Different control practices including pesticides must be adopted in proper and balance order to achieve the optimal plant growth. If unbalance pesticides are used, insect pests are resistant afterward and thus reduced the crop growth and yield. In a research trial in California, pesticides affected the fertility, birth rate, reproductive function and development and normal growth plants. Many pesticides are known to defect endocrine functions. Methylparathion effect the stomatal conductance and photosynthesis of Lettuce. Excessive and unbalance use of pesticides can cause structural change in chromosome and chromotids also create sterility and lethality. Over-spraying of pesticides may create mutation in somatic and generative cells. Excessive and unbalance use of pesticides can affect any part of a plant like stems, blossoms, foliage and fruit. This reaction may vary with the plant age, with the plant species and with the weather at the time of exposure. Excessive pesticides reduced the nitrogen fixation and thus results in reduced the crop yields. Excessive spraying affects photosynthesis by disrupting gas exchange or resulting damage to plants. New growth of the plant also stops in extreme conditions.
Excessive dose of pesticides may cause phytotoxic reactions. Phytotoxicity is not usually resulted by the active ingredient, it is usually due to specific formulations: the formulation solvents, excessive dose of pesticides than listed on the lable, impurities in spraying water and poorly mixing the spray solutions. Condition of plant treated time may affect phytotoxicity, stressed plants are more susceptible. Temperature, humidity and light also play their role in phyto-toxicity. High temperature can boost up pesticide volatilization and degradation. UV light rapidly degrade many pesticides. Soil texture, moisture, microbial activity, temperature and pH also affect phytotoxicity. High pH soils resulted in less binding and can increase phytotoxicity. High microbial activity may decrease phytotoxicity. Pesticides can kill honeybees which act as pollinators of crops that are in blooms, disturb the fruit setting and thus reduced the crop yields. Thus pesticides reduce pollination and create deficiency in the quantity of grains.
Over-spraying of pesticides have direct and harmful effects on plant like root hair development, yellowing shoot which ultimately reduced the plant growth. Some fungicide can create pollen / male sterility by changing the pollen morphology. In garden pesticides like Roundup and Rodeo having glyphosate chemical, inters the environment by spraying through drift, interferes with photosynthesis in order to reducing chlorophyll and resulted in physical damage of plant leaves. Pesticide phytotoxicity appears in several ways on ornamental plants, but probably fice types of damage occur most commonly.
1. Burn: This damage may appear on the margin, the tip, as spots on entire leaf surface. The growing bud and tip can be killed.
2. Necrosis: Similar s burn and defecting plants in same manner.
3. Chlorosis: Many spots appear, yellowing tip, or as a chlorosis on the entire leaf.
4. Leaf distortion: Curling or crinkling of the leaf as appeared.
5. Stunting: Reduced or abnormal growth.
Dr. Muhammad Anjum Aqueel1,3, Dr. Rashad Mukhtar Balal1,2, Dr. Muhammad Adnan Shahid1,2, Dr. Muhammad Mansoor Javaid1 andShafqat Rasool1
1 University College of Agriculture, University of Sargodha, Pakistan;
2 Cornell University, NY, USA
3 Imperial College London, Silwood Park Campus, Ascot, SL5 7PY, U.K.