PROTECTION OF SORGHUM AGAINST SOIL FUNGI, SOIL PESTS AND COVERED SMUT BY COMBINED INSECTICIDE-FUNGICIDE SEED DRESSINGS

Treatment of sorghum ( Sorghum vulgare ) seed with fungicide dressings controlled covered smut ( Sphacelotheca sorghi ), the major disease of sorghum in the Sudan, and usually resulted in appreciably better stands. In the Sudan Gezira, powder dressings containing 20–40%γ-benzene hexachloride (γ-BHC) applied at the rate of 1g./1b. of seed effectively protected sorghum seedlings from root attack by chafer grubs ( Schixonycha sp.) and significantly increased stands and yields. No certain evidence of this effect was obtained with dolichos bean ( Dolichos lablab ) or groundnut ( Arachis hypogaea ), and the different responses shown by these plants as compared with sorghum are attributed largely to differences in seed germination and root system. An application rate of 0·08 %γ-BHC/seed was sometimes slightly but appreciably phytotoxic to sorghum in the field and more markedly so in greenhouse experiments. A powder containing 25% thiram and 20%γ-BHC applied at the rate of 1g./1b. of seed is recommended as the standard seed dressing for sorghum in the Sudan.     

EXPERIMENTS IN THE SUDAN GEZIRA ON CONTROL OF WILT OF DOLICHOS BEAN (DOLICHOS LABLAB) ASSOCIATED WITH ATTACK BY COCKCHAFER GRUBS (SCHIZONYCHA SP.)

Wilt of dolichos bean ( Dolichos lablab ) in the Sudan Gezira appeared to be due primarily to cockchafer grubs ( Schizonycha sp.) in the soil attacking the hypocotyls or roots of plants up to about 6 weeks after sowing. Many wilted plants also showed symptoms of ashy stem blight ( Macrophomina phaseoli ), but in these the fungus was probably a secondary invader rotting roots weakened or damaged by unfavourable soil conditions or insects. Wilt was often severe in dolichos sown on land cropped to sorghum ( Sorghum vulgare ) in the preceding season, sorghum roots in the soil harbouring the grubs. Under moderate grub attack seed dressings containing organomercurial and γ-benzene hexachloride (BHC) gave satisfactory-protection at 0.089%γ-BHC/seed but were inadequate when wilt was severe. Dieldrin and aldrin at 0.044 or 0.089%/seed gave excellent protection in all experiments, but their performance under exceptionally severe wilt conditions has yet to be tested, as also the relative efficiencies of seed treatment and soil treatment under such conditions. Fungicide-insecticide seed treatment also reduced preemergence rotting of germinating seeds due to grub attack.
Wilt rarely occurred in dolichos planted on land fallow in the preceding season, but, even in the apparent absence of wilt, seed treatment often appreciably improved emergence, plant populations, growth and yields. These effects possibly resulted from control of root damage by soil insects, such damage reducing growth and yields but not sufficiently severely to cause wilting. Pending further investigation a powder seed dressing containing organomercurial plus 20% dieldrin, and applied at 1:450 by weight to seed (about 5–6 g./acre of dieldrin), is recommended for dolichos bean in the Gezira.     

THE USE OF SEED DRESSINGS CONTAINING γ-BHC IN THE ESTABLISHMENT OF SUGAR-BEET SEEDLINGS

From 1949 to 1952 field trials were made to determine the effect of seed dressings containing γ-BHC, with and without the addition of organic mercurial compounds, upon the establishment of sugar-beet seedlings. Most of the trials were made in fields where no serious pest problems were anticipated. The 1949 trials established the concentration of γ-BHC non-phytocidal to sugar-beet seedlings. Later trials tested the effect on pre- and post-singling plant populations of dressings applied to natural or rubbed seed sown at standardized rates. Parallel tests of dressed seed were made on farms representing a variety of soil types, It was found that the phytotoxiCity of γ-BHC varied with season and soil type, but that a dressing containing 40 % was usually safe. In these trials, the benefits from seed dressing were, as a rule, slight. Generally the combined mercury-γ-BHC seed dressing gave the best pre-singling stand of plants. Most of the improvement was attributable to the organic mercury rather than to the γ-BHC, but where pest attacks occurred, γ-BHC gave marked improvements in stand. Wireworm appeared to be the chief pest controlled: control of pygmy mangold beetle was only partial.     

Seed treatments with benomyl and other fungicides for the control of Ascochyta pisi on peas

In three experiments, using laboratory, glasshouse and field tests, seed dressings of benomyl-1½ (42.4 g) to 2 oz (56.6 g) Benlate 50% w.p. per 28 lb (12.7 kg) of seed-gave complete control of Ascochyta infection of pea seeds. Mixtures of benomyl and captan and benomyl and thiram were also effective. Carboxin, captan, and thiram used as seed dressings, either singly or in mixtures, did not eliminate the pathogen from peas. Germination, emergence and seedling vigour were not impaired by any dressing.     

THE PRACTICAL CONTROL OF WIREWORM BY γ-BENZENE HEXACHLORIDE ('GAMMEXANE'): COMPARISONS WITH DICHLORODIPHENYLTRICHLORETHANE (D.D.T.)

Benzene hexachloride containing 13% of the insecticidally active gamma isomer known as 'Gammexane' has been used successfully in a considerable number of field trials in the control of wireworm. On heavily infested land the effective dosage rates associated with an appreciable reduction in wireworm population, and giving a marked improvement in plant establishment and substantial increases in yield, range between 1 and 6 lb./acre (2–12 oz./acre of Gammexane), on oats and wheat. The effective dosage rates vary and depend upon whether the insecticide is combine-drilled, broadcast, or applied as a seed dressing.
Although D.D.T. applied by similar methods was associated with similar reductions in wireworm population, the use of this insecticide resulted in smaller yield increases.     

CONTROL OF SEED-BED LOSSES OF GROUNDNUTS BY SEED TREATMENT

Fungicide treatment of groundnut ( Arachis hypogaea L.) seed usually reduced seed-bed losses and improved emergence, plant populations and yields of this crop when cultivated under rain in the sandy soils of Kordofan (west-central Sudan) or under irrigation in the alkaline clay soils of the Gezira. These beneficial effects were greatest with slightly damaged seeds, such as would occur with machine sowing, but were present even when selected undamaged seed was sown by hand; they were attributed to protection against a number of soil micro-organisms, including Aspergillus niger van Tieghem, A.flavus Link and Rhizopus spp. Agrosan GN (organo-mercurial, 1% mercury equivalent) or 50% thiram powder, both applied at the rate of 1 g./lb. of seed, are suggested as suitable dressings for groundnut sowing seed in the two areas studied. Combined fungicide-insecticide dressings containing up to 40% by weight of γ-BHC did not control a late attack of wilt, due to root attack by cockchafer grubs ( Schizonycha sp.), which developed some 8 weeks after sowing in the Gezira.     

The prevention of seed-borne diseases of flax III. The dusting, short wet and fixation methods of seed disinfection in relation to storage of the seed

Flax seed containing up to 10% of moisture was disinfected with a proprietary dry fungicide containing tetramethylthiuram disulphide (Nomersan) at the rate of 12 oz./cwt. of seed, and stored for periods of up to 18 months, without its germination being impaired.
Experiments were made with samples of seed the moisture content of which, before treatment, varied within the range of 5-8-13-2% and which were kept in a commercial store after disinfection. Treatments were carried out with an 8% solution of a soluble organo-mercurial (Ceresan U. 564) at the rates of 0-67 and 0-9 gal./cwt. applied by the short wet method, and with an organo-mercurial powder (Ceresan UT. 1875 A) at the rate of 12 oz./cwt. applied by the fixation method using 0-9 gal. of separated milk per cwt. The results obtained show that treatment by either method has the effect of lowering the percentage of viable seeds during subsequent storage and that the higher the moisture content of the seed before treatment the earlier this effect becomes apparent. It is suggested that seed to be treated by the short wet method on a commercial scale should be dried to contain about 5% of moisture, that not more than 0-67 gal./cwt. of liquid be applied and that the seed should not be stored for longer than 3 months after treatment. Following upon these suggestions, 10-ton lots of seed were treated commercially by the short wet method using a Kontramix machine and no ill effects on the crop were observed.     

Pearl millet downy mildew as affected by integrating seed dressing,sowing date and cultivar

The effects of seed dressing, sowing date and cultivar on incidence and severity of downy mildew of pearl millet induced by Sclerospora graminicola and yield were studied in a two-year field trial conducted at the Research farm of University of Maiduguri. The millet cultivars, Ex-Borno, SOSAT-C88, GB 8735 and Gwagwa were each dressed with metalaxyl at 0.75 and 1.50 g a.i./kg seed; and a batch of undressed seeds of each cultivar served as control. Both dressed and undressed seeds were used for dry-planting and wet-planting in early and late seasons. The results showed that seed dressing with the fungicides significantly (p ≤ 0.05) reduced the incidence and severity of downy mildew and increased grain yield. Dry-planting also significantly (p ≤ 0.01) increased grain yield irrespective of disease incidence. Delay in sowing led to a significant reduction in incidence and severity of downy mildew. Differences between the cultivars in relation to incidence and severity of downy mildew and grain yield were significant. SOSAT-C88 developed low or no downy mildew in both seasons. Sowing of dressed SOSAT-C88 as soon as rainfall established appeared most beneficial in the control of downy mildew. Dry- or wet-planting Ex-Borno dressed with any of the metalaxyl formulations proved to be effective for downy mildew management and for high yield.     

THE EFFECT OF SALINITY AND TEMPERATURE ON THE GERMINATION OF POLYMORPHIC SEEDS AND GROWTH OF ATRIPLEX TRIANGULARIS WILLD.

Polymorphic seeds of Atriplex triangularis were germinated at various temperatures (5–15 C, 5–25 C, 10–20 C, 20–30 C) and salinity regimes (0 to 1.5% NaCl) in order to determine their germinability and early seedling growth under these conditions. Larger seeds generally had a higher germination percentage in saline medium. The rate and percentage of germination decreased with increased salinity stress. A thermoperiod of 25 C day and 5 C night, 12 hr/12 hr, temperature enhanced germination of seeds. Early seedling growth is promoted in larger seeds at lower salinity, and at high-day and low-night temperatures. Polymorphic seeds have different physiological requirements which provide alternative situations for seed germination in natural habitats.     

狼毒种子萌发特性与种群更新机制的研究

研究了采集于植株上的和收集于土壤种子库的狼毒(Stellera chamaejasme)种子在不同温度、光照和5种预处理(即破裂种皮、去除种皮、98％H2SO4浸种5min、0．2％KNO3浸种24h、10℃低温保存1周)条件下的萌发力。结果表明,狼毒种子萌发率较低,25℃恒温、黑暗条件下萌发率为13％,较适宜的萌发温度为30℃恒温或10～30℃变温,破裂种皮和去除种皮萌发率显著提高,25℃恒温、光暗交替条件下萌发率分别为49％和47％,浓硫酸浸种5min处理萌发率可达到32％,KON3浸种和10℃低温保存两个处理对促进狼毒种子萌发效果不明显,狼毒种子萌发对光照条件不敏感,种子硬实性是导致狼毒种子萌发率较低的主要原因,取自土壤种子库内的狼毒种子萌发率高于当年采集的种子,在自然条件下,并非每年都有狼毒种子萌发长成幼苗,种群更新时机是随机的或周期性的。     

Chemical control of onion fly, Delia antiqua

In nine trials done in 1972-4 seed treatments reduced attacks of onion fly larvae very effectively and most of the organophosphorus formulations gave protection up to harvest, 12–17 wk after sowing. Pirimiphos-ethyl and isofen-phos each at 10 or 20 g a.i./kg seed controlled onion fly larvae well and they were not seriously phytotoxic in any of the trials. Chlorpyrifos, trichloronate, ethion, iodofenphos, chlorfenvinphos wettable powder or triazophos all at iog a.i./kg seed were also effective, but they were tested in fewer trials. Diazinon at 10 or 20 g a.i./kg seed, carbophenothion and chlorfenvinphos liquid seed dressing at 10 g a.i./kg seed controlled onion fly well, but in some trials they were phytotoxic; methiocarb, mecarphon and oxamyl were much less effective. At 1–12 kg a.i./ha chlorfenvinphos granules applied over the rows shortly before the attack was expected was the best granular formulation, but it was not as effective as the better seed treatments.     

濒危植物秦岭冷杉种子萌发特性的研究

 秦岭冷杉(Abies chensiensis)为中国特有种,主要分布于中国秦巴山地,现为渐危种,被列为国家二级保护植物。经测定,秦岭冷杉种子千粒重为(33.92±1.01)g,与其它冷杉属的种子比较,其种子千粒重较大。四唑（TTC,1.0 %）染色测种子生活力的结果表明:有生活力的种子占26.00%,空粒占20.50%,涩粒占33.75%,说明秦岭冷杉种子饱满度很差,反映了比较高的种子败育率;染色结果与对比发芽实验的结果很接近,说明用四唑染色来测定秦岭冷杉种子的生活力是较准确的方法。把种子进行0、14、21、28d低温(4℃)层积处理,发现低温层积可以显著提高种子发芽率和发芽势,但是层积21d与28d发芽势没有差异。设置恒温20℃、25℃和变温20～30℃ 3种温度条件下发芽比较,发现最终的发芽率并没有差异,但是发芽势差异显著,恒温25℃达到最大发芽率的90%的时间要比另外两种温度下提前9d,可见25℃是秦岭冷杉种子发芽的适宜温度。光照(8 h·d-1,100μmol·m-2·s-1)和黑暗下种子的最后发芽率差异不显著,但是光照发芽势高,可见光照可以促进秦岭冷杉种子发芽迅速、整齐。实验证明,用砂床做发芽基质与用纸床做发芽基质相比,前者的发芽率和发芽势均比后者高。     

Seed germination ecology of Portulaca oleracea L.: an important weed of rice and upland crops

Portulaca oleracea , a C₄ species, is reported to be a serious weed in 45 crops in 81 countries. Experiments were conducted in the laboratory, the screenhouse and the field to determine the influence of environmental factors on seed germination and seedling emergence of P. oleracea . In the laboratory, germination in the dark was low and was not influenced by the tested temperatures (35/25°C, 30/20°C and 25/15°C alternating day/night temperatures). In the light/dark regime, however, germination was lower at 25/15°C and 35/25°C than at 30/20°C (70%, 75% and 81% germination, respectively). In conditions of 106 mM sodium chloride or −0.34 MPa osmotic potential, seeds germinated to only 50% of maximum germination of the control. Germination was not influenced by buffered pH solutions ranging from 5 to 9. In the screenhouse, germination was greatest for seeds placed on the soil surface, but emergence declined with increasing seed burial depth in soil; no seedlings emerged from the depth of 2 cm. Seedling emergence and seedling dry matter were markedly reduced by the addition of rice residue to the soil surface at rates equivalent to 4 to 6 t ha⁻¹. In the field, seedling emergence of P. oleracea was greater under zero till (ZT) (17–20%) than under minimum tillage (6–10%), a likely reflection of low seed burial and exposure of seeds to light with a ZT system. This study identifies some of the factors enabling P. oleracea to be a widespread weed in the humid tropics, and the information could contribute to improved control strategies.     

PHYSIOLOGICAL ECOLOGY OF GERMINATION OF VIOLA RAFINESQUII

Seeds of the winter annual Viola rafinesquii Greene exhibit true dormancy at the time of maturity and dispersal in mid to late spring. During the summer rest period the seeds pass from a state of true dormancy to one of relative dormancy and finally to what may be called a state of complete nondormancy. As the seeds enter relative dormancy they will germinate mostly at relatively low temperatures (10, 15, 15/6, and 20/10 C), but as after-ripening continues they gain the ability also to germinate at higher temperatures (20, 25, and 30/15 C). During June, July, and August seeds will not germinate at field temperatures even if kept continuously moist. But by September and October seeds may germinate to high percentages over a wide range of temperatures, including September and October field temperatures. This pattern of germination responses, involving breaking of true dormancy and widening of the temperature range for germination during relative dormancy, appears to be an adaptation of the species to a hot, dry season. Seeds of V. rafinesquii stored on continuously wet soil (field capacity) or on soil that was alternately wet and dried during the summer did not after-ripen at low temperatures (10, 15, 15/6, and 20/10 C) but did after-ripen fully at high temperatures (20, 25, 30/15, and 35/20 C). Thus, the high temperatures that V. rafinesquii “avoids” by passing the summer in the dormant seed stage actually are required to break seed dormancy and, therefore, are essential for completion of its life cycle.     

The influence of the testa, damage and seed dressing on the emergence of groundnut (Arachis hypogea)

The effects of damaging the testa and the application of seed dressings were examined in field trials on several short-and long-season cultivars of groundnut (Arachis hypogea) with differently-pigmented testas at Samaru, Nigeria, in 1967. There was a high correlation between the number of seedlings which emerged in these trials and the resistance or susceptibility of the seed to invasion by the fungus Aspergillus flavus, as assessed by laboratory tests. When the testa was undamaged the emergence of white (susceptible) seed was only 50% while that of coloured (resistant) seed was between 95 and 98%. Damage to the testa by scratching greatly decreased emergence. The application of seed dressing increased the emergence of susceptible seed and also restored the emergence of scratched seeds to the level of undamaged seeds. The effect of the complete removal of the testa was not counteracted by seed dressing; naked seeds, with and without dressing, gave c. 10% emergence. The importance of pigment in the testa, the condition of the seed and the effects of seed dressing are discussed.     

Seed germination and seedling growth ofCarex doenitzii growing on alpine zone of Mt. Fuji

Carex doenitzii on the upper timberline of Mt. Fuji were studied to determine the effect of thermal conditions on their seed germination and seedling growth. Mature seeds collected at the end of the growing season were divided into five test groups, and each was germinated at constant temperature, the temperatures being 15 C, 20 C, 25 C, 30 C and 35 C. Seed germination percentage was highest (93%) at 25 C. Seedlings germinated at 25 C were grown in chambers at 15/10 C, 25/20 C and 35/30 C. Growth of seedlings was greatest at 25/20 C. The data suggest that the seed germination and seedling growth ofC. doenitzii occur only under limited conditions in the field.     

THE EFFECT OF MANURES ON THE BOLTING OF THE BEET PLANT

In sugar beet, the effect on bolting of additions of potash manures, of superphosphate, and of the mixture of these was not significant, whether applied at the time of sowing or previously. Dung applied in the previous autumn slightly increased the number of plants which went to seed, and when applied just before sowing it had a more marked effect. An amount of sulphate of ammonia which would have approximately the same stimulating effect as the dung gave a slightly larger amount of bolting.
On red beetroot, it was possible to compare larger and smaller dressings of various coarse organic manures, and of each of these with and without dressings of sulphate of ammonia. In all cases the sulphate of ammonia and each of the organic manures largely increased the amount of bolting, and a doubling of the organic manure dressing or the addition of sulphate of ammonia to it caused a further increase. Sewage sludge gave an abnormally large amount of bolting, but it is doubtful whether this was due to the larger amount of organic matter and nitrogen applied in this manure. In general, any manurial addition causing more vigorous growth leads to an increase in bolting. There is a very large variation in the amount of running to seed in the crop of red beetroot from different parts of the same field, but the effect of the manures on the proportion which bolted was not widely different.
The general question as to the reason why beet plants should bolt more in one season than in another is discussed, and it is suggested that a check to the plants in an early stage, whether caused by dryness or waterlogging, or by low temperature, followed by a vigorous growing period may have something to do with the matter. This would agree with the experiences recorded in the present paper.     

THE PHYTOTOXIC EFFECTS OF D.D.T., B.H.C., PARATHION AND TOXAPHENE ON TOBACCO

No phytotoxic effect was seen following a pre-sowing spray of tobacco seed-beds with 27 lb./acre technical D.D.T. or after an application of the same material at 75.6 lb./acre to 3-week-old tobacco seedlings.
A pre-sowing application of parathion (diethyl para nitrophenyl thiophosphate) (2 % dust) at 1–8 lb. parathion per acre had no harmful effect. Used on 3-week-old tobacco seedlings at the excessive rate of 22.7 lb./acre it caused serious stunting and many deaths.
Toxaphene (chlorinated camphene: empirical formula C₁₀H₁₀Cl₈), applied as a 25 % wettable powder in a pre-sowing spray at 6-4 lb. toxaphene per acre, did not injure tobacco seedlings.
No residual phytotoxic effects appeared in beds re-sown 4 months after being treated with parathion or toxaphene at the pre-sowing doses given above.
Benzene hexachloride, applied before sowing at doses above 1.6 lb. technical B.H.C. per acre, suppressed root development in newly germinated tobacco seedlings. B.H.C. dusts used on n-day-old seedlings at 2–25 lb. technical B.H.C. per acre caused temporary distortion and stunting. Up to 11 lb./acre these symptoms were transitory: at 37.5 lb./acre many plants were killed and the remainder severely stunted. Resistance to these phytotoxic effects increased with age of plant, but 3-week-old tobacco seedlings showed considerable mortality after the application of 75.6 lb./acre of technical B.H.C.
Beds re-sown 4 months after the application of 6-4 and 12.8 lb. respectively of technical B.H.C. per acre showed no phytotoxic effect, but, as tobacco seed is sown on the soil surface, the effect of the B.H.C. may have been merely masked, and it is not safe to assume that there was no residual effect. The actual persistence of B.H.C. in the soil was not determined.
The possible mechanism of action of the B.H.C. effect is discussed.     

EXPERIMENTS ON THE MODE OF ACTION OF DIELDRIN SEED-DRESSINGS AGAINST SEEDLING ATTACK BY THE LARVAL FRIT FLY, OSCINELLA FRIT L

Experiments with dieldrin seed-dressings were done to see whether the conditions favouring their action against wheat bulb fly larvae apply also to frit fly.
Experiments with oats and wheat in boxes and a small field trial with oats showed that fewer newly hatched larvae were killed when dieldrin-treated seed was sown deeply than when sown 1/4 - 1/2 in. deep; shallow sowing probably puts the insecticide where the larvae are likely to meet it before they attack the plant. Kill was never complete even with dieldrin applied at almost forty times more than the highest rate normally used. This is partly because some larvae hatch from eggs on the plant and these, unlike those from soil eggs, can enter the shoot without touching the seed dressing.
Even in the most favourable circumstances (large doses of dieldrin applied to the shallow-sown seed and the plant at the one-leaf stage at the time of attack) there was little evidence that frit fly larvae are killed inside the shoot by systemic action of dieldrin translocated from the seed. This is not because the pales which normally surround the oat seed impair the uptake of insecticide, or because of any other factor specific to oats. Frit fly larvae also survived in wheat from seed dressed with doses of dieldrin that can kill almost all wheat bulb fly larvae by systemic action. Possible reasons for this difference are discussed.     

一种可止血的富血小板血浆壳聚糖/丝素蛋白多孔伤口敷料的制备及性能表征

为了进一步提高伤口敷料的止血性能,文中在生物相容性良好的壳聚糖溶液中引入含有多种生长因子的人源性富血小板血浆(Humanplatelet-richplasma,hPRP),并加入不同体积比例(1∶1、1∶3、3∶1、1∶0)的丝素蛋白溶液以提高材料的多孔性与止血性,通过冷冻干燥法制备不同配比的hPRP-壳聚糖/丝素蛋白敷料,并将纯壳聚糖敷料作为对照组,研究hPRP和丝素蛋白对敷料的止血性能的影响以及丝素蛋白对PRP中生长因子控制释放的影响。结果表明,在壳聚糖敷料中引入hPRP对敷料的止血性有所提高,但对敷料的多孔结构及吸水率无明显改善,若在hPRP-壳聚糖溶液中按照体积比为1∶1的比例加入丝素蛋白溶液,会得到具有较为均匀的多孔结构的敷料,敷料的孔隙率与吸水率分别可达到86.83%±3.84%与1 474%±114%,且该比例的敷料在快速止血性能上表现优异。此外,加入丝素蛋白与壳聚糖比例为1∶1的PRP敷料能有效减少PRP中生长因子在初始阶段的爆裂释放。因此,含hPRP的壳聚糖/丝素蛋白复合敷料有望成为一种能快速止血且能促进伤口愈合的新型伤口敷料。