Browsing by Author "Hocking, D."
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Item Cordyceps Barnsii Thw, a Fungal Parasite of White Grub in Sugarcane(1966) Hocking, D.; Tropical Pesticides Researcb Institute, Arusba, TanzaniaWhite grub, the larva of the cockchafer, (Cochliotis Melolonthoides) Gerst, is the major pest of sugar cane at the Tanganyika Planting Company’s irrigated estate at Arusha Chini. Although it is not known as a serious pest elsewhere, other similar estates have not been in existence long enough or have not sufficient records for a build-up to occur or be noticed.Item Disease Resistance in Coffee Berries(1967) Hocking, D.From these initial preliminary data, the following suggestions arise:- (a) That these coffee berries possess an inherent antifungal compound(s) which is heat-labile. (b) They have a phytoalexin type response to attempted infection (c) In vivo, the CBD form must have mechanisms to inhibit the phytoalexin response and either to destroy or tolerate the inherent antifungal compound(s). These are of sufficient interest and promise to justify a continuation of the study in detail.Item Disease Resistance in Coffee Berries -Loss and Recovery after Heating(1967) Hocking, D.Pre-treatment with heat has long been known to decrease the resistance of plants to disease Salmon (l905a and b) successfully infected various species of Gramineae with normally incompatible physiologic races of Erysiphe, by heat pre-treatments of detached leaves. Later investigators have obtained similar results (Kassanis 1952, Yarwood 1956 and 1963), while others have correlated heat-induced susceptibility with reduced phytoalexin output (Mulller 1956, Jerome and MulIer 1958, Uehara 1960, Chamberlain and Gerdemann 1966).Item Disease Resistance In Coffee Berries IV—Reversible Susceptibility Induced by Metabolic Inhibitors(1967) Hocking, D.; E.A. Tropical Pesticides Research Institute, Arusha, TanzaniaMature green berries of Arabic·a coffee normally are resistant to fungal attack except by a virulent strain of Colletotrichum cofjeanllm Noack. Disease resistance in many plants has been explained by the responsive production by the host of an antifungal substance, termed a phytoalexin (Muller 1961); only after stimulation by attempted infection. This implies that the host responds with an active, dynamic, metabolic conversion of biochemical precursors into the compounds which inhibit development of the attempted infection.Item Disease Resistance in Coffee Berries Reversible Susceptibility Induced By Metabolic Inhibitors(1967) Hocking, D.Mature green berries of Arabica coffee normally are resistant to fungal attack except by a virulent strain of Colletotrichum cofJeanum Noack. Disease resistance in many plants has been explained by the responsive production by the host of an anti-fungal substance, termed a phytoalexin (Muller 1961); only after stimulation by attempted injection. This implies that the host responds with an active, dynamic, metabolic conversion of biochemical precursors into the compounds which inhibit development of the attempted infection. Such a process has been demonstrated in a number of host-parasite combinations and the active principles have been isolated and assayed (Cruickshank 1963, review).Item Disease Resistance in Coffee Berries-Comparative Resistance in Single Trees(1967) Hocking, D.The fungus Colletotrichum coffeanum Noack (Glomerella cingulata) (Stonem, Spauld and Schrenk) can cause a destructive disease of coffee berries (Macdonald, 1926; Nutman and Roberts, 1960) to which the best long-term approach is breeding for resistance. There have been early reports of studies on resistance to Coffee Berry Disease (Nutman and Roberts 1960, Firman 1964) which describe inoculation and other experiments on detached berries of named varieties of coffee.Item Fungicides For Arabica Coffee - Improved Laboratory Assessments and Further Tests against Hemileia Vastatrix(1967) Hocking, D.; White, P. J.; Jaffer, A. A.The last reports in this series which were concerned with laboratory work on leaf rust were issued early in 1965. The present paper describes some improvements in the method.Item Fungicides For Arabica Coffee - Improved Laboratory Assessments and Further Tests against Hemileia Vastatrix(1967) Hocking, D.; White, P.J.; Jaffer , A.A.; Tropical Pesticides Research Institute, Arusha, TanzaniaThe last reports in this series which were concerned with laboratory work on leaf rust were issued early in 1965. The present paper describes some improvements in the method. in addition , those new fungicides Received during the interval which were claimed claimed to show promise against rust disease, have been tasted and results are given here.Item Fungicides for Arabica Coffee -A Laboratory Method for Assessment against Leaf Rust (HEMILEIA VASTATRIX BERK. ET BR.)(1967) Whitehead, P.J.; Hocking, D.The practical control of coffee leaf rust is often not satisfactory. Existing practice of timed sprays with 50 per cent copper wettable powders, while effecting large increases in yield, does not give good control of the rust pathogen. The reasons for this are several, and include problems of application and timing, but it is reasonable to assume that some at least may be overcome by improved active ingredient or formulation of the fungicide.Item Fungicides for Arabica Coffee -Phytotoxicity of Cycloheximide(1967) Hocking, D.The use of cycloheximide in coffee clearly presents hazards not present in the use of copper fungicides. Exceeding the effective laboratory dose by a factor of 2.5 causes up to 5 per cent necrosis, and by a factor of ten, complete death of young leaves. Leaf discussed in the experiments reported earlier were cut from the centres of leaves 8-12 weeks old, which explains the absence of phytotoxic symptoms, the present symptoms on older leaves being restricted to tips and edges. Field control with copper fungicides probably requires an average deposit about ten times the effective laboratory dose (Hocking, 1967a). The translaminar action of cycloheximide may enable field control to be achieved with little or no increase in average deposit. However, the danger of local over-deposition, causing phytotoxic symptoms, would still exist. Thus great caution would need to be exercised in application.Item Fungicides for Arabica Coffee-Biological Assessment of Protective Capacity against Leaf Rust (HEMILEIA VASTATRIX BERK. ET BR.)(1967) Hocking, D.The need for and requirements of developed chemical (Control of coffee-leaf rust and the details of a technique for laboratory assessment have been outlined (Hocking and White, 1967). The first results of the use of this technique are now reported.Item Fungicides for Arabica Coffee-Curative Activity against Leaf Rust (HEMILEIA VASTATRIX BERK. ET BR.)(1967) Hocking, D.Present practice for control of leaf rust depends in part upon careful timing of copper sprays so that a protective layer of fungicide is present whenever dispersal of the pathogen occurs. Spraying with copper after the pathogen has been dispersed and established is too late.Item Phytotoxicity of Triphenyl Tin Acetate to Rice Seed(1967) Hocking, D.; White, P. K.During experiments in Swaziland rice paddies, it was shown that aerial application of triphenyl tin acetate at a rate of 1 lb. a.i. per acre resulted in good control of the snail Lanistes ovum, a destructive pest of rice seedlings (Crossland 1964). However, rice seed sown immediately and at 24 and 48 hours after treatment gave rise to stunted and etiolated seedlings, suggesting phytotoxicity.
