Effect Of Sowing Dates Of Wheat Varieties On Aphid Population And Its Natural Enemies

The wheat crop is often infested with aphids during the growing season when both adults and nymphs take on a heavy load by absorbing cell sap that reduces plant energy. The full leaves turn brown, wither, and wear a silk look. Some species have toxic saliva, and a strong infestation can kill young shoots. Honeydew emissions are often very common and sooty fungi are often associated with aphid infections that eventually affect the level of photosynthesis in plants.

Poor wheat yield is mainly due to its instability from aphid infestation. Aphids are the worst crop for wheat harvest. They can grow very quickly under favourable conditions on leaves, stems, and inflorescence. The infection causes severe deformation of the leaves and inflorescence and can significantly reduce yields through direct feeding. Four species of aphids have been reported to be abundant in Pakistan (Hashmi et al. 1983). Although most insects attack wheat (Triticumaestivum L.) in Pakistan, the main damage is caused by lice.

Aphids cause loss of yield directly (35-40%) by ingesting plant milk or indirectly (20-80%) by transmitting bacterial and fungal infections (Aslam et al 2005). The size of the aphid population also depends on the abiotic characteristics (Aheer GM et al 2007, Wains MS 2008). During the spring (February-March) the number of aphids increases, at the same time biocontrol agents such as Coccinellids also increase as a natural check in the insect (Khan et al. 2011) Reducing dependence on pesticides, traditional practices such as Carson / canola planting the number of people eating some, changing the sowing days can help. Therefore, this study is designed to determine the effect of planting days on the formation of lice population in wheat so that the planting date coincides to reduce the penetration of aphids.

Wheat is a staple food for the people of Pakistan and provides 72% of the calories and protein in a balanced diet (CIMMYT, 1989). Pakistan is the 8th largest grower of wheat in the world. (Anonymous, 2017). In Pakistan, about 25492 thousand tons of wheat is produced from an area of about 8950 thousand hectares in the Punjab province, the area under wheat crop was 6917 thousand hectares and its production remained at 19526.67 thousand tons during 2016-17. (Anonymous, 2017). The wheat crop has undergone extensive damage and stress that disrupts its normal functioning and development at all phases.

Material & Methods:

This study was organized at Adaptive Research Farm, Sheikhupura. The experiment was comprised of four treatments and deliberated in Randomized Complete Block Design (RCBD) with three repeats for all treatments. Treatments were four different dates of sowing viz. 10.11.2020, 20.11.2020, 30.11.2020 and 10.12.2020. Five wheat varieties were sown in each block of sowing dates i.e., Galaxy-2013, Ujala- 2016, Faisalabad-2008, Johar 2016, and Punjab- 2011. The area of the trial was 2024m². Data on aphid infestation was recorded after every seven days from the incidence of pests. 

For each sample day, 10 wheat plants were selected randomly for each plot and the number of aphids per grower for each crop and natural enemies in the five plants was counted. All the agronomic practices remained the same for each treatment. Data concerning abiotic factors (RH% and °C) was measured from an observatory of Agriculture Ext. department. The data were based on variance analysis and comparison was made for mean values with the LSD variance test at the 0.05 probability level (Steel and Torrie., 1980).

Result and Discussion:

Table : 1.Germination Counts(m^-2) of different varieties sown at different times

1^st date of sowing

Table: 2 Different counts of aphid Population per tiller on different wheat varieties sown on 10^th November 2020: 

Mean aphid Population per tiller of eight counts on different wheat varieties sown on 10.11.2020:

2^nd date of sowing:

Table: 3 Different counts of aphid Population per tiller on different wheat varieties sown on 20^th November 2020:

Mean aphid Population per tiller of eight counts on different wheat varieties sown on 20.11.2020:

3^rd date of sowing:

Table: 4     Different counts of aphid Population per tiller on different wheat varieties sown on 30^th November 2020:

Mean aphid Population per tiller of eight counts on different wheat varieties sown on 30.11.2020:

4^th date of sowing:

Table: 5 Different counts of aphid Population per tiller on different wheat varieties sown on 10^th December 2020:

Mean aphid Population per tiller of eight counts on different wheat varieties sown on 10.12.2020:

Table: 6. Comparison of mean aphid Population per tiller on different wheat varieties sown at different times 

Table: 7. Metrological data during the wheat growth period at AR Farm Sheikhupura

Table: 8. Average predators per five plants of eight counts at different sowing dates on wheat varieties

Data presented in Tables- 2, 3, 4 & 5 showed that aphids were seen initially on 4 February on the crop sown on 10.11.2020, and a maximum of 2 aphids per tiller was recorded on the varieties Punjab 2011 but no aphid was seen in the rest of planting dates at that time. During the recording of data on 11.02.2021, the population of aphids was noted on all the dates of sowing but a maximum of 5.00 and minimum of 1.00 aphids per tiller was counted in planting dates 1^st date of sowing and last date of sowing, respectively.

During the season it was noted that the aphid population begins to expand promptly from mid-February to mid of March on the planting dates 10.11.2020 & 20.11.2020 but on the other planting dates, the increasing trend of aphid population was recorded from the end of Feb to mid-March.

After the sixth count decreasing trend of aphid population was noted on the first two planting dates it might be due to the turning of crop towards maturity, increasing trend of predators, and rise in temperature while on the 3^rd and 4^th planting dates exponential increase in population was noted during 7^th count because crop stage was favourable to aphids and after 7^th count, its population started to decrease due to increasing trend of predators and rise in temperature.

Maximum aphid population on 10-20 November the grown crop was noticed from 25^th  February to 18^th March  (Table 2,3) while on the third and fourth planting dates maximum aphid populace was observed from March 4 to 18. On the late sown (10.12.2020) wheat crop, the highest aphid populace was observed in comparison with the timely sown crop 10-20 November. 

This is because in those days the weather allowed for the development of insects. The temperature in the study area ranged from 5.9 ^oC to 22.54 ^oC (table 6) during the experimental time. These results are consistent with those of Abou-Elhagag and AbdeHafez (1998), who disclosed that the number of aphids gradually increased by 3 weeks in February. Bhambrro (2002) also told that the aphid reproduces at a rapid rate in cold conditions and reaches its peak in February-March when the ears begin to ripen.

In the current study, the aphid count has dropped since the end of March and thoroughly faded in the first week of April. This may be due to the escalated temperature in April, the maturation of plants, and possibly the emergence of predators. Abou-Elhagag and Abdel-Hafez (1998) observed that daily temperatures, natural enemies, and related humidity play a critical role in controlling the aphid value in a wheat field. Zou et al. (2002) also reported that natural enemies of insects could play a key role in lessening insect numbers.

Conclusion:

In conclusion, it is presumed that the aphid value was higher in early sown plants and the lowest aphid value was seen in late sowing. This specified that changing the date of sowing of wheat will affect aphid infestations. Ideally, wheat in Sheikhupura should be planted in the first and second week of November to keep away from severe aphid attacks.

Muhammad Atif¹, Muhammad Haris², Syed Jahanzaib Rasool³, Iqra Laraib⁴ 

1. School of Soil and  water conservation, Beijing Forestry University, China; [email protected] 
2. School of Soil and  water conservation, Beijing Forestry University, China; [email protected] 
3. Department of Agronomy, China Agriculture University, China; [email protected] 

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