APHID DYNAMICS IN WHEAT AS AFFECTED BY WEATHER AND PLANTING TIME

Aphid infestation is assuming an alarming position in wheat. A study was initiated to understand the dynamics of aphid infestation as affected by weather and crop planting time. Daily aphid count was taken in the field by placing yellow water trays at appropriate places in the wheat fields starting 1^st January in 2004 and 2005. In 2004-05 natural aphid infestation was also recorded in six wheat varieties planted at 15 days interval from Oct. 25, 2004 to Jan. 10, 2005. Aphid count was low in January due to cold but started increasing in February both years. It touched the peak in mid March and thereafter dropped. The infestation was high in 2004 but considerably low in 2005 due to high rains. Apparently, weather, other than rains and cold had little effect on aphid infestation. In 2004 and 2005 both years despite considerable temperature difference the pattern of aphid infestation was same. Infestation kept increasing till mid March and started declining. Planting time similarly had no pronounced effect on pattern of appearance of aphid. In all six plantings, the aphid infestation continued peaking and dropped after mid March. Early planting in November had, however, markedly low infestation but the infestation was progressively higher in later planting except the last where the infestation was low due to rising temperatures.

Wheat aphids has assumed scary proportions in wheat cultivation in the Pakistan for the last few years. Hashmi et al (8) found four species of aphid damaging the wheat crop (viz; Sitobion avenae (F.) Schizaphis graminum Round), Rhopalosiphum rufiabdominalis (Sasaki) and  Rhopalosiphum maidis (Fitch). Anonymous (1) reported that Macrosiphum granarium (F.) is a major species causing 100% losses in grains production in sever attack. Most of the worker observed that maximum aphid population during February to March (2,3,4,5,6). Stufkens and Ferrel (9) reported that production of winged aphids on forage, oats and colonization was apparently reduced by cool winter weather. Acreman and Dixon (7) from U.K. reported that growing early maturing varieties could reduce aphid attack. Aheer et al (2) concluded that wheat sowing at various dates played an important role in increasing or decreasing aphid population. They observed that the crop sown not later than November 25 gave highest yield and the lowest aphid population.

The present studies were under taken to determine the role of abiotic factors in fluctuating the alate aphids density in wheat by using yellow water traps as well as to find out best sowing time of wheat crop in order to escape from the attach of aphids.

A. Studies were carried out for two years during 2003-04 to 2004-05 at Wheat Research Institute, Faisalabad. The collection of aphid was by using three trays each measuring 59 x 46 x 75 cm, painted with yellow color inside. These trays were placed at three spots, two and half feet (75 cm) above the ground level on wooden stands at a distance of 100 feet from each other. Data on alate aphids trapped in trays were recorded daily from 9-11 a.m. from each spot. Weather data, i.e., maximum and minimum temperature, R.H %, rainfall and wind velocity of the coinciding dates were also collected from the meteorological observatory of Ayub Agricultural Research Institute, Faisalabad and correlated with aphid density for each year. The data was analyzed and presented in Table 1 and 2.

B. The experiment was carried out to study the effect of sowing times, on the incidence of aphid population. The wheat crop was sown on six different dates, i.e. October 25, November 10, 25, December 10, 25, 2004 and January 10, 2005 at Wheat Research Institute, Faisalabad in randomized complete block design with replications, having plot size of 5 x 1.62 sq. m. and the variety sown was Inqilab-91. The data regarding aphid population were recorded by observing 10 randomly selected tillers from each plot at eight days interval starting February 16 to March 28, 2005. The selected tillers were clipped off with the help of pair of scissors. The numbers of aphids on each tiller were counted by dropping them on a white paper sheet with the help of a camel’s hair brush. The data was analyzed and presented in Table 3.

The results (Table 1) reveal that aphid population reached at maximum level (1821.90 aphids/tray) during second weak of March, 2003-04. Aphid counts was high in 2003-04 than during 2004-05. This was due to heavy rain during the later year. Population of aphid started to appear in January and gradually increased afterwards. In both the years population was increased upto 2^nd week of March and declined thereafter. The present findings agree to those of Wolfenbarger (10). The weather factors had effect on aphid population. The maximum temperature at day and night during the season had +ve and non-significant correlation with aphid population density. Relative humidity had negative and non-significant correlation with aphid population. Rainfall had negative and non-significant correlation (-0.208) during 2003-04 but it had it had –ve and significant correlation (-0.617*) with aphid population during 2004-05. In case of wind velocity the correlation with aphid population was negative but non significant. These results are partially agreement with Aheer et al. (6). Apparently, weather, other than rains and cold had little effect on aphid infestation. In 2004 and 2005 both years despite considerable temperature difference the pattern of aphid infestation was same. Infestation kept increasing till mid March and started declining. Planting time similarly had no pronounced effect on pattern of appearance of aphid. In all six plantings, the aphid infestation continued peaking and dropped after mid March. Early planting in November had, however, markedly low infestations but the infestation was progressively higher latter painting except the last where the infestation was low due to rising temperature.

The results obtained during study, regarding the effect of date of sowing on aphid attack were completely in agreement with the previous workers (7) who also reported that early maturing or early sown wheat crop averted aphid attack. Hence no severe damage was occurred.

1. Anonymous. 1987. Wheat traveling seminar, Pak. Agric. Res. Council, Islamabad. PP: 31.

2. Aheer, G.M., I. Haq, K.J. Ahmad and A. Ali, 1993. Varietal resistance and sowing date effect on aphid density and wheat yield. J. Agric. Res. 31 (#): 63-68.

3. Aheer, G.M., R. Ahmad, M. Afzal and A.Ali, 1993. Varietals resistance/susceptibity of wheat to aphids. Sitobion avenae F. and Rhopalosiphum rufiabdominalis sasaki- J. Agric. Res. 31(3): 307-311.

4. Aheer, G.M., K.J, Ahmad and A. Ali, 1994. Role of weather in fluctuating aphid density in wheat crop. J. Agric. Res. 32(3):295-301.

5. Aheer, G.M., M.A. Zia, K.J. Ahmad and A. Ali, 1999. Role of Abiotic factors on population dynamics of alate aphids on wheat in different ecological zone of the Punjab. J. Agric. Res. 1999. 37(2-3): 187-194.

6. Aheer, G.M., M. Munir and A. Ali. 2002. Role of Abiotic factors in fluctuating aphid population in wheat crop under the ecosystem of Mandi Bahaud-din District. J. agric. Res. 2002,04 (1):47-53.

7. Acreman, T.M. and A.F.G. Dixon. 1985. Development patterns in wheat and Resistance to cereal aphids. Crop protection. 4(3):322-328. (Wheat, Barley and Triticale Absts. 3(2), 1308, 1986).

8. Hashmi, A.A., M.M. hussain and M.Ulfat: 1983. Insect Post Complex Wheat Crop. Pak. J.Zool;15(2): 169-176.

9. Stufkens, M.W. and J.A. Farrel. 1985. Observations on the phenology of rose-grain aphids in mid-Canterbury. Proc. N.Zea. Weed and Pest Control Conf. No.38, 184-187. (Ibid.3(5): 550;4754, 1986).