ii The Population Council confronts critical health and development issues-from stopping the spread of HIV to improving reproductive health and ensuring that young people lead full and productive lives. Through biomedical, social science, and public health research in 50 countries, we work with our partners to deliver solutions that lead to more effective policies, programs, and technologies that improve lives.

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Cotton productivity is severely hampering by various diseases and insect pests especially cotton leaf curl virus (CLCV) worldwide. Losses caused by CLCV are far more than any other factor affecting cotton productivity. Growing of early and resistant genotypes is of vital significance in alleviating the adversities of these pests in crop plants. The current field trial was conducted at Central Cotton Research Institute (CCRI) Multan, Pakistan, to investigate the role of varying sowing dates in managing the CLCV infestation on different elite cotton genotypes. The crop was sown on five different dates i.e. D1= 15th April, D2 = 1st May, D3 = 15th May, D4 = 1st June and D5 = 15th June and three different elite cotton genotypes, i.e. V1= CIM-612, V2 = CIM-591 and V3 = CIM-573 to optimize a suitable sowing date and to screen out high productive and tolerant genotype against the CLCV. Seeds were drilled manually on finely crafted seedbed by using single row hand drill keeping seeding density of 20 kg ha-1 and inter row spacing of 75cm. CLCV severely hampered the crop performance by delayed planting of cotton from 15th April, while increased the chances of disease incidence. It is concluded that early sowing of all tested genotypes especially CIM-592 reduces the problem of CLCV and enhanced cotton productivity.

Cotton growth and development is effected by various ecological issues like temperature fluctuations, distribution and quantity of rainfall, relative humidity and winds which are the climate change attributes. A field experiment was carried out to find out the response of cotton to weather variables in terms of total variation in yield and quality. The effect of planting times and thermal temperatures (cumulative heat units) on yield of 4 cotton cultivars viz; CIM-600, CIM-616, CIM-622 & CRIS-641 was evaluated. Plants were sown on 6 planting times during the year 2015-2016 and 2016-2017 in an experiment conducted in randomized complete block design having three replications. Cotton cultivars depicted significant variances for number of bolls plant −1 , boll weight and seed cotton yield. The cultivar CIM-616 depicted the highest seed cotton yield of 2083.60 kg•ha −1 on interpretation of highest bolls and boll weight. Maximum seed cotton yield was noted in planting time from 1 st April to 15 th April whereas early and late planting decreases the seed cotton yield on account of less accretion of cumulative heat units. Regression analysis depicted that rise of one unit (15 days) from early to optimal date (15 th March to 15 th April) enhanced the seed cotton yield by 93.76 kg•ha −1 (y = −93.764x 2 + 521.04x + 1364). Delayed planting also reduces the seed cotton yield with the same ratio. It is therefore established that cotton must be cultivated from 1 st April to 1 st May to harvest good production in this type of climate.

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