The occurrence and population changes of the northern corn rootworm, Diabrotica longicornis (Say), and the western corn rootworm, D. virgifera LeConte, were reviewed on the basis of information assembled at the Department of Agriculture of the State of Minnesota; and the Department of Entomology, Fisheries, and Wildlife and the Extension Entomologist\u27s Office of the University of Minnesota.
The review shows no record of the northern species in Minnesota before 1899, but it appeared between 1899 and 1915. Populations were probably very law until 1932. Sporadic infestations were reported between 1932 and l 953. Progressive increase in infestation from 1954 paralleled an increase in continuous planting of corn. The western species reached Minnesota in 196 l. By 1968 it was found in practically all counties where the northern species was found . There was no displacement of the northern species by the western in Minnesota, as happened in some other localities

Chiang, H. C.

Flaskerd, R. G.

English

University of Minnesota, Morris (UMM): Digital Well

Journal of the Minnesota Academy of Science Volume 36 Number 1 Article 16 1969 Northern and Western Corn Rootworms in Minnesota H. C. Chiang University of Minnesota, St. Paul R. G. Flaskerd Minnesota Department of Agriculture Follow this and additional works at: https://digitalcommons.morris.umn.edu/jmas  Part of the Entomology Commons Recommended Citation Chiang, H. C., & Flaskerd, R. G. (1969). Northern and Western Corn Rootworms in Minnesota. Journal of the Minnesota Academy of Science, Vol. 36 No.1, 48-51. Retrieved from https://digitalcommons.morris.umn.edu/jmas/vol36/iss1/16 This Article is brought to you for free and open access by the Journals at University of Minnesota Morris Digital Well. It has been accepted for inclusion in Journal of the Minnesota Academy of Science by an authorized editor of University of Minnesota Morris Digital Well. For more information, please contact skulann@morris.umn.edu. lowship from the National Institute of Health. The au-thor is grateful for the assistance and advice of Dr. H. T. David of the Statistical Center at the University of Min-nesota, Dr. F. M. Williams, and Miss Maureen Bell. References ALLEN, M. M. Simple conditions for growth of unicellu-lar blue-green algae on plates. J. Phycol. 4 (l) : 1-4. DAVIES, D.R. 1967. Absence of an oxygen effect and the genetically determined repair process. Nature 215: 829-832. HAYNES, R. H. 1966. The interpretation of microbial in-activation and recovery phenomena. Radiation Res. Supp. 6: 1-29. HuTCIIlNS0N, F. and F. POLLARD. 1961. Target theory and radiation effects on biological molecu]es. In BIOLOGY "Mechanisms in Radiobiology" Vol. 1. M. Errera and A. Forssberg Eds. Academic Press. KUMAR, H. D. 1962. Apparent genetic recombination in a blue green alga. Nature 196: 1121-1122. KUMAR, H. D. 1963. Effects of mutagenic agents on blue-green algae. Ph.D. Thesis, University of London. MARLER, J.E. and C. VAN BAALEN. 1965. Role of H 2O2 in single-cell growth of the blue-green alga, Anacystis nidulans. J. Phycol. 1: 180-185. PIKALEK, P. 1967. Attempt to find genetic recombination in Anacystis nidulans. Nature 215:666-667. YAN BAALEN, C. 1965. Quantitative surface plating of coccoid blue-green algae. J. Phycol. 1: 19-22. ZIMMER, K. G. 1961. "Studies on Quantitative Radia-tion Biology." Hafner Publishing Co., New York. Northern and Western Corn Rootworms ,n Minnesota H . C. CHIANG* and R. G. FLASKERD** ABSTRACT - The occurrence and population changes of the northern corn rootworm, Diabrotica longicornis (Say), and the western corn rootworm, D. virgifera LeConte, were reviewed on the basis of information assembled at the Department of Agriculture of the State of Minnesota; and the Department of Entomology, Fisheries, and Wildlife and the Extension Entomologist's Office of the University of Minnesota. The review shows no record of the northern species in Minnesota before 1899, but it appeared between 1899 ond 1915. Populations were probably very law until 1932. Sporadic infestations were reported between 1932 and l 953. Progressive increase in infestation from 1954 parallelled an increase in continuous planting of corn. The western species reached Minnesota in 196 l. By 1968 it was found in practically all counties where the northern species was found . There was no displacement of the northern species by the western in Minnesota, as happened in some other localities. The northern corn rootworm, Diabrotica longicornis (Say), has been in Minnesota for many years, but the western corn rootworm, D. virgifera LeConte, is a rela-tively newcomer to the state. It is acknowledged that in-festations of both species have been encouraged by con-tinuous planting of corn. The present review attempts to establish, by retrospect, the occurrence of both species and the increase of infestation as related to continuous corn planting in Minnesota. Information was gathered from several sources: pub-lished material; and files, correspondence, and interim re-ports at the Division of Plant Industry, Department of Agriculture, State of Minnesota; the Department of En-tomology, Fisheries, and Wildlife; and the Extension En-tomologist's Office, University of Minnesota. The events are presented chronologically in several periods. ''' Member of Department of Entomology, Fisheries, and Wild-life, University of Minnesota, St. Paul. ''"" Staff member, Department of Agriculture, State of Minne-sota. 48 Scientific Journal Series, Paper no. 6837, Minnesota Agri-cultural Experiment Station. St. Paul 55101. BEFORE 1899. The earliest mention of corn rootworm in Minnesota publications was by Dr. Otto Lugger, the state entomotogist, in his report of 1899, as follows: "In the western and central states a third species is found, the "corn root Diabrotica," named as from its long feelers. Its larva is a very serious pest. As this species winters in the egg state in corn fields, a simple rotation is all that is necessary to keep it in check. It is not found in Minnesota, at least no specimens have been seen or received, while D. 12-punctata and D. vittata are very common, and the latter seems to be rapidly on the increase." From the above, it seems fairly certain that D. longi-cornis was not present in Minnesota at that time. 1899 TO 1931. No further information was available until 1916, when C. W. Howard reported "The western (sic) corn root-worm (Diabrotica longicornis) has been reported in Minnesota for the first time during the past summer, appearing in several widely separated localities in the southern quarter of the state." Further search of the literature and the files of the The Minnesota Academy of Science State Department of Agriculture, the Department of En-tomology, University of Minnesota, and the County Agri-cultural Agent Offices uncovered no records of this insect for the period of 1916-31. Thus the available infonnation suggests that D. longi-cornis appeared in Minnesota some time between 1899 and 1 915, and was in very low populations up to I 931. 1932 TO 1953. In 1932 Dr. C. E. Mickel of the De-partment of Entomology instituted a system to record the insects which he identified for the county agents and the public. The records included, among other items, the scientific name, locality, and date of collection. The avail-able records in 1932 through 1953 are given in Figure 1. Unfortunately, it is not possible to compare this dis-tribution pattern with that of 1915, since Howard did not state exact localities. It is to be noted that most of the records since 1932 were from the east central counties, rather than counties at the state borders or with large corn acreage. One pos-sible explanation is that only the agents of counties near the University campus in St. Paul (Ramsey County) sent in specimens for identification. . Records at the State Department of Agriculture showed that damage on corn due to D. longicornis was reported in Wabasha and Dodge counties around 1944 to I 946, and in Rock, Jackson, Faribault, Murray, and Blue Earth counties in 1953. Thus, there have been sporadic noticeable infestations during this period. 1953 TO 1954. In 1953, the agricultural agents in the southwest and southcentral counties noted injuries in the form of root rot and lodging. Coupled with the fact that the populations of the northern rootworm were extremely high in Iowa and Nebraska, a plan was made to deter-mine the extent of the problem in Minnesota. The pro-gram included treatment of plots with insecticide for comparison with untreated areas. Twenty five fields were located in the spring of 1954, each 10 acres or more, which had been planted to corn in 1952 and 1953 and X \ X I 7 X would again be planted to corn in 1954. The counties are shown in Figure 1. Insecticides were applied as follows during the first two weeks of May. Two one-acre strips were sprayed across each field, and an untreated strip was left between them. In each field one strip was sprayed with aldrin and one with heptachlor, each at a rate of three-pound techni-cal material per acre. In late May and early June, soil samples were taken to determine the populations of soil insects. Only 35 wireworms and white grubs and no corn rootworms were noted in all the plots checked. The fact that no corn rootworms were found is to be expected, since the time of sampling was too early for the larvae and the technique was not suited to extract the eggs. Yield data were taken in 19 of the 25 fields. The average bushels of shefled corn, at 14 per cent moisture, per acre were 84.6, 81.6, and 80.3 in aldrin-treated, heptachlor-treated and untreated check plots respectively. The differ-ence between aldrin-treated and the check plots was sta-tistically significant. Since the wireworm and the white grub populations were low, we may assume that this dif-ference reflected the presence of at least some corn root-worm infestation in these areas. County agents became aware in 1954 that some farm-ers had applied insecticide in 1953 or planned to do so in 1954. Thus we may conclude that up to that time, al-though neither the Institute of Agriculture of the Univer-sity of Minnesota (county agents and extension special-ists) nor the State Department of Agriculture (insect sur-vey personnel) had any estimates of the populations or infestations, damage symptoms, if not actual crop losses, were severe enough to warrant treatment. 1954 l'O 1960. Farmers and county agents became aware of the presence and damage of corn rootworm. But no records on the population levels were taken. The increasing area of soil treatment may reflect the increas-ing extent of rootworm infestation. Estimates by the State Department of Agriculture showed an increase from 9 Figure 1. X=counties in Minnesota included in the soil insect survey in 1954. Localities having records of specimens of D. /ongicornis sent to the Department of Entomology, University of Minnesota, for identification between 1932 and 1953 were: 1, Hutchinson, 1932; 2, Castle Rock, 1940; 3, Caledonia, 1942; 4, Northfield, 1943; 5, Dassel, 1943; 6, Belle Plaine, 1944; 7, Worthington, 1952; 8, Jordon, 1952; 9, Albert Lea, 1953. Journal of, Volume Thirty-six, No. I, 1969 49 15,000 acres treated in 1955 to 336,150 acres in 1960 (Table 1). It is generally known that crop rotation inter-rupts the life cycle of the corn rootworm, and continuous cropping of corn encourages this insect. No statewide sta-tistics were available at that time, but information on farms in Waseca County, Minn. (Chiang et al, 1961) showed that fields planted to corn after corn increased from 10% in 1955 to 20% in 1959 (Table 2). There was a continuous increase in corn rootworm infestation in Minnesota from 1954 to 1960, a period when the per-centage of fields in continuous corn planting also in-creased. 1961 TO 1968. Until 1960 only the northern species was involved. In 1961 the western species first appeared in the State. It moved progressively eastward and north-ward and now is found practicaBy in all counties where the northern species is found (Fig. 2). With the combined infestation of both species, the number of acres treated for corn rootworms increased from 336,150 in 1960 to 2,000,000 in 1965 (Table 1). This increased infestation again may be related to the in-crease in continuous corn planting. On the basis of information from Waseca county, fields in continuous com were 33 per cent and 43 per cent in 1961 and 1963, respectively (Table 2). In 1967, fields sampled by State Department of Agriculture personnel for rootworm adult populations also were checked to de-termine if each was first-year com or continuous corn. Table 3 summarizes the percentages of fields in contin-uous corn in different districts. Of 55 fields in the south-central district, in which Waseca county is situated, 69 per cent were in continuous corn. It is significant to note that for the State as a whole, 67 per cent of 230 fields were in continuous corn, very close to the 69 per cent in TABLE I. Estimates of number of acres of corn treated for corn rootworms in Minnesota, 1955-1967. Year 1955 1959 1961 1963 1967 Year 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 No. acres treated 15,000 7,000 125,500 71,000 244,830 336,150 1,000,000 1,000,000 1.000,000 2.000,000 2,000,000 1,500,000 1,600,000 TABLE 2. Percentage of fields planted to continuous corn in Waseca County, Minn. Percent 10 20 33 43 69 Sources of information Chiang et al. 1961 Chiang et al. 1961 Hill et al. 1967 HiU et al. 1967 State Department of Agriculture• • see also Table 3. 50 1961 :::::::::: 1962 ;:;::::::::: 1963 .fl.fl.fl. 1964 1965 ll!lffllll 1966 ==: 1967 ::::::_:,: 1968 Figure 2. Years in which D. vergifera was first recorded, by counties in Minnesota's principal corn-growing area. the south-central district. This relationship suggests that the general trend of continuous corn planting in the south-central district is an approximation of the state average. Thus during the 13 years 1955 to 1967, the continuous planting of corn increased approximately from IO per cent to 69 per cent. In 1967, the records on beetle populations were kept separately in fields in first-year corn and in fields in con-tinuous corn. These are summarized in Table 4. Among the continuous plantings, 71 per cent of the fields had beetles, but among the first-year corn fields, only 32 per TABLE 3. Percentage of fields planted to continuous corn in different districts in Minnesota, 1967. No. fields Fields in continuous corn District checked No. % Southwest . . . . . . . . . . . . . . . . 45 Southcentral . . . . . . . . . . . . . . 55 Southeast . . . . . . . . . . . . . . . . . 45 Westcentral . . . . . . . . . . . . . . . 35 Central . . . . . . . . . . . . . . . . . . 40 State as a whole . . . . . . . . . . . 220 24 38 38 20 29 149 55 .6 69.1 84.4 57.1 72.5 67.0 TABLE 4. Comparison of adult populations in first-year corn and continuous corn in 46 Minnesota counties, 1967. 1st-yea r corn Fields checked . . . ..... . . .. . .. . Fields with beetles at time of check Beetles present at time of check Northern species ..... ....... . . Western species ... .. . . .. . ... . . Total .............. ......... . Fields with no beetles at time of check ........ . ... .. . . . .. .. . Beetles/field Fields with beetles . ... .. . . . . . All fields ..... . .. .. .. . ..... . 71 16 (32 % ) 22 19 41 55 (68 % ) 2.5 0.6 Continuous corn 149 116 (71%) 2102 496 2598 33 (29%) 22.4 17.4 The Minnesota Academy of Science TABLE 5. Percentage of western beetles according to counties and to the magnitude of 1968 populations. 1964 With 5 years data Jackson ......... 56 Faribault . . . . . . . 11 Lyon ........... 44 Lac Qui Parle . . 53 Nobles ......... 72 Murray . . ..... . Rock ... .. . .. . . Freeborn . . . . .. . Blue Earth . . ... . Watonwan .. . . . . M artin ..... .. . . Brown .. . .... . . Nicollet .... . . . . Cottonwood . .. . . Pipestone .. . ... . Mower .. . ... . . . Yellow Medicine . Lesueur ..... .. . Sibly .. . . . .... . . Fillmore ....... . W aseca . ... . ... . Steele .. ....... . Dodge .. . . . .. . . . Lincoln .. .. .. .. . Houston ... . .. . . Redwood ... . .. . Scott ....... . .. . 56 51 5 5 37 48 30 17 64 34 8 40 0 26 I 0 2 7 31 0 35 2 With 4 or fewer years da ta Big Stone ...... . Swift .......... . Carver .... . ... . Olmsted ....... . Rice ......... . . Winona ........ . Wabasha ..... .. . Kandiyohi .... . . Goodhue ...... . Hennepin ...... . Dakota . .... . .. . Wright . .. . .... . McLeod . ... .. . . Meeker ... . ... . Chippewa .. . ... . Renville ... . ... . Washington ... . . Pope ...... . . . . . Stevens . . ... . .. . Stearns .. . ... . . . Sherburne .. ... . Isa nti . . . . ..... . Anoka ... . ... .. . 1965 89 24 6 11 9 81 81 0 7 67 18 2 2 17 0 5 0 2 0 0 12 12 7 4 0 18 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0 0 0 1966 67 57 5 6 65 44 62 14 13 56 19 50 7 14 29 6 I 20 0 I 9 33 0 24 0 9 9 0 0 0 5 15 I 0 0 0 17 9 3 0 0 0 0 Journal of, Volume Thirty-six , No. I, 1969 1967 67 48 28 19 8 5 81 100 27 5 54 26 7 38 8 40 0 0 0 4 17 28 35 12 4 14 20 0 0 0 36 24 19 17 15 9 0 0 0 0 0 0 0 I 1968 87 75 74 62 56 46 42 40 31 30 27 22 19 11 10 8 7 6 4 2 0 0 0 0 0 0 0 47 14 4 0 0 0 0 0 0 0 0 0 0 0 0 0 3 20 0 0 0 0 0 cent had beetles. The continuous corn fields had an aver-age of 17 .5 beetles/sample at the time of checking, while first-year corn fields averaged only 0.6 beetles. These data reaffirm the role of continuous corn planting in en-couraging rootworm infestation. Since the western species is highly tolerant to some in-insecticides, it is considered more destructive than the northern species. The western species also virtually dis-placed the northern species in some areas outside this state (Hill 1967). Thus eastward expansion of the western species in different counties of Minnesota is sum-marized in Table 5. Unlike previous reports from other areas, however, there was no consistent trend of displace-ment of the northern species by the western species in Minnesota. Acknowledgements The authors wish to express appreciation for the as-sistance of extension agents Raymond Palmby, Wayne Weiser, and Gene Williams, who contributed information for this study. References Cited CHIANG, H. c., J . L. JARVIS, C. C. BURKHARDT, M. L. FAIRCHILD, G. T. WEEKMAN, and C. A. TRIPLEHORN. 1961. Populations of European corn borer, Ostrinia nubilalis (Hbn) in field corn, Zea mays (L.) in the northcentral United States. Missouri Agr. Exp. Stat. Res. Bull. 775. 95 p. HILL, R. E. 1967. Changes in distribution and domi-nance of rootworm species in Nebraska, 1948-66. Proc. N.C. Br. Entomol. Soc. Amer. 22: 163-4. (Ab-stract.) HILL, R. E., A. N. SPARKS, C. C. BURKHARDT, H. C. CHIANG, M. L. FAIRCHILD, and W. D . GUTHRIE. 1967. European corn borer, Ostrinia nubilalis (Hbn) popu-lations in field corn, Zea mays (L.) in the North Cen-tral United States. Nebr. Agr. Exp. Stat. Res. Bull. 225. 100 p. HOWARD, C. W. 1916. Three important insect pests. J. Econ. Entomol. 9: 236. LUGGER, 0. 1899. Fifth Annual Report of the Entomolo-gist of the State. 248 p. State of Minnesota. 51 

Northern and Western Corn Rootworms in Minnesota

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Northern and Western Corn Rootworms in Minnesota

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