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Abstract (11) the other inclUding six cotton growing-provinces in Upper Egypt but are common.lyregarded as of secondary importance as far as leaf’wo.rminfestations are cOncerned (Giza, Bani-Suet’, Fayyoum,Menya, A.ssiout and Bohag :Provinces). The grand totals of the cotton’ leafworm eggmasses collected from the whole country were also worked out and made use of. Th~ s~C?_9nHd-0l.!I2 comprised the annual areas for cottoncUltivations in each of the 14 provinces. These were obtained, again, from the Ministry of Agriculture fOr the years 1960-1968. ~he t~rdE.roU~ constituted the daily records of the major thermal factors in each of the eight Delta Provinces under consideration. These records covered the period from 1A!:January 1960 up to the end of June 1968 and were obtained from the Central Meteorology Department, MinistrY of Scientific Ressarch, U.A.R. The factors are : The day minimumtemperature (00.), the day maximumtemperature (00. ), and the daily average temperature (00.). In addition, records of the average soil tempera’ture (00.) as taken in the Giza area, again, for .the period January 1960 _ December1967 were eventually used; a10llg with the sbove factors, in the analysis. The daily readings of ’the day minimum. ’temperature (°0.) in the same period (January 1960 _ June 1968) were also available for five of ~he six proVinces of Upper Egypt. -~- _.----._. __ ..- ....•----, --.--- .~~----~-~.--------- c ,:::~,:.,,,...~~. ,_. ,2•••••• ’...- - -- - ~- - - - . 1. - 165 - 8eve~al preliminary trials involving the above data were attempted at first. Those finally adopted as procedure are the following : 1. The daily readings of each factor were grouped into a series of 5-day intervals. The averages of these intervals were considered in all subsequent analyses. 2. The annual average number of 2. 1ittoralis eggmasses per feddan were calculated for : (a) Every province separately, (b) the Delta area (as averages of 8 provinces), and (c) for the whole-country~ The egg-mass averages in each case were regarded as representatives of the annual population level of the cotton leafworm in the respective area. 3. The annual averages denoting the level of the infestation in every province were further represented in terms of index numbers on log. basis.. This transformation was quite helpful. It gave a relative categorical definition to each year thus rendering the comparisons more practical. In the meantime the calculated (predicted) levels of the infestation became more precise and mean;ngful than when expressed as expected nUlllbers of eggm.asses. 4. The ndssing data of the soU ’teper-sture, which was lackiDs in most of the provinces, were ..-tiJla1ied. The eB1iiaations were based on the standard mathematica~ re~a~ionsbip (regression value) -- ._~ --._- -_.- --.---._- -- ---~--- -~. .-- -- - ._.~ .. _.-.~.~ - 166 - between the minimum.temperature and the soil temperature at Giza. The data contributing towards this linear relationshi.p involved the ave~ages of these two factors in 18 successive 5-day intervals for eaah 0 P the nine years 1960-1968. The intervals considered in tihf.s step were those extending between I§!. Feb- ”ruary and 50th April in eac.h year. Part II,±: Alf:(ect of certain ecological factors prevailing during the ori tical period, on the .J)Opulatio~ ~e~~ity of the cotton leafworm and the poc’ediction- PFocedure of the i.n:festa.t.i.on level in the pelts Pr2vinces In this part of the studyt the following analytical st~s and procedures were carried out : 1. r~~”7l.”:ifJ.;:.a~;·70 s·::;udiesbetween all years in each prOVince wi ~~ re,gard to the level of infestation This was conducted Over three steps and resulted in ’the following : B~~(?l : The calculation of deviations of ”each thermal factor in the years wi.th ”normal or below-normal” infestation from its cOl.”responding .readings in ”above-no.rmal”infestation , years. This indicatedt in all cases, a conspicuous positive departure during a certain critioal period. ~tep QU-: The gzoaphical area-saes for each ”theraal factor during the aritioa1 period. This showed that the - 167 - averages of the areas for the ”normal or below-normal” infestation years were much larger than those in the Case o’f If abovenormal,” infestation years. Ste]2 Ccl: The comprehensive statistical analysis. This analysis involved each thermal factor during the critical period, and was mounted mainly on : 0-1. A regular HF” test for all the years under consideration together. c-2. A contrast analysis for the two groups of years, in each province; the nabove-normallt infestation years versus the ”normal or below-normal” infestation years .• In all cases and for each factor considered, a significant difference existed between the years when taken together (step c-l). This is expected since such a group usually includes different ”types of years, Itabove-normalll and ”normal Or below-normaltt infestation years. Whenthe latters were contrasted (Step c-2) again a significant difference occurred indicating the biologicall.y-diffe.rent natures of the two groups of years. But when a regular ”]’I’ test (Step 0-1) ·was applied to each group separately no significant or just significant differences could be traced, thus ~erring the homogene1’ty of the years within each. The results 1Dd.i.cate tJ’lat £or B~~c;,~~, Gbaz’b1a.~ia, SbarJd.a, lIenoufia, Dakabll8 P.ro’riDces and the De11;a Region, ’the c.ritieal period extended from ll!!:!, February to 10!A! April; whereas that period extended between.6~ Feb~ and l5j& .April for both Ka~ El-Sheikh and Damiet1ia PrO’V1pces. - -,~ ._. ~~ -- _. ._-- .~. -- -- -.-,e ..•. - 168 - 2. T_hepia-statistioal relationships between ’the cl1matiic factors and J!!le seasonal average number of ee;gmasses per feddan In this analysis the climatic factors were represented by thtir averages during the critical period while the eggmasses were rep~eaented both as actual figures (regular data) and as index num-oers(transformed data). The analysis involved groups of years: Q-f’.2.,Ul2...A: which included all years together. Gr”oupB: which included the same years but divided into two subgroups : Sub.frollP B l comprising the Habov&-normaJ.” years; i.e. ’the years of high infestation. p]lbf:5.L:.oBup2 consisting of the years 01’ ”normal or belownormal” infestation. In each case, the simple correlation and regression coefficients were calculated, and the combined latent effect of three thermal factors on the level of infestation was knownthrough the partial regression. The responsibility of these three factors for the degree of variability in that level was expressed in terms of ”percentage of variance explained”. The obtained results and ’the ensuing discussions led to the foliowing biological explanation that the oonsiderable reduction in the general. air 811Ld soil t_peratures, duriDg the critioal period, below its general averases delays the _argenee of ’the insects’ adul’ts, hol4iDg its 4nelopleD.’taJ. stages •• in],. as pupae. Mass emergence of moths from these pupae would ’then be ..’ ~- ._” - J.69 - enforced by the prevalence of W8.rm.ewr eather, normally taking place during April. The sudden. emergence of a relati ve].y large number of adults, especially at that time when it is, st:tll! so early in the season, offers tre!J1endOU8 possibi.lities for mating and oviposition not likely ·to occur when normal or warmer eritical periods prevailo Hence, a high. infestation ~akes place 2-3 months later (through multiplied reproducibility) ~ On the other hand, with normal or relatively warmcritical periods, mating chances become limited due to sparse emergence of adults, hence, the subsequent generations atrcaf,n, proportionality, normal or even below-normal levels. In other words, low temperature averages, during the critical period induce high population levels of the insect, through a series of fairly synchronized subsequen’t-generations; and vice versa. }. PL’edict1on of the .average number of egnnasses. in each PfOvi.nce. duriBs; 1.9§9 and 1970 The prediction of the cot1ionleafworm in any particular year and ’for each provin~e was based on the information, analytical procedure, and results already outlined in the previous sections. This couJ.d be worked out, by mid-April, using the averages of each ’thermal factor during the critiCal period ”which, by tha’t date, would have just ended. Accordingly , it was possible to calcul.ate the eXpected average DUIIlber of’ .:i ; - 170 - eggmasses and, hence, the level of infestation during the follOwing season. The results indicated that the years 1969 and 1970 are of the ”normal, or below-normari type. Part IV: ~J’1ec~ertain ecolog..i,£.alfactors, prevailing, 9F the population dens~t:y of the cotton leafworm .in tJle Upper Egypt Provinces The provinces investigated in this part are Giza, Beni- Suef, Fayyoum, MeDYa, Assiout and Bohag. ~hough these represent the main cotton-growing of Upper Egypt, yet no strjking outbreaks or even high infestation levels, by Delta-standards, coilld be detected in any of them throughout the period 1960- 1968. Neither there have been a marked difference between the generally low-levels of infestation from one year to another and from one province to the next adequate tor a reliable analysis. It was, therefore, finally concluded that there has always been a marked inconsistency in the level of infestation did not exceed 5.2% of its total for the country during the established outbreak-years in the U.A.R. In other words, the term ”outbreak years” or even ”high i.D:testa’tion year” does not apply to this part of ’the country. ___________-+------- Summary -170- SU¥MARY >, Onion (Allium eepa 1.) lis~ undoubtedly, one of the important I I vegetable crops in Egypt, for local consumption and Exportation. Due to I the steady increase of areas cultivated with this crop, the present study was carried out at the Experime1tal Farm of the Faculty of Agriculture at Moshtohor throughout two sudcessive onion seasons (1993 / 94 and I 1994 / 95) in the nursery and Ipennanent field to study the relationship between three factors (onion tariety, seeding or transplanting date and I the rate of nitrogen fertilization) and the infestation rate of onion plants f by two main onion pests; the pnion thrips, Thrips tabaci Lind. and the onion maggot, Delia a/liaria Fons, Another study was carried out to evaluate the possibility of usJg traps of different colours placed in different directions of the onion ifield for attracting and trapping adults of r the mentioned pests. The obtained results may be summarized as follows 1- Nursery experiments: The obtained results of two onion seasons (1993 /94 and 1994/ 95) indicated the following: A- The Improved Giza 6 onion variety was more susceptible to infestation by T.tabaci larvae and adults than Giza 20 variety, the two season mean numbers of Tsabaci larvae / 10 plants were 60.95 ± 10.41 and 41.15 ± 6.37 while those of adults were 7.90 ±1.45 and 5.58 ± 0.93, respectively. ~ for infestation of the two onion varieties by Dialliaria larvae, the djfferences between mean counts recorded from the two varieties were insignificant. This may be attributed to that the larvae were detected in onion seedlings in very low numbers _-----------1~:---- Summary i -171- I (two season mean counts were 0ry O.16±O.04 and O.15±O.031arvae / 10 plants of Giza 20 and Improv~ Giza 6 varieties, respectively). B- The population of T tabaci jarvae and adnlts was found to be increased by retarding the S1eding date. The two season mean numbers of T.tabaci individuals ~ere 35.09±4.88 ,43.54±7.10, 55.34 ±11.52 and 69.93 ± 12.24 / ~O seedlings, while the corresponding counts of adults were 4.30±O.~9) 5.36±l.06, 7.23±1.15 and 10.06± i 1.75 by sowing in the first (Sep., 25th), second (Oct., 11th), third (Oct., 27th) and fourth (Nov., 12th) dates, respectively. Generally, by seeding in either of the fo dates, T.tabaci larval and adults population showed low abun ce in October and increased gradually I from first of November till the second half of January. : I The larvae of D.alliaria w~re found in low numbers in all seeding I dates, but larval counts in seedling from the third seeding date were, relatively, higher than those fro~ the three other dates. The two season mean larval counts were 0.06±O.03, 0.08±O.04, O.28±O.lO and O.22± 0.05 larva / 10 seedlings from the 1.s1 , 2nd., 3m. and 4th-dates, respectively. The lowest number of D.alliaria larvae was recorded in October and increased gradually from the end of November till the second half of January. c- By studying the combined effect of onion variety and seeding date on the rate of T.tabaci larval and adults’ infestation to onion seedlings, data indicated ~at seedlings of Improved Giza 6 variety that grew after sowing ~ the latest date suffered the heaviest infestation level (overall means of twa seasons 81.04±11.75 larvae and 11.91 ± 1.96 adultsl~O seedlings) than all recorded on the remaining 7 treatments. 0$ the contrary, seedlings of Giza 20 onion -----------+1------ Summary -172- , I variety that grew after sowfng in the earliest date harboured the lowest counts of larvae and ,dults (28.06±4.79 larvae and 3.26±0.59 adults / 10 seedlings). II I 11- Permanent field experimenb : A - Date indicated that Improved Giza 6 onion variety was more liable I to infestation with T.tabaci larvae and adults than Giza 20. (Two season means of 49.2±7.82 larvae and 4.4±0.56 adults on Improved I Giza ~ plant opposed to 35.~±5.17 larvae and 3.7±0.47 adults on an Giza 20 plant). As for the I onion maggot, D.alliaria larvae, those were detected in, relatively, ~ery small numbers in the two seasons of study with no significant b~tween the two varieties. The two season mean counts were only 0.178±O.022 and 0.084±0.023 larva / plant for the two mentioned varietirs, respectively. i, B- Infestation by T. tabaci larvae and adults on onion plants increased significantly as the transplanting date was delayed. The lightest infestation rates (means of )O.71±4.83 larvae and 3.13±0.42 adults) were detected on plants of the earliest transplanting date (December, 6th.) while on the contrary ithe heaviest infestation level (overall means of two seasons, 56.$9±9.12 larvae and 4.91±O.64 adults) occurred on plants of the ~test transplanting date (January, 20th). The intermediate transplanting dates (December, 21st) and January, 5th.) gave plants that sowed intermediate positions between the earliest and latest transplanting dates. from inspection of the weekly samples, it was noticed that ~e number of T.tabaci larvae and adults I started low in January and ifcreased from the end of February to the end of May. Concerning ~festation of onion plants transplanted at ___________ -+- Summary -173- different dates on the infestati n level by D.al/iaria, the larvae of this pest appeared in very low n bers also and the differences between the mean infestation rates er transplanting at different dates were, statistically, insignificant. Th~ recorded means, for the number of D’.alliaria larvae were 0.040 0.010, 0.035±0.010, 0.071±0.024 and 0.067±0.023 larvae/plant aft r transplanting on December, 6th and 2ls1and January, 5th and 20 ., respectively I C- Evaluation of the effect Of+onium nitrate, as a nitrogen fertilizer, to soil after transplanting of o*ion at 3 rates (60, 90 and 120 N units / feddan) revealed a positive Srgnificailt correlation in both seasons of study between the applied r~te of nitrogenous fertilizer and the rate T.tabaci infestation. That w~ clearly evident in cases of the pest larvae and adults. The lightest infestation level occurred on plants of the control check which di~ not receive any N - fertilization as the two season averages were 15.34±2.l3 larvae and 1.68±O.l9 adults / plant apposed to 36.98 ±5.Sl8, 50.34±7.75 and 66.34±10.57 larvae, and 3.55±0.47, 4.81±0.64 and 6.l6±O.79 adults / plant in treatments that received N - fertilization at 60, 90 and 120 N-units / feddan, respectively. D.alliaria larvae were detected in onion plants of all treatments in very low numbers (mean of two seasons; 0.024±0.007, 0.OI9±O.006, O.037±O.015 and 0.027±0.008 larvae / plant in the control treatment and the three treatments of ammonium nitrate applications, respectively). T)Ie differences between the mentioned means were found, statistically, insignificant. I D- The combined effect of both Ionion variety and transplanting date on the rate of T.tabaci and D.al~iariainfestation were also studied. The I two factors’ effect was found significant on T.tabaci larval and adults ______ ------+------ Summary -174- count. The lightest rate of . estation occurred on plants of Giza 20 variety that were transplanted n December, 6th., i.e.; the earliest date (26.65±4.44 & 24.14±4.7 I ae, and 4.49±0.71 & 4.41±0.8 adults I plant in 1994 and 1995 seas ns, respectively. On the other extreme, plants of Improved Giza 6 ariety transplanted at the latest date (January, 20th) harboured highest rates of (.tabaci infestations (77.08±12.35 & 63.l±12.54 larvae, and 6.51±O.83 & 4.83±O.88 adults /plant in both seasons, espectively). The remaining treatments gave intermediate values of .tabaci infestations, although the same trend of higher infestation 0 Improved Giza 6 variety and delaying the transplanting date could be, easily, detected. As for D. alliaria larvae infestations in onion pl ts, the recorded counts were very low in both seasons of study so t most of the inspected samples were found free from any onion m ggot infestation. The calculated F value between the obtained means indicated that the differences between means of D.alliaria larvae from different treatments were I I insignificant. E- By studying the impact of onion variety and the rate of nitrogenous fertilization on infestation by the two pests under investigation, significant F values were detected between treabnents when T.tabaci larvae and adults’ infestatio* rates to onion plants were concerned. , The highest rates of infestation occurred significantly to onion plants i of Improved Giza 6 variety that received the nitrogen fertilizer ( I ammonium nitrate) at the $gbest rate; i.e., 120 N-units/ feddan I (80.01±13.75 & 78.43±13.~8 larvae and 6.84±O.85 & 6.53±1.03 adults/plant in 1994 and ~995 seasons, respectively), while the lightest infestation rates 04urred, significantly, on Giza 20 onion I plants that grew without ~Y N-fertilization (13.93±2.05 & 15.39± 2.38 larvae and 1.49±O.22 & 1.4 ±O.23 adults /plant in both seasons, respectively). The general tren of data indicated higher rates of T.tabaci infestation on Improve iza 6 than Giza 20 variety, and also the rate of infestation increased by increasing the’ N-fertilization rate. As for Diolltaria infestation t onion plants of different treatments, the larval counts ranged betw en 0.022 - 0.079 and 0.006 - 0.014 larva / plant of Giza 20, and be een 0.009 - 0.044 larva and 0.009 - 0.016 larva / plant of Improv d Giza 6 variety in 1994 and 1995 seasons, respectively with ins gnificant differences between mean larval counts from different eatmen.ts, and accordingly no fixed correlation could be detected between both factors and the rate of _-----------+----- Summary -175- ” D.alitaria infestation. I ! F_ The combined effect of tran~planting date and nitrogen fertilization level on Titabaci infestation ~ate to onion plants proved significant. Generally, infestation with larval and adult stages of the pest increased by increasing the dose of ammonium nitrate added to soil, on one hand, and by delaying the transplanting date, on the other hand. The highest overall mean of T.tabaei larval and adults’ counts occurred on plants of the l.est transplanting date and received the I highest dose of ammonium pitrate (91.44±14.25 & 82.36±17.65 larvae, and 8.71±1.16 & 8.~2±1.1 adults / plant in 1994 and 1995 I I seasons, respectively). On ~e other extreme the lowest counts occurred on onion plants tba~ did not receive any N-fertilization and were transplanted at the two Fliest dates 15.98±2.36 & 11.04±1.76 larvae/plant in 1994 and 11.~4±1.83 & 14.72±1.98 larvae I plant in 1995 on the unfertilized ptcfts transplanted on December, 6th. and 21.st., respectively, while in ejase of adult counts, the receptive counts were 1.31±O.23 & 1.76±0.3~ adults / plant in 1994 and 1.10±O.15 & i I ____________ ------ Summary -177- with lower populations of T’tabaci. As for the onion maggot the recorded rates of infestation were very low throughout the two seasons of study to the level that no: definited recommendation could be concluded. III. Efficiency of colour traps and their directions in attracting T.tabaci andD.alliaria adults to colour traps: 1- Attractiveness of T.tabaci an. D.alliaria adults to colour traps. The efficiency of different colour. traps in attracting adults of T.tabaci and D.alliaria was assayed. Five different colours were evaluated (white, yellow, blue, ’green and red). Results showed the following: A- Attractiveness of T.tabaci adults : White colour traps proved as superior in attracting adults of the cotton thrips adults (922.78 and 1392.38 adults / trap left in position in 5 day in 1994 and 1995 seasons, respectively). Blue traps came the next in both seasons (689.25 and 918.91 adults / trap), while the yellow traps took the third position (372.41 and 528.97 adults. respectively). The green and red colour traps were of minor efficiency compared to the formerly mentioned colours. B- Attractiveness of D.alliaria adults: Significant differences between mean adult counts attracted to traps from different colours were, statistically, detected. The white colour traps caught the highest adult nwnbers, followed by the yellow and the blue colour traps (means of two season counts 17.06, 15.02 and 11.59 Dialliaria adults / trap, respectively). The green and red colour ___________ --”* Summary -178- traps were always of minor efficiency (4.81 and 2.44 adults / trap, respectively). 2- Distribution of T.tabaci and Dialliaria adults in different directions of onion field : A- T.tabaci : In both seasons of study; the highest mean count of T.tabaci adults were those attracted to traps placed in southern direction of the onion field (669 and 793 adults / trap in 1994 and 1995 seasons, respectively), while the lowest count was detected in traps placed in the eastern direction (247.93 and ~35.23 adults, respectively). Traps of different colour, that were placed in the north or west directions showed intermediate positions. Superiority of southern direction may be due to the normal wind direction from north to south. B- D.alliaria : Dialltarta adult counts that were detected in traps placed in different directions averaged 4.35-9.19 in 1994 and 10.2 - 14.25 adults/ trap in 1995 indicating low abundance of the onion maggot throughout the two seasons of study. According to the means of both seasons data, the density of D.alliaria adults in the 4 directions may be arranged descendingly as east (11.41 adults), south (10.28), north (9.63) and west (9.3 adults / trap). The differences between the mentioned means were statistically, significant. 3- Combined effect of the colour and place of trap on the catch: A- T.tabaci adults : Highest mean counts of T.tabaci adults caught to traps occurred by using white traps placed in the southern direction of the onion field _____________ ----- Summary -179- (1481.38 and 1895.25 adults/trap in 1994 and 1995 seasons, respectively). While the lowest count was, on the other hand, detected in case of red traps placed in the eastern direction of the field (only 31.13 and 112.25 adults/trap in both .seasons, respectively). It could be generally concluded that the colour of trap was more effective on the distribution of T. tabaci adults than wind direction. Using of white traps placed in either the south or; north directions may be fairly, recommended as efficient tool tc insure higher catch of T.tabaci adults to be used for estimating the population, It is thought that using the white colour traps in southern or northern directions to control T.tabaci is a point that needs further investigations before any recommendation. 3- D.alliaria : The caught numbers of Ir.alltaria adults 10 traps of different colour placed at different directions were, relatively, low, although this numbers varied from one colour to another and also between the different directions. It could be also stated, from the obtained results, that the colour of trap was more effective in attracting Dialliaria adults than the wind direction. It was clear that the white colour traps attracted highest D.alliaria adult numbers, whether these traps were placed in the east, west or southern directions (19.88,18.07 and 15.94 adults / trap, respectively). That was followed by the yellow traps placed in the east, south, north or western directions, then came the white traps placed in the northern direction (15.88, 14.88, 14.51, ”14.44 and 13.88 adults / trap, respectively). Accordingly, the white or yellow colour traps may be, fairly, considered valuable in monitoring the population of Dialltaria adults in onion fields wherever these traps are placed. |