The type of damage has to be considered in terms of the plant stage and its ability to compensate for losses. Early foliar damage is rarely a problem as the plant can compensate. Very heavy leaf loss (>50%) may delay development and maturity. Early tiller loss upto and just after Panicle Initiation may not be problematic if other tillers can compensate. Late panicle and grain loss will likely reduce yield as rice has little flexibility in terms of kernel weight. None the less studies on white heads caused by stem borers have indicated up to one white head per hill in hills producing 20 or more productive tillers do not effect yield. Pests typically are more mobile and multiply more quickly than beneficial insects therefore early pesticide applications will generally and ultimately benefit pests. Effects depend on life cycles and their ability to reproduce. All losses must be balanced against the cost. Calculate the amount of grain required to cover the cost of application. Then calculate the amount of damage required to equal the cost.

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