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ALFALFA WEEVIL, Hypera
postica (Gyllenhal) -- Coleoptera, Curculionidae (Contacts) First found in the United States near Salt Lake City, Utah in
1904, Hypera postica is believed to have invaded from
Europe (Titus 1907, 1910). The weevil
was confined to 12 western states until 1952 when it was detected in Maryland
(Bissell 1952). From Maryland it
spread rapidly and is now found throughout North America. There is one generation per year and winter is spent as
aestivating adults and as eggs. Eggs
hatch in spring about the time that alfalfa begins to grow. In the Midwest, larval feeding continues
through May when pupation occurs.
After emergence adults leave the field for available cover where they
undergo summer aestivation. In autumn
adults return to the field and begin laying eggs (Manglitz & App 1957). Parasitoids were first introduced from Europe into the United
States in 1911, and by 1919 they were well established in many areas of the
western United States (Chamberlin 1924).
Bathyplectes curculionis
(Thomson) is the most widely distributed and most successful introduced
parasitoid in the Midwestern U. S.
During the 1960's and 1970's, both B. curculionis and B.
anurus (Thomson) were released in Illinois by USDA personnel and are
now found in most midwestern populations of the weevil (Dysart & Day
1976) (also see Michelbacher 1940a,b; Hamlin et al. 1949, Poinar 1963, Dysart
& Puttler 1965, Streams & Fuester 1967, Hagen & Mangalitz 1967,
Brunson & Coles 1968). A fungal disease of alfalfa weevil larvae was found in Ontario,
Canada in 1973 (Harcourt et al,. 1974), and was similar to that reported
active on cloverleaf weevil, Hypera punctata
(Arthur) by Arthur (1886). The
fungus is believed to be Erynia phytonomi
(Thomson) and actually differs from that attacking cloverleaf weevil. It was found to spread rapidly out of
Ontario to other portions of North America (Muka 1976, Puttler et al. 1978,
Barney et al 1980, Los & Allen 1983, Nordin et al. 1983). It is now considered to be the major
naturally occurring biological control agent of the alfalfa weevil throughout
most of its range (Carruthers & Soper 1987). A similar fungus causes comparable mortality in Hypera variabilis in Israel
(Ben Ze'ev & Kenneth 1982). Erynia phytonomi overwinters in the soil as thick-walled resting spores that
germinate in springtime to produce germ conidia, which infect weevil
larvae. Conidia
produced by infected larvae are responsible for the horizontal transmission
of the disease (Ben Ze'ev & Kenneth 1982). Younger larvae tend to produce conidia and older larvae resting
spores (Barney et al. 1980). Brown
& Nordin (1982) developed a detailed model of this disease and estimated
that the first incidence occurs in Kentucky after an accumulation of 220 to
290 degree days. Then the alfalfa
weevil population has to reach a threshold density in order to allow for
sufficient horizontal transmission for an epizootic. Brown & Nordin (1982) estimated this
threshold to be 1.7 weevil larvae per stem.
Mortality rates caused by the fungus are often quite high (30-70%) at
the time of peak larval occurrence and often 100% later in the season (Morris
1985). It is restricted in effectiveness
as a biological control agent because it often appears late relative to
currently recommended harvest dates (Ambrust et al. 1985). Brown & Nordin (1982) proposed using
computer-directed harvest dates that are earlier than normally recommended. The microenvironment in windrows promotes
an earlier than normal epizootic and reduces the need for insecticides. The appearance of the fungus
as a major mortality factor after the two above mentioned parasitoids were
established poses the question of how these all will now coexist, especially
as they attack the larval stage.
About five days elapse from infection to death in diseased larvae and
parasitized larvae die within 10 days.
Such time periods suggest that an alfalfa weevil larva infected and
parasitized simultaneously would probably die from the fungus before the
parasitoid completed its development.
Field studies indicate that the disease has a negative impact on the
two parasitoids (Los & Allen 1983, Loan 1981, Morris 1985). REFERENCES: [ Additional references may be found at: MELVYL
Library ] Arthur, J. C. 1886. A new
larval Entomophthora. Bot. Gaz. 11: 14. Barney, R. J., P. L. Watson, K. Black, J. V. Maddox & E. J.
Armbrust. 1980. Illinois distribution of the fungus Entomophthora phytonomi (Zygomycetes:
Entomophthoraceae) in larvae of the alfalfa weevil (Coleoptera:
Curculionidae). Great Lakes Entomol.
13: 149-50. Ben-Ze'ev, I, & R. G. Kenneth. 1982. Zoophthora phytonomi and Conidiobolus
osmodes (Zygomycetes: Entomophthoraceae), two pathogens of Hypera species (Coleoptera:
Curculionidae) coincidental in time and place. Entomophaga 25: 171-86. Bissell, T. L. 1952. U. S. Bur. Entomol. Plant Quarantine Coop.
Econ. Insect Rept. 2: 4. Brown, G. C. & G. L. Nordin.
1982. An epizootic model of an
insect-fungal pathogen system. Bull.
Math. Biol. 44: 731-40. Brunson, M. H. & L. W. Coles. 1868. The introduction,
release and recovery of parasites of the alfalfa weevil in the eastern United
States. U. S. Dept. Agric. Prod. Res.
Rept. 101. 12 p. Burton, V. E., C. G. Summers, K. S. Hagen & V. M. Stern. 1987.
Insects and mites, p. 1-13. In: IPM Manual Group, Univ. Calif., Davis, Alfalfa Pest Management
Guidelines. Burton, V. E., C. G. Summers, K. S. Hagen & V. M. Stern. 1989.
Alfalfa pest management guidelines 1989. Univ. Calif., UCPMG Publ. No. 2. 14 p. Carruthers, R. I. & R. S. Soper. 1987. Fungal diseases,
p. 357-416. In: J. R. Fuxa
& Y. Tanada (eds.), Epizootiology of Insect Diseases. John Wiley & Sons, New York. Chamberlin, T. R.
1924. Introduction of
parasites of the alfalfa weevil into the United States. USDA Dept. Circ. 301. 9 p. Cothran, W. R. & C. G. Summers. 1971. Biology and
control of the Egyptian alfalfa weevil, Hypera
brunneipennis (Boh.) in
California. Proc. Alfalfa Prod. Symp,
Fresno, CA., Dec 7-8, 1971. p.
59-62. Cothran, W. R. & C. G. Summers. 1972. Sampling for the
Egyptian alfalfa weevil: a comment on
the sweep-net method. J. Econ. Ent.
65: 689-91. Cothran, W. R., C. G. Summers & D. Gonzalez. 1971.
Egyptian alfalfa weevil-- population and ecology research. Calif. Agr. 25(5): 5. Cothran, W. R., C. G. Summers & C. E. Franti. 1975.
Sampling for the Egyptian alfalfa weevil: comparison of two standard sweepnet techniques. J. Econ. Ent. 68: 563-4. Dysart, J. R. & W. H. Day.
1976. Release and recovery of
introduced parasites of the alfalfa weevil in eastern North America. Agric. Res. Ser., USDA Prod. Res. Rep.
167: 61 p. Dysart, R. J. & B. Puttler.
1965. The alfalfa weevil
parasite Bathyplectes curculionis in Illinois and
notes on its dispersal. J. Econ. Ent.
58: 1154-55. Gutierrez, A. P., J. U. Baumgaertner & C. G. Summers. III. A
case study in an alfalfa ecosystem.
Canad. Ent. 116: 950-63. Hagen, A. F. & G. R. Manglitz. 1967. Parasitism of the
alfalfa weevil in the western plains states from 1963 to 1966. J. Econ. Ent. 60: 1663-66. Hamlin, J. C., F. V. Lieberman, R. W. Bunn, W. C. McDuffie, R. C.
Newton & L. J. Jones. 1949. Field studies of the alfalfa weevil and
its environment. U. S. Dept. Agric.
Tech. Bull. 975. 84 p. Harcourt, D. G., J. C. Guppy, D. M. MacLeod & D.
Tyrrell. 1974. The fungus Entomophthora phytonomi
pathogenic to the alfalfa weevil, Hypera
postica. Canad. Ent. 106: 1295-1300. Lamp, W. D., K. V. Yeargan, R. F. Norris, C. G. Summers & D.
G. Gilchrist. 1986. Miltiple pest interactions in alfalfa, p.
345-64. In: R. E. Frisbie
& P. L. Adkisson (eds.), Integrated Pest Management on Major Agricultural
Systems, Texas A. & M. Univ., College Sta., TX. Lehman, W. F., C. G. Summers & V. L. Marble. 1990.
Notice of release of UC 73 germplasm with resistance to Egyptian
alfalfa weevil, Hypera brunneipennis (Boheman). Crop Sci. Loan, C. 1981. Suppression of the fungi Zoophthora spp. by
captafol: a technique to study
interaction between disease and parasitism in the alfalfa weevil, Hypera postica (Coleoptera: Curculionidae). Proc. Ent. Soc. Ont. 112: 81-82. Los, L. M. & W. A. allen.
1983. Incidence of Zoophthora phytonomi (Zygomycetes: Entomophthorales) in Hypera postica (Coleoptera: Curculionidae) larvae in
Virginia. Environ. Ent. 12: 1318-21. Manglitz, G. R. & B. A. App.
1957. Biology and seasonal development of
the alfalfa weevil in Maryland. J.
Econ. Ent. 50: 810-13. Michelbacher, A. E.
1940a. Effect of Bathyplectes curculionis on the alfalfa-weevil
population in loland middle California.
Hilgardia 13: 81-99. Michelbacher, A. E.
1940b. Further notes on Bathyplectes curculionis in lowland middle
California. J. Econ. Ent. 33: 892-95. Morris, M. J. 1985. Influence of the fungal pathogen, Erynia sp. (Zygomycetes:
Entomophthorales), on larval populations of the alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae) in
Illinois. M. S. Thesis, University of
Illinois, Urbana. 47 p. Muka, A. A. 1976. A disease of the alfalfa weevil in New
York. proc. Forage Insect Res. Conf.
18: 28-29. Nordin, G. L., G. C. Brown & J. A. Millstein. 1983.
Epizootic phenology of Erynia
disease of the alfalfa weevil, Hypera
postica (Gyllenhal) (Coleoptera:
Curculionidae) in Central Kentucky.
Environ. Ent. 12: 1350-55. Poinar, G. O., Jr.
1963. Hymenopterous parasites
of the alfalfa weevil, Hypera
postica, in New York. J. Econ. Ent. 56: 533-34. Puttler, B., D. L. Hostetter, S. H. Long & R. E.
Pinnell. 1978. Entomophthora
phytonomi, a fungal pathogen
of the alfalfa weevil in the mid-great plains. Environ. Ent. 7:
670-71. Streams, F. A. & R. W. Fuester. 1967. Biology and
distribution of Tetrastichus
incertus, a parasite of the
alfalfa weevil. J. Econ. Ent.
60: 1574-79. Summers, C. G. 1976. Population dynamics of selected arthropods
in alfalfa: influence of two
harvesting practices. Environ. Ent.
5: 103-10. Summers, C. G. 1989. Insect pests of forage alfalfa. Proc. 1989 Alfalfa Symp., Univ. Nevada,
Reno. Special Publ. 89-1. p. 134-46. Summers, C. G., R. L. Coviella & W. R. Cothran. 1975.
The effect on selected entomophagous insects of insecticides applied
for pea aphid control in alfalfa.
Environ. Ent. 4: 612-4. Summers, C. G., R. E. Garrett & F. G. Zalom. 1984.
New suction device for sampling arthropod populations. J. Econ. Ent. 77: 817-23. Titus, E. G. 1907. A new pest on the alfalfa. Desert Farmer 3: 7. Titus, E. G. 1910. The alfalfa leaf weevil. Utah Agric. Expt. Sta. Bull. 110: 72 p. |