**7. Increases temperature conditions and different weeds, insects and diseases of sugarcane**

Climate change effect the agriculture sector in different direction, directly by changing in temperature and/or precipitation as well as through indirect by changing pest pressure and availability of pollination service [31]. Diseases are main threat to the food security and the responsible for 10% reduction in globally food production [70], **Figure 4**. Many abiotic and biotic stresses such as weed competition, soil nitrogen and water deficit can exert the stress on sugarcane and increase the herbivores attack. Among herbivores arthropods, sugarcane borer, stalk insect borer and Mexican rice borer are the most important for sugarcane production [71]. A change in temperature under climate change conditions will have effects on some weeds, insects and diseases of sugarcane [10]. Smut disease (caused by *Sporisorium scitamineum*) is likely to increase under high temperature conditions [60]. But Sanguino [72] discus the different diseases of sugarcane, such as *Ustilago scitaminea* (Smut), *Sugarcane mosaic virus* (SCMV) and *Xanthomonas albilineans* (leaf scaled disease) and told that all these diseases are systemic and only changed by direct human interference. However Chakraborty [30] told that leaf scaled may spread by severe storms.

Extreme weather events have caused more disease pathogen and overwintering pest and also increased the input cost for control them. Sugarcane leaf and orange rust are bid challenges for sugarcane production in Florida [32]. Reduced rainfall will also reduce the growth of crops and pasture and decrease canopy covers which favor the weed infestation [73]. *Eoreuma loftini* is a major sugarcane pest [74]; drought results in greater abundance of dry leaf tissue and number of *E. loftini* egg have been positively associated with number of dry leaves [75]. Under well water conditions sugarcane plant had 82.8–90.2% less *E. loftini* eggs than water deficit conditions [75]. In wet tropics, cyclones will disperse weeds seed through flood and wind. Moderate drought can increase the population of many herbivorous arthropods and cause the injury in crop [76] drought also enhanced host plant suitability for herbivores arthropods [77].

Summer weeds such as *Rottboellia cochinchinensis*, *Ipomoea plebeia* and *Digitaria sanguinalis* are expected to increase under high temperature conditions. Dormancy

*Climate Change and Agriculture*

**stress**

rate occurs [52, 53].

after stress [56].

ity under water deficit conditions [25].

crop is highly sensitive to water deficit [43] and water deficit reduce the crop productivity up to 60% [44, 45]. Under water deficit conditions, sugarcane providing a key impetus to develop bio-technological strategies [43]. Under drought conditions, plant adopt various tolerant strategies such as modulation of growth, changes in life cycle, evolution of stress perception for rapid expression of stress tolerance and balance allocation of resources for stress adaptation and growth [25, 46, 47]. Molecular Breeding and biotechnology techniques are helpful tools to enhance crop productiv-

**6. Morphological and physiological response of sugarcane to drought** 

according to duration, intensity of stress, type of tissue affected and genotype of plant [26, 48]. In sugarcane, common water responses are stomatal closure, inhibition of stalk and leaf growth, leaf rolling, reduce leaf area [26] and cell elongation and division are interrupted [49]. Stem and leaf elongation are most seriously affected [50]. Under water deficit conditions, root development also influence [51]. Sugarcane crop have C4 photosynthetic pathway and under water stress, decrease in transpiration rate, stomatal conductance and photosynthesis

Water stress, decline the photosynthesis activity by decrease in phosphoenolpyruvate carboxylase and Rubisco activity [43]. Sugar accumulation in leaves also change the photosynthesis rate [54] and high sugar content moderates carbon fixation [55]. Under water deficit conditions, increase level of trehalose sugar, reducing the damage to cell membrane [34]. In reduce CO2 fixation conditions, increase in starch hydrolysis helped in sustain carbon supply, which facilitate growth recovery

Climate change can affect agriculture through rise in temperature, variation in precipitation, increase in CO2 concentration and weather vulnerabilities like flood, drought etc. Held et al. [57] predicted the more droughts in future; small changes in rainfall in future [58]. Extreme changes in rainfall have impact on sucrose yield [59] and frequent drought has negative effect on sugarcane as crop requires more water. Water stress also alters the photosynthesis, respiration and stomatal conductance [35]. For mitigate the drought conditions, farmer likely to more irrigate and increased the salinity problem and risen the water table. Reduce precipitation during harvesting period is likely to increase harvesting efficiency [60]. Nitrogen is the most limiting factor for sugarcane production [61]. Wetter years are likely to cause flood which may leach the nitrogen and farmer are use high rates of fertilizer during wetter years. Water logging may reduce the oxygen availability for root system and inhibit the uptake of nutrients [62]. Increased precipitation also reduces the quality of cane by inadequate "dry off" period. Changing in precipitation also has prevalence of weeds, diseases and insect pest. Termite and nematodes is expected to increase under warm and dry conditions. Some weeds such as Cyperus spp. may decrease under frequent drought conditions [20]. Effect of drought on sugarcane production depends upon plant growth stage and duration of stress. Drought at early and mid-growth stages mainly reduce sucrose yield. During the late growth stage, Moderate drought, increase the sucrose content in stalks. In china drought is

**6.1 Changing rainfall pattern and sugarcane production**

the most important stress for production [63].

Physiological and morphological response of sugarcane to drought stress varies

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of some summer weeds will have been broken under high temperature and these weeds may appear in winter. Insect pests such as *Heteronychus licas* and *Margarodes* spp. Will not be spared by temperature changes. Matthieson [60] told that temperature changes creates favorable condition for introduce new pests and diseases in sugarcane. Due to climate change, shift in temperature will have effect on diseases, weeds and insect pests [78]. Matthieson [60] discus that attack of smut diseases is likely to increase under high temperature condition. High temperature induced the pollen sterility, poor anthesis and reduce the grain filling duration [79]. High temperature stimulates the stomata conductance and increases the permeability [80] and reduce the uptake of herbicides. Above discussion will help in identifying possible measure for weeds control under changing atmospheric conditions. So it is need to evaluate the climate change effects on weed flora and herbicides efficacy for adaptation and mitigation strategies.
