FACTORS TO AFFECT THE VOLTINISM OF THE PINE CATERPILLAR DENDROLIMUS TABULAEFORMIS IN BEIJING AREA

The pine caterpillar Dendrolimus tabulaeformis (in short: PC) enter diapause in response to short day length. The key factor to determine whether PC can continue its development in 3rd-4th instar larvae is photoperiod in Beijing area. The 1st instar larvae of PC have the most sensitivity to photo-period. The PC eggs start to hatch in the mid of July and the peak is usually in late July while the natural photoperiod out of door is just shorter than the critical photoperiod required by PC. Thus, the 3rd-4th instar larvae begin to fall into diapause and will overwinter under the trees in late Oct. and remain still till the following spring. Temperature and food nutrition can modify the voltinism of PC by affecting its growth and development.