Survival of Pratylenchus jordanensis Hashim was studied in a field in fallow after the harvest of a crop of alfalfa and in storage under laboratory conditions. The nematodes survived in dry roots/ root residues under field conditions for 100 days. Vertical migration of the nematodes to deeper soil layers was observed when the top soil layer dried up. High numbers of nematodes survived at both 0-15 and 16-30 cm depths for 100 days. Then the field was ploughed under, which caused the soil to dry and the populations to decline. The nematodes survived for 380 days in a fallow field. They survived for 270 and 272 days under laboratory conditions in wet and shade-dried soil, respectively, and for 124 days in natural field soil at 30 degrees C. Significant negative correlation between nematode populations and storage temperature and positive correlation between nematode populations and soil moisture were observed. P. jordanensis did not survive for long in a drop of water on a glass slide, whereas it survived in filter paper discs for varying periods at different relative humidity levels. Survie de Pratylenchus jordanensis Hashim dans les jacheres suivant la recolte de luzerne - La survie de Pratylenchus jordanensis Hashim dans les jacheres suivant la recolte de luzerne et dans du sol stocke au laboratoire a ete etudiee. Au champ, le nematode survit 100 jours dans les racines dessechees ou les fragments de celles-ci. Il a ete observe une migration verticale des nematodes vers les couches plus profondes du sol lorsque la surface de celui-ci se desseche. Un grand nombre de nematodes survivent 100 jours a des profondeurs de 0-15 et 16-30 cm apres quoi les populations declinent du fait de la dessiccation causee par le labourage du champ. A 30 degrees C, le nematode survit 270 jours dans du sol humide, 272 jours dans du sol seche a l'ombre - l'un et l'autre dans les conditions du laboratoire - et 124 jours dans le sol naturel au champ. Il a ete observe des correlations significatives, negatives, entre populations du nematode et temperature de stockage, et positives, entre populations du nematode et humidite du sol. P. jordanensis ne survit pars longtemps dans une goutte d'eau placee sur une lame porte-objet, tandis qu'il est capable de se maintenir pendant des periodes plus ou moins longues si place sur des disques de papier filtre soumis a des taux d'humidite relative varies.
Effects of sinusoidal magnetic fields on chawki silkworm rearing have been studied. The experiment was conducted using a multi X Bi silkworm hybrid, PM x CSR 2. Disease-free layings were reared from hatching to cocooning and by subjecting first and second instar to three magnetic field frequencies: 0.1, 1.0, and 10 Hz at 1500 nT, pp, for six days at six hours per day. Controls were maintained simultaneously. Larval durations for both young-stage chawki (I and II) and late stage (III, IV, V) were calculated in days and hours, including the feeding and moulting periods for I to IV instars, and the feeding period for V instar up to the time of spinning. The study revealed that the magnetic exposures reduced both feeding and moulting times with no adverse effects on larval growth. The substantial reductions in time, 33 hours in instars I and II, and 64 hours in total larval duration, could be commercially important in chawki rearing, saving time, leaf consumption, and labor expenses.
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