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Removal of flower heads markedly decreased infection of tobacco by Sclerotinia and Botrytis. Infection was correlated with the density of corollas falling on to the leaves; a greater proportion of those falling from axillary shoots than of those falling from apical shoots incited the diseases. It was not possible to determine whether differences in varietal susceptibility arose from differences in leaf susceptibility or from differences in the ability of the corollas to carry the diseases. Any change in agronomic practice which tended to extend the life of corollas on the plant could lead to increased incidence of these diseases. (i) Agronomic trialsObservations were made on 3 X 3 X 3 factorial trials used to study effects of various cultural practices on tobacco production. Plants, variety 'Hicks', were grown in rows 1.22 m apart and the population varied by spacing the plants 38, 46, or 53 em apart in the rows. Plants were topped at three different heights and at three different stages of growth, i.e., as soon as the flower buds appeared, when the corollas were developing, or when the corollas had started to senesce. The plants were 'clean suckered' by removing all axillary shoots before they had grown 5 em.Three-row plots were planted and disease assessments made on plants in the central row by estimating the proportion of leaf area destroyed approximately 3 weeks after the late-topped plants had flowered.

The cultivars, Jonathan, Delicious and Granny Smith apple (Malus domestica Borkh.) trees on MM.106, Northern Spy, Seedling and MM.102 rootstocks were trained as-vase, central leader, palmette and Hawkes Bay multi-leade; systems for 18 years. Rootstock significantly affected tree size, and there were interactions of rootstock with training systems or cultivars. There was also an interaction between training ' systems and cultivars. In the early years, while the training systems were being established, fruit yield was inversely related to the severity of the pruning; central leader- and palmette-trained trees had higher yields and tree efficiency than Hawkes Bay trees whose yields and tree efficiency were higher than vase trees. When yields reached maximum and the training systems became well established (after about 8 years of cropping), the total annual yield and tree efficiency per tree of individual training systems within a cultivar and rootstock differed only slightly. Cumulative yields of central leader, palmette and Hawkes Bay were higher than vase in the early years of all training systems and cultivars, while tree size was often smaller. In the latter years, cumulative yields of the central leader, palmette and Hawkes Bay systems remained slightly higher than vase, except with the less vigorous Jonathan and Granny Smith/ MM.102 combinations where yields were similar.

A foliar spray of succinic acid-2, 2-dimethylhydrazide (daminozide) applied in late summer to Delicious and Jonathan apples delayed fruit maturity and softening in subsequent storage. This difference was usually retained throughout storage especially with Jonathan. Development of superficial scald was effectively delayed in stored Delicious. Jonathan spot, and, to a lesser extent, low temperature breakdown, were reduced in Jonathan. After three consecutive years of application at 1000 p.p.m. there was no reduction in effects on firmness or breakdown in Delicious. There was also a carryover effect into the third season when daminozide at 1500 p.p.m. was applied in the first two years but not used in the third.

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