2024-03-29T07:27:29Z
https://jppp.journals.ekb.eg/?_action=export&rf=summon&issue=18062
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
EVALUATION THE EFFICACY OF SOME PLANT EXTRACTS AGAINST THE BULB MITE, Rhizoglyphus echinopus (Fumouze & Rabin) (Acari: Acaridae :Astigmata)
Alyaa
Tawfik
M.
Mahmoud
The efficacy of two plant (ethanol&hexan) extracts namely:Geranium, Geranium macrorrhizum Album and Oleander, Nerium oleander L. Were assayed against the bulb mite Rhizoglyphus echinopus (F.&R.).
Obtained results showed that ethanol oleander extract exhibited the highest toxic action against adult females for both disk of yeast and dipping techniques, followed by hexane- geranium , hexane-oleander and ethanol-geranium extracts , where as values of LC50 were :26.958 ,35.059 ,52.212 and 54.989 respectively.
On the other hand , the same trend occurred with ethanol-oleander against eggs but differ with hexane-geranium , extrac produced higher activity than ethanol extract.
2009
02
01
1275
1282
https://jppp.journals.ekb.eg/article_121977_346cf141ec935b58d6d6b141a0f7979b.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
INCIDENCE OF SOME WILD BIRDS AT ASSUIT GOVERNORATE
A.
Metwally
N.
Mahmoud
M.
Ahmed
M.
Omer
This article deals with the incidence of some wild birds at Assiut and their suburbs during 2003 & 2004 .Twenty seven bird species belonging to 9 orders and 21families were recorded from different habitat in the old land at Assiut , while at the new reclaimed area only seventeen bird species belonging to 7 orders and 14 families were observed . The statistical analysis of data showed insignificant positive correlation between the density of birds versus temperature during 2003 and 2004(r=0.374and t=.339 ). On the other side , the relative humidity also showed insignificant negative correlation with the population density of birds during the two years of study (r=-0.202and -0.052).
2009
02
01
1283
1289
https://jppp.journals.ekb.eg/article_121978_50e17267c67a9da267f4c54949a51b65.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
FIELD TRIALS TO EVALUATE DAMAGE CAUSED BY WILD BIRDS TO CERTAIN FIELD CROPS UNDER DIFFERENT HABITATS AT ASSIUT GOVERNORAT
A.
Metwally
M.
Ahmed
N.
Mahmoud
M.
Abdel-Aal
Field trials were carried out under different habitats at Assiut Governorate to assess the damage caused by house sparrow birds in some field crops during the year of 2003 and 2004. Two experiments were carried out on the wheat crop as well as on long and short variety of sorghum crop; the first one in old lands the other in newly reclaimed land. The damage percentage was recorded in different growth stages till crop harvesting.
The obtained results indicated that there were significant differences between the damage which caused by house sparrow in old land (1.6 & 1.23%) and that happened in newly reclaimed land (0.40 & 0.34%) during 2003 & 2004. The Sparrows attacked the eaten crop starting from formation milky stage with highest damage percent in dough stage during the two seasons (2003 & 2004). The damage percentage was not recorded in appearance of ears stage and flowers that prevent the sparrow from attacked the ears during completion mature of seeds.
Concerning different habitat, the results revealed that there were highly significant differences between damage percentage in sorghum crop for both varieties (Giza 15 & Dorado) in old land, the value being 14.26 and 12.94% during 2003 and 2004, respectively. While in the newly reclaimed land, the values of damage percentage were 5.54 and 2.32% during 2003 and 2004, respectively. The highest damage percentage was noticed in the long variety of sorghum (Giza 15) at old land and newly reclaimed land (15.56 & 12.24%), while the damage percentage in short stem variety (Dorado) was 2.24 and 3.02% during 2003 and 2004, respectively. The bird caused damage by attacking the sorghum crop starting from the milky and doughy stages then increased gradually till the harvest time.
house sparrow
damage percent
Wheat
Sorghum
old land
newly reclaimed land
2009
02
01
1291
1300
https://jppp.journals.ekb.eg/article_121980_fbbc169b051b15846c2376ff7b46f6f9.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
EFFICIENCY OF SOME ALTERNATIVE INSECTICICEDS ON THE WHITE PEACH SCALE, Pseudaulacaspis pentagona (HEMIPTERA: DIASPIDIDAE).
Fayza
Kwaiz
M.
Soliman
Sawsan
Radwan
The present work was conducted to evaluate the efficiency of some alternative insecticides on the nymph and adult female populations of P. pentagona under laboratory and field conditions.
Two groups of alternative insecticides were evaluated, these groups were Mineral oils (Misrona oil 85% mayonnaise & Alboleum oil 80% mayonnaise were used at rate of 2.5 %.) and Neem extracts (Neemix 4.5 % EC & Trilogy 90 % EC were used at rate of 1% and 1.5 %, respectively). One Organophosphorus insecticide (Fenitrothion 50 % EC at rate of 0.15%) was used as control measure for the two alternative groups.
Laboratory bioassays of the tested alternative groups were carried out under laboratory conditions, by dipping the infested branches in the solution of each tested compound where the field evaluations were carried out in peach orchard at Qalubiya Governorate by spraying the tested alternative compounds with motor sprayer (Kobota).
The obtained results showed that, the toxicity of the alternative insecticides on the white peach scale, P. pentagona were varied under laboratory conditions. The highest toxicity of the tested compounds on the nymphal stage according to their LC50 were fenitrothion (0.183%) followed by Neemix (0.357%). Mineral oils came in the 3rd order [Misrona oil (0.844%) & Alboleum oil (0.924%)] whereas Trilogy came in the last order (1.027%). The toxicity of the tested compounds on the adult female populations had the same trend, the highest toxic compounds were fenitrothion (0.226%) followed by Neemix (0.709%). Mineral oils came in the 3rd order [Misrona oil (1.368%) & Alboleum oil (1.388%)] and Trilogy came in the last order (2.310%).
The efficiency of the tested alternative insecticides under field conditions after five weeks of application showed that, Mineral oils were more effective on P. pentagona populations, they reduced the insect populations to 89% (Misrona oil) and 88.3% (Alboleum oil), whereas Neem extracts were less effective on the insect populations 66.4% (Neemix) and 57 % (Trilogy), respectively. Fenitrothion had a moderate effect on the insect populations (79.3%).
The obtained results proved that, the Mineral oils are highly efficient as alternative insecticides for controlling the white peach scale, P. pentagona compared with Neem extracts. So, it prefers to use the Mineral oils for controlling the scale insects in IPM program and more studies should be carried on neen extracts to improve their efficiency for control insect pests to minimize the environmental pollution with pesticides.
2009
02
01
1301
1309
https://jppp.journals.ekb.eg/article_121984_ba3af296068afbdc26479dc1ffbcdd73.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
MECHANICAL PROCEDURES AS AN ENVIRON-MENTAL CONTROL ALTERNATIVELY WITH CHEMICALS ON LAND SNAILS AND SLUGS ON FRUIT TREES
M.
Awad
Y.
Ramaddan
Experimental studies were conducted under field conditions by adopting methods friendly with the environment at Damietta Governorate represented at Fareskure, El-Zarka and Kafr Saad districts in addition to Sherbeen district in El-Dakahlia Governorate aimed to study the effect of tillage process and agricultural control of land snail of Monacha theba cartusiana (Muller) and slug deroceracas reticulatum (Muller) infecting some fruit trees such as lemon, orange, guava and peach, during winter and spring seasons, 2007/2008. The tillage process in each treatment was carried out into two levels according to the tillage depth of 15cm and 25cm in comparison with samples treated by Lanit 90 as molluscicides in each district. These three treatments were compared with others un- treated as a control to show the natural population of land snail and slug to tillage on 15cm depth (site1), tillage on 25 cm depth (site 2) and plots which treated with Lanit 90 (site 3). The effect of tillage in site 2 was more effective than site 1 in most samples and was similar to site 3 and sometimes more effective on lemon and guava than in orange and peach, respectively.
2009
02
01
1311
1320
https://jppp.journals.ekb.eg/article_121994_f6ab6ed8130ca0345313d89b8f96e182.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
FACTORS AFFECTING THE POPULATION FLUCTUATIONS OF TERRESTRIAL SNAILS Monacha cantiana (MÜLLER) AND Succinea putris (LINNAEUS) AT FARASKOUR DISTRICT, DAMIETTA GOVERNORATE
M.
Awad
M.
Osman
A.
Hamad
These studies were carried out at Faraskour district in four locations differed in its soil such as Sharabass which located very closely to Nile river coast with fine loamy clay soil and highly infested with land snails to El-Rodda with heavy clay soil reclaimed from ManzalaLake. Ecological factors were studied by measuring the population in moist and dry soil in the same village under all field conditions. Also, toxicological studies were conducted on these land snails under field conditions to know, the best compound which effective and cheaper in addition to avoid environmental pollution and harmful residues on plants, animal and human health. Tested compounds stated that superphosphate mixed with hyderated lime by percentage of 3:1 and foliar fertilizer improved plant growth and quality in addition to limiting individuals of these pests in relatively similar effect of some pesticides. Data showed high differences between moist and dry soil which recorded (64.6/34.8), (35.5/15.9), (35.8/18.0) and (38.5/17.4) respectively , also stated that high recorded individuals in moist soil of clover fields (64.8 per m2 at sharabass).
2009
02
01
1321
1327
https://jppp.journals.ekb.eg/article_122023_7962e6a0544615f758f45af7493feca7.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
ECOLOGICAL STUDIES ON THE GREEN SHIELD SCALE, Pulvinaria psidii (MASK.) (HEMIPTERA: COCCIDAE) INFESTING MULBERRY TREES IN QALUBYIA GOVERNORATE, EGYPT.
Sawsan
Radwan
Nagwa
Hassan
The present investigation was carried out through two successive years (2005/2006 and 2006/2007) in Qalubyia governorate to determine some ecological aspects of the green shield scale, Pulvinaria psidii (Mask.) (Hemiptera: Coccidae) on mulberry trees.
The obtained results showed that, P. psidii had two main periods of seasonal activity occurred in autumn (one generation) and summer (two overlapping generations) per each year. The 1st period of seasonal activity lasted for 4 months, started from mid September to early January and had one generation, peaked in mid November or early December with mean numbers of 26.5-69.6 insect/leaf. The 2nd period of seasonal activity extended from early May to mid August with duration of 4 months and had two overlapping generations. The 1st generation peaked in early June and the 2nd in mid July / early August in both studied years.
The population abundance of P. psidii considerably decreased from mid January to mid April (in both studied years) forming a long depressive period due to falling of the infested leaves in winter and occurrence of unfavorable environmental conditions as well as emergence of new leaves in spring.
The combined effect of the tested weather factors (daily mean max. & min. temperatures and %R.H.) on the seasonal activity of P. psidii ranged 65.7-74.7% in autumn and 68.9-89.4% in summer seasons, respectively.
2009
02
01
1329
1338
https://jppp.journals.ekb.eg/article_122024_76b775390ea856aadfdce61ebb24e11d.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
PLANT-PARASITIC NEMATODES ASSOCIATED WITH GRAPEVINE IN SANA’A AND SADAH GOVERNORATES OF YEMEN
R.
Mohamed
A survey of plant parasitic nematodes associated with vineyards was undertaken in Sana’a and Sadah governorates, the two major grapevine-producing areas in Yemen. A total of 139 soil samples were collected and plant parasitic nematodes were extracted by a combination of sieving and Baerman-pan technique. Identification revealed presence of twenty four genera i.e., Antarctenchus, Aphelenchoides, Aphelenchus, Basiria, Criconemoides Ditylenchus, Dolichodorus, Gracilacus, Helicotylenchus, Hoplolaimus, Longidorus Meloidogyne, Paratylenchus, Pratylenchus Rotylenchulus, Rotylenchus Scutellonema, Telotylenchus, Tetylenchus, Trichodorus Tylenchorhynchus, Tylenchus, Xiphinema and Zygotylenchus. All nematode genera except Aphelenchoides on Asemi, Aphelenchus on Asemi and Raziki, Helicotylenchus on Black, Longidorus, Meloidogyne, Paratylenchus, Pratylenchus, Tylenchorhynchus and Xiphinema in Bani-Hushaisharereported for the first time on grape in Yemen. The most predominant plant nematode genera on grape cultivars in all locations were Tylenchus, Xiphinema, Helicotylenchus, Tylenchorhynchus, Rotylenchulus and Pratylenchus, while Paratylenchus and Meloidogyne had high frequency occurrencein Sana’a and Sadah governorates, respectively. In Sana’a governorate Paratylenchus and Xiphinema exhibited the highest population densities of 646 and405nematode/250gm soil withfrequencyoccurrence attaining54% and 67% respectively. In Sadah governorate Xiphinema and Meloidogyne had relatively high population densities of 502 and 429 nematode/250 gm soilswith 25% and 50%frequency occurrence, respectively
Survey
Nematode genera
Grape cultivars
Yemen
2009
02
01
1329
1345
https://jppp.journals.ekb.eg/article_122025_b44571548c66a24ed6c3c86cede95725.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
RELATIVE ABUNDANCE AND FLIGHT ACTIVITY OF THREE COTTON LEAF WORM MOTHS, Spodoptera littoralis BIOSD. , Spodoptera exigua HB. AND Spodoptera latebrosa LED. AND THEIR PREDATORS USING A LIGHT TRAP AT MANSOURA DISTRICT.
Nadia
Mohamed
A.
Ghanim
A.
Abdel-Salam
A.
Saleh
The population fluctuations and effect of certain weather factors on the flight activity of three leaf worms moths, Spodoptera littoralis Boisd. ; Spodoptera exigua Hb. and Spodoptera latebrosa Led. and their predators were studied by a light trap at Mansoura district. The obtained data showed that the peaks of S. littoralis according to biweekly catch occurred in the fourth week of April; the first week of June; the first week of July; the end of July; the second week of September; the end of October and the third week of November; represinting seven peaks of moths per year during the two years of study. The results showed that, S. exigua moths had five peaks per year during the two years of study. These peaks were occured in the first week of May; the first week of July; the end of August; the end of September and the fourth week of October, respectively. In addition, S. latebrosa moths had five peaks per year during the period of study. These peaks were occured in the first week of June; the first week of July; the end of July; the second week of September and fourth week of October, respectively. The statistical analysis showed that there was a highly significant positive correlation between the temperature parameters and the number of trapped moths of the three leaf worm species during the two years of study. The maximum relative humidity had a highly positive significant effect on populations of the three leaf worm moths in the first year and a slight negative effect in the second year of investigation. The other relative humidity parameters exerted a slight negative effect during the two years of investigation. The obtained results showed that there were four predators caught by a light trap during this study namely: Coccinella undecimpunctata L. ; Cydonia vicina isis Cr.; Paederus alfierii Koch. and Labidura riparia Pall.. The data cleared that C. undecimpunctata had four peaks and C. vicina isis had five peaks per year while that was two and three peaks for P. alfierii and L. riparia, respectively.
The statistical analysis showed that there was a highly significant positive correlation between the temperature parameters and the number of trapped predators during the two years of study. The maximum relative humidity had a highly positive significant correlation on the population density of L. riparia and C. vicina isis in the first year of study, while the minimum relative humidity had a negative significant effect on the population density of L. riparia in the first year, while minimum relaive humidity had a possitive significant effect on the population density of P. alfierii in the second year of investigation.
Spodoptera littoralis
Spodoptera exigua
Spodoptera latebrosa
Coccinella undecimpunctata
Cydonia vicina isis
Paederus alfierii
Labidura riparia
Light trap
2009
02
01
1347
1360
https://jppp.journals.ekb.eg/article_122027_6e96e01d489e688a95ea1c41e0b2c193.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
FIELD EFFICACY OF ENTOMOPATHOGENIC NEMATODES AND EGG WASPS FOR BIOCONTROL OF TOMATO FRUIT WORM, Helicoverpa zea, IN EGYPT
A.
Atwa
The potential of entomopathogenic nematodes (EPNs) and an egg parasitoid for biological control of the tomato fruit worm, Helicoverpa (= Heliothis) zea (Boddie) was evaluated under field conditions for three successive seasons (2005-2007). The EPNs, all strain of Steinernema carpocapsae (Weiser) (SC), the “HP88” strain of Heterorhabiditis bacteriophora Poinar (HB) and the egg wasp Trichogramma evanescens (Westwood) (TE) were applied to control H. zea on tomato field. Three releases of each biological control agent were conducted at 10-day intervals, 15 days after tomato plants reach 30-50% effloresce. Fruit damage on untreated plots (control) was compared with plots treated by TE, SC or HB. Percentage of fruit damage was significantly reduced in all treatments when compared with untreated plants. However, the mean percentage fruit damage was significantly lower in TE-release plots when compared with plots treated with SC or HB. The obtained results suggest that using EPNs or egg wasps is a promising strategy to manage H. zea in tomato fields. SC nematode was more potent in decreasing the fruit damage than HB nematode. However, TE seems to be a potential biocontrol agent for the tomato fruit worm
Tomato
Helicoverpa zea
Trichogramma evanescens
Steinernema carpocapsae
Hetrorhabiditis bacteriophora
fruit damage
2009
02
01
1361
1371
https://jppp.journals.ekb.eg/article_122028_bcb9e7ad2023839b150e6659eb2dc659.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
SURVEY THE NEUROPTEROUS PREDATORS AND THE RELATIVE ABUNDANCE OF Chrysoperla carnea (STEPH.) AND Chrysopa septempunctata WESM. BY USING A LIGHT TRAP AT MANSOURA DISTRICT
A.
Ghanim
M.
El-Naggar
N.
Abd El-Baky
Eman
Abd El-Halim
A survey of certain neuropterous predators and the relative abundance of the important neuropterous predatory insects were studied by using a light trap during two successive years at Mansoura district. The obtained results recorded four neuropteruos predators trapped during the two years of study. These species belonging to two families : Chrysopidae and Myrmeleonidae. These predators were namely: Chrysoperla carnea (Steph.) ; Chrysopa septempunctata Wesm.; Cueta variegata Klug. and Palpares cephalotes Klug. The dominant species was C. carnea during the two years of investigation. The data showed that C. carnea had six peaks in the first year and five peaks in the second year of study. These peaks were recorded in the fourth week of March; fourth week of April; first week of June; third week of July; third week of August and second week of October; while in the second year these peaks were recorded in the first week of April; first week of June , first week of July, first week of August and fourth week of September, respectively. The obtained data revealed that C. septempunctata had four peaks in the first years and three peaks in the second years. These peaks were recorded in the first week of June, third week of July, fourth week of August and second week of October, respectively in the first year, Meanwhile, these peaks were found in the second year of study, in the first week June, first week of July and fourth week of August. The statistical analysis assured that, there was a highly positive significant correlations between the biweekly catch of C. carnea and C. septempunctata and temperature parameters during the two years of study. While, the relative humidity parameters had insignificant effect on the population density of the two predators during the two years of investigations.
2009
02
01
1373
1384
https://jppp.journals.ekb.eg/article_122029_cf8e33e76baea712394eef784aa2c266.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
NON CHEMICAL CONTROL OF WEEDS ACCOMPANIED WHEAT UNDER SALINE SOIL CONDITIONS
A.
Mohamed
Two field experiment were conducted in Tegzerte, Siwa Research Station; Desert Research Center during winter seasons of 2003 and 2004 to study the effect of phosphorus fertilization levels (0, 15.5, 31.0 and 46.5 kg/fed.), nitrogen fertilization levels (0, 80.0, 100.0 and 120.0 kg/fed.) and wheat grain rates (70.0, 80.0 and 90.0 kg/fed.) on weed control and relationship to wheat production. The experimental design was a split split-plot design with four replicates in both seasons, where the phosphorus fertilization treatments occupied the main plots, nitrogen fertilization treatments were arranged in the sup main plots and grain rates treatments in the sub-sub main ones, respectively. Weeds interference treatments were broad leaf weeds, grassy weeds and total annual weed.
Results showed that increasing phosphorus and nitrogen fertilization levels and wheat grain rates led to decrease significantly broad leaf weeds (Chenopodium album, Malva parviflora, Cichorium pumpilum, Beta vulgaris, Convolvulus arvensis, Melilotus indicus and Medicago polymorpha), grassy weeds (Zygophyllum album, Phragmites australis, Setaria viridis and Echinochloa colonum), while wheat biological, grain and straw yield were increased significantly as a results of applied the treatments.
Higher observation of biological, grain and straw yield were taken from the interaction between the three main factors, especially with (31.0 p kg./fed. & 100.0 N kg./fed. and 90.0 kg. wheat grains /fed. ), which led to 6.0, 2.4 and 3.6 ton. /fed., respectively compared to other treatments
phosphorus
nitrogen
fertilization
wheat grain rates
annual weeds
Wheat
2009
02
01
1385
1397
https://jppp.journals.ekb.eg/article_122031_4e6162ab4f5d5524c1e9db5890a317cc.pdf
Journal of Plant Protection and Pathology
2090-3677
2090-3677
2009
34
2
EFFECT OF PLANTING DATE AND HOST CULTIVAR AND THREE COMMERCIAL MICROBIAL PRODUCTS ON DEVELOPMENT OF DAMPING-OFF, ROOT ROT AND WILT OF SOYBEAN PLANTS
Ebtehag
El-Barougy
E.
Fayzalla
M.
El-Rayes
Soybean (Glycine max (L.) Merr) is subject to stand injury and yield loss due to several diseases. Fusarium oxysporum, Macrophomina phaseolina, Rhizoctonia solani and Sclerotium rolfsii are found to be pathogenic to soybean causing damping off, root rot and wilt diseases. All isolates of the tested fungi were pathogenic but varied in virulence for pre and post- emergence damping off and their behavior. The highest level of pathogenicity was exhibited by R.solan. Chemicals are effective in controlling these diseases but, these chemicals are expensive and not environmental friendly. There are great efforts to reduce environmental pollution by reducing the dependence on agrochemicals to control pests. Biological control and resistant soybean cultivars are used means to control many diseases. Some microbial products such as Mycostop®, active microbial ingredient; Streptomyces griseoviridis; Bio-ARC® Bacillus megaterium and Biozeaid ®, Trichoderma a/bum were evaluated as compared with the fungicide Rhizolex for their efficacy against Fusarium oxysporum, Macrophomina phaseoli, Rhizoctonia solani and Sclerotium rolfsii. , all tested microbial products or fungicide were significantly reduced the percentage of damping-off, infested plants and increesed the `ercentage of healthy survival plants. Susceptibility of some soybean cultivars was tested in potó and under field condition. In pots experiment, none of the cultivars was completely resistant, however Giza 111 cultivar could be cnsidered tolerantl while Gmza 22 cultivar considered thå most susceptible one. Under natõrally infested soil in the fiåld conditions,(the reactions of seven cultivars (Giza 111, Giza 22, Giza 35, Giza 82, Giza21, Kilarce and Crawford) to root-rot and wilt diseases complex were evaluated in two seasons. In 2006/2007 season Giza 111 had the least incidence % of diseases plants but Giza 35 cultivar had the highest one. In 2007/2008 season, the same trend was noticed with light grade. Plant weight and plant height did not correspond with the level resistance.
Delaying of soybean planting from May to July caused increasing in damping-off. Where, the percentage of damping-off increased from about 13.3 to 53.3%; 20 to 56.6% and from 33.3 to 60% with delayed planting from May to July in presence of F.oxysporum, M.phaseoli and S.rolfsi respectively. But it decreased from 46.7% t0 33.3% in presence of R.solani.
Soybean
biological control
Mycostop®
BioARC®
BioZaied®
Streptomyces griseovirides
Bacillus megaterium
Trichoderma album Fusarium
Rhizoctonia solani
Macrophomina phaseolina
Sclerotium rolfsii
2009
02
01
1399
1418
https://jppp.journals.ekb.eg/article_122033_a10269c1b4458073fcda57fba95d7ce4.pdf