Hq« . ^ • /^ 1 r\os AMERICAN AND EUROPEAN FOULBROOD IN COLONIES OF HONEY BEES IN CONNECTICUT John F. Anderson Harry K. Kaya BULLETIN 752 3T m t The Connecticut Agricultural Experiment Station, New Haven American and European Foulbrood In Colonies of Honey Bees In Connecticut John F. Anderson and Harry K. Kaya The Office of the State Entomologist, in accord- ance with Section 22-89 of the General Statutes, inspects colonies of the honey bee. Apis mellifera L., for diseases, the most important of which are the bacterial diseases commonly known as foulbroods. Inspections have been carried out yearly since 1910. In this Bulletin the incidence of foulbrood in 1974 is compared with the incidence in previous years. METHODS Bacillus lan'ue, which causes American foulbrood, kills mature larvae and young pupae after the brood cells ha\e been sealed. Slreplococcus ptuion which causes European foulbrood usually kills young larvae. in 1974, 6% of the registered colonies, selected at random in each county, were examined, infections were identified by characteristic odors and were verified microscopically. Samples of brood comb were taken to the laboratory for examination. Dead larvae were examined for spores of B. larvae. During the period 1910-1973 as many colonies as possible were examined by the inspectors. All known colonies were inspected from 1941-1946 and possibly in 1949. in the other years between 1910 and 1973 the inspectors tended to inspect colonies in areas where toulbrood vsas known to occur. Thus the disease incidence recorded lor these years rs higher than the actual level throughout the slate. RESULTS In 1974, less than 1% of the colonies examined were found infected with American foulbrood (Table i). This incidence was similar to rates of infection Table 1. Incidence of American Foulbrood in Connecticut, 1974 No. of colonies County Examined Infected Litchfield Hartford Windfiam Tolland Fairfield New Haven Middlesex New London Total 68 78 28 27 56 64 26 66 423 recorded in previous years (Table 2). Infected colonies were encountered in the 1974 random sample of hives only in Tolland and New London counties although American foulbrood occurs in ail counties in Connecticut. European foulbrood was prevalent at the time the inspection service was initiated in 1910 (Table 2). However, the disease declined rapidly until 1% or less of the inspected colonies were infected in 1921 Table 2. Incidence of American and European Foulbrood in Connecticut, 1910-)973* Apiaries No. % infected Year inspected EFB AFB Colonies No. % infected inspected EFB AFB Apiaries No. % infected Year I inspected EFB AFB Colonies No. % infected inspected EFB AFB 1910 208 76 0 1595 50 0 1943 2635 0 7 14903 0 3 1911 162 52 0 1571 27 0 1944 2451 <0.1 8 12360 <0.1 3 1912 1913 1914 153 189 463 48 44 33 0 0 1 1431 1500 3882 24 25 14 0 0 1 1945 1946 1947 2589 2827 1925 <0.1 0 0 6 6 6 13353 11920 9648 <0.1 0 0 2 2 3 1915 494 26 1 4241 10 0.2 1948 2165 <0.1 7 11837 0.1 2 1916 467 19 1 3898 7 0.2 1949 2423 0 8 13416 0 3 1917 1918 1919 473 395 723 17 10 7 0.4 1 3 4506 3047 6070 5 3 1 0.2 0.3 1 1950 1951 1952 2277 2632 2299 <0.1 0 0.1 7 4 6 12899 13895 9691 <0.1 0 <0.1 2 1 3 1920 762 4 1 4797 2 0.3 1953 2324 0 6 11406 0 3 1921 751 4 2.5 6972 1 1954 2201 0 5 11605 0 2 1922 1923 1924 797 725 953 4 2 2 1 1 1 8007 6802 8929 0.4 0.3 0.3 0.2 1955 1956 1957 2316 2355 0.1 <0.1 3 3 13166 9294 9253 < 0.1 < 0.1 1925 766 2 3 8257 0.5 1958 2218 0.1 4 9712 0.1 1926 814 3 2 7923 0.3 1959 2409 0 3 10146 0 1927 1928 1929 803 852 990 1 1 0.2 3 4 5 8133 8023 9559 0.3 0.3 <0.1 1960 1961 1962 2425 1720 1702 <0.1 0 0 3 1 3 9517 7013 7186 <0.1 0 0 0.5 1930 1059 0.3 5 10335 < 0.1 1963 1737 0 3 7371 0 1931 1232 0.1 3 10678 < 0.1 1964 1583 0 3 7198 0 1932 .1933 1934 1397 1342 1429 0 0 0.1 4 2 2 11459 10927 7128 0 0 <0.1 0.5 1 1965 1966 1967 1700 1690 2073 0 0 <0.1 3 3 3 7572 7179 7800 0 0 < 0.1 1935 1333 0 6 8855 0 2 1968 1655 0 4 6668 0 2 1936 1438 0.1 6 9278 <0.1 2 1969 1520 0 4 7241 0 2 1937 1938 1939 1438 1609 1627 0 0 0 7 8 5 10253 10705 8936 0 0 0 2 2 2 1970 1971 1972 1396 1592 1301 0 0 0 3 3 3 4983 6157 5184 0 0 0 2 1 1 1940 1719 0 9 8552 0 4 1973 651 0.2 7 3013 <0.1 3 1941 1942 2222 2354 0 0 8 10 10720 13777 0 0 4 4 'Data taken from Entomologist. the annual re port of the Office of the State and thereafter. European foulbrood was not found in the random sample of colonies. American foulbrood was first found in Connecticut in 1914 (Table 2). Incidence of colony infection rose to 4% in the 1940s, but has fluctuated from less than 1% to 3% since then. The percentage of American foulbrood-infected apiaries reached as high as 10% in 1942, although in more recent years the incidence has averaged 4%. Table 3 shows the average annual incidence of foulbrood in Connecticut by county from 1910-73. Incidence was highest in Fairfield County and lowest in Windham and Tolland Counties. It is apparent that the incidence of American foulbrood has not increased in the past 30 or more years, although the disease is present in all parts of the slate and is a potential hazard to beekeepers. European foulbrood is now rarely encountered in Connecticut. Table 3. Average Annual Incidence of American Foulbrood in Connecticut Colonies of Honey Bees, 1914-1973, by County. County Litchfield Hartford Windhann Tolland Fairfield New Haven Middlesex New London Percent infected piaries Colonies 3.9 1.4 3.4 1.2 2.3 0.8 2.1 1.0 7.3 2.3 6.4 2.0 3.7 1.3 6.3 1.8 ACKNOWLEDGMENTS Emil Pagan inspected the bee hives in the field, Mrs. Bonnie Hamid summarized the rates of foulbrood infection from the annual reports of the State Entomologist, and George Schuessler faithfully maintained the annual inspection records. We thank Dr. David Newton, Central Connecticut State College, for reviewing the manuscript. liVH )nnfl >vi3 amHi 101 nov 3iini-in3iiiov dO lN3WUIVd3a SO aivd saaj onv aovisod jaXojdm^ XjiuniJoddQ ]vnb^ uy S161 '3Nnr ZSZ Nli31in9 OOCS '3Sn 3ivAiUd UOJ AllVNSd HOiiTsnanw Noiivis iN3wia3dX3 iviinnnDidOv in3UD3NNOD 3H1