Initial Spray Research Articles

Some Observations on Size and Biological Activity of Spray Deposits Produced by Various Formulations of Copper Oxychloride

Summary Chemical estimations and biological assays, using Botrytis fabae, of spray deposits on beans (Vacia faba) in the laboratory have shown that the amount of an initial spray deposit of copper oxychloride is dependent on the volume of application used per unit area and the concentration of copper in the spray liquid. The addition of 0.1% of an anionic surfactant (dioctyl sodium sulpho-succinate) greatly reduced the amount of these initial deposits although another anionic surfactant did not. In the laboratory trials the fungitoxicity of the spray deposit was related to the actual copper levels initially present. In general, the addition of surfactants improved the fungitoxicity of the initial deposit. The addition of surface-active agents did not materially affect the rain-resistance of the spray deposits, while their presence in emulsions of PVA, PVC and PVB gave an improved biological performance. All three polymeric materials greatly improved the tenacity of copper oxychloride spray deposits withou...

Some observations on size and biological activity of spray deposits produced by various formulations of copper oxychloride

SUMMARYChemical estimations and biological assays, using Botrytis fabae, of spray deposits on beans (Vicia faba) in the laboratory have shown that the amount of an initial spray deposit of copper oxychloride is dependent on the volume of application used per unit area and the concentration of copper in the spray liquid. The addition of 0.1 % of an anionic surfactant (dioctyl sodium sulpho‐succinate) greatly reduced the amount of these initial deposits although another anionic surfactant did not. In the laboratory trials the fungitoxicity of the spray deposit was related to the actual copper levels initially present. In general, the addition of surfactants improved the fungitoxicity of the initial deposit.The addition of surface‐active agents did not materially affect the rain‐resistance of the spray deposits, while their presence in emulsions of PVA, PVC and PVB gave an improved biological performance. All three polymeric materials greatly improved the tenacity of copper oxychloride spray deposits without reducing their fungitoxicity in laboratory tests.When examined in field experiments against potato blight (Phytophthora infestans) these apparent biological advantages due to the tenacity and good distribution of the polymeric emulsion formulations did not materialize. An explanation for this apparent contradiction between laboratory and field data has been given based on certain features of the epidemiology of the pathogen.

Epidemiology of potato early blight in Colorado 1. Initial infection, disease development and the influence of environmental factors

The dissemination of primary inoculum ofAlternaria solani and the infection of potato plants in the field was shown to occur early in the season under Colorado conditions. Secondary spore dispersal was easily detected by spore traps. The use of such measurements may serve as a basis for timing initial spray applications.

PRECOCIOUS FLOWERING OF ARIZONA CYPRESS WITH GIBBERELLIN

Extremely early flowering (production of staminate strobili 88 days from germination) of Arizona cypress (Cupressus arizonica Greene) was obtained with foliar application of gibberellin A3 commencing at age 55 days. Trials with differing concentrations of gibberellin at various ages indicated that flower bud differentiation depends on both age and gibberellin concentration, younger seedlings requiring more exogenous gibberellin. Simultaneous application of two growth retardants (AMO-1618 and B-995) had no effect upon the number of flowers, but flower size was increased where B-995 and gibberellin were given together. The period of time between initial spraying and first visible appearance of staminate strobili is 23 to 25 days. On most plants 60 to 80% of the growing vegetative meristems are changed into flower buds within 60 days of the initial treatment, often resulting in over 500 flower buds on one plant. The pollen is viable.

EVALUATION OF PARAQUAT AND DIQUAT FOR WEED CONTROL IN RUBBER

Summary. In Malayan rubber plantations where the weed flora was dominated by grasses paraquat was superior to diquat as a herbicide. At the rates needed to give satisfactory grass weed control paraquat also gave an adequate control of broad‐leaved weeds.The rate of paraquat needed varied between 0.75 and 1.25 lb/ac depending on the weed flora and the growth stage of the rubber trees. In young rubber 1.0–1.25 lb/ac gave 8–10 weeks' control, but in mature rubber there was only 20% recovery 6 months after an application of 0.75 lb/ac. Where weed regrowth was very rapid after the initial spray, as in the case of Paspalum conjugation in young rubber, a second application some 2–3 weeks after the first was an advantage. The volume of water in which it was applied was not critical.Rain falling soon after application did not reduce the herbicidal activity of paraquat. Paraquat did not injure rubber trees providing it was not sprayed onto green tissue and this feature combined with its inactivation by soil made it safe to use from a very early stage in the growth of the rubber trees.L'évaluation du paraquat et du diquat pour la lutte contre les mauvaises herbes dans les plantations de caoutchouc

A comparison of certain physical characteristics of bordeaux mixture and a copper oxychloride wettable powder, and their possible significance in relation to biological performance

During comparative studies of certain physical characteristics of-Bordeaux mixture and a wettable powder formulation of copper oxychloride, certain marked differences have been recorded. (1) The size of the initial spray deposit from a single application of Bordeaux mixture is greater than that of a copper oxychloride suspension of equal copper content. (2) The weathering characteristics of the two preparations examined may or may not be significantly different. (3) Repeated applications of Bordeaux mixture lead to a marked increase in the level of the final deposit, the level being defined as the amount of copper cm.2 leaf area. Similar treatment with copper oxychloride gave much smaller deposits than those of Bordeaux mixture. (4) The build-up of a deposit on repeated applications as witnessed with Bordeaux mixture is suggested as being related to the gelatinous characteristic ofthat spray liquid.

Antibiotics as protectant fungicides against rice blast

(1) The activity in vitro of the three antifungal antibiotics Antimycin A, Blastmycin, and Blasticidin against rice blast (Piricularia oryzae) was studied. The germination of spores was completely prevented at a concentration of 50-100 mcg/ml of these antibiotics when tested by the drop culture method. The concentration at which the growth of mycelium was completely inhibited, when grown in shaken liquid media containing one of these antibiotics, was about the same as those of spore germination. In experiments to determine the concentration which completely inhibit growth, the concentration which prevented growth after 48 hours was insufficient to prevent growth after a week. The antibiotics required a concentration of 50-100mcg/ml in order to completely inhibit a week's growth.(2) The stability of the antibiotics on slide-glasses, and on leaves of rice plants growing in the greenhouse was studied by the cup or paper disc method using agar plates seeded with Piricularia oryzae. Antimycin A and Blastmycin were so stable that most of the original activity remained after 2 weeks on the leaves. Blasticidin was stable in the dark places, but decomposed gradually when exposed to sunlight. Little activity was detectable after a week on rice leaves in the greenhouse.In the simulated rain tests, Antimycin A, Blastmycin, and Blasticidin were found to be comparatively resistant simulated rainwashing. The simulated rain was approximately 10 millimeters per 10 minutes.(3) In the greenhouse Antimycin A, Blastmycin, and Blasticidin were found to be effective as a protectant fungicide, but less effective than phenyl mercuric acetate against rice blast. Rice seedlings of uniform size were selected. When their top leaves were about half expanded, and other leaves were completely expanded, plants were sprayed with a solution containing 500mcg/ ml of the antibiotic, and inolulated with the spore suspension of Piricularia oryzae after their top leaves were completely expanded. The plants were then placed in a moist chamber at about 26°C. Seven to ten days after inoculation, the number of spots on the leaves was compared.On all the leaves except the top leaves, almost the same number of leaf-spots developed on plants treated with the antibiotics as on those treated with phenyl mercuric acetate. The systemic effect of the antibiotics on the top leaves that expanded during the 4 days between the initial spraying and subsequent inoculation was inferior to that of phenyl mercuric acetate.