Assessment of production and dispersal of inoculum ofAlternaria Macrospora in various parts of the cotton canopy
Morning and evening counts of spores ofAlternaria macrospora in a cotton (Gossypium barbadense) field were assessed for the number of spores (a) produced on the last night, (b) dispersed during the day, and (c) retained in the spore reserve on leaves. Throughout the season, 1 m2 of the field produced (P) and dispersed (D) approximately 163 x 106 and 137 x 106 spores, respectively. The 16% discrepancy between P and D values reflects experimental errors. Most spores were produced on shed leaves on the ground, fewer on leaves in the lower part of the canopy, and least on leaves in the upper canopy. The contribution to total D decreased from leaves in the lower part of the canopy, to shed leaves, and to leaves in the upper canopy. In tests with potted plants with spore-bearing lesions attached to various heights of the canopy under various conditions of weather, dispersal of spores at these heights was conditioned mainly by wind velocity, which decreased from the upper to the lower part of the canopy. In leaves close to the ground, approximately 29% of the released spores were removed by sedimentation to the ground. On any one day, the daily rate of D differed from the daily rate of P. On days in which D was higher than P, the difference was due to a reserve of spores remaining on lesions after dispersal during the previous days. In weather adverse for production of new spores, the reserve was depleted within 4 and 6 days in the top and bottom leaves, respectively, but remained relatively high in the shed leaves on the ground; a similar number of days was needed to restore the depleted reserve in sporulation-favorable weather.
Insights Into the Etiology of Gummosis Syndrome of Deciduous Fruit Trees in Israel and its Impact on Tree Productivity.
Fungal gummosis syndrome of deciduous fruit trees was reported from several countries, including Israel. Symptomatic 5-7 to 10-14-year-old trees exude large amounts of gum on the trunk, limbs, branches, and twigs, accompanied by sunken lesions on the bark. The necrotic area extends to the xylem to form black to brown staining of the tissue. The general conception is that "this is a nuisance that can be pruned out of trees during the dormant season with no economic significance." In this study we attempted to: (i) identify the fungi associated in the gummosis syndrome of deciduous trees in Israel and (ii) quantify the significance of gummosis syndrome on tree and fruit development and on crop value. Branches from symptomatic and asymptomatic deciduous trees were collected during 2012 to 2015 from 29 orchards including peach (14 orchards), nectarine (six orchards), apricot (six orchards), plum, cherry, and almond (one orchard each). In all cases, fungi associated with the Botryosphaeriaceae family were isolated from tissues exhibiting the typical gummosis symptoms. The decay fungus Phellinus sp. was isolated from 53.3% of the samples. The dynamics of fruit growth in symptomatic and asymptomatic trees was recorded in 2014 and 2015 in an 11-year-old peach orchard. In trees exhibiting the gummosis syndrome, yield was lower by 11.5 to 22.5% and its value was reduced by 14.7 to 19.4%, compared with those of asymptomatic trees in 2014 and 2015, respectively. Although these are substantial losses, the grower of the orchard was not aware of the losses occurring in his orchard. The reason for this situation is explained and discussed. The outcome conclusion of the current study is that the gummosis syndrome of deciduous trees imposes significant, hence undistinguishable, losses in mature deciduous fruit trees.
The Tsetse Problem on the Eastern Cattle Route in the Gold Coast
1. Primary fly-belts round Makongo consisted of three different vegetational communities: a Cynometra-Vitex association along the main length of the Makongo river, on a clay soil; a Ficus congensis association along the river close to the town, on a sandy soil; and Isoberlinia doka woodland on moist sandy soil north-west and south of Makongo. 2. Secondary fly-belts of less dense vegetation occur in the orchard bush savannah round Makongo, and these are not colonised until the commencement of the rainy season. 3. Glossina tachinoides and G. palpalis both occurred in the riverside communities, and G. palpalis alone in the Isoberlinia woodland. 4. Along the river G. palpalis outnumbered G. tachinoides by 3:1 in the dry season. At the commencement of the rains G. tachinoides increased more quickly than G. palpalis , bringing their numbers very nearly equal, but at the end of the rains there was a decrease in G. tachinoides which restored the original proportion. 5. G. morsitans had been found at Makongo formerly but was not met with at the time of this investigation, its absence being due to the disappearance of the larger antelope from the neighbourhood. 6. Smaller game animals, small mammals and reptiles afforded an adequate food supply for tsetse in the fly-belts, and also passing herds of cattle, as well as natives from the village and travellers. 7. The distribution of G. palpalis within the fly-belts was markedly influenced by the proximity of a cattle road along which herds of cattle passed almost daily, and by village water-holes. 8. During the dry season the primary foci were always found to be the places of greatest relative humidity, and the fly does not tend to move out of these until the general atmospheric humidity has reached a certain fairly high degree. 9. In clearing the fly-belts the removal of all primary foci within a quarter of a mile of the town and of thick bush within 100 yards of water-holes was undertaken. The work lasted from the beginning of February to the end of March 1931. 10. The effect of clearing the Isoberlinia doka woodland was to banish G. palpalis completely, and it never returned to these clearings. 11. On clearing the riverside Ficus congensis fly-belt, G. tachinoides was practically eliminated for the first three months, but reappeared in the clearings in June when there was a general increase and up-stream migration of this fly. G. palpalis remained in this clearing in fluctuating numbers up to June, when observations were suspended. 12. 565 marked tsetse were liberated in the fly-belts immediately previous to clearing. Of G. palpalis 12·7% were recaptured in the clearings and 11% outside the clearings. Of G. tachinoides 5·5% were recaptured in the clearings and 6·8% outside.