In-Vitro and In-Vivo Effects of Aldicarb on Survival and Development of Heterodera schachtii

Aqueous solutions of 5-500 μg/ml aldicarb inhibited hatching of Heterodera schachtii. Addition of hatching agents, zinc chloride, or sugarbeet root diffusate, to the aldicarb solutions did not decrease the inhibition of hatching. When cysts were removed from the aldicarb solufions and then treated for 4 wk in sugarbeet root diffusate, larvae hatched and emerged. Treatments of newly hatched larvae of H. schachtii with 5-100 μg/ml aldicarb depressed later development of larvae on sugarbeet (Beta vulgaris). Similar treatments with aldicarb sulfoxide had less effect on larval development, and aldicarb sulfone had no effect. Numbers of treated larvae that survived and developed were inversely proportional to concentration (0.1-5.0 μg/ml) and duration (0-14 days) of aldicarb treatments. Development of H. schachtii on sugarbeet grown in aldicarb-treated soil was inversely proportional to the concentration of aldicarb in the tested range of 0.75 - 3.0 μg aldicarb/g of soil. Transfer of nematode-infected plants to soil with aldicarb retarded nematode development, whereas transfer of plants first grownin treated soil to nematode-infested soil only slightly suppressed nematode development. Development of H. schachtii was inhibited in slices of storage roots of table beet (B. vulgaris), sugarbeet and turnip, (Brassica rapa), that had grown in soil treated with aldicarb.     

Resistance of Trisomic and Diploid Hybrids of Beta vulgaris and B. procumbens to the Sugarbeet Nematode,Heterodera schachtiis Arnold

Trisomic and diploid hybrids of sugarbeet (Beta vulgaris L.) X wild beet (B. procumbens Chr. Sin.) inherited the gene for resistance to Heterodera schachtii Schm. from B. procumbens. The hybrids showed partial resistance to H. schachtii, manifested in failure of larvae to reach maturity. Although significantly greater numbers of female nematodes developed on plants inoculated with populations from the Netherlands or Italy than on plants inoculated with a population from the Salinas Valley, California. the totals for all populations on resistant plants were small. Greater numbers of males than females developed on root-slice cultures of resistant hyhrids when compared to a susceptible cultivar.     

Self-interactions of Meloidogyne hapla and of Heterodera schachtii on Beta Vulgaris

Double inoculations of sugar beet with larvae of Meloidogyne hapla resulted in a higher galling incidence in only one treatment than did a single inoculation using the same number of larvae. Double inoculations with larvae of Heterodera schachtii, however, resulted in three- to five-fold more cysts in most cases than did single inoculations using the same number of larvae. In general, plants died more quickly after double inoculations than after single inoculations of the same total number of either nematode. Ratios of total soluble carbohydrates to reducing carbohydrates were lower in multiple inoculated treatments than in other treatments. Plants infected with M. hapla had lower quantities of B, K, and P in leaf tissue than noninoculated plants, but no differences were correlated with type of inoculation. Plants inoculated with H. schachtii had lower quantities of B, K, and Mg than noninoculated plants. Also, quantities of Mn, Cu, and Zn were much lower in plants inoculated twice with H. schachtii larvae than in plants inoculated with the same total number of larvae in a single dose.     

Effects of Aldicarb on the Behavior of Heterodera schachtii and Meloidogyne javanica

The toxic effects of sublethal concentrations ofaldicarb were studied on eggs and second-stage larvae and males of Heterodera schachtii and second-stage larvae only of Meloidogyne javanica in a quartz sand substrate. Aldicarb was more toxic to eggs of H. schachtii than to those of M. javanica. Complete suppression of hatching occurred between 0.48 and 4.8 μg/ml aldicarb for H. schachtii whereas 100% inhibition of hatch of M. javanica occurred between 4.8 and 48.0 μg/ml. M. javanica hatch was stimulated at 0.48 μg/ml aldicarb. Migration of second-stage larvae of H. schachtii and M. javanica in sand columns was inhibited under continuous exposure to 1 μg/ml aldicarb. Infection of sugarbeet and tomato seedlings by larvae was inhibited at 1 μg/ml. H. schachtii males failed to migrate toward nubile females at 0.01 μg/ml aldicarb. This was partially confirmed in a field study in which adding aldicarb to soil resulted in fewer females being fertilized.     

Effects of Oxime Carbamate Nematicides on Development of Heterodera schachtii on Sugarbeet

Treatment of sugarbeet, Beta vulgaris L., with aldicarb, aldicarb sulfoxide, or aldicarb sulfone 10 days after plants were inoculated with Heterodera schachtii prevented development of the nematode, but second-stage larvae penetrated the roots. These chemicals had no measurable effects on nematodes in plants treated 15 days after inoculation. The tests established that soil treatments of aldicarb are directly or indirectly lethal to larvae developing within roots of sugarbeet. Heterodera schachtii failed to develop on root slices of red table beet grown in soil treated with aldicarb or aldicarb sulfoxide. Similar treatment of plants with aldicarb sulfone or oxamyl did not affect subsequent development of H. schachtii on root slices of treated plants.     

Efficacy of Oxamyl Against Heterodera schachtii on Cabbage

The efficacy of oxamyl in controlling Heterodera schachtii on cabbage was determined by applying various contbinations of soil drenches at 6.7 kg (a.i.)/ha and foliar sprays at 0.04 kg (a.i.)/100 liters of water to cabbage seedlings. Pretransplant drenches provided some control of H. schachtii over a 13-week period. A single foliar spray of oxamyl 1 week before transplanting apparently prevented penetration of H. schachtii larvae; post-transplant sprays were relatively ineffective. A pretransplant or transplant drench combined with a foliar application 2 weeks after transplanting provided the most effective control. The effectiveness of drenches plus post-transplant sprays is probably due to the spray augmenting the action of the drench in inhibiting the development of larvae after penelration.     

Pathological Differences in Heterodera schachtii Populations

Five populations of Heterodera schachtii Schm. from Oregon, Idaho, and Utah did not differ significantly in seedling penetration and rate of emergence and virulence. Another Utah H. schachtii population (Utah 2), however, differed from these five populations in all of the above-mentioned characteristics. More H. schachtii larvae of the Utah 2 population than the other populations penetrated sugarbeet seedlings at 10, 15, 20, and 25 C. Root and top weights of sugarbeet plants were signiticantly less when roots were parasitized by the Utah 2 population than when they were parasitized by larvae of the other nematode populations under similar experimental conditions. Also, the period of larval emergence was shorter in the Utah 2 population than in any of the other H. schachtii populations.     

Effect of Phenamiphos on Heterodera schachtii and Meloidogyne javanica

Aqueous solutions of technical-grade phenamiphos [ethyl 3-methyl-4-(methylthio) phenyl (1-methylethyl) phosphoratnidale] were used in hatching chambers to test, under laboratory tory conditions, the effect of phenamiphos on the hatching and movement of Meloiclogyne javanica and Heterodera schachtii. Hatch of M. javanica and H. schachtii eggs was depressed 70 and 88% by nematicide at 0.48 and 4.80 μg/ml, respectively. The infectivity of second-stage larvae of both species was affected by concentrations as low as 0.01 μg/ml. At least 0.5 μg/ml was required to decrease the movement of larvae of M. javanica and H. schachtii. To decrease the movement of H. schachtii males toward females, 10 μg/ml was required. In a field experiment using a 15% granular formulation, 5 kg/ha a.i. significantly reduced infection of sugarbeet roots by H. schachtii.     

The Relationship of Plant Age,Soil Temperature,and Population Density of Heterodera schachtii on the Growth of Sugarbeet

There were direct relationships between inoculum density of Heterodera schachtii Schm. (nematode population density), initial soil temperature, the growth of sugarbeets in the greenhouse under controlled temperatures, and nematode populations. Heterodera schachtii was least pathogenic on plants inoculated at 6 wk of age and most pathogenic on plants grown from inoculated germinated seed (0 wk of age). In the field, H. schachtii was least pathogenic on sugarbeets grown at an initial soil temperature of 6 C and most pathogenic on those grown at an initial soil temperature of 24 C. The growth period for sugarbeets at the different soil temperatures was determined by heat units; since penetration of sugarbeet roots by H. schachtii larvae is accelerated at soil temperatures above 10 C, each hour-degree ahove 10 C was counted as one effective heat unit (HU). Using this guideline it was determined that root weight depressions in the greenhouse, for each degree-unit population (HU-UP) where unit population = one larvae/g soil, were 0.052, 0.09, 0.12, and 0.17 mg at initial soil temperatures of 6, 12, 18, and 24 C, respectively. Root weight depressions were 0.28, 0.23, 0.15, and 0.086 mg when plants were inoculated at 0, 2, 4, and 6 wk of age.     

Improved Methods of Hatching Heterodera schachtii Larvae for Screening Chemicals

The rate of hatching of Heterodera schachtii larvae was greatly increased by placing cysts in sieves enclosed by small disposable cups. An apparatus that permitted rapid storage of second-stage larvae at 10 C prolonged the viability of the larvae.     

Comparative Morphometrics of Eggs and Second-Stage Juveniles of Heterodera schachtii and a Race of H. trifolii Parasitic on Sugarbeet in The Netherlands

Measurements of second-stage juveniles of Heterodera schachtii from California and The Netherlands and a race of H. trifolii from The Netherlands were obtained and compared to determine if these populations can be differentiated by morphometrics. Juvenile lengths of 10 specimens from each of 10 cysts of each population were measured. Dimensions of tail regions of 20 juveniles from individual cysts of H. schachtii (California) and a like number of juveniles of H. trifolii (The Netherlands) were also obtained. The mean lengths of juveniles of H. schachtii from California and The Netherlands were not significantly different, but similar measurements of H. schachtii and H. trifolii were different (P = 0.05). Mean dimensions of tail lengths, tail widths, tail hyaline lengths, and tail length/tail width were significantly greater for H. trifolii than for H. schachtii. Also, dimensions of eggs of H. trifolii were significantly greater than dimensions of H. schachtii eggs. The investigations established that H. schachtii can be readily differentiated from H. trifolii by morphometrics of eggs and juveniles, Minimum sample sizes required for specified confidence intervals for each criterion measured are provided.     

Effect of Liquid Nutrient Culture,Vacuum Distillation and Dialysis on Hatching Activity of Sugar Beet Root Diffusate for Heterodera schachtii

Roots of sugar beets grown in liquid culture excrete substances that stimulate egg hatch and emergence of larvae from cysts of Heterodera schachtii. Their hatching effect is comparable to that of sugar beet root diffusate leached from soil-grown sugar beet plants. Consequently, liquid culture provides a way of obtaining H. schachtii hatch-stimulant free of contaminants from soil. Root diffusate, concentrated 50-fold or dried by vacuum distillation, retained hatching activity. The active principle of diffusate is dialyzable with a diffusion rate between those of inorganic salts and compounds with molecular weights greater than 15,000.     

The Relationship of Heterodera schachtii Population Densities to Sugarbeet Yields

Sugarbeet yields were contpared with field populations of Heterodera schachtii Schmidt. The correlation between sugarbeet yields and viable larvae/g of soil was negative and high, but that between sugarbeet yields and viable cysts/g of soil was lower. Sugarbeet yields were also compared with H. schachtii populations by years of rotation with a nonhost crop. The coefficients of correlation (r) between yield and viable larvae/g of soil were negative and high: 0 yr of rotation, -0.935; 1 yr, -0.922; 2 yr, -0.954; 3 yr, -0.935; and combined years, -0.965, with 95% confidence limits of -0.91 to -0.98 for combined years. The comparable correlation coefficients between yield and "viable cysts"/g of soil were negative and lower: 0 yr of rotation, -0.151; 1 yr, -0.022; 2 yr, -0.490; 3 yr, -0.456; and combined years, -0.586, with 95% confidence limits of -0.22 to -0.80 for the combined years.     

Optimization of a medium for a high yield production of spore-crystal preparation ofBacillus thuringiensis effective against the Egyptian cotton leaf wormSpodoptera littoralis Boisd.

Summary The continuous culture (chemostat) technique was used for the optimization of a medium which supported the production of a high yield spore-crystal preparation ofBacillus thuringiensis (isolate Bt 24) (a maximum of 4 × 10⁹spores/ml) on a pilot-scale. The preparation demonstrated a high insecticidal activity against second-instar larvae ofSpodoptera littoralis Boisd.     

Plant regeneration from cultured cell-derived protoplasts of Pelargonium aridum,P. x hortorum and P. peltatum

Cultured protoplasts from cell suspensions of Pelargonium aridum, P.x hortorum and P. peltatum divided and formed callus. On agar-solidified regenerative medium, such protoplast-derived calli (p-calli) underwent plant regeneration at frequencies approaching 100% for P. aridum and 10% for P.x hortorum. Under similar conditions shoot primordia arose in 5% of P. peltatum p-calli, but these never developed into normal shoots. However, following a liquid-shake culture regime, whole plants were induced in 20% of P. peltatum p-calli. This approach also improved regeneration of P.x hortorum to 60%.Abbreviations NAA napthaleneacetic acid - 6-BAP 6-benzylaminopurine     

Population Dynamics of Dactylella oviparasitica and Heterodera schachtii: Toward a Decision Model for Sugar Beet Planting

A series of experiments were performed to examine the population dynamics of the sugarbeet cyst nematode, Heterodera schachtii, and the nematophagus fungus Dactylella oviparasitica. After two nematode generations, the population densities of H. schachtii were measured in relation to various initial infestation densities of both D. oviparasitica and H. schachtii. In general, higher initial population densities of D. oviparasitica were associated with lower final population densities of H. schachtii. Regression models showed that the initial densities of D. oviparasitica were only significant when predicting the final densities of H. schachtii J2 and eggs as well as fungal egg parasitism, while the initial densities of J2 were significant for all final H. schachtii population density measurements. We also showed that the densities of H. schachtii-associated D. oviparasitica fluctuate greatly, with rRNA gene numbers going from zero in most field-soil-collected cysts to an average of 4.24 x 10⁸ in mature females isolated directly from root surfaces. Finally, phylogenetic analysis of rRNA genes suggested that D. oviparasitica belongs to a clade of nematophagous fungi that includes Arkansas Fungus strain L (ARF-L) and that these fungi are widely distributed. We anticipate that these findings will provide foundational data facilitating the development of more effective decision models for sugar beet planting.     

A radioimmunoassay for chironomid hemoglobin

A double antibody, competitive radioimmunoassay was developed for the quantitation of stage-specific hemoglobin from the insect Chironomus thummi. The radioimmunoassay will detect as little as 150 picograms of Hb 3, a hemoglobin synthesized and secreted into the hemolymph of larvae during the 4th, but not the 3rd instar. The assay also detects cross-reacting hemoglobins purified from 4th instar larvae and in freshly laid eggs. Application of this radioimmunoassay is discussed in light of the cross-reacting Hbs in the insect.     

A new medium for growth and delta-endotoxin production by Bacillus thuringiensis var. kurstaki

Summary The influence of composition of media used for growth and delta-endotoxin production by B. thuringiensis var. kurstaki was studied with the idea of finding a cheap medium for attaining high yields of spore-crystal preparations. A new medium, based on malt sprouts is proposed. Data on growth and bioinsecticidal activity are given. A concentration of 2.1 × 10⁹ spores.ml^-1 was attained in a 48 h process. The spore-crystal preparations obtained present a LC₅₀ of 2.18 × 10⁸ spores.g^-1 against larvae of Galleria mellonella.     

The Effects of Hot Water Treatments on Survival of Heterodera schachtii

Cysts of Heterodera schachtii were treated in a water bath at constant temperatures ranging from 45 - 62.5 C for 1 sec to 28 hr. Treated and untreated cysts were incubated 8 weeks in sugarbeet root diffusate at 24 C to measure emergence of surviving larvae. Within the temperature range of 49 - 54 C, the minimum lethal temperature was proportional to the log time of treatment. No larvae emerged from cysts exposed 10 sec at 60 C. Although treatment of cysts for 8 hr at 45 C significantly reduced emergence, increasing the treatment period to 28 hr did not completely suppress emergence.     

Susceptibility of plant selections to Heterodera schachtii and a race of H. trifolii parasitic on Sugarbeet in The Netherlands

Similar host ranges were found for Heterodera schachtii and a race of H. trifolii parasitic on sugarbeet in The Netherlands. Twenty-nine of 41 plant accessions evaluated were susceptible to H. trifolii. Five breeding lines of the interspecific hybrid Beta vulgaris-B. procumbens which are resistant to H. schachtii were highly susceptible to H. trifolii. An accession of B. maritima with partial resistance to H. schachtii was resistant to H. trifolii.