that the issue of genetic modification or engineering was as sensitive when it came to eradicating pests or disease.
Related Content
High-tech tool could boost bid to make New Zealand predator-free
Wellington to be 'world's first pest-free capital'
"Yes it is unpopular with a lot of people. I wonder whether that is something people feel more keenly when it's about food, and a little bit less keenly when it's about killing a mosquito that spreads a virus that causes so much misery."
Any breakthroughs would have to be tested against public opinion, she said.
Barry also emphasized that genetic solutions were "some way off". She pointed to other pest control technologies which were already showing promise, including self-setting traps and the use of audio recordings of baby rats to lure stoats.
Conservation biologist James Russel, from the University of Auckland, said scientists were now able to identify "the entire genetic architecture" of some species.
"That gives us great potential to minimise risk by being very specific to that species," he said.
"The challenge we have is translating that from the lab to the real world," he said.
The background papers to the Predator Free NZ policy also underlined the uncertainty in depending on an as-yet-unknown scientific breakthrough.
"The predator free goal is dependent on breakthrough science... but research outcomes are very uncertain", a Cabinet paper from July says.
Officials noted that a New Zealand consortium spent 13 years searching for a possum biocontrol, at a cost of $30m, without any breakthrough.
Predator Free NZ
• Govt has set goal of eradicating all mammalian predators by 2050 • By 2025, it expects to have a made a scientific breakthrough that will kill off an entire species of predator • Rats, stoats, and possums kill around 25 million native birds a year • $3.3 billion cost to the economy and primary sector a year
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TECHNICAL HINTS
PYRETHROIDS – Mode of Action To understand how the pyrethroids kill insects we need a basic understanding of the insect nervous system.
The nerve cell or neuron consists of a cell body from which processes called dendrites spread, like the branches of a tree. In addition to the dendrites, there is the axon, which is like a long, thin wire, also ending in treelike branches. At the ends of the axon, the branches end in small bulblets. The bulblets of one neuron approach close to the dendrites of the next neuron, almost touching them. This point of contact is called a synapse.
Each neuron receives an impulse which it passes on to the next neuron. Through a chain of chemical events, the dendrites pick up an impulse that's passed along the axon as an electrical impulse, and then transmitted to the next neuron by a chemical reaction. The entire impulse passes through a neuron in about seven milliseconds — faster than a lightning strike!
Pyrethroids interrupt this process when the message is travelling along the axon as an electrical impulse.
Each neuron has an outer cell membrane. When the neuron is not stimulated, this is polarized, with a positive electrical charge on the outside of the membrane, and a negative charge on the inside. This is because the outside of the cell has an abundance of sodium ions, while the inside of the cell has an abundance of potassium ions.
When a stimulus reaches a resting neuron, ‘gates’ in the axon membrane open suddenly, and the sodium ions rush into the cell, so the inside of the cell becomes positive too. An action potential is created as the neuron continues to open sodium gates all along the axon.
After the inside of the cell is flooded with sodium ions, gates on the inside of the membrane open to allow the potassium ions to move to the outside. This restores the electrical balance, although it's now the opposite of the resting potential, with a negative electrical charge on the outside, and a positive charge inside.
Immediately after the potassium gates open, the sodium gates close, and after this the potassium and sodium ions return to their original sides, (sodium on the outside and potassium on the inside). This occurs through sodium/ potassium pumps. Thus the nerve returns to its original resting potential until another impulse comes along.
The message therefore travels along the nerve axon as an electrical impulse until it reaches a synapse, the small gap between two nerve cells. When the impulse reaches the end of the axon, a calcium gate opens and calcium ions enter the cell. This causes a chemical called a neurotransmitter to be released into the synapse. The neurotransmitter moves across the gap and binds to proteins on the next neuron. These proteins are called receptors, and different proteins serve as receptors for different neurotransmitters. But that is a story for when we look at other insecticides!
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So what happens when a pyrethroid gets into the system?
Pyrethroids are axonic poisons. They cause paralysis of an insect by keeping the sodium gates open. When the pyrethroid keeps the sodium gates open, the nerve cannot return to its resting state as the sodium keeps pouring in; so the insect goes into convulsions. Eventually the insect is knocked-down, or paralysed. At this point the insect may not always be dead. Pyrethroids may be detoxified by enzymes and the insect may later recover. This is why it is important to use products at the correct label rate.
Pyrethroids are less toxic to people for a number of reasons. The human nervous system is less susceptible to them because of our larger size and because we have more effective enzymes to detoxify them. Also the nerve axon in humans, and many other higher animals, is protected by a fatty coating known as a myelin sheath. This makes it harder for the pyrethroids to penetrate to the axon where they block open the sodium gate.
It is important to note though that, while dogs are able to detoxify pyrethroids; cats are more susceptible and can suffer tremors, twitching, convulsions, and even death if pyrethroids are misused.
This article is courtesy of Ensystex New Zealand Ensystex New Zealand Ltd Postal Address: P O Box 301 710 | Albany Auckland 0752 Telephone: 0800 ENSYSTEX | 0800 367 978 | Mobile: (021) 882 715 www.ensystex.co.nz
