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PROLINK® OVERVIEWThe active ingredient in all PROLINK products is (S)-methoprene, an insect growth regulator (IGR). IGR's are classified as biorational control agents. IGR's control insects by interrupting normal development. (S)-methoprene interferes with normal metamorphosis, preventing the immature insect from emerging as an adult (S)-methoprene is a true analogue of the mosquito's own juvenile hormone. During the fourth larval instar, juvenile hormone (JH) levels drop to very low levels. PROLINK, when applied into the larval habitat, releases (S)-methoprene which artificially maintains the JH levels at a higher than normal titer. The higher than normal level during the latter instar stages, prevents the insect from developing into normal pupa. Mortality occurs during the emergence of biting adult mosquitoes.
Unlike conventional pesticides, (S)-methoprene is not a direct toxin. It is target-specific and does not harm mammals, waterfowl, or even beneficial predatory insects. In fact, methoprene has been recommended by the World Health Organisation (WHO) for the use in drinking water supplies to control container-breeding mosquitoes in developing countries. By working specifically on fourth instar mosquito larvae, PROLINK offers effective control without upsetting the food chain relationships between larvae and their natural predators, and, most importantly, without impacting non-target species. Environmental PropertiesGeneral: (S)-methoprene insect growth regulator (IGR) is a biodegradable compound of very low environmental persistence. The (S)-methoprene molecule contains only carbon, hydrogen and oxygen. Persistence in Soil: The half-life of methoprene when applied to soil at 1 Kg per Hectare is less than 10 days. This is a highly exaggerated application rate with regard to the intended use pattern. Movement in Soil: In leaching studies, it has been shown that methoprene remains in the top 10 cm of the soil even after repeated washings with water. Persistence in Water: Technical methoprene degrades rapidly when applied to water under normal conditions of sunlight and temperature. Methoprene is degraded by aquatic microorganisms and sunlight. Slow release and microencapsulated formulations allow its operational use for mosquito control. Persistence in Plants: When applied at the rate of 1 Kg per Hectare to alfalfa, methoprene has a half-life of less than two days. In rice, the half-life is less than one day. Rapid biodegradation is evident even after treatment at exaggerated rates. Uptake by Plants: Studies show that wheat grown in methoprene-treated soil does not contain residues of methoprene. Fate in Animals: Laboratory and field experiments have shown that methoprene is rapidly degraded by mammalian metabolic systems. When mice, rats, guinea pigs, steers, or cows are treated orally with methoprene, the compound is metabolised quickly and eliminated via urine, faeces, and expired breath. Fate in Fish: In model ecosystem experiments, methoprene is shown not to accumulate in fish and does not inhibit growth or development of fry. Effects on Non-Target Organisms: Toxicity studies have been conducted both in the laboratory and as part of field research programs. The action of methoprene is selective. When applied at the recommended use rate, methoprene does not harm wild fowl, amphibians, crustaceans or beneficial insects. Effects of PROLINK in the FieldPROLINK, an insect growth regulator (IGR), acts by inducing morphological changes which interfere with normal development. These effects, not immediately apparent, result in the failure of adult mosquitoes to emerge from pupae. Because the effect of PROLINK is neither total larval death nor widespread mortality immediately following pupation, the number of emerged adults is the only criterion for accurately assessing control. Checks by dip counts during larval and pupal stages are valid only for subjective evaluation by trained inspectors familiar with the subtle effects of labelled rates of PROLINK on larva and pupa. After application of PROLINK to 2nd, 3rd, or 4th instar larvae, direct toxic effects on larvae are not likely to be observed. They will continue to develop and will pupate. Pupae will also live for a short time but will eventually die. Adults will not emerge. Infrequently, a few adults may be seen at the water surface, but will have abnormalities preventing flight and will not survive. Subjective evaluation of PROLINK treated areas is routinely practiced by many professional mosquito control experts using PROLINK operationally. Inspectors who have familiarised themselves with subtle changes in appearance and behaviour of treated larvae and pupae advise us that a general determination can be made on whether or not an effective level of PROLINK has been delivered to the breeding site. Some of the subtle changes to look for are:
Any one or all of these abnormalities may be found in a treated area. Close observation during the first few uses of PROLINK may allow the field operator to forecast results of a treatment. Application ChecklistDo the following:
Do not do the following:
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