Dr. William P. Ventura
Pace University
Professor - Dept. Biological Sciences
Pleasantville Campus
MOSQUITOES
AND LARVICIDES
Family - Culicidae
Key examples -
- Aedes
- Culex
Life Cycle - eggs, larvae, pupa, adults
EGGS - laid on surface of water - either singly or in rafts.
LARVAE - most feed on organic debris.
PUPAE - aquatic and very active.
ADULTS - males do not bite
Females are vectors of several important diseases: malaria, yellow fever, dengue, filiariasis, and enchalitis.
Mosquitoes have a very delicate water balance requirement. The adult contains about 3 microliters of water - about one-twentieth of a drop. If a mosquito were to take to the air in dry weather for more than a few minutes without finding a meal, its water loss from increased respiration would be fatal. Hence it is most active in humid weather.
Larvae and pupae of mosquitoes are known as "wigglers" and "tumblers", respectively.
Some species of mosquitoes produce several generations per year.
The flight habits of adults vary with species; some Aedes migrate many miles from their aquatic, larval habitat.
Aedes overwinter in the egg stage, while Culex overwinter in the adult stage.
Culex pipiens - House Mosquito
Life cycle - eggs deposited in raftlike masses of 100-300 on water surface film. They hatch in 1-5 days.
Larvae feed head down in water. They pupate after 1-2 weeks. Adults emerge after a few days. Many generations are possible; the last overwintering as adults.
Male feeds on plant juices; females feed on blood of birds and mammals.
LARVICIDES
Active Chemical - Methoprene
Trade Names - Altosid, Apex, Diacan, Dianex, Kabat, Minex, Pharorid, Precor, and ZR-515.
According to literature on Altosid Larvicidal Products (http://www.zanus.com/larvicide.html)
"methoprene is target-specific and will not affect fish, waterfowl, mammals or beneficial predatory insects".
According to: http://ace.orst.edu/cgi-bin/mfs/01/pips/methopre.htm), EXTOXNET -
Methoprene is a compound which mimics the action of an insect growth regulation hormone. It interferes with the normal maturation process by making it impossible for insects to mature to the adult stages.
To be effective, it must be applied at the proper stage of the target pest's life cycle. Methoprene is not toxic to the pupal or adult stages. Treated larvae will pupate but adults do not hatch.
It is used to control mosquitoes and several types of ants, flies, lice, moths, beetles, and fleas.
It is available in suspension, emulsifiable and soluble concentrate formulations, as well as in briquette, aerosol, and baith form.
Key facts reported:
Methoprene is practically nontoxic when ingested or inhaled and slightly toxic by dermal absorption.
Not an eye or skin irritant.
No reproductive, teratogenic, mutagenic or carcinogenic effects in mammals.
Possible organ problem LIVER.
Slightly toxic to BIRDS.
Slightly to moderately toxic to FISH.
Very highly toxic to some species of freshwater, estuarine, and marine invertebrates.
Very little, if any toxic effects on waterfleas, danselflies, snails, tadpoles. NONTOXIC TO BEES.
Environmental fate of methoprene.
Field half-lives up to 10 days; degraded by sunlight; microbial degradation by microbes rapid; slightly soluble in water.
Half lives in pond water about 30 to 40 hours.
Dr. Bill again poses the question - even though larvicides appear to be safer than sumithrin or malathion - How often will larvicide have to be applied to be an effective deterent to mosquitoes?
Will we see landscaper/sprayer companies offering their clients treatments for mosquitoes in addition to usual spraying this spring and summer?
Who will monitor this use?
