Introduction

Wheat is a staple food for the people of Pakistan and provides 72% of 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 While in the Punjab province the area under wheat crop was 6917 thousand hectares and its production remained 19526.67 thousand ton during 2016-17. (Anonymous, 2017). The wheat crop has undergone extensive damage and stress that disrupts its normal functioning and development at all phases.

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.

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 of aphid’s 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

Varieties	DOS 1	DOS 2	DOS 3	DOS 4
V1	204.67	205.33	211.33	206.00
V2	215.00	214.00	214.33	212.00
V3	213.00	224.67	219.33	216.33
V4	214.00	215.33	226.67	219.00
V5	215.33	215.00	214.67	213.00
LSD	7.17	5.62	3.47	4.15

1^st date of sowing

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

Varieties	Sampling dates
4/2/21	11/2/21	18/2/21	25/2/21	4/3/21	11/3/21	18/3/21	25/3/21
Galaxy 2013	0.66a	3.00b	4.66a	11.00a	10.33b	40.00a	48.33 ab	11.33a
Ujala 2016	1.66a	5.00a	4.33ab	7.33a	14.00ab	43.33a	40.00ab	1.33a
Punjab 2011	2.00a	4.00ab	3.66ab	10.66a	19.66a	38.33a	50.00a	2.00a
Anaj 2016	1.00a	2.33b	3.66ab	8.33a	20.66a	49.00a	45.00ab	1.33a
Faisalabad 2008	1.33a	3.33ab	3.00b	11.00a	19.66a	47.66a	38.33b	1.33a
LSD (p≤5%)	1.49	1.68	1.53	6.75	6.92	11.33	10.74	0.97

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

Varieties	Aphids’ population per tiller
Galaxy-2013	15 a
Ujala 2016	15 a
Punjab 2011	15a
Anaj 2016	16 a
Faisalabad 2008	16 a
LSD (p≤5%)	2.77

2^nd date of sowing:

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

Varieties	Sampling dates
4/2/21	11/2/21	18/2/21	25/2/21	4/3/21	11/3/21	18/3/21	25/3/21
Galaxy 2013	1.33a	2.00a	3.33a	5.66ab	13.33ab	34.00b	45.00a	2.33ab
Ujala 2016	0.66a	1.33a	4.66a	10.66ab	17.00ab	39.66 ab	39.33a	3.00a
Punjab 2011	1.00a	2.33a	5.66a	8.00ab	12.00b	41.00ab	45.66a	1.33bc
Anaj 2016	1.66a	1.66a	4.33a	4.66b	20.66a	33.33b	43.33a	1.66bc
Faisalabad 2008	1.00a	1.66a	4.00a	12.00a	11.00b	45.33a	36.66a	1.00c
LSD (p≤5%)	1.55	1.43	3.48	6.42	7.41	10.59	16.64	1.16

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

Varieties	Aphids’ population per tiller
Galaxy-2013	13 a
Ujala 2016	15 a
Punjab 2011	15 a
Anaj 2016	14 a
Faisalabad 2008	14 a
LSD (p≤5%)	2.35

3^rd date of sowing:

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

Varieties	Sampling dates
4/2/21	11/2/21	18/2/21	25/2/21	4/3/21	11/3/21	18/3/21	25/3/21
Galaxy 2013	0.66a	1.00b	1.66ab	3.00a	9.33b	45.00a	55.00a	2.66ab
Ujala 2016	0.66a	1.00b	2.33ab	4.00a	16.33a	32.66b	32.66b	3.66a
Punjab 2011	0.33a	2.00a	3.00a	2.66a	6.00c	46.66a	26.33b	1.33b
Anaj 2016	1.00a	1.66ab	1.33b	3.33a	11.33b	21.33c	50.66a	2.33ab
Faisalabad 2008	0.33a	1.00b	2.00ab	3.00a	11.00b	30.33b	24.66b	1.33b
LSD (p≤5%)	1.00	0.97	1.55	1.75	2.94	8.20	16.59	2.06

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

Varieties	Aphids’ population per tiller
Galaxy-2013	14 a
Ujala 2016	12 b
Punjab 2011	11 b
Anaj 2016	12 b
Faisalabad 2008	9 b
LSD (p≤5%)	2.67

4^th date of sowing:

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

Varieties	Sampling dates
4/2/21	11/2/21	18/2/21	25/2/21	4/3/21	11/3/21	18/3/21	25/3/21
Galaxy 2013	0.00a	1.66a	1.66a	4.33a	3.33d	64.66a	47.33a	5.00a
Ujala2016	0.33a	0.00c	1.00ab	3.00ab	7.00ab	17.33b	27.00b	5.33a
Punjab 2011	0.00a	1.00b	0.66b	2.33b	4.33cd	85.00a	42.33ab	1.33b
Anaj 2016	0.33a	1.00b	1.00ab	2.33b	6.00bc	25.00b	34.00ab	1.33b
Fsd- 2008	0.33a	0.66b	0.66b	4.66a	8.66b	30.33b	25.66b	1.33b
LSD (p≤5%)	0.94	0.59	0.84	1.98	2.25	23.15	18.35	1.41

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

Varieties	Aphids’ population per tiller
Galaxy-2013	16a
Ujala 2016	8 b
Punjab 2011	17a
Anaj 2016	9 b
Faisalabad 2008	9 b
LSD (p≤5%)	3.86

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

Varieties	No. of aphids per tillers (Ave. of eight counts) at the different date of sowing
01.11.2020	10.11.2020	20.11.2020	30.11.2020
Galaxy-2013	15 a	13 a	14 a	16 a
Ujala-2015	15 a	15 a	12 b	8 b
Punjab 2011	15a	15 a	11 b	17 a
Anaj-2016	16 a	14 a	12 b	9 b
Faisalabad -2008	16 a	14 a	9 b	9 b
LSD (p≤5%)	2.77	2.35	2.67	3.86

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

Months	Max.Temp	Min.Temp	Humidity	Rainfall
February	18.11	6.47	68.6	3.01
March	22.54	11.25	52.1	0.29

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

Var.	Dos1	DOS2	DOS3	DOS4
V1	3.37	3.75	2.87	2.12
V2	3.37	3.62	2.25	2.5
V3	3.25	2.75	2.62	2.62
V4	2.75	2.52	2	1.75
V5	2.75	2.37	1.75	2.12

Data presented in table- 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 favorable 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 late sown (10.12.2020) wheat crop, highest aphid populace was observed in comparison with 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 the 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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