Mosquitoes in Oklahoma

1. Mosquitoes in Oklahoma Dr. Russell Wright, Prof. Emeritus

2. General Biology of Mosquitoes • Insects that belong to Order DIPTERA which includes all the flies. • Have four life stages: • Egg -- laid on surface or edge of water. • Larvae -- live only in water. • Pupae -- live only in water. • Adults

3. Eggs • Laid on singly on surface or edge of water. • Some species lay eggs in rafts on surface of water. • Some sp. hatch 24-36 hrs. • Some hatch after one, two or three years. • Over wintering stage for some species

4. Larvae • Four stages: 1st, 2nd, 3rd, 4th instars. • Called “wrigglers”,very active, come to surface for air. • Total length 6-12 days. Some species even weeks.

5. Pupae • Stage that changes from larvae to adult. • Called “tumblers” very active, come to surface for air. • Stage lasts from 3-6 days.

6. Adult (Male) • Emerges first • Feeds on nectar sources for energy. • Mates within 3 to 7 days and dies

7. Adult (Females) • Emerges and feeds on nectar. • Mates, usually only once. • Searches for blood meal. • Needs blood meal to develop eggs. • 1-5 blood meals over life of 7 to 28 days.

8. Mosquito Life Cycle

9. Mosquito Species Present in Oklahoma: • Approximately 60 known species in Oklahoma. Over 230 species in U.S. • Usually only 6-8 species will be a nuisance pest in any given area.

10. Genus and species • Every species is more different from each other genetically than you and I are from any other human on earth. • So I will need to use at least Genus names, sometimes species as I refer to biology. • Think of these names as the folks you know as Jane, Linda, Ann , Tom. Dick, Harry etc. • However if you think of any of your friends by these names, don’t tell them I told you to do so.

11. Classification Based on Larval Habitat • Flood Water Mosquitoes • Permanent Water Mosquitoes • Permanent Pool Group • Transient Water Group • Container Mosquitoes

12. Larval Habitat • Important to know which mosquitoes cause problems and when. • Identify larval habitats based on adults present. • Most effective to find and map larval habitats and eliminate or treat in this stage.

13. Flood Water Mosquitoes • Mosquitoes in Genera Aedes, Ochlerotatus, and Psorophora • Some species from these three genera are the most important pest species. • Bite humans, livestock, pets. And can have very large populations in spring and early summer. • Do not believe that most vector WNV

14. Flood Water Mosquitoes (cont.) • Eggs are laid on the soil surface at the edge of standing pools of water that are left from heavy rains or floods. • Often woodland pools; roadside ditches or low areas along creeks rivers that collect flood water. • Eggs hatch when flooded by run off from heavy rains or flood water.

15. Flood Water Mosquitoes (cont.) • Eggs are over wintering stage. In most cases must spend winter in egg case, called diapause stage. • Can survive in egg stage for several years until flooded. • However, can have different hatches within several days if increased water levels hatch new eggs.

16. Flood Water Mosquitoes (cont.) • Adult populations peak in late April, May, and June, some species hatch with late summer fall rains . • Adults die quickly during hot weather. • Any flooded pools usually dry up too fast to support larvae in hot weather. • Females most active around sunset or in shady areas when disturbed.

17. Floodwater Pool – Aedes vexans

18. Floodwater Pool – Aedes vexans

19. Permanent Water MosquitoesPermanent Pool Group • Genera Anopheles, Coquillettida, Mansonia some Culex sp. • Found in quiet bodies of freshwater with sunlight, much surface vegetation and very little wave action. • Shallow edges of ponds, some lakes backwaters of rivers even slow moving streams. • Never in main lake or pond areas with much wave action.

20. Permanent Pool Group (cont.) • Anopheles lay eggs singly on surface of water, each egg with a float. • Eggs hatch in 24-36 hrs. Many generations a year tend to peak mid late summer • Adults over winter triggered by photoperiod. • Deep south perhaps cycle can go all year, slower in winter.

21. Permanent Pool Group (cont.) • Genera Coquillettidia and Mansonia • Mansonia mosquitoes lay eggs in groups attached to plant stems underwater; Coquillettidia in rafts onwater surface. • Larvae insert breathing siphon into plant and takes oxygen directly from plant tissues. Cattail marshes and similar type water. • Appear to have one prolonged generation per year and at least in south over winter in larval stage. • Not much of a nuisance pest.

22. Permanent Water MosquitoesTransient Water Group • Genera Culex and Culiseta • Canals, long standing ground pools or roadside ditches, catch basins, storm sewers , clogged sewers long standing irrigation pools, water often becomes very foul polluted for some species others need fairly clean water. • These mosquitoes lay eggs in rafts on the surface of the water. • Eggs hatch within 24-36 hours.

23. Transient Water Group (cont.) • These mosquitoes normally over winter in the adult stage. • Adults emerging in late summer or fall do not search for a blood meal, but mate and female searches for sheltered areas to spend winter. • Caves, burrows, sewers, basements etc. • Populations low in spring peak in mid to late summer. Vary some with species.

24. Culex spp. Laying Eggs

25. Transient Water Group (cont.) • Populations of these mosquitoes low in spring. • Takes awhile to build large populations. • Peak abundance July-October. • Many species prefer birds as hosts. • Are often best vectors of viruses. • Bite more readily at night.

26. Transient Water Mosquito Habitat

27. Container Mosquitoes • Certain species in 5-6 Genera • In nature larvae live in tree holes, rock pools even leaf axils. • Many species now associated with man made containers or materials that hold water. • Tires, cans, buckets , birdbaths, gutters, pet water dishes, plant container bottoms that catch water, even cans, paper cups etc.

28. Typical Container Mosquito Habitat

29. Asian Tiger Mosquito • Aedes albopictus • Larvae in containers of any size.

30. Aedes albopictus Eggs in Container • Efficient container breeder utilizing available sources. • Eggs laid on surface of water, on sides of container, and on stick. • Immediate egg hatch of some eggs, delayed hatch for others.

31. Asian Tiger Mosquito • First found in OK 1990-91, Tulsa, SE Counties. • By 2000 was found in all counties we surveyed. • Most important pest in most areas. • Bites in mid to late afternoon. • Abundant from mid June through Sept.

32. 1990-91 Thru 2000 Distribution of Asian Tiger Mosquito in Oklahoma

33. Mosquito Species of Greatest Concern • Belong to Genus Culex • Include C. pipiens/quinquefasciatus, southern house mosquito most likely vector • C. restuans, C. salinarius, C. tarsalis. • Note: all are permanent water mosquitoes, populations peak in summer through fall at same time virus activity peaks • All prefer to feed on birds.

34. Possible WNV Vector Speciesin Oklahoma • Bridge vectors to humans & horses. • Culex tarsalis – Cx. salinarius Permanent transient water but not very stagnant • Aedes vexans –floodwater; spring through mid summer • Aedes albopictus • Ochlerotatus triseriatus. Oc. hendersoni • Container or tree hole species

35. Surveillance • Knowledge of the mosquito species in a given area and relative abundance is necessary in planning control measures. • Some species do not vector WNV, control not as important. • Accurate records must be kept of surveillance locations. • Species I.D. is essential.

36. Larviciding • Controlling mosquito larvae most effective control measure because life stage is confined to aquatic habitat. • Water management by drainage or source reduction. • Larvicides can be used if drainage not available or adequate. • Not as practical in Oklahoma until we have identified larval sites.