Overwintering of the Japanese bayberry whitefly,parabemisia myricae,in Israel

The Japanese bayberry whitefly,Parabemisia myricae (Kuwana), was discovered in Israel on citrus and avocado trees in 1978. In order to clarify its mode of overwintering, observations and counts were carried out during the winters of 1979/80, 1982/83 and 1983/84, with the following findings. Larvae and adults were detected on citrus and avocado trees throughout the winter; only females were found. The oviposition rate ofP. myricae in winter was low, and rose steeply in spring. The density of larvae on the lower side of leaves was higher than on the upper side. Substantial numbers of larvae survived the winter on avocado trees. Emergence of adults became intensified at the end of February, reached a peak in early March, and ceased at the end of March or beginning of April.     

Sex differences in circulating steroid hormone levels in the red drum, Sciaenops ocellatus L.

Steroid profiles of cultured and captive red drum (Sciaenops ocellatus L.) were investigated to evaluate the potential use of circulating sex steroid levels as a tool for gender identification in this species. Cultured 18‐month‐old fish were maintained on a 120‐day shortened photothermal cycle to induce precocious maturation. Additionally, wild‐caught fish were maintained in captivity under simulated natural photothermal conditions from late spring to early fall. Circulating 11‐ketotestosterone (11‐KT) levels were significantly higher in males compared with females during the early stages of gonadal growth in both cultured and captive fish. Plasma testosterone (T) levels showed a similar trend; however, the differences were significant only when males were already producing sperm. 17β‐estradiol (E₂) concentrations were low in males and females before gonadal recrudescence but increased significantly with the progression of vitellogenesis in females. These results show that a test using a minimum concentration of circulating 11‐KT could be developed to differentiate between sexes in the early stages of gonadal maturation in red drum. Moreover, plasma E₂ concentrations could be used to identify vitellogenic females. The two steroids considered together could help avoid possible error in gender identification due to unusually high levels of certain steroids encountered in some individuals.     

Strawberry-cultivar Identification using Randomly Amplified Polymorphic DNA (RAPD) Markers

Accurate and rapid cultivar identification is important for breeders'-rights protection, especially for vegetatively propagated plants. The objective of this study was to test the feasibility of developing cultivar-specific RAPD markers in commercial strawberries (Fragaria ananassa Dutch). Efforts were focused on distinguishing between two newly developed Volcani cultivars, ‘Ofra’ and ‘Dorit’, and six other cultivars, ‘Douglas’, ‘Chandler’, ‘Oso Grande’, ‘Dover’, ‘Nurit’ and ‘Parker’. Reproducible RAPD fingerprints were generated, each containing at least one polymorphic DNA product. A combination of 10 polymorphic DNA products exhibited cultivar-specific patterns enabling the distinction between closely related varieties, such as ‘Ofra’ (which is the progeny of ‘Dorit’ and ‘Parker’) and ‘Dorit’ (which is the progeny of ‘Nurit’ and ‘Dover’). This study shows that RAPD markers can help in the protection of breeders’ rights to strawberry cultivars.     

Control of the honeydew moth,Cryptoblabes gnidiella Mill. (Lepidoptera: Phycitidae), withBacillus thuringiensis berliner in avocado plantations

Field trials were conducted in 1971–1974 to control the honeydew moth,Cryptoblabes gnidiella Mill, withBacillus thuringiensis. Dipel, a commercial preparation containingBacillus thuringiensis var.kurstaki (HD-1 strain), was highly effective (at concentrations ranging from 0.25% to 1.5%) in killing caterpillars of all developmental stages. In both the field trials and additional laboratory trials, it had no adverse effect on the mealybugPseudococcus longispinus Targ.-Tozz., or on its parasites,Hungariella peregrina Compere andAnagyrus fusciventris Girault.     

Soil amendments and seed priming influence nutrients uptake,soil properties,yield and yield components of wheat (Triticum aestivum L.) in alkali soils

The effects of soil amendments [i.e., control, gypsum, farmyard manure (FYM), and gypsum?+?FYM] and seed priming (i.e., unprimed, seed soaked in water for 10?hr prior to sowing, and seed soaked in 0.4% gypsum solution for 10?hr prior to sowing) were assessed on growth and yield of wheat (Triticum aestivum L.) crop in alkali soil in northwestern Pakistan. A split plot design was used, keeping priming methods in main plots and soil amendments in sub-plots. The results showed that the effects of soil amendments and seed priming on grain yield, straw yield, harvest index and number of spikes were significant but their interactive effect was non-significant. The highest crop yields and yield index were obtained with gypsum?+?FYM amendments, and seed priming with gypsum solution. The effect on seed emergence, plant height and number of grains per spike was, however, not significant. Grain yield increased by 104% in gypsum?+?FYM treatment over control and by 16.8% with seed primed in water, followed by 8.5% with priming in gypsum solution, as compared to non-priming. The weight of 1000 grains was significantly increased by 35% in gypsum?+?FYM treatment and by 15.8% in gypsum priming. The phosphorus (P) and potassium (K) content increased with soil amendments. Soil pH and gypsum requirement reduced significantly with soil amendments. The blend of gypsum and FYM has improved the properties of salt-affected soil and enhanced fertility for optimum production of wheat in addition to the beneficial effect of seed priming in gypsum solution on crop yield. Using these amendments could be ameliorative in removing the adverse effect of the salt-affected soils, rendering the soil a good medium for plant growth.     

Morpho-physiological Responses of Tomato Genotypes Under Saline Conditions

Gesunde Pflanzen - Salinity is a complex abiotic stress that affects physiology and biochemistry of plants and significantly reduces both crop yield and quality. Considering the global...     

Nitrogen rates in strawberry (Fragaria ananasa) nursery on growth and yield in the field

Strawberry (Fragaria ananassa cv. Aliso) plants were grown under three N‐rates in the nursery: 80, 320 and 640 kg N/ha, and then transplanted to the fruiting field. Plants from each nursery treatment were given 150, 300 and 450 kg N/ha. The fertilizer was given as ammonium sulfate in the nursery and as ammonium nitrate in the field, a part broadcasted before planting and the other part applied as top dressings. Biomass production, plantlets size distribution and N content were restricted by the lowest level of N given in the nursery. Plants grown at 320 kg N/ha in the nursery gave significantly earlier and higher total yields than those grown at the other rates. Fruit yields were not significantly influenced by the N‐application in the field. N fertilization in the early stages of strawberry plant development in the nursery is more important than later field application.

The influence of N fertilization on the growth and yield of strawberry plants has been studied by several workers. In some reports yields were increased when the rate of N applied was increased (1, 2, 3). In other studies no influence was found (4, 5, 6), or even a decrease in yield was reported as the rate of applied N was increased (7). While in some studies detrimental effects of N‐fertilizer on fruit yield were observed at 200–300 kg N/ha (8, 9), in other studies (6, 7) N applications up to 400 kg/ha did not affect yield. In Spain (3), adding up to 680 kg/ha caused an increase in fruit yield.

Even at relatively low applied‐N levels, up to 150 kg N/ha, strawberry response reports are not consistent. Some workers found that increasing N in this range caused an increase in fruit yield (8, 9, 3, 7, 10), while no effect was observed (4, 5, 6, 11) in several other studies. Most of the reported experiments with N‐fertilizer were carried out after plants were transplanted from the nursery to the field. To the best of our knowledge no attempt was made to evaluate the effect of fertilizer applied in the nursery.

The objective of this work was to evaluate the influence of different levels of N‐fertilizer, in both the nursery and the field, on strawberry plant development and composition, earliness, yield level and yield distribution.     

Biological data onApanteles cerialis Nixon (Hymenoptera: Braconidae), a parasite ofBoarmia (Ascotis) selenaria Schiff. (Lepidoptera: Geometridae)

Apanteles cerialis Nixon, a thelytokous braconid parasitoid ofBoarmia (Ascotis) selenaria Schiff., attacks young caterpillars (preferably 2–5 days old) of this pest in avocado plantations of Israel. At 27±1°C, oviposition rate is 2.04 progeny per day and 18.3 progeny over the entire life span. The development time of preimaginal stages is 16.1 and 15.2 days at 25° and 30°C, respectively, and increases to 37.3 days at 17°C. The pupal stage averages 4.4 days at 30°C and 13.5 days at 17°C. The average longevity of adults is 24.2 and 7.9 days at 30° and 17°C, respectively. In avocado orchardsA. cerialis appeared in considerable numbers in late summer and autumn; it was slightly hyperparasitized by the ichneumonid waspStictopisthus sp. (1 and 2% of the samples at one site).

     

The effectiveness ofBacillus thuringiensis Berliner onBoarmia (Ascotis) Selenaria Schiff. (Lepidoptera,Geometridae) in laboratory tests and field trials

The effectiveness of a commercial preparation ofBacillus thuringiensis Berliner (Dipel) against eggs and larvae ofBoarmia (Ascotis) selenaria Schiff. of different age was examined in laboratory and in field tests. The mortality rate ofB. selenaria was proportional to the concentration ofB. thuringiensis and inversely related to the age of the treated larvae. In neonate larvae, 100% mortality was obtained even with a low concentration (0.5%). Egg hatch was not affected, but the survival rate of larvae hatched from treated eggs was very low (2.2%). No phytotoxicity of the commercial microbial preparation was observed on fruit or leaves of avocado. High doses ofB. thuringiensis persisted on avocados, probably because of specific conditions:i.e., absence of rainfall, moderate temperatures and limited penetration of sunlight. Tests carried out in large commercial orchards, using motor-guns and helicopters, yielded good results.     

Sulfur diagnostic criteria for French prune trees

One year old Marianna 2624 (Prunus cerasifera X P. munsoniana) trees grafted with French prunes (P. domestica) were grown in the greenhouse in pots containing vermiculite and supplied with graded amounts of sulfate‐sulfur (SO₄‐S) to study the methods of evaluating sulfur (S). Tree fresh weight gain was recorded. Leaf samples were analyzed for different S fractions. Chlorophyll concentration of leaves was better than fresh weight gain as an indicator of tree S status. Sulfate in recently matured leaves is a better diagnostic index for prunes than total‐S, organic‐S, or N:S ratio which are not suitable for this purpose. Using chlorophyll as an indicator of growth potential, critical SO₄‐S level of recently matured leaves is 97 ppm. Sulfate‐sulfur as a percent of total‐S can also be used as a diagnostic tool. Critical level for this index in the recently matured leaves is 7.85%. External critical S level is 80 μM (8 ppm as SO₄).