Mustard aphid infestation and yield of raya as affected by dates of sowing and meteorological parameters

Field experiments were conducted at Punjab Agricultural University, Ludhiana during rabi season 2003–04 and 2004–05 to evaluate the effect of date of sowing on mustard aphid infestation and yield of raya. Raya (variety PBR-91) was sown on two different dates viz. first week of November (D₁) and last week of November (D₂). Peak infestation index was lower while raya yield was higher during 2003–04 as compared to 2004–05. The aphid infestation index in D₂ was higher as compared to D₁ during both crop seasons. The aphid infestation index generally showed a negative correlation with temperature both during 2003–04 (D₁) and 2004–05 (D₁ and D₂). The multiple regression between aphid infestation index (Y) and meteorological parameters using pooled data over dates of sowing during 2004–05 was as follows:

Y = 0.97–0.01 Tmx-0.17Tmn + 0.02 RHm-0.01RHe-0.16SSH-0.01RF (r=0.88)

Where, Tmx is maximum temperature, Tmn is minimum temperature (°C), RHm is morning relative humidity (%), RHe is evening relative humidity (%), SSH is sunshine hours and RF is rainfall (mm)