Abundance of leaf miner and some piercing sap sucking pests on some bean ( Phaseolus vulgaris l . ) Varieties

The field experiment was conducted during summer and winter seasons to evaluate seven varieties of beans (Phaseolus vulgaris L.) for their relative susceptibility against some sap sucking pests Tetranychus urticae Koch, Bemisia tabaci (Gennadieu), Aphis craccivora Koch, Thrips tabaci Lindquist and leaf miner, Liriomyza trifolii (Burgess). The tested bean varieties were: Medina (V1), R9251 (V2), Teresa (V3), Luvalde (V4), Al-Hanna (V5), Alexandria (V6) and Excalibur (V7). None of the varieties escaped the infestation of all these pests. Generally the population of T. urticae and T. tabaci were higher in summer than in winter, while population of B. tabaci and L. trifolii were higher in winter. Relative susceptibility of bean plants changed according to plantation season as, V6, V6, V5, V6 and V3 hosted the less number of T. urticae, B. tabaci, A. craccivora, T. tabaci and L. trifolii in winter season, respectively. While in summer plantation, V5, V1, V4, V1 and V7 hosted the less number of the same pests, respectively.


INTRODUCTION
Bean plant, Phaseolus vulgaris L. is one of the most important leguminous vegetable crops in Egypt.It is considered of great nutritive value, containing relative high percentage of protein where consumed freshly as green pods or as dry seeds.Also its leaves encourage pest development, increased egg production and their longevity (Braikel and Post, 1959) which threatens both quality and quantity of the resultant yield and cause serious damage either directly by sucking plants juice or indirectly as vectors of virus diseases.
Beans are attacked by serious pests which reduce productivity and quality such as, the spider mite, Tetranychus urticae Koch, the whitefly, Bemisia tabaci Genn., the aphid, Aphis craccivora Koch, the trips, Thrips tabaci Lindquist and the leaf miner, Liriomyza trifolii (Burgess).The spider mite, Tetranychus urticae considered the major pest of vegetables causing great less in yield, the effect of which is reduce photosynthesis, transpiration (Golam, 2002).Cardona et al. (2002), indicated that there is genetic variation for resistance to the melon thrips in beans that it is possible to screen for resistance to pest.Also, he identified genotypes with moderate level of resistance that can withstand damage under high levels of infestation.
Another pests (aphids, leaf miner and whitefly) are widely spread attacking a wide variety of agricultural crops and causing considerable damage, either directly by sucking plant juice or indirectly as vector transmitting plant diseases.(Carter, 1990).Damage by aphids is due to consumption of phloem sap, and then the excretion of honey dew, which cover the leaves.Sooty molds may develop on this carbohydrates rich medium (Carter, 1990).
The choice of variety may be depend on market preference, farmers should emphasized cultivation of cultivars that show resistance to different pests and the effectiveness in population reduction should be given priority while selecting the variety among other properties.Some bean varieties exhibit natural resistance to certain insect pests.
The present study was carried out as a trial to throw light on the susceptibility of common beans varieties to pest's infestation.

MATERIALS AND METHODS
Two field experiments were conducted at Sennoures region in Fayoum Governorate for screening seven bean varieties: Medina (V 1 ), R9251 (V 2 ), Teresa (V 3 ), Luvalde (V 4 ), Al-Hanna (V 5 ), Alexandria (V 6 ) and Excalibur (V 7 ), in winter, 2009 and summer, 2010 plantation seasons.An area of about 2100 m 2 in each season was prepared and divided into 28 plots of 75 m 2 each, and then each variety was replicated four times.Plots were seeded on October 15, 2009 for winter plantation and on March 5, 2010 for summer plantation.Samples of 10 leaves per plot were picked every week randomly from the lower, middle and upper levels of plant.Each sample was kept in a tight closed plastic bag and transferred to the laboratory for examination.All experimental plots received the recommended normal agricultural practices and no insecticides were used.
The number of movable stages and eggs (for spider mite), nymph and eggs (for whitefly), nymph and adults (for aphid and thrips) and larvae (for leaf miner) were recorded for each sample for twelve weeks in winter and eight week in summer plantations.

Statistical analysis:
Analysis of variance for each experiment was conducted to determine the significance between means of cultivars and the means were compared according to Duncan's multiple range tests (Snedecor and Cochran 1981).

-Spider mite, Tetranychus urticae Koch
Data illustrated in figure (1) showed the infestation level of T. urticae on beans along winter plantation.As indicated in this study the spider mite started their activity by a few numbers in November and increased slowly until the mid of January then reach the maximum at the end of January.As it is illustrated in figure (4) V1 hosted significantly the highest population among all tested varieties in summer season, while V2 came the second variety.Other varieties hosted significantly less mite populations than V1 and V2.Comparing the two seasons, it could be concluded that the mite infested bean plants in the summer season more than the winter season.

-Whitefly, Bemisia tabaci (Gennadieu).
Fluctuation abundance of B. tabaci in winter plantation which illustrated in figure (5) showed that B. tabaci started its activity in the mid of November and continued along all the season until the beginning of February.Based on seasonal average of B. tabaci in winter plantation, as it is shown in figure ( 6) taking LSD values in our consideration, tested varieties could be categorized into three groups.The first group include V6, V1 and V7, was significantly the least susceptible to infestation.The second group include V5 and V2 was moderate while the third group, V3 and V4 received significantly the highest infestation of B. tabaci.In summer plantation, as it is illustrated in figure (7) a little abundance was recorder in the first of the season in the mid of April then the population decreased until the end of the season.Data in figure (8) revealed that V1 received the lowest population of B. tabaci while V4 received the highest population in summer plantation, but no significancy was recorded.Generally, it could be observed that winter plantations received less amount of B. tabaci than summer plantation.These results fully agreed with El-Lakwah et al. (2010), who reported that the common bean infestation by B. tabaci as expressed as mean number of adults and immature stages increased gradually showed high rate of infestation in all plantations (early summer, summer and winter).

-Aphid, Aphis craccivora Koch
As it is illustrated in figure ( 9) Aphis craccivora started early on bean plants in winter plantation.The aphid recorded the highest abundance at begin of December with almost 40 individuals per leaf, then the population decreased gradually until the end of the season..  4. Thrips, Thrips tabaci Lindquist.low abundance of Thrips tabaci was recorder in winter plantation on bean plants (figure 13&14).Abundance of leaf miner and some sucking pests on (Phaseolus vulgaris l.) Varieties.163 In summer plantation, thrips recorded higher abundance as infestation started in the beginning of the season and increased gradually until reach its maximum in mid of may(Fig.15).The cultivar V1 recorded the lowest population of thips which was significantly less than V6 and V3 which recorded the highest population (Fig. 16).The result of El-Lakwah et al. (2010), had the same trend as our result; in which the average number of T. tabaci were started at the first of April in few number and increased to reach peak in mid and end of May.Also, this finding agree to that obtained by Helal et al. (1996) who indicated that the mean number of T. tabaci appeared at May 4th increased gradually to reach its maximum level of infestation during the mid of May.

-leaf miner, Liriomyza trifolii (Burgess)
As it is illustrated in figure ( 17), the leaf miner, L. trifolii attacked beans plants in winter plantation along all the season but it reached its maximum abundance at the end of December.Relative susceptibility was recorded and presented in figure (18).Based on LSD value, V4 and V5 were significantly the most attractant varieties while V3 and V1 were significantly the lowest attractant varieties.A little abundance of L. trifolii was recorded at the beginning of the Summer season and disappeared before the end of April as it is represented in figure (19&20), so it could be neglected as a pest in summer season.

Fig. 4 .
Fig.4.Average numbers of T. urticae Eggs and movable stages on 7 bean varieties in the summer plantation.

Fig. 5 .
Fig.5.Fluctuation of Bemisia tabaci Eggs and nymphs on beans in the winter plantation.

Fig. 6 .
Fig.6.Average numbers of Bemisia tabaci Eggs and movable stages on 7 bean varieties in the winter plantation.

Fig. 7 .
Fig.7.Fluctuation of Bemisia tabaci Eggs and nymphs on beans in the summer plantation.

Fig. 8 .
Fig.8.Average numbers of Bemisia tabaci Eggs and movable stages on 7 bean varieties in the summer plantation.

Fig. 9 .Fig. 10 .
Fig.9.Fluctuation of Aphis craccivora on beans in the winter plantationRelative susceptibility of certain bean varieties which is represented in figure (10), according to LSD values, V1 and V7 were significantly the most susceptible varieties.V5 was significantly, the lowest susceptible variety, while other varieties came in between.Aphis craccivora recorded rare abundance on bean plants in summer plantation as it is illustrated in figures(11, 12)

Fig. 15 .
Fig.15.Fluctuation of Thrips tabaci on beans in the summer plantation.

Fig. 16 .
Fig.16.Average numbers of Thrips tabaci on 7 bean varieties in the summer plantation.

Fig. 18 .
Fig.18.Average numbers of Liriomyza trifolii on 7 bean varieties in the winter plantation.