Klamath Weed biological control program now is in the second of three phases

3. K. Holloway and C. B. Huffaker

Beetles selected for release In the Klomath weed biological control rogram thrive on the Approximately 97% of the 122 col- body to become photosensitized-sensi- plant pest and starve in !s absence. onies of Klamath weed beetles released tive to the sunlight. Blisters form on these in 19 counties of the State are considered areas when the is exposed to the established. direct rays of the sun with the result The Commonwealth of Australia, like The establishment of colonies of the that the animal becomes scabby, sore- California, has the problem of Klamath beetles-natural enemies of the Klamath mouthed and underweight. weed-or St. Johnswort-and as early as weed-completes the first part of a three- Chemical control of the weed has been 1920 began a search for enemies phase program designed to effect control attempted. In most places the cost of of the weed. The preliminary work cen- of the noxious weed by the biological the materials and the inaccessibility of tered in Europe, where the plant origi- method. The program is the first of its the land to be treated have been limiting nated. kind in the United States and was set up factors. The application of borax has Starvation and reproduction tests of as a cooperative undertaking between the been satisfactory in controlling new and a considerable number of insect species United States Department of Agriculture small infestations, but this method is im- were made on representative plants of and the University of California Division practical in large-scale control programs. economic importance. These tests were of Biological Control. made on 42 species of widely distributed Klamath weed ( perfora- plants representing 19 families, to de- tun L.) is known in Europe, where it Three Phase Program termine whether there was either feeding originates, as St. Johnswort. It was first Biological control of Klamath weed by or reproduction upon them. reported in California about 1900, when -natural enemies-was considered The progress of the Australian experi- it was discovered in the vicinity of the possible and efficient; so a three-phase ment was watched closely by California Klamath River. program was planned. scientists. About eight years after the It is an aggressive plant, and since its The first phase demanded the discovery first field releases of two species of the discovery along the Klamath River it has of natural enemies of the weed and their insect , encouraging results taken over about 400,000 acres of Cali- importation and establishment in Cali- were reported. These reports led to ne- fornia open-range grazing lands, greatly fornia. The second phase was concerned gotiations between the University of Cali- cutting their carrying capacity. with the devlopment of parent colonies fornia and the Bureau of Entomology and Klamath weed is detrimental to the in each of the infested counties of the Plant Quarantine, United States Depart- thrift of .sheep and cattle, particularly State so that ultimately each county ment of Agriculture, which resulted in an cattle. Though the weed is not palatable, would be independent of further intro- authorization by the Department for im- livestock will graze it when forced to do ductions. The third phase would be the portation from Australia to California of so by the absence of better forage. actual control of the weed in the field the two species of leaf-feeding beetles The eating of the weed causes the as the successful result of the first two about the size of a ladybird and of a white-skinned portions of the animal's phases. Continlid on page 10

Left: Klamath weed in bloom. Center dark strip: The weed dying under the attack of the hungry beetles. Right: Field cleared of the noxious weed. KLAMATH ter and spring months on the basal CITRUS growth of the weed. Apparently, this de- Continued from page 3 Continued from page 5 struction occurs at a very critical time shiny, dark blue-green color-Chrysolina for the plant, as it is later unable to send further support to the view that the poor hyperici and Chrysolina gemellata-with up seed stalks and the roots die during growth in old citrus soils is possibly due the proviso that feeding tests be made the following summer. to a build-up of detrimental organisms. on the following plants: Sugar beet, flax, Late in the season of 1945four colonies, Examination of the roots of seedlings hemp, sweetpotato, tobacco, and cotton. of the beetles were released in areas in- grown in these fumigated old citrus soils A cooperative project for the importa- fested with Klamath weed. One of these showed a great reduction in the amount tion, testing and colonization of these colonies became established, but the sur- of root rotting and in the numbers of species then was set up between the Bu- vivors were so few that it was not pos- fungi and nematodes. These results indi- reau of Entomology and Plant Quarantine sible to make recovery collections of the cate that microbial factors are at least and the University of California. beetles until 1947. partly responsible for reduced growth in Importations were begun in October At one test location in Humboldt second and third citrus plantings. 1944. Most of the shipments consisted of County where the beetles were released adult beetles in the estivating stage-lying in January of 1946, they have increased dormant during the summer months- rapidly and have destroyed a continuous Possible Explanations when they were shipped from the South- stand of about 20 acres of Klamath weed. In every experiment growth of seed- ern Hemisphere. The successful establishment of these lings in the fumigated old citrus soils was The first problem encountered after the beetles in California completed the first not as great as that in untreated or fumi- arrival of the beetles in California was phase of the biological control program. gated noncitrus soils. to change their life cycle so it would be The second phase, the distribution and There are several possible explana- in accord with the seasons of the North- development of colonies in each of the tions. First, it is possible that the fumi- ern Hemisphere. infested counties, is now well underway. gants did not kill all the detrimental By subjecting the dormant adults daily During the winter and spring of 1947-48 organisms. Second, assuming that all to fine sprays of water-imitating the some 557,000 adult beetles were released were killed, it is possible that conditions winter rains of Australia-the beetles at 122 locations in 19 counties. in the fumigated old citrus soils are more were brought out of their estivation and The third phase of the program, the favorable for the reestablishment of the into the egg-laying stage of their life actual control of Klamath weed on the detrimental organisms than for their es- cycle, so that fertile eggs were obtained range, will require millions of the beetles, tablishment in noncitrus soil. Third, some within two to three weeks after the adult and it will be several years before the toxic material may accumulate in the soil. beetles arrived in California. present field colonies can grow to the Such a hypothetical toxic substance could During the first year of importation, necessary numbers. It is recommended originate either from the citrus roots sufficient numbers of the beetles were re- that in the meantime growers and ranch- themselves or from organisms decompos- ceived to conduct the required feeding ers use the current control methods of ing root excretions and dead root mate- tests. These tests were completed in May, cultivation, application of borax, and rial. If the latter should be the case the 1945, with no feeding or egg laying tak- good management practices. cause of reduced growth would be indi- rectly microbial in nature; that is, al- ing place on any of the test plants. It was J. K. Holloway is Entomologist, United States found that both species of beetles would Department of Agriculture, and Associate in the though the adverse microorganisms may starve and die on any plant other than Experiment Station, Division of Biological Con- be killed, substances produced by their Klamath weed. trol, Berkeley. previous activity could continue to retard C. B. Huflaker is Assistant Entomologist, Di- growth of citrus, at least for a time. The larval, or immature, stages of both vision of Biological Control, Experiment Station, species feed and develop during the win- Berkeley. Observations The number of adults of species of Klamath weed beetles and the nuqber of two Although studies suggest that detri- locations at which beetles were released in 19 counties in California, 194748. mental soil organisms and possibly other Chrysolina gemellata factors cause reduced growth of citrus County No. adults No. locations No. odults No. locations trees in old soils, other and interrelated Amador 15,000 3 7,500 3 factors may be involved under field con- Butte 20,000 4 5,000 1 ditions. Calaveras 15,000 3 7,500 2 Any condition which decreases tree Del Norte 5,000 1 vigor such as adverse climatic factors, El Dorado 10,000 2 7,500 2 heavy bearing, insect infestation, or in- Humboldt 70,000 14 1 12,500 23 secticides might render the tree more sus- Lake -2,500 1 ceptible to the activities of soil organisms. Madera 5,000 2 Undoubtedly several interrelated factors Mariposa 4,000 1 cause reduced growth of citrus in old Mendocino 20,000 4 5,000 1 citrus soils. Some of these factors are Nevada 7,000 2 primary in nature while others are of a Napa 5,000 1 secondary type. Shasta 40,000 8 16,000 6 A wide range of studies are currently Siskiyou 35,000 7 underway both in the field and in the Sonoma 20,000 4 5,000 1 greenhouse to find efficient ways and Tehama 10,000 2 1 1,000 3 means of overcoming these unfavorable Trinity 40,000 8 5,000 1 conditions. * Tuolumne 10,000 2 7,500 3 James P. Martin is Assistant Chemist in the Yuba 30,000 6 4,000 1 Experiment Station, Riverside. The above progress report is based upon Re- Total 345,000 70 2 12,000 52 seaich Project No. 1263.

10 CALIFORNIA AGRICULTURE, FEBRUARY, 1949