Systemic effect of aldicarb,dimethoate and ethiofencarb on mortality and population dynamics of the spirea aphid, Aphis citricola Van der Goot

A bioassay using detached citrus leaves, the petioles of which were immersed in solutions containing insecticides, was used to assess the systemic activity of aldicarb, dimethoate and ethiofencarb on the spirea aphid, Aphis citricola Van der Goot (Homoptera: Aphididae). At identical concentrations in the treatment solutions the order of toxicity to insects of these compounds was aldicarb > dimethoate > ethiofencarb. The toxicity of the residue of aldicarb in the leaves (LC₅₀=2·5 μg/g) resembled that of dimethoate (LC₅₀=1·8 μg/g) and both were more potent than ethiofencarb (LC₅₀=30 μg/g). The amount of aldicarb accumulated in the leaves, 3 days after application, was 25±0·5% of that present in the treatment solution, compared with 4±0·4% of dimethoate and 3±0·3% of ethiofencarb. Thus, the more efficient uptake of aldicarb may be the reason for its high toxicity. When sublethal concentrations of aldicarb incorporated in treatment solutions were taken up by detached leaves, a significant reduction in the pre-reproductive development time, and increased longevity and fecundity were observed. This hormoligosis phenomenon was further emphasized by a considerable increase in aphid weight. This effect seems to be plant mediated, as it was not observed when aldicarb was added to a synthetic diet. Dimethoate showed an effect similar to that of aldicarb, but less pronounced and not statistically significant, whereas ethiofencarb had no such effect.     

Accelerated transformation of aldicarb,oxamyl and ethoprophos after repeated soil treatments

Distribution and transformation of the nematicides aldicarb, oxamyl and ethoprophos was measured on annually treated plots and plots not previously treated on two potato fields. This trial plan was chosen because the effect of the nematicides decreased in the annually treated plots on these fields. In the field, the contents of the nematicides decreased more rapidly in soil of the annually treated plots than in the untreated ones. This rapid disappearance of the active compounds was found to be the cause of the decreased nematode control on the annually treated plots. The considerably more rapid transformation of the nematicides in treated soils than in untreated ones was also measured in incubation tests at 15°C. Sterilization of the treated soils drastically reduced the rates of disappearance. The repeated applications of the nematicides must have induced microbial adaptation, which resulted in accelerated transformation. The carbamoyloximes aldicarb and oxamyl were transformed at about the same rates in previously untreated soils and in soils from plots previously treated with ethoprophos. However, oxamyl was transformed very rapidly in soil previously treated with aldicarb and also aldicarb in soil previously treated with oxamyl: this indicates that cross-adaptation occurred for the two carbamoyloximes.     

Influence of treatment of soil with carbofuran on the subsequent performance of insecticides against cabbage root fly (Delia radicum) and carrot fly (Psila rosae)

A sandy loam soil was treated with 2·5 kg carbofuran/ha on each of five occasions between May and October 1984. In 1985, the field performance of benfuracarb, carbofuran, carbosulfan, chlorfenvinphos and furathiocarb against cabbage root fly (Delia radicum) and carrot fly (Psila rosae) was studied in this soil and in identical but previously untreated soil by applying exponentially increasing doses of granular formulations to radish and carrots at drilling. Chlorfenvinphos reduced numbers of larvae of both pests by >90% in both soils but the performance of all the carbamates was significantly worse in the previously treated soil than in the previously untreated soil. Dazomet, a partial soil sterilant, was applied to part of the experimental area in October 1985 and the performance of aldicarb, carbofuran, carbosulfan, chlorfenvinphos and thiofanox against cabbage root fly was assessed in 1986. The efficiency of aldicarb and chlorfenvinphos was not affected by any of the pre-treatments but that of carbofuran and carbosulfan was reduced in all the pre-treated soils, including the soil treated with dazomet. Carbofuran residues in radish were detectable only in plants grown in previously untreated soil. In laboratory incubations, a dustless base formulation of carbofuran was degraded more quickly in pre-treated than in untreated soils but a granular formulation was degraded more slowly and at a similar rate in both soils.     

The joint action of nitrogen and nematicides onPratylenchus penetrans and potato yield

The joint action of nitrogen fertilizer and nematicides onPratylenchus penetrons and yield was investigated using three potato varieties (Superior, Onaway and Russet Burbank), three rates of nitrogen (84, 168 and 336 kg/ha), five edaphic pesticides (disulfoton, aldicarb, 1,3-D + MIC, carbofuran and thiofanox), and an insecticide spray to minimize the role of foliar feeding insects In 1977, disulfoton, aldicarb, and disulfoton plus 1,3-D + MIC significantly increased the yield of Superior at all nitrogen rates. The yield increases ranged from 37–56% for Superior, 15–35% for Onaway and 13–27% for Russet Burbank. Nitrogen had no detectable influence on yield. Population densities ofP. penetrans were significantly reduced by disulfoton plus 1,3-D + MIC and by aldicarb. Superior was most susceptible toP. penetrans, Onaway intermediate, and Russet Burbank moderately tolerant. Neither the potato variety or nitrogen significantly influenced the population densities ofP. penetrans In 1978 aldicarb, 1,3-D + MIC and thiofanox significantly increased yields of Superior at all nitrogen rates. Nitrogen also significantly increased yields, but only where aldicarb and 1,3-D + MIC were applied. Total yield was increased 12–14% and 17–23% by 1,3-D + MIC and aldicarb at 168 and 336 kg N/ha, respectively. Aldicarb, 1,3-D + MIC, and thiofanox appeared to increase tuber set, while nitrogen increased tuber size. Although all of the nematicides provided some control ofP. penetrans, aldicarb had the highest degree of efficacy and gave excellent season-long control     

The effect of nematicides onPratylenchus penetrans and potato yields

Aldicarb applied as Temik 10% or 15% granular at 1.68, 2.24 or 3.36 kg/ha active ingredient (a.i.) in the row at planting reduced the size of populations ofPratylenchus penetrons in experimental plots and commercial fields. Both aldicarb and the soil fumigant, Telone-II, were associated with yield increases of about 40% in Superior and Sebago potatoes in experimental plots in 1978, but there were no significant increases in yield in 1979 and 1980. A comparison was made between areas treated with aldicarb 10% granular at 2.24 kg/ha a.i. or disulfoton 15% granular at 3.36 kg/ha a.i. in 24 commercial fields. Average yields from the combined results of Kennebec, Superior, Sebago, and Russet Burbank cultivars were about 13% higher in the aldicarb treatments. Yields in six fields where aldicarb was applied at 3.36 kg/ha a.i. were not different from yields in adjacent fields treated with the lower rate of aldicarb. Superior potatoes inoculated withP. penetrons, or uninoculated, were grown in pots in the greenhouse in fine sandy loam at moisture levels of 35–55% or 70–100% field capacity. The lower soil moisture level and the nematode treatment reduced tuber weights. The nematode-soil moisture interaction was significant in one of the two experiments.     

Field and laboratory studies on the control of nematode and aphid virus vectors in potatoes by pesticides applied as side-bands

Field trials were undertaken with a prototype machine to determine whether virus vector nematodes and aphids were controlled by the carbamoyl oxime pesticides aldicarb (Temik 10G) and oxamyl (Vydate 10G) incorporated into the ridge of a growing potato crop. The treatments were applied at tuber initiation (7 or 8 weeks after planting) and were compared with similar amounts of the same pesticides applied in-furrow at planting. All aldicarb treatments significantly decreased the incidence of tobacco rattle virus spraing transmitted by trichodorid nematodes. However, the side-banded treatments were less effective than the in-furrow treatments applied at similar rates. Numbers of aphids infesting the crop were significantly and similarly decreased by both methods of application. Pesticide treatments did not significantly increase yield, and total tuber yields from the standard infurrow and the side-banded treatments were similar. To provide further information on the efficacy and movement of carbamoyl oxime pesticides between different isolated root systems on single parent tubers, replicated pot experiments were made. Parent tubers were maintained with a physical barrier between a root system treated with pesticide and another left untreated. In a nematode bioassay Meloidogyne incognita was added to both the treated and untreated root systems to test for the presence of nematicidal activity. The number of root-galls which developed in 8 weeks were counted. Both aldicarb and oxamyl decreased the number of galls on the treated root system. However, little evidence of translocation through the parent tuber was found, the number of galls on the untreated roots being largely unaffected. The roots of plants grown from tubers treated in a similar manner were tested for the presence of aldicarb and oxamyl residues by gas-liquid chromatography. No translocated pesticide was detected. In aphid bioassays, using excised leaves, 3–5 weeks after applying aldicarb at 20 and 40 mg a.i./pot or 4–9 weeks after applying aldicarb at 80 mg a.i./pot, aphid survival was always significantly less on treated stems than on non-treated stems growing at the opposite end of the tuber or on control stems growing from untreated tubers. However, there was some evidence for translocation through the parent tuber as fewer aphids survived on leaves from non-treated stems than from untreated control stems.     

Management of Soil Salinity and Alkalinity Problems in India

SUMMARY

Like the problem of salt-affected soils afflicting many other countries with arid and semi-arid climates, these lands occupy about 8.6 M ha in India out of which 3.5 M ha are in canal commands, commonly referred to as man made or wet deserts. Starting from the early systematic work of Dr. Leather about a century ago, real impetus to development and application of reclamation technologies has occurred in the post independence period, especially the seventies. Salt-affected soils are grouped into saline and alkali/sodic soils on the considerations of soil management and crop responses. Out of the 3.4 M ha of alkali lands in Indo-Gangetic Plains, about 1.0 M ha has been reclaimed by the hydro-chemical technology. Application of amendments like gypsum, equivalent to 50% gypsum requirement, to the surface 15-cm soil only was enough to start cropping with rice. Light and frequent irrigation are ideal for upland crops. Application of higher doses of nitrogen in splits to compensate for volatilization losses, organic matter additions through green manure to increase reclaiming action, skipping phosphorus application in the initial years and the application of zinc to each crop were some of the emerging recommendations. Application of low-grade pyrites also gave encouraging results in calcareous soils. Feasibility of drainage has been successfully demonstrated in 1980s for the quicker rehabilitation of saline and waterlogged soils. Provision for subsurface drains at 1.5–2.0 m depth and 50–75 m spacing in alluvial soils and 12–24 m interval in vertisol was sufficient for facilitating growing crops within 2–3 years on lands lying barren for considerable period. However, technological, economic, social, and political considerations are the major bottlenecks for large-scale amelioration of saline soils, in addition to the safer disposal of drainage waters. Strategies worked out for successful crop production on saline soils after drainage include initial leaching management (minimizing water requirement for leaching by synchronizing with monsoon rains, etc.), proper selection of crops/cultivars, irrigation (method, controlled frequency for enhancing water-table contribution, canal water use during the initial stages including presowing for conjunctive use with drainage waters) and cultural practices (furrow planting, increasing seed rate and fertility management). Some of the future issues for combating salinity and also preventing further land degradations in India are also highlighted.     

Using dazomet to reduce broomrape seed banks in soils with low moisture content

Dazomet (Basamid^®) is a dry powder formulation that releases the toxic gas methyl isothiocyanate for the control of soil borne pests and weed seeds when applied to moist soils. We evaluated its efficacy for destroying Phelipanche mutelii (branched broomrape) seed banks. Dazomet is typically used where effectiveness can be improved with the addition of water but we examined its performance in soils with low moisture content in container experiments and field trials. In containers, less than 10% of P. mutelii seed remained viable 30 days after dazomet applications of 112.8–338.4 kg ha⁻¹ at soil moisture content from 0.05 to 0.15 g g⁻¹. Seeds buried at a depth of 5 cm needed to be in contact with the product for longer than one week before viability was affected. An initial field trial did not detect a decline in seed viability 7 days after dazomet application. Viability assessments in a second field trial were made 30 days after dazomet application with an airseeder at a rate of 338.4 kg ha⁻¹. Less than 10% of P. mutelii seeds at a depth of 5 cm survived and dazomet was as effective as two other soil fumigants, methyl bromide and a methyl iodide/chloropicrin mixture. The release of methyl isothiocyanate is reduced in soils in containers with low soil moisture content but occurs over a long time period. Methyl isothiocyanate dissipated more rapidly in soils in containers with higher soil moisture content and at lower dazomet application rates. A higher application rate is required in the field to ensure the dazomet powder is evenly distributed through the soil profile and there is adequate methyl isothiocyanate resident in the top soil layer to achieve seed kill. This has consequences for plant back times in fumigated land following dazomet application.     

Effect of initial water content on saturated hydraulic conductivity in desalinization with slaking and drying

Soil slaking is an environment-friendly technique that is gaining importance in restoring saline soils. The objective of this article is to evaluate the effect of initial water content (IWC) on saturated hydraulic conductivity (K _s) in desalinization with slaking and drying. Accordingly, a slaking test was carried out during February, 2009 for evaluating the effects of slaking and drying on K _s, sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) under various IWC. We prepared natural and air-dried soils of paddy field in Kojima Bay Polder, Japan to give different pre-drying, air-dried, and not dried (natural). The air-dried soils were resaturated. Each soil was well mixed, then dried to different initial moisture contents (60, 50, 40, 30, 20, and 10% by weight). The specimens were immersed into water in the pot for 24 h. The K _s was measured, and cations in slaked and unslaked soils were analyzed. The K _s was high under the water content below 30% in both the natural and the air-dried soils. But the effects were more pronounced in the natural soil. The air-dried soil showed far smaller K _s than the natural soil. In outer solution, the highest SAR was noted at 30% in the natural and 30 and 20% in the air-dried soils. Significant decrease in ESP of the soils (slaked + unslaked) was also observed at the same water content. Lower water content was more effective in decreasing the soil ESP after desalinization from saline soil. The natural soil showed lower ESP and higher porosity, which was considered as a reason for higher K _s of natural soil than that of air-dried soils. The results indicated that lower water content (10–30%) had no hazardous effect on K _s by slaking and drying of soil.     

Simulating the effects of chemical and non-chemical fertilization practices on carbon sequestration and nitrogen loss in subtropical paddy soils using the DNDC model

Understanding the long-term and quantitative effects of different fertilization practices on carbon sequestration and nitrogen loss is important when establishing the best fertilization regime. In this study, the DeNitrification–DeComposition (DNDC) model was validated first for the change of soil organic carbon (SOC) at the site mode and at the regional mode, and then it was used to simulate the effects of three fertilization practices including rice straw (RS) returning, chemical fertilizer application (CF), and green manure planting (GM) on C and N dynamics in paddy soils from a subtropical area of China. The prevailing fertilization practices in the study area were set as the baseline scenario, and alternative scenarios were assigned by varying only one of the three fertilization practices. All three fertilization practices increased SOC content but had different effects on rice yield, N₂O emission, and nitrate leaching loss. Compared with a baseline RS rate of 15 %, the SOC contents less than RS rates of 30, 50, and 80 % were increased on average by 12.84, 29.48, and 53.50 %, respectively. SOC content also increased as the CF rate rose from 70 to 130 % of the baseline scenario and then leveled off from 130 to 160 %. SOC contents under GM were higher than that without GM by 35.74 %. Both the N₂O emissions and the nitrate leaching were increased with the increasing CF rate, while they decreased under GM treatment. However, RS increased the N₂O emissions but decreased the nitrate leaching. The polygon-based modeling method with the DNDC could accurately evaluate the general trend of SOC dynamics and nitrogen loss from paddy soils.     

Relationship of relative maturity and storage temperatures to weight loss of potatoes in storage

Harvest date had no significant influence on weight loss in storage of tubers which were grown under a low fertilizer regime (vines died prematurely). However under a higher fertilizer regime, tubers harvested 21–45 days after vine kill lost significantly less weight than those harvested 2–13 days after vine kill. An average of 4 years’ data indicates that tubers stored continuously at 45 F (7.2 C) lost significantly less weight than those stored at 42 F (5.5 C) or 48 F (8.9 C). This is attributed to lack of suberization and delayed maturation of tubers at 42 F resulting in increased weight loss and to higher respiration at 48 F in comparison to tubers held at 45 F storage. Considerable seasonal differences in weight loss were recorded. The 1971 growing season which was characterized by a prolonged period of extremely high temperatures resulted in tubers which lost significantly more weight during storage than was the case in the other seasons. Air ventilization rates from 20 to 80 cfm/T were used to cool potatoes from 60 F to ambient temperatures of 48 F. No significant differences in weight loss were obtained after 3 week’s continuous cooling with air at 93–95% R. H. regardless of air ventilation rate.     

EFFECT OF SOIL PARENT MATERIAL, ELEVATION, ASPECT AND FERTILIZER TREATMENT ON UPLAND GRASS YIELDS

Grass production was measured at 24 sites in the Strathdon area of West Aberdeenshire. The mean total yields of DM from two cuts taken from unfertilized plots in 1967 and from three cuts taken in 1968 were 3014 and 3864 kgJha, respectively. Yields from soils formed on basic parent material were 30–40% more than yields from soils formed on more acidic material; and well-managed swards yielded over 40% more than poorly-managed ones. Aspect did not affect yields significantly, nor did elevation within the range 260–440 m. NItrochalk applied at the rate of 75 kg N/ha in 1968 increased the DM yield by an average of 35% but the efifect of 75 kg P₂O₅/ha, applied as triple superphosphate, was not significant at the 10% level. The benefits from N declined, wbereas those from P tended to increase, with elevation. There was no significant NP interaction overall, but tbe response from this treatment was better than from N alone on sites with acidic parent material. In 1968, 46% of the total yield was obtained by the end of June and only 10% after the end of August. Whereas yield declined with elevation in May–June, it increased during July–August     

THE CATTLE DUNG PATCH

Soil samples were taken at 0–1 in. (0–2.54 cm) and 1–3 in. (2.54–7.62 cm) depths on five occasions over a period of 55 days from under (3 in. (7.62 cm) radius from centre) and around (9 in. (22.86 cm), 12 in. (30.48cm) and 18 in. (45.72 cm) radius from centre) dung patches deposited on pasture. The samples were analysed for available N, K and P. There was a significant increase in the level of all three elements in the 0–1 in. samples beneath the dung patch. The increase persisted throughout the experiment. K exhibited the greatest increase, but was not detected beyond the edge of the dung patch. The increase in soil N was smaller but was detected up to 6 in. (15.24 cm) from the edge of the dung patch. P also increased, but was more variable than either N or K. Soil N, P and K did not increase in the 1–3 in. samples. The weight and fibre content of the dung patch was also measured throughout the experiment. After high initial losses (25%) the dung patch decayed only slowly. The loss of ammonia from dung patches was followed over 13 days in a separate experiment During the relatively hot weather over this period approximately 5 % of the N iu the dung was lost as ammonia, mainly in the first five days. During the experimental period of 13 days 60% of the original weight of the dung patch was lost through evaporation. The results are discussed in relation to the growth of herbage surrounding a dung patch reported in the previous paper (12).     

The critical period for weed control in dry-seeded rice

The critical crop-weed competition period in a dry-seeded rice system is an important consideration in formulating weed management strategies. Field experiments were conducted in the summer seasons of 2012 and 2013 at the Punjab Agricultural University, Ludhiana, India, to determine the extent of yield loss in two different rice cultivars (PR 114 and PR 115) with different periods of weed interference. Twelve weed control timings were used to identify critical periods of weed competition in dry-seeded rice. PR 114, a long-duration rice cultivar (145 d) having slower initial growth than PR 115 (125 d), was more prone to yield losses. In both years, 100% yield loss was observed where weeds were not controlled throughout the season. In weed-free plots, the grain yield of PR 114 was 6.39–6.80 t ha⁻¹, for PR 115, it was 6.49–6.87 t ha⁻¹. Gompertz and logistic equations fitted to yield data in response to increasing periods of weed control and weed interference showed that, PR 114 had longer critical periods than PR 115. Critical weed-free periods to achieve 95% of weed-free yield for PR 114 was longer than for PR 115 by 31 days in 2012 and 26 days in 2013. Weed infestation also influenced the duration of critical periods. Higher weed pressure in 2012 than in 2013 increased the duration of the critical period of crop-weed competition in that year. The identification of critical crop-weed competition periods for different cultivars will facilitate improved decision-making regarding the timing of weed control and the adoption of cultivars having high weed-suppressing abilities. This will also contribute to the development of integrated weed management in dry-seeded rice systems.     

Digestibility of legumes and available lysine content

While legumes are regarded as good sources of protein they are poorly digested so improved digestibility would be a desirable objective in a breeding programme. From the point of view of protein quality they are limited by the sulphur amino acids (SAA) so an increase in these is a primary nutritional objective of a breeding programme and their lysine content is regarded as being of secondary importance. However, some traditional methods of preparation are far more severe than that necessary to cook the food and may result in loss of lysine. These two problems are being investigated. (1) True digestibility of the nitrogen (TD-N) of cooked, white haricot beans (Phaseolus vulgaris) was measured by feeding to rats at 20, 40 and 80% levels in the diet (5, 10 and 20% protein), for 10 days periods when 23 days old and again when 63 days old. TD-N at the three dietary levels was 80, 74 and 67% for the young animals and 63, 55 and 51% when more mature. True digestibility of dry matter (TD-DM) was very much higher at 97, 92 and 83% for younger and 95, 90 and 81% for older animals. The considerable difference between TD-N and TD-DM together with the apparently greater TD-N by the younger rats suggests that the extra faecal N does not come from the undigested food but possibly from residues of digestive juices. Results suggest that it is necessary to standardise the conditions for measuring TD. Five legumes were boiled for 2 h and 8 h; available lysine fell by 5–10% after 2 h and by 15–20% after 8 h. Improvement in flavour appeared to parallel development of the Maillard reaction and loss of available lysine. SAA were still limiting so that NPU does not reveal loss of available lysine. However, in diets where legumes are used to supplement cereals in such proportions that lysine is limiting this loss may become of nutritional importance.     

Effects of incubation times and moisture regimes on pH values and exchangeable cations in acid sulfate soils as influenced by application rates of basic slag

Severe acidifications in acid sulfate soils (ASSs) have occurred worldwide due to sulfuric acidity, which requires sustainable measures for their reclamation. Accordingly, an incubation study was conducted with the topsoil of two different ASSs (Cheringa and Badarkhali) to evaluate the effects of basic slag (BS; size <1 mm, pH 9.6, Ca 20.8%, Mg 9.8%, etc.), on reduction of acidity and changes in exchangeable cations. It is noted that BS is a byproduct of steel industry in Bangladesh and can be collected almost free of charge. These soils received BS at the rate of 0 (T₀), 11 (T₁), 22 (T₂) and 33 (T₃) t ha⁻¹ under various moisture regimes (saturated condition M₁,_, i.e., 100% moisture content, wetting–drying cycles of 100 and 50% moisture M_2, and moisture at field condition M₃, i.e., 50%). The impacts of these treatments on some selected parameters in these soils were studied within 180 days of incubation. The application of BS was found to increase the pH of soils from 3.6 to 5.1 for Cheringa, 3.9 to 5.2 for Badarkhali soils at the end of incubation. These increments were more striking with the highest doses of BS under saturated moisture conditions in both of the soils. The ECe of the soils was not much influenced by the application of BS regardless of time. The treatments exerted significant (P ≤ 0.05) effects on exchangeable cations in different periods of incubation. The striking changes were recorded for the rate of increments of Ca²⁺ and Mg²⁺, which were about 2–3 times higher for Ca and more than 2 times higher for Mg²⁺ compared with the control after 180 days of incubation. These results suggest that the application of BS not only increased the Ca²⁺ to the higher amount than that of the increment of Mg²⁺ in the soils, but also improved one of the important criteria of Ca²⁺ and Mg²⁺ ratio in the soils.     

Insecticides for control of potato tuberworm and green peach aphid on potatoes in California

Six insecticides were evaluated in a replicated field experiment at Gonzales, California, for control of the potato tuberworm,Phthorimaea operculella (Zeller), and the green peach aphid,Myzus persicae (Sulzer). Azodrin^®, methomyl, Stauffer N 4543 (O-isobutyl ethylphosphonodithioate S-ester with N-(mercaptomethyl) phthalimide) and azinphosmethyl were applied as foliage sprays by ground sprayer at 2-week intervals. The systemic insecticides, aldicarb (Temik^®) and carbofuran (Furadan^®) formulated as 10% granules, were applied to the soil as side dress treatments on the same day that the spray treatments were begun. Aldicarb granules were also applied topically so that the granules fell on the young plants and on the soil surface. Azinphosmethyl, Stauffer N 4543, Azodrin^® and methomyl effectively controlled the tuberworm larvae in the foliage but effective control of tuberworms in the harvested tubers occurred only where azinphosmethyl, methomyl and Stauffer N 4543 were used. The granule applications of carbofuran and aldicarb were totally ineffective in controlling the potato tuberworm. Effective green peach aphid control was obtained with Azodrin^® spray and the two granular aldicarb treatments. The side dressed application of aldicarb appeared to provide better green peach aphid control than did the soil surface application.     

Systemic insecticides,soil fumigation,and nitrogen fertilization for verticillium wilt control

Fumigation of Verticillium infested soils with Telone®+chloropicrin in 1966 increased yields of Russet Burbank potatoes 178 and 147 cwt/a (200 and 165 q/ha) over yields in unfumigated plots near Othello and Prosser, Washington, respectively. Systemic insecticides disulfoton and aldicarb banded at planting, sidedressed after planting, or applied in combination treatments did not increase yield at either location. Plots fumigated with Telone®+chloropicrin and fertilized with ammonium nitrate (150 and 350 lb N/a?168 and 392 kg N/ha) in 1967 significantly increased yields over that of the unfumigated, fertilized plots. Application of disulfoton and aldicarb to plots fertilized with ammonium nitrate (150 and 350 lb N/a?168 and 392 kg N/ha) did not increase yields over that of fertilized plots receiving no systemic insecticide.     

Developing equations to estimate potato yield loss caused by early blight in Minnesota

Regression analyses were performed on field data from 1981 and 1982 to determine models for estimating yield loss caused by early blight in potato cvs. Norland and Russet Burbank. Percent yield loss (total tubers and US# 1 tubers) caused by early blight could not be satisfactorily explained by any regression model using only a single disease assessment as the input variable. Several multiple point models, which explained more than 70% of the variation in yield loss due to early blight, were determined for each cultivar. The models for cv. Norland used either early blight severity assessments on days 56, 66, 76 and 86 after sprout emergence, or blight severity increments for 10-day periods among days 46–86, as the input variables. The models for cv. Russet Burbank used the same input variables as for cv. Norland and additionally, blight severity on day 96. Yield loss in US#1 tubers was a more stable variable than loss in total tubers for estimating early blight effect.     

Response of potato tubers to hypoxia followed by re-aeration

Summary Potato tubers kept under hypoxia (1%) showed improved viability in comparison to anoxia, which was associated with the maintenance of intermediate adenylate energy charge values (A.E.C.=0.6) and stable adenylate pools at 50% of the initial levels. Re-admission of oxygen to the tuber resulted in an almost full recovery of adenylate energy charge and total adenylates after up to 3 days of hypoxic pretreatment. Tubers exhibited a mixed fermentation. The high lactate, ethanol and acetaldehyde levels proved to be non toxic. Ethanol was degraded to acetaldehyde during re-aeration. Posthypoxic lipid peroxidation was indicated by malondialdehyde and ethane formation. Both products occurred with a temporary delay and in lower amounts compared to post-anoxia. Ethylene release was also considerably smaller. Severe hypoxia and posthypoxia postponed tissue death compared to anoxia. Survival was correlated with an improved energy supply which stabilized membranes.