Control of potato cyst-nematode, Heterodera rostochiensis, in three soils by small amounts of aldicarb, Du Pont 1410 or Nemacur applied to the soil at planting time

Aldicarb or Du Pont 1410 (S-methyl 1-(dimethylcarbamoyl)-N-[(methylcarbamoyl) oxy] thioformimidate) at 2.6–11.2 kg a.i./ha applied to the soil at planting time controlled potato cyst-nematode, Heterodera rostochiensis, in sandy loam, peaty loam and silt loam and greatly increased tuber yields of susceptible potatoes. Nemacur (O-ethyl-O-(3-methyl-4-methylthiophenyl) isopropylamido-phosphate) controlled potato cyst-nematode in sandy loam at 2.9–10.3 kg a.i./ha and in silt loam at 11.2 kg a.i./ha but did not control the nematode well in peaty loam even at 22.4 kg a.i./ha. In peaty loam aldicarb and Nemacur were more effectively incorporated by rotavation than by a modified power harrow.     

Effects of D-D, Telone or dazomet applied to potato ridges in spring on potato cyst-nematode, Heterodera rostochiensis, in sandy loam and silt loam soils

Large amounts of dazomet (329, 439 kg/ha) applied to potato ridge soil in spring, before potatoes were planted, controlled potato cyst-nematode (Heterodera rostochiensis) in sandy loam and silt loam more effectively than large amounts of D-D (359, 448 kg/ha). In heavily infested sandy loam, 329 kg dazomet/ha or 857 kg methyl bromide/ha applied in spring 1969 or 439 kg dazomet/ha applied in autumn 1968, greatly decreased the number of larvae able to invade potato roots, so Majestic potatoes grew and yielded well without increasing the number of nematodes left in the soil after harvest. Large amounts of D-D or Telone applied to the topsoil in autumn or to the ridges in spring were less effective in controlling potato cyst-nematode or increasing potato yields. Applied in spring 1969 to silt loam ridges, 439 kg dazomet/ha had more effect than 448 kg D-D/ha on potato cyst-nematode and on the increase in yield of Majestic potato. The yield of Maris Piper potatoes (resistant to H. rostochiensis pathotype A) in infested silt loam was increased greatly by D-D, as much by 112 as by 224 or 448 kg/ha.     

Control of potato cyst-nematode, Heterodera rostochiensis, in sandy, peaty and silt loam soils by dazomet and Telone applied in different ways

Dazomet applied in the ridges in autumn or in spring, before potatoes were planted in them, controlled potato cyst-nematode (Heterodera rostochiensis), British pathotype A, better in sandy loam and peaty loam than Telone (1,3-dichloropropene mixture). In sandy loam dazomet controlled potato cyst-nematode as well when applied in spring as when applied in autumn and as well when the soil was ridged after treatment as when it was not. Telone was as effective when applied to ridges in autumn as when applied to ridges in spring. In peaty loam potato cyst-nematodes were least abundant after a crop of Maris Piper potatoes. The yields of King Edward potatoes were greatly increased and nematode multiplication was greatly reduced by dazomet incorporated in the ridges in autumn. Two equal doses of dazomet, one incorporated in the topsoil before, the other after ploughing, controlled potato cyst-nematode as well and increased the yield of King Edward potatoes more than an equivalent amount of dazomet applied after ploughing. Dazomet applied to silt loam soil in two dressings, one before, the other after, ploughing, controlled potato cyst-nematode better than an equal amount applied as a single dressing after ploughing. The nematode was controlled best by two large dressings of dazomet or by a combined treatment of dazomet and Telone.     

Control of potato cyst-nematode, Heterodera rostochiensis, in sandy loam, by Du Pont 1410 (S-methyl l-(dimethylcarbamoyl)-N-[(methylcarbamoyl) oxy] thioformimidate) applied to the soil at planting time

When applied to heavily infested sandy loam soil at planting time, as little as 5 ppm Du Pont 1410 (5-methyl I-(dimethylcarbamoyl)-N-[(methylcar-bamoyl) oxy] thioformimidate) in pots, or 2–5 ppm in field plots, effectively controlled potato cyst-nematode, Heterodera rostochiensis Woll., and greatly increased the growth and yield of susceptible potatoes. Dipping the shoots of potted King Edward potatoes once in aqeuous solution containing 2000 ppm did not control potato cyst-nematode. Nematode control was not increased when 2 or 4 kg a.i./ha was sprayed on the foliage of young Pentland Crown potatoes growing in soil already treated with the nematicide.     

Control of potato cyst-nematodes, Heterodera rostochiensis and H. pallida, in sandy, peaty and silt loam soils by oximecarbamate and organophosphate nematicides

Small amounts (5.6 or n-2 kg a.i./ha) of aldicarb or oxamyl, incorporated in the soil before potatoes were planted in spring, controlled potato cyst-nematodes (Heterodera rostochiensis and H. pallida) on susceptible cultivars equally well in sandy, peaty and silt loam soils. In soils treated with either nematicide, nematode numbers increased little or decreased; in untreated soils nematode numbers increased greatly. In contrast organophosphate nematicides, similarly applied, fenamiphos (proposed BSI common name for O-ethyl-O-(3-methyl-4-methylthiophenyI)-isopropylamido-phosphate), ethoprophos (proposed BSI common name for (O-ethyl S, 5-dipropyl phos-phorodithioate), CGA 12223 (O, O-diethyl O-[i-isopropyl-5-chloro-i,2,4-triazoIyl-(3)] phosphorothioate) and Dowco 275 (O, O-diethyl O-(6-fluoro-2 pyridyl) phosphorothioate), were ineffective at one or more of the experimental sites. Potato yields were greatly increased by oximecarbamate or organophosphate nematicides only in soils heavily infested with the nematodes.     

Control of potato cyst-nematode, Globodera rostochiensis, and root-knot nematode, Meloidogyne incognita, by organosphosphorus, carbamate, benzimidazole and other compounds

Control of potato cyst-nematode, Globodera rostochiensis, was examined on potato or tomato in pots and on potato in field plots by various chemicals incorporated into the soil at planting. The most effective nematicides were organophosphorus compounds, generally of the type O,O-diethyl O-phosphoro-thioates or O,O-diethyl phosphorodithioates, carbamates and benzimidazoles. In organic soils, the more lipophilic compounds were less effective, presumably because of sorption onto soil organic matter. Foliar sprays of chemicals, including oxamyl which is known to be translocated to roots, gave poor control of G. rostochiensis. The root-knot nematode, Meloidogyne incognita, on tomato, widely used in screening for nematicidal activity, was controlled by aldicarb or phoxim incorporated into the soil at planting, but not by benomyl or thiabendazole, in contrast to the moderate effectiveness of these latter two chemicals against G. rostochiensis.     

The effect of formalin on potato cyst-nematode, Heterodera rostochiensis

Applying 5 ml of a 38% aqueous solution of formaldehyde to 1500 ml of sandy loam prevented potato cyst-nematode, Heterodera rostochiensis, from increasing on the roots of Arran Banner potatoes planted in the soil and increased the weight of tubers produced. A comparable dosage applied to plots of sandy loam and sandy clay in winter did not prevent the nematode from multiplying on Pentland Crown potatoes but increased tuber yields. Smaller amounts of formalin had less effect on tuber yields and drenching dilute formalin solutions onto the soil was no more effective than incorporating undiluted formalin into the soil by rotavation 15 cm deep.     

Control of potato cyst-nematode, Globodera pallida, on tomatoes grown under glass, by applying steam or chemical nematicides to the soil

In a sandy loam under glass, potato cyst-nematode, Globodera pallida, was controlled in soil to 20 cm deep, and tomato yields were greatly increased by sheet steaming for 4 h, by 977 kg methyl bromide ha^-1 or by 448 kg Telone (1,3-dichloropropene mixture or Di-Trapex CP (20% methyl isothiocyanate: 15% chloropicrin:65% dichloropropene-dichloropropane mixture) ha^-1 followed by 441 kg dazomet or 11.2 kg oxamyl ha^-1. Sheet steaming, unlike the other treatments, had relatively little effect on the nematode in soil 20 to 40 cm deep. Until the apices of the plants were cut off production of fruit was curvilinear against time in all treated soil but linear against time in untreated soil.     

Control of potato cyst-nematode, Heterodera rostochiensis, in peaty loam soil by D-D, aldicarb and a resistant variety of potato

In peaty loam soil in Cambridgeshire, 5.2 or 10.3 kg aldicarb/ha incorporated in the top-soil before potatoes were planted controlled potato cystnematode (Heterodera rostochiensis Woll.) better than 384, 769 or 1153 kg D-D/ha injected 15 cm deep into the top-soil in the preceding autumn. 10.3 kg aldicarb/ha applied in 1968 and 1969 permitted King Edward potatoes (susceptible to H. rostochiensis) to grow well in infested soil and prevented multiplication of pathotypes of H. rostochiensis on Maris Piper potatoes (resistant to H. rostochiensis pathotype A). Although large amounts of D-D applied in 1968 and 1969 increased the yield of King Edward potatoes in both years they did not control potato cyst-nematode in the second year.     

Effects of rotation length and oxamyl on potato yield and the potato cyst-nematode, Globodera rostochiensis, in a sandy loam soil

In sandy loam infested with golden potato cyst-nematode, Globodera rostochiensis, oxamyl at 5.6 kg a.i. ha^-1 incorporated in the top 15 cm of the soil just before planting potatoes greatly reduced nematode population increase on susceptible cv. Désirée grown six, seven or eight years after the last susceptible potato crop, but did not significantly increase tuber yields. In four-course and two-course rotations, oxamyl also controlled increase of G. rostochiensis and greatly increased yields of both cv. Désirée and resistant cv. Maris Piper. Oxamyl maintained tuber yields in a four-course rotation at the same level as in a six to eight-course rotation. Decline of G. rostochiensis in the soil was much faster under barley in some two-course rotations than under barley in four-course rotations.     

Control of potato pale cyst-nematode, Globodera pallida, with a granular nematicide and partially resistant potatoes

The effects of oxamyl applied to the seedbed and growing partially resistant potatoes in controlling potato pale cyst-nematode, Globodera pallida, were assessed in eleven field experiments on sandy, peaty and silty loam soils in England from 1986 to 1988. Standardised procedures allowed valid comparisons to be made between data from the three experiments in 1987 and from the seven experiments in 1988. In soil moderately or heavily infested with G. pallida, oxamyl frequently increased tuber yields of susceptible cv. Désirée and of partially resistant potatoes and lessened crude nematode increase (Pf/Pi) significantly at some sites but not at others. Although 2.8 kg oxamyl ha“¹ often increased tuber yields significantly, it was significantly less effective than 5.6 kg in controlling G. pallida at one site and at another site G. pallida increased more than in untreated plots. Potatoes partially resistant to G. pallida were more effective that oxamyl in controlling nematode increase at some sites but not at others. Combined use of oxamyl and partially resistant potatoes was generally more effective in controlling G. pallida than either measure alone. As measured by a ‘control coefficient’ (weight of tubers over 40mm diameter (t ha“¹) 4-crude nematode increase (Pf/Pi)), the most effective integrated control of G. pallida was obtained by growing cvs Glenna, Morag or Santé in soil treated with 5.6 kg oxamyl ha^-1.     

Observations on the control of potato cyst-nematodes, Globodera rostochiensis and G. pallida in 35 English potato soils in pots by oxamyl and resistant potatoes

The increase of 35 English field populations of potato cyst-nematodes (Globodera rostochiensis and/or G. pallida) was measured on Désirée, Maris Piper, Caxton (A25/11), Cromwell (A27/20) and clone 11233 ab 22 in pots of sandy, silty or peaty loam soil. Désirée was susceptible to all populations tested and, as in field soils, the final population (Pf) was inversely related to the initial population of potato cyst-nematode eggs (Pi) in the soil. Maris Piper and Cromwell were resistant to all G. rostochiensis populations, with one possible exception. Maris Piper was susceptible to all G. pallida populations. Caxton was susceptible to some and fairly resistant to other populations of G. rostochiensis, indicating the existence either of two biotypes within the one pathotype (Rol) as yet encountered in Britain, or the existence of an additional pathotype. Caxton and Cromwell were fairly resistant to G. pallida. Clone 11233 ab 22 was only moderately resistant to both species. Resistance to potato cyst-nematode increase varied considerably, especially in Caxton (to G. rostochiensis) and in 11233 ab 22 (to both species). Oxamyl greatly reduced the increase of G. rostochiensis populations on Désirée potatoes, with the notable exception of one population but it generally had much less effect on G. pallida populations, regardless of soil type. The difference in effect on the two species may be due to a longer period of hatching in G. pallida than in G. rostochiensis and also perhaps to a second generation in G. pallida.     

Control of pea cyst-nematode, Heterodera goettingiana, by small amounts of aldicarb, Du Pont 1410, Ciba-Geigy 10576 or Dowco 275 applied to the soil at planting time

Aldicarb, or Du Pont 1410 (S-methyl-I-(dimethylcarbamoyl)-N-[(methyl-carbamoyl)oxy]thioformimidate), at 2.8–22.4 kg a.i./ha incorporated in the seed-bed before sowing greatly increased the yield of peas in a clay loam and two sandy clay soils infested with pea cyst-nematode, Heterodera goettingiana, and lessened or prevented increase in the number of nematodes. CibaGeigy 10576 (an organophosphorus compound) at 5.6–22.4 kg a.i./ha was similarly effective in a sandy clay soil. Dowco 275 (O, O-diethylO-(6-fluoro-2 pyridyl) phosphorothioate) at 5.6 or 11.2 kg a.i./ha also controlled the nematode well in the clay loam and in a sandy clay soil but although it greatly increased the yield of peas in the clay loam, it did not increase yield in the sandy clay.     

Control of potato cyst-nematodes, Globodera rostochiensis and G. pallida, in different soils by small amounts of oxamyl or aldicarb

In eleven field trials on peaty, sandy or silt loam soils, aldicarb or oxamyl, incorporated in the soil to 15 cm deep before susceptible potatoes were planted, controlled potato cyst-nematodes (Globodera rostochiensis (Woll.) Mulvey & Stone, 1976 and G. pallida (Stone) Mulvey & Stone, 1976) better at 5–6 kg than at 3–4 or 2-2 kg a.i./ha. Incorporated in the soil to 7-5 cm deep 5–6 kg/ha of aldicarb or oxamyl controlled the nematodes less effectively at some sites. At 3–4 kg a.i./ha there was no difference in nematode control between the two incorporation depths.     

Effects of potato genotype, oxamyl and the numbers of potato cyst-nematodes, Globodera rostochiensis or G. pallida on tuber yields and nematode increase

A new technique is described for establishing different numbers of the potato cyst-nematode Globodera rostochiensis in field soil, which leaves the soil homogeneous in nutrient status. Field plots established in this way were used to compare yield losses in four potato cultivars (Maris Piper, Pentland Crown, Pentland Dell and Désirée) associated with different numbers of G. rostochiensis. Over the range of 7.4 to 148.4 eggs g^-1 soil at planting, yield losses were 18.7% (Maris Piper), 53.2% (Désirée), 55.7% (Pentland Crown) and 63.5% (Pentland Dell). Similar results were obtained in another experiment on the same field in a different year using only lightly and heavily infested plots. Treating the seedbed soil with oxamyl before planting prevented significant injury to potatoes by G. rostochiensis but increased the yield of Pentland Dell and perhaps Désirée (but not Maris Piper or Pentland Crown) more than expected from nematode control alone. Treating heavily infested soil with such a nematicide cannot therefore be recommended as part of a valid procedure for establishing lightly and heavily infested plots for comparing tolerances of attack by potato cyst-nematodes in a range of potato genotypes. In peaty loam soils moderately or heavily infested with G. pallida, oxamyl at 5.6 kg a.i. ha^-1 incorporated into the seedbed before potatoes were planted generally increased tuber yields, though the effects varied considerably with the cultivar grown. Increase of G. pallida in these soils was controlled better by growing potatoes bred for resistance to it (ZB 35 – 29, Caxton, Santé, Morag, 11233 ab 22, Fingal, A27/23, Cromwell). Increase of G. pallida on susceptible cultivars varied greatly and Romano increased G. pallida no more than the resistant Morag. G. pallida is probably controlled best in peaty loam by growing a resistant cultivar in soil treated with a granular (non-fumigant) nematicide.     

Chemical control of potato cyst-nematode in sandy clay soil

In sandy clay soil in Bedfordshire, potato cyst-nematode (Heterodera rostochiensis Woll.) was controlled and yields of Majestic potatoes greatly increased when i-2g aldicarb, 4-0 g fensulphothion or 10-3 g diazinon, disulphoton, ‘Isolan’ (i-isopropyl-3-methyl-5-pyrazolyl dimethylcarba-mate) or thionazin per m² were incorporated in the top soil before potatoes were planted. Diethyl phosphorothioates controlled H. rostochiensis better than dimethyl phosphates. One hundred and eleven g methyl bromide, 47-6 g carbon disulphide or 45-2 g D-D per m² applied to the soil and covered with polyethylene sheeting greatly increased the yield of potatoes, but also increased the number of nematodes in the soil. Estimates of the number of larvae able to invade potato roots in treated soil after harvest and of cysts, total eggs or live eggs selected the same range of treatments as effective in controlling H. rostochiensis.     

Control of potato cyst-nematode, Globodera rostochiensis Rol, by picrolonic acid and potato trap crops

Small, sprouted tubers of potatoes (cv. Pentland Crown) grown for 6 wk and then pulled out of soil infested with potato cyst-nematode, Globodera rostochiensis Roi, increased the hatch of larvae, so that 100 days after planting the top 20 cm of the soil contained only one third of the original number of eggs. The artificial hatching agent picrolonic acid alone at 8-6, 17*2 or 34-4 kg/ha rotavated into the soil did not increase hatch but 17*2 kg, incorporated in the soil after potatoes grown for 4 wk, did.     

Chemical control of beet cyst-nematode, Heterodera schachtii, in some peaty loam soils

In peaty loam soils, aldicarb or oxamyl mixed with the top 15 cm of the soil in spring before sugar beet seeds were sown, minimised invasion of the roots by larvae of the beet cyst-nematode, Heterodera schachtii, so preventing injury to the seedlings, and greatly increased sugar yields in heavily infested soil. Small amounts of both compounds were often as effective as larger amounts. Nematode increase on sugar beet roots was slow. Aldicarb or oxamyl lessened nematode increase in four years out of five. Fumigating predetermined row positions with dichloropropene mixtures (D-D, Telone) or incorporating aldicarb or methomyl shallowly in soil, later occupied by the roots of sugar beet seedlings, did not control the nematode, although sugar yields were sometimes increased.     

Assessment of the losses caused to potatoes by the potato cyst nematodes, Globodera rostochiensis and G. pallida

Nine field trials were carried out from 1967 to 1973 on sandy loam soils in Staffordshire and Worcestershire to study the relationship between potato yield and numbers of potato cyst nematodes (Globodera spp.). Three (probably five) of these trial sites appeared to be infested with G. rostochiensis only, whereas both species occurred on the remaining four sites which grew the resistant variety, Maris Piper. Although mixtures of the two species occurred on some plots they tended to have different distributions within each trial site. The results from this work have been analysed, together with those from earlier work in the Eastern Counties on peat and silt soils, over two population density ranges, 0–40 eggs/g (5 sites) and 0–160 eggs/g (16 sites). There is no evidence of any difference in the regression of yield on eggs/g amongst the five sites in the lower range (b =–0.90 + 0.11) nor amongst 15 of the 16 sites in the higher range (b = -0–40 ± 0–02). Analysis of 10 sites with sufficient data in the 40–160 eggs/g range gave b = -0.24 ± 0.06. Thus the regression lines are essentially parallel for each of the two ranges, covering several potato varieties, soil textures and different potential yields and suggest that the varieties used are equally tolerant. The losses are 6.25 t/ha/20 eggs/g for the 0.40 eggs/g range, 1.67 t/ha/20 eggs/g for the 40–160 eggs/g range, and 2.75 t/ha/20 eggs/g as a mean for the whole range. A maximum loss of 22 t/ha is indicated. Peat soils are less dense than mineral soils but there was no need for adjustment in nematode counts. Losses caused by potato cyst nematodes are better expressed as actual yield losses rather than as percentage decreases.     

Effect of Burkholderia (Pseudomonas) cepacia and soil type on the control of crown rot in wheat

A rifampicin-resistant isolate of Burkholderia (Pseudomonas) cepacia (A3R) reduced crown rot (Fusarium graminearum Group 1) symptoms significantly (P 0.05) in wheat in glasshouse and field experiments and increased grain yield significantly (P 0.05) in one of two field experiments. In glasshouse experiments, applying the bacteria as a soil drench (2.5 × 109 cfu/g soil) was more effective than coating the bacteria on wheat seed (3.4 × 107cfu/seed). In field experiments, the bacteria were applied as a soil drench at the rate of 1.8 x 10¹⁰ cfu/m row. In both the glasshouse and the field, disease severity in the bacteria-inoculated treatments was significantly less in a silt loam than in a sandy loam. The silt loam had a large proportion of fine clay and silt particles (51.7%), which may have favoured the biocontrol activity and survival of the introduced B. cepacia. In a glasshouse experiment, control by B. cepacia was significantly greater in the silt loam than in the sandy loam, which in turn was greater than in a loamy sand. The loamy sand appeared to favour crown rot development but not the activity or survival of the bacterial antagonist. The latter was reflected by the relative populations of the rifampicin-resistant bacteria re-isolated from the various soils during a 5-week period after application of the bacteria (silt loam > sandy loam > loamy sand). This study further confirms that soil type can influence the populations and the level of biocontrol activity of some bacterial antagonists.