ABSTRACT

Mustard aphid, Lipaphis erysimi (Kalt), is one of the most nefarious biotic constraints of rapeseed -mustard in the tarai region of Uttar Pradesh. During the investigation on ecologically sound and sustainable management of L.erysimi it was found that Brassica carinata sown on October 8 (normal sowing) escaped from the attack of L.erysimi in the tarai region of India whereas the crop delayed in the sowing by 10 days than normal one is damaged economically by the aphid which may be control by one spray of fresh extract of neem seed kernel (5%) or endosulfan (0.035%), safe to parasitoids. Whereas, the crops, B.carinata, sown delayed by 20 days, may be save from the damage caused by the aphid by 2 sprays of fresh extract of neem seed kernel (0.5%). Therefore, it was concluded that L. erysimi may be manage ecoenvironmentally on B.carinata with normal sowing and use of extract of neem seed kernel.

INTRODUCTION

Among the oleiferous brassicas, karan rai (Brassica carinata) is an important oilseed crop in India which plays a key role in Indian economy. It is attacked by 43 insect species, the most important being mustard aphid, Lipaphis erysimi as it can inflict losses upto 100% in severe infestation in Brassicas. It sucks sap from all the above-ground plant parts. In heavy attack, the plants wither resulting in a drastic loss in seed yield and oil content (Bakhetia, 1984). Though, the pest can be controlled by insecticide spraying but the indiscriminate use of the chemicals has created many problems like infamous 3’Rs viz., resurgence, resistance and residue aspects besides the health hazards. As the modern technology of pest control recommendations emphasize the economic and ecological importance of justifying pesticide use the present investigation was undertaken to manage the L. erysimi on B.carinata by the use of cultural practices, botanicals and ecologically sound like endosulfan.

MATERIALS AND METHODS

The experiment was conducted in two factorial randomized block design with three replications in rabi (Post-rainy season) of 1997 at the Crop Research Centre, G.B. Pant University of Agriculture and Technology, Pantnagar, Nainital (U.P.) India. Six different dates of sowing at interval of 10 days and protected and unprotected were taken as first and the second factors, respectively. The weekly observations were taken from ten randomly selected plants on 10 cm terminal shoot length starting from the first appearance of the aphid till the population become negligible. The plot wise yield and yield parameters from ten randomly selected plants per treatment were recorded at harvest. The need base protection was provided by 0.035% endosulfan or 5% of neem seed extract.

RESULTS

The aphid appeared on the second week of the vegetative stage of the crop and activity continued till 14th standard week. The peak activity was observed between 8th to 9th standard week (Table 1). The aphid population showed increasing trend at slow rate and reached at its peak in the 10th standard week and thereafter started to decline and reached to the tune of zero in 14th standard week.

The interaction of the two factors had significant effect on the aphid population (Table 1) from the peak to down fall phase of the population (7th to 9th standard week).

The highest aphid population (48.5) was observed in 9^th standard week in crop sown on 17th November 1996 under unprotected conditions whereas this result showed that aphid incidence increased progressively with delay in sowing. The crop sown on the first two dates of sowing escape aphid attack as the aphid incidence remain very low throughout the crop season. The last date of sowing had highest aphid incidence followed by the second throughout the crop season due to susceptible crop stage during the peak period of the aphid activity.

Table 1 : Interaction of date of sowing and protected and unprotected treatments on aphid population in Brassica Carinata during 1997.

P₁ = Protected, P₂ = Unprotected,

Perusal of Table 2 revealed that the yield and its component were significantly differed on different dates of sowing while between protection and unprotection treatments there was no significant difference. However, siliquae and seed weight per plant as well as yield differed significantly (Table 3).

DISCUSSION

The intensity of aphid infestation and its population pressure differed with date of sowing as well as the susceptible crop growth stages (initiation of flowers, flower and pod initiation). The crop sown on normal date (first fortnight of October) escapes the susceptible growth stage of the crop from the aphid attack and its multiplication which is greatly affected by the conducive weather conditions in the Tarai (humid moist environment) (Singh and Sachan 1995). Due to delay in sowing time the flower and pod initiation stage of the crop synchronises with the peak population of the aphid, above the economic threshold level which is influenced with date of sowing, soil type, crop season, crop growth stage and insecticides used (Singh and Sachan 1997).

Table 2 : Effect of date of sowing on the yield and its components of Brassica carinata during 1996-97

Table 3 : Effect of protection measures on the yield and its components of Brassica carinata during 1996-97

Sowing Date D₁ = 8th Oct. 96, D₂ = 18th Oct. 96, D₃ = 25th Oct. 96

D₄ = 17th Nov. 96 D₅ = 7th Nov. 96 P₁ = Protected, P₂ = Unprotected

CONCLUSION

The mustard aphid can ecoenvirontally be manage by altering the date of planting of the Brassica carinata and use of ecologically sound pesticides in the Tarai region of Uttar Pradesh, India.

ACKNOWLEDGEMENT

The authors are grateful to the Director, Experiment Station, G.B. Pant University of Agriculture & Technology, Pantnagar for providing research facilities.

REFERENCES

1. Singh, C.P. and Sachan, G.C. 1995. Estimation of losses in yield of rapeseed mustard, Brassica campestris by the mustard aphid, Lipaphis erysimi (Kalt.) in tarai, India Insect Sci. Applic. 16 : 283-286.

2. Singh, C.P. and Sachan, G.C. 1997. Economic injury levels and economics of control of the mustard aphid, Lipaphis erysimi (Kalt.) on mustard in tarai, India Insect Sci. Applic. 17 : 243-296.

3. Bakhetia, D.R.L. 1984. Chemical control of Lipaphis erysimi (Kaltenbach) on rapeseed mustard crops in Punjab. J. Res. Punjab. Agri. Univ. 21 : 63-75.