Monday, January 31, 2011

La Niña Brings Insect 'Plagues'

The La Niña weather pattern is not only bringing New Zealand a warm moist summer, it is also bringing ‘plagues’ of pest insects.

Last month saw a record of over 20,000 visits to the Kiwicare website from New Zealanders, nearly double the same period last year. Sales of all insect control products are up this year and some such as flea products are as much as double sales last year. Enquiries for fleas are up 117%, wasps 110% and spiders, cockroaches, ants and flies all up more than 50%.

The pests causing most concern in these conditions are fleas, mosquitoes, wasps, flies, cockroaches and ants. These pests pose a risk of causing harm to people and animals; fleas and mosquitoes bite us and our pets, wasps sting and even threaten life on rare occasions, flies and cockroaches transfer disease from rubbish and drains to our food and kitchens, and ants are a general nuisance in homes and workplaces.

Because insect metabolisms are governed by temperature, insects are generally more active and breed more quickly when it is warm. Moisture levels are also critical for many insects. In dry conditions many insects experience stress due to water loss and this slows their breeding. However, when moisture levels are high, as they are this year in many parts of New Zealand, then numbers are not limited. The third vital ingredient of this recipe for ‘plagues’ of insect pests is food supply, and there are reasons to believe conditions are also increasing food sources, for example:
  • Adult fleas and mosquitoes feed on the blood of animals, often including people. In warm weather, blood is more easily available to fleas and other blood sucking pests because mammals such as cats, dogs and ourselves move blood into capillaries near the surface of our skin to radiate heat and keep us cool. Also, the larvae of fleas feed on dust, including skin cells from animals and people. In warm conditions there is more of this dust available.
  • Wasps feed on a variety of food sources including nectar, pollen, other insects and decaying animal material. The weather conditions have been good for flowers, giving wasps a head start in food supply this spring and the general increase in insects has provided more insect prey for their carnivorous habits.
  • Flies and cockroaches feed largely on decaying organic matter. The warm weather encourages more rapid decay and easier feeding for fly maggots and cockroach nymphs as well as adults.
  • Ants feed on a variety of foods depending on the species and the requirements of the colony at the time. For example, Argentine Ants feed on other insects and invertebrates when they invade a new territory; thus removing competition. Then they change to feeding on higher levels of sweet foods such as the honeydew from aphids with which they have a symbiotic relationship; protecting them in return for the honeydew.
This all means that we are more at risk from pest insects this year than normal. There is more likelihood of being bitten by fleas and mosquitoes, stung by wasps, given food poisoning by flies and cockroaches and generally pestered by ants and other insects.

Pro-active prevention of problems with pest insects is preferable to having to deal with an infestation. Think prevention and remove food that insects could feed on and create barriers to stop pests entering your home. Don’t forget to treat your pets with flea treatment from your vet but also spray places where pets sleep as this is where the fleas spend most time. I advise extra caution in dealing with wasp nests this year as they seem to have formed particularly large nests already. One wasp sting is almost always painful and can be life threatening in a few sensitive individuals. To avoid stings treat wasp nests with powder insecticide as powder tends to keep wasps calm, and treat at dusk or night time when wasp activity is low.

A man walks into a bar. There is a flea behind the bar serving drinks. The man stares at him amazed.
The flea says "What are you staring at. Have you never seen a flea serving drinks before?"
"No. Its not that" says the man. "It's just I never thought the ant would sell the place."

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