922 NATURE August 29, 1964 VOL.2.C)3

THE MELLON INSTITUTE, PITTSBURGH HE fifty-first annual report of the Mellon Institute, infra-red spectroscopy has taken two new directions, one T Pittsburgh, covering the year endcd Fcbruary 29, involving torsions of methyl groups attached to a phenyl 1964*, includes the usual list of publications and records ring, and the othor, torsions round the central single bond expenditure on independent and sponsored research in the butadiene glyoxal and acrolein systems. amounting to 6·4 million dollars. At the end of the year A new vacuum ultra-violet spectrophotometer with low the Institute had a staff of 541, including 347 professional dispersion is being used to obtain the absorption spectra and technical workers. During the year arrangements of systems which have electronic transitions of interest were made for much closer working with the Carnegie beyond the range of most commercial instruments. Institute of Technology and the University of Pittsburgh: Studies on the chemical bonding of tris-2,2-dipyridyl a non-profit corporation was formed under their joint complexes with transition metal ions in unusual sponsorship, with the major objective of promoting closer low oxidation states continued, while an investigation contact and co-ordinated efforts among members of the of the different intermediate products isolated during staffs and local industry. the chemical or electro-chemical reduction of solutions In theoretical chemistry, the judicious application of containing tungstates was started. In a direct investigation the principles of molecular orbital theory and its simplifica­ of hydrogen content of acidic catalysts, it was found the tion, ligand field theory, can yield a striking clarification total hydrogen content could be accurately determined by of the various colours exhibited by transition metal ions exchange with deuterium. The isomerization of cyclo­ with the architecture of the crystal lattices housing them. propane to propylene has been examined over series of Work on the nature of a chemical binding in transition alumina and silica-alumina catalysts, and spectro­ metal cyanides has been resumed and a general invostiga­ scopic investigations of the chemisorption of triphenyl­ tion initiated of the relative placement of energy-Ievcls in methane and of polynuclear aromatic hydrocarbons other families of transition metal elements. In continuum continued. physics, mathematical methods were developed for finding Other work was concerned with tho total synthesis of the restrictions which the Second Law of Thermodynamics diterpenes and diterpene alkaloids, and the effect of ring places on constitutive equation!;' and solutions have been size on the nuclear magnetic resonance shifts of the obtained for some unsteady flow problems in the theory of saturated cyclic hydrocarbons from cyclopropane to a second-order fluid, a fluid the behaviour of which cycloheptodecane was investigated. A survey of the approximates that of general viscoelastic fluids in slow chemical and physical characteristics of the asphaltic flows. The coefficient of thermal expansion was determined fractions of some 40 crude oils and other bituminous for several copper germanium alloys with hexagonal close­ materials was completed, while a broad research packed structure by investigating their lattice spacings as programme of the separation, concentration and a function of temperature between 24° and 6000 C. Thc identification of volatile components of potential food influen.ce of temperature, strain rate, an.d interstitial flavour import was continued. A soluble poly-cyclopenta­ impurities on the plastic deformation of poly-crystalline diene of relatively high molecular weight has been obtained niobium has been investigated, and results from a thermal using a new homogeneous catalyst system conveniently activation analysis supported the view that the mechanism formed in situ, and the theoretical investigation of controlling the rate of flow of dislocations at low tempera­ branched polymers in dilute solution was extended to tures is that of overcoming the Peierls-Nabarro barrier by include a statistical mechanical calculation of the second the nucleation of kinks on dislocations. Electron spin virial coefficient in the equation of state for 'comb' resonance investigations continue to provide very detailed molecules. A detailed investigation was undertaken of the information on the structure of free radicals. An investiga­ crystallization, kinetics and morphology of poly (tetra­ tion of internal rotation in molecules by low-frequency methyl-p-phenylene) siloxane. A rapid method of electrophoresis on cellulose acetate strips has been found • Mellon Institute. Fifty-first Annual Report of the Institute for the for developing the electrophoretic components of brome­ Fiscal Year ended February 29, 1964. Pp.39. (Pittsburgh, Pa.: Mellon Institute, 1964.) grass mosaic virus.

MIRIDS AND OTHER INSECT PESTS OF COCOA N view of the common problems which prevail in the sing'ularis Hag!., were prosented_ D. theobroma and S. I field 0f agricultural research in West Africa, the singularis being the most important insect pests of cocoa Governments of the then British and French Territories in West Africa, it was the feeling of the 1963 conference decided to institute a series of conferences on cocoa that the problems of resistance and control should be the (Theobroma cacao L.), oil palms, rice, groundnuts and subject of another meeting in March of the following year other crops to which the Belgian, Liberian, Portuguese when the results of experimental work in the intervening and Spanish Governments would be invited. The first of season of high mirid populations would be available. The these conferences was on cocoa and was held at the West opportunity was also taken to include other insect pests African Cocoa Research Institute (now Cocoa Research of cocoa, and the conference was held during March 24--27, Institute (Ghana Academy of Sciences» at Tafo in Ghana 1964, at the West African Cocoa Research Institute in December 1953 (ref. 1). Apart from a conference on (Nigeria) at Ibadan, Western Nigeria. In view of the Cacao Brooding2, held in Ghana in 1956, no further con­ prevalence of mirid attack on cocoa in many producer ferences on cocoa occurred in this series until August cOlmtries outside Africa and of other common entomo­ 1963, when a conference on Cacao Mirid Contro!"" was logical problems, this conference was given an inter­ held in Ghana. At this conference information was national bias. released on the existence within Ghana of populations of The emphasis of the conference was naturally on mirid the mirid (= capsid) Distantiella theobroma (Dist.) (Hemi­ resistance and control, but Mr. P. F. Entwistle and Mr. ptera; Miridae) resistant to lindane (gamma-BHC) and A. Y oudeowei presented a general, but preliminary, to other cyclodiene insecticides. world review of cocoa mirids. Attack on cocoa by a mirid At the same conference, data suggesting the existence (Helopeltis antonii Sign.) was first noted in Ceylon in within Nigeria of a similarly resistant mirid, Sahlbergella 1863 (ref. 5), and since then at least 34 more species have

© 1964 Nature Publishing Group No. 4948 August 29, 1964 NATURE 923 appeared on cocoa throughout the world. The only Nations World Health Organization. H e found eleven significant producing area which appears to have remained compounds to have a higher index than lindane. Dr. entirely free from attack is the Caribbean archipelago. B. M. Gerard suggested that 'index of acceptability' would New adaptations of mirids to cocoa have occlUTed ill. be a better name and thought it best to ignore the index recent times; for example, during the past tell. years, altogether when the insecticide is 'obviously safe', and to five species have appeared on cocoa in the Territory of consider only its efficiency and cost. On this basis, and Papua and New Guinea (1954- 57), one species in Mada­ from some additional data, Dr. Gerard considered only gascar (1960), and two species in the State of Sabah seven or eight of these candidate compounds worthy of (Malaysia) (1961-62). In addition, H. antonii appears to field t ests. have been completely replaced on cocoa in Ceylon by Dr. D. G. Peterson and Mr. E. F. Bond described the Helopeltis ceylonensis De Silva, a species not described final phase of their field control experiments in Ghana until 1957. S. singularis, which at one time appeared to with 'Sumithion' and carbaryl ('Sevin 85·S') which, when be the dominant species in Ghana, has, since the wide­ applied by motor-powered knapsack machines adjusted scale use of lindane, become much less common than D. to deliver 0'19 gal. per mill., were equally effective, in 4 theobroma • This dynamic situation extends to behaviour contrast to laboratory findings which suggested that, within the crop; for example, D. theobroma, which now when applied in acetone solution, carbaryl has eight times attacks both mature and seedling trees, was at one time the efficiency of 'Sumithion' . In Nigeria , Mr. Entwistle, restricted to seedlings. It is not easy to make a world Mr. Youdeowei and Mr. W. Eguagie conducted trials with assessment of the status of mirids as pests, but there is these two insecticides applied with pneumatic knapsack little doubt that attack is most severe in West Africa. machines fitted with spray lances 5 ft. long, a type which Ill. the New World, attack tends to be locally restricted, many farmers already possess. These machines have a and this is also true of Papua and New Guinea and of shorter distanee of throw (about 5 ft. with the m odel Sabah, but not of Ceylon and Java, where attack is by used) and distribute the spray deposit less satisfactorily species of the genus Helopeltis (which have a very wide than motor-powered ones. Two oz. carbaryl or 1 oz. host-plant range). 'Sumithion' in 5 gal. water per 100 trees gives approx­ Mr. G. R. Conway reported that in Sabah a hitherto imately 86 per cent control. At the same toxicant level, undescribed mirid species, Platyngomiriodes apiformis but at lower volumes, less control was achieved, and Ghauri. and Helopeltis clavifer Walle (which first attacked increasing the toxicant by 50 per cent, at the 5-gal. rate, cocoa ill. Papua and New Guinea in 1954), has recently did not appear to improve control. Hence volume, begun to attack cocoa. P. apiformis initially confined its probably as coverage, seems to be the limiting factor. attacks to pods, but later began to damage stems severely Dr. G. E. Marshall commented on some of the problems and is considered a potentially more serious pest than inherent in the conduct of mirid control trials. Among H. clavif er. Mr. G. S. Dun submitted notes on a list of variables are the mechanically disturbing effeet of counting 249 cocoa pests in the Territory of Papua and New on mirid populations, recorder and spray application Guinea, prepared by Dr. J. J. H. Szent·Ivany, among efficiency and differences in coverage resulting from the which were five species of mirids which did not begin to use of different types of machine. He pointed to the attack cocoa until 1954. nacessity for developing both intra- and inter-nationally Mr. M. Wessel presented a paper 011. the climate of the standardized experimental procedures which will allow a cocoa-growing areas of Western Nigeria, in comparison comparison of findings. There is a need for developing with some other producer countries in West Mrica, which additional screening steps between purely laboratory provided a necessary background to discussion of species assessment and full-scale field trials. distribution and the design of regionally adapted spray Extension work in mirid control was described by Mr. programmes. M. J. E. Decelle and Dr. G. Nonveiller J. O. Akinwolemiwa for Western Nigeria, where 600,000 reported there was no resistance ill. the Ivory Coast or farmers have been trained in mirid control during Cameroun, though one popUlation of D. theobroma in the 1956-63, and by Dr. Nonveiller for Cameroun, where Ivory Coast showed a bimodal distribution of kill when the 1964 anti·mirid campaign is designed to treat 350,000 exposed to cydodiene insecticides. Mr. J. N. Telford said acres. D. theobroma was found to be resistant in a large area of Dr. J. Miyamoto reported that- the poorer penetrability Ghana comprising a portion of Ashanti and Eastern of 'Sumioxon' than methylparaoxon (the oxygen analogues Region and also in a number of smaller isolated areas of 'Sumithion' and methylparathion) into brain, together within these two Regions. The intensity of resistance with the poorer formation of acid-precipitable phosphorus had not been fully measured, though three areas tested therein, were assumed to be the main factors in reducing contained 90-100 per cent resistant individuals. While the toxicity of 'Sumithion'. M. Decelle reported that no indication of resistance in S. singularis had been found carbaryl and 'Sumithion' caused no alteration in cocoa in Ghana, Mr. Entwistle reported that a population of flavour, but that "three or four tasters" , out of a total of this species containing resistant individuals has been "22-24", showed slight allergic reactions after tasting the located in Western Nigeria. D. theobl'oma occurs sparingly 'Sumithion' ·treated samples. within the area of resistance of S. singularis in Nigeria, Mr. Youdeowei reported on progress in the development but does not itself appear to be resistant. of artificial methods of rearing mirids (particularly S. In the Ivory Coast, M. Decelle reported that nine phos­ singulari8) in Nigeria, work which is of importance not phoric esters were tested in the laboratory on cocoa mirids only for the investigation of the genetics of resistance to and the action of dichlorovos (DDVP) was noted to be insecticides, but which could also provide a supply of particularly fast, though in comparison with 'Sumithion' mirids for laboratory work at times of the year when it gave poor control in field trials at 0·3 per cent. Mr. G. they are scarce in the field. Prins described the laboratory assessment of 16 organo­ Experiments in Ghana, where most of the cocoa is phosphates, five carbamates, one vegetable and one grown beneath the shade of forest trees, have shown that vegetable insecticide plus a synergist sprayed on to shade removal leads quickly to greatly increased yields". various parts of ana"sthetized fourth and fifth instal' Dr. Gerard presented a paper on the insect pests of nymphs of D. theobroma in Ghana. He assessed his unshaded cocoa in Ghana and advised that before wide­ results by the spread shade removal is recOlnmended its side-effects , . , ( oral LD50 to rats ) should be investigated on large trial plots. Index of effectIVeness = LD50 to insects x 1,000 Mr. W. R. Ingram described the development of in­ jurious infestations of the aphis Toxoptera aurantii B. de which is all. attempt to combine safety to humans with Fon. on seedlings in nurseries in Uganda, which he thought insecticidal activity, and is used primarily by the United might be partially attributed to the previous use of DDT

© 1964 Nature Publishing Group 924 NATURE August 29, 1964 VOL. 203 to control caterpillars. Menazon, a systemic insecticide, tien-Ievcls of other insect pests. Insects normally of only applied at 0·25 per cent, gave excellent control. minor importance have been known to increase to pest 7 Mr. C. O. R. Everard assessed the rodent problem on status on cocoa following applications of insecticides • cocoa in West Africa. Most losses were of pods from the While sevBral of the species involved occur throughout trees rather than during drying er in storage. Under con­ West Africa, parasite and predator complexes of some of ditions of good husbandry pod losses should not normally these have been shown to differ regionally. Population exceed 3 per eent. The use of the most efficient traps increases resulting from the removal of such biological available would be unlikely to reduce losses appreciably, restraints will vary with the effect of insecticides on the and probably the best means of protection lies in the use particular species complex concerned. of relatively non-toxic repellents applied directly to the Delegates to the conference visited the Institute's pods. experimental station at Gambari, twelve miles from The working session on the final day of the conference Ibadan, where spraying machinery and methods in use concerned itself mainly with plans for the future, and it in Nigeria were demonstrated and local entomological was agreed that entomologists at present concerned wit.h problems illustrated in the field. experiments in mirid control in West Africa would com­ The Proceedings of this conference will shortly be avail­ municate further with the view of developiIlg standardized able from the Secretary, West African Cocoa Research systems for evaluating candidate insecticides in the field Institute (Nigeria), P.M.B. 5244, Moor Plantation, Ibadan, and, if possible, for sharing some of the labour involved Nigeria. P. F. ENTWISTLE in the conduct of tests designed to provide fcrmented and 1 Anon., Proc. TV. Afr. Internat. Caeao Res. Conf., 1953 (1953). dried samples of beans for taint and toxic residue tests. , A non., Proc. Cacao Breeding Conf., 1956 (1957). An appeal was made to the manufacturers to develop , Gerard, B. M., Nature, 201,353 (1964). methods which would allow the use of smaller samples , Dunn, J. A., Nature, 199, 1207 (1963). in taint tests, ar.d embody greater accuracy. Some prob­ , 'Wright, IT., Theobroma cacao or Cocoa. its Botany. Cultivation, Chemistry and Diseases (Colombo, Messrs. Fergnson, 1907). lems could not be dealt with on a joint basis, for example, , Cunningham, R. R., and Lamb, J., Nature, 182,119 (1958). testing candidate insecticides for their effects on popula- , Entwistle, P. F., Johnson, C. G., and Dunn, E., Nature, 184, 2040 (1959).

SOIL-PLANT-ANIMAL COMPLEX

MEETING of the Nutrition Society was held in the The vital role of increased irrigation in increasing crop A University of Reading on July 17 under the chair­ production in arid and semi -arid countries was emphasized. manship of Prof. R. G. Baskett (National Institute for Nevertheless, doubt was expressed as to whether present Research in Dairying, Shinfield). This meeting took the nutritional standards could be maintained in many of form of a symposium entitled "The Effects of Soils, these countries if the present-day population forecasts Fertilizers and Environment on the Yield and Nutrient turn out to be correct, even if potentially irrigable land Content of Plants". In his introductory remarks, the and water supplies are fully exploited. The considerable chairman mentioned that the subject of the symposium value of supplemental irrigation for increasing crop was something of a departure from the range of subjects production in countries such as the United States and normally discussed by the Nutrition Society, but it was Western European countries, including the United clear from the reactions of members and guests throughout Kingdom, is much less generally recognized and it is a the meeting that they considered it entirely appropriate technique which no country in the humid zone can afford that nutritionists should concern themselves with problems to neglect. of food production. Dr. Olivier ended his paper by considering the present The first paper of the day was one by Prof. J. N. Black outlook for food production and concluded that no reliable (Edinburgh) on "The Ultimate Limits of Crop estimate of world potential was possible at present owing Production". He began by reviewing the major factors to a lack of basic information on such vital matters as limiting the yield of plants which have been omphasized potential agricultural land and effective rainfall, particu­ in the past-soil fertility, including nutrient status, larly in areas where the most serious food shortages temperature, water supply, pests and disease and the occur. He stressed the need for the extension of soil genetic make-up of the plant. He continued by asking surveys, for the reorganization of meteorological obsorva­ the question "If it were possible to remove all the factors tions to make them more meaningful for agricultural acting to maintain yields at a low level, what would then purposes and for the compilation of statistical data on determine yield and what might the yield then be 1". crop yields by region and by soil types. The significance of this question lies in the fact that, if The relationship between plant nutrient content of answered, it would provide a yardstick with which to soil and leaves and crop yield was discussed by Dr. C. measure the efficiency of an agricultural system and the Bould (Long Ashton Research Station). He began by rate of progress of improvements in technique. Recent summarizing the present state of knowledge concerning work on the efficiency of the photosynthetic process was thc factors affecting the availability to plants of the then discussed, culminating in the conclusion that, in the inorganic ions in the soil and outlined the difficulties absence of other limiting factors, the productivity of crop inherent in chemical methods of assessing the nutrient plants is determined by the amount of solar radiation status of soils. A biological method, namely leaf analysis, available. The complex interrelationship between solar has been shown to provide a more reliable assessment of energy, leaf area index (the ratio of leaf area to ground plant nutrient availability. It is possible to establish for area) and crop-growth rate and ultimate yield was many species a range of nutrient concentrations at emphasized, and the necessity for interpreting the results specific stages of growth associated with gross deficiency, of field trials, involving fertilizer and other treatments, marginal supply and sufficiency, based on crop yield. in the light of these relationships was stressed. However, it is not yet possible to predict how much In his paper on irrigation as a factor in increasing food fertilizer is required to raise the nutrient status of a crop production, Dr. H. Olivier (Sir Alexander Gibb and from deficiency to sufficiency, although this may be Partners) surveyed the history of irrigation practices possible when more precise information relating soil from pre-historic times up to the present day, followed by nutrient status to plant nutrient content is available for a critical assessment of the potential increase in food different soils and crops. production in selected countries and regions in relation to Prof. A. H. Bunting (University of Reading) read a their land and water resources. paper on "Effects of Organic Manures on Soils and Crops"

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