Nematode Multiplication Rate Research Articles

Effect of different organic amendments with Paecilomyces lilacinus for the management of soil nematodes

Oil seed cakes of neem/margosa (Azadirachta indica), castor (Ricinum communis), mustard (Brassica compestris), rocket salad/duan (Eruca sativa) were found to be highly effective in reducing the multiplication of nematodes and consequently plant growth and bulk density of woody stem of pigeonpea increased significantly. The multiplication rate of nematodes was less in presence of Paecilomyces lilacinus as compared to the absence of P. lilacinus. Damage caused by the nematodes was further reduced when P. lilacinus was added along with oil-cakes. Most effective combination of P. lilacinus was with neem cake.

The potential of Brassica green manure crops for controlling root-knot nematode (Meloidogyne javanica) on horticultural crops in a subtropical environment

In glasshouse experiments, Meloidogyne javanica reproduced on Brassica juncea, B. napus and BQMulch, a commercial biofumigant crop consisting of both B. napus and B. campestris. Although nematode multiplication rates were only 3–23% of the rate on a highly susceptible crop (tomato), they were high enough to suggest that Brassica rotation crops will increase root-knot nematode populations to potentially damaging levels in situations where temperatures do not limit nematode reproduction. A field study showed that this problem could be prevented in subtropical climates by restricting the growth of Brassica crops to June, July and August, when low temperatures limit nematode development and eggs are not produced until about 10 weeks after planting. Field and pot experiments in which M. javanica was introduced into soil following incorporation of Brassica residues failed to demonstrate a 'biofumigation' effect, possibly because the soil was too dry or the degree of tissue disruption was insufficient to maximise isothiocyanate release. Numbers of root-knot nematodes were reduced when Brassica roots, leaves and stems were incorporated into soil at 17 t DM/ha, but it is unlikely that this was due to the production of nematoxic chemicals, as large numbers of free-living nematodes multiplied during the decomposition process. From a practical perspective, these results suggest that green-manured Brassica rotation crops are unlikely to be useful for controlling root-knot nematodes on some subtropical horticultural crops that are currently fumigated for nematode control. The susceptibility of brassicas to M. javanica and the need to grow them during winter limits their potential in the vegetable industry, while difficulties in obtaining a biofumigation effect in dry soil will reduce effectiveness in non-irrigated pineapple soils. Brassicas are likely to be most useful in the ginger industry, as they can be grown during the winter break between ginger crops and fields can be irrigated before the Brassica crop is incorporated into soil.

The effect of granular nematicide incorporation depth and potato planting depth on potatoes grown in land infested with the potato cyst nematodes Globodera rostochiensis and G. pallida

Summary Field experiments at Harper Adams, Shropshire and Wisbech, Cambridgeshire investigated the effect of nematicide incorporation and seed tuber planting depth on the yield of the potato (Solamum tuberosum L.) cultivars Estima and Maris Piper and the population control of the potato cyst nematodes Globodera rostochiensis Woll. (Skarbilovich) and G. pallida (Stone). The nematicide fosthiazate was applied at 3 kg−1 ha and either not incorporated, or incorporated to 20 cm or 35 cm. Potatoes were mechanically planted to three depths; approximately 10 cm, 15 cm and 25 cm. Incorporation to 20 cm with tubers planted at a depth of 10 cm or 15 cm, reduced root invasion compared with the other treatments. Incorporating nematicide to 20 cm also gave consistently higher ware yields and better nematode control than the other incorporation methods, which were not significantly different to the control. However, ware yield and nematode multiplication rate were not significantly affected by planting depth.

Control of Meloidogyne incognita and Rotylenchulus reniformis singly and concomitantly on chickpea and pigeonpea

The root‐knot nematode, Meloidogyne incognita caused greater reduction in plant growth, chlorophyll content, water absorption capacity of roots and root nodulation of chickpea and pigeonpea and bulk density of pigeonpea stem, than the reniform nematode, Rotylenchulus reniformis. These nematodes inhibited each other in concomitant infections. However, both the nematodes together caused more damage to the test plants than was caused by either of them singly, but it was less than the sum total of the damage caused by them individually. Oil‐seed cakes of neem/margosa (Azadirachta indica), castor (Ricinus communis), mustard (Brassica campestris), rocket salad/'duan’ (Eruca sativa) were found to be highly effective in reducing the multiplication of nematodes and consequently plant growth, the water absorption capacity of the roots, root nodulation and bulk density of woody stem of pigeonpea increased significantly. The test nematodes were found to be less damaging in the presence of Paecilomyces lilacinus. The multiplication rate of nematodes was less in presence of P. lilacinus as compared to the absence of P. lilacinus. Damage caused by the nematodes was further reduced when P. lilacinus was added along with oil‐cakes. Most effective combination of P. lilacinus was with neem cake.

Progress in breeding wheat for tolerance and resistance to root-lesion nematode (Pratylenchus thornei)

Root-lesion nematode (Pratylenchus thornei) is a serious pathogen of wheat and other crops and is estimated to cost the Australian wheat industry $36M per year in lost production. Use of tolerant and resistant wheat cultivars is the most important component of integrated control of this nematode. A targeted approach has been adopted to develop such cultivars for the northern grain belt of Australia. Methods are described that have been used successfully to screen for tolerance in the field and resistance in the glasshouse. Backcross programs used to incorporate superior tolerance into locally adapted cultivars have doubled tolerance levels, which translates into double the grain yield on severely infested sites. Resistance from the bread wheat line GS5Oa backcrossed into locally adapted cultivars has reduced the nematode multiplication rate more than tenfold in advanced lines. New sources of resistance have been located in Aegilops tauschii, in durum wheat and in synthetic hexaploid wheats derived from them. Other new sources have been identified in landrace wheats and wheat cultivars from the Middle East and North Africa. A concerted effort is required to exploit these new found resistances and knowledge to accelerate the production of suitable cultivars for farmers’ use.

Nematode Population Changes under Crop Rotation Sequences: Consequences for Potato Production

AbstractSoils of the Klamath basin of northeast California and southeast Oregon that are used for a potato (Solanum tuberosum L.) cropping system are frequently infested with Meloidogyne chitwoodi (Golden, O'Bannon, Santo & Finley) and Pratylenchus neglectus (Filipjev & Schuurmans‐Stekhoven). These studies were conducted over a 7‐yr period to determine nematode population changes under crop rotation sequences, and the impact of those changes on potato crop yield and quality. The surface blemish rating of a summer‐grown potato crop has a log‐linear relationship with the population level of M. chitwoodi measured either the previous fall, or with lower reliability, in the spring before potato planting. Yield of Grade no. 1 potato was negatively related to population levels of M. chitwoodi measured the previous fall, although total yields were not affected. On crops that are hosts to M. chitwoodi or P. neglectus, seasonal multiplication rates of the nematodes were log‐linearly related to populations measured the previous fall. The relationship between crop yields, or nematode multiplication rates, and spring nematode population levels were weaker due to the imprecision of spring population assessments. Overwinter survival rates of both nematode species were log‐linearly related to population levels measured in the fall. Preliminary analysis of the impact of seasonal climatic variation suggests that the models may underpredict potato tuber blemish and nematode population increase one year in five, when higher soil temperatures prevail. The predictions of crop damage and nematode population change allow crop and nematode management decisions based on population assessment.

The effect of partially resistant potato clones and aldicarb on the multiplication of the potato cyst nematode Globodera pallida in field trials

SUMMARYPotato cultivars with different degrees of resistance to Globodera pallida (PCN) were trialled at three infested sites in 1983, 1984 and 1985. These trials were primarily intended to assess the effects of PCN damage on the yield of tubers and consequently the sites chosen had high initial population densities of G. pallida. The population density of G. pallida was determined from samples taken both pre‐planting and post‐harvest and results showed that there were significant differences between the clones in the nematode multiplication rates. Although actual rates of multiplication varied between sites the relative differences between clones were maintained across sites. Under the susceptible control cultivars the populations generally increased even in the presence of nematicide. The partially resistant clones gave best control, as measured by nematode multiplication, at the sites with the highest initial population densities but gave good control at all sites when treated with nematicide irrespective of initial population density. The role of partial resistance in integrated control systems and the effectiveness of nematicides against G. pallida is discussed.

Integrated control of potato cyst nematodes using small amounts of nematicide and potatoes with partial resistance

SUMMARYThe control of potato cyst nematode (PCN) by less than approved amounts of nematicide combined with partially resistant potato clones was studied in a series of field experiments. On a site heavily infested with Globodera pallida only the most resistant clone (12380ac2) decreased the population density in untreated soil. With aldicarb at its full approved rate (3·36 kg ha‐1) numbers of PCN were decreased under all the genotypes, including the non‐resistant Maris Piper. Aldicarb at 1·68 kg ha‐1significantly decreased populations on all clones except 12380ac2. Aldicarb at 0·84 kg ha‐1still significantly decreased population densities and multiplication rates of G. pallida on two clones with intermediate resistance (12243acl and 11233ab22). At two G. rostochiensis sites with light infestations nematode multiplication rates were greater and the control given by aldicarb and partially resistant genotypes of potato was not as great as that at the site with G. pallida.Tuber yields were not increased by the application of aldicarb at the G. rostochiensis infested sites. However, at the site heavily infested with G. pallida the yield of the most intolerant genotype (12380ac2) was increased seven‐fold by the full rate of aldicarb (3·36 kg ha‐1) and four‐fold by the quarter rate (0·84 kg ha‐1)‐Yield of the most tolerant genotype (12243acl) was unaffected by the application of aldicarb.

Environmental differences and their effect on the assessment of quantitative resistance to potato cyst nematodes1

Experiments assessing the quantitative resistance of potato clones to potato cyst nematodes tend to produce variable results because of genotype‐environment interactions. Despite these interactions clones are ranked in the same way even when a major environmental factor such as initial nematode population density is changed. It is also argued that as the reproductive rate is so environmentally sensitive the use of fixed levels of nematode multiplication rate as criteria for classifying clones is inappropriate. It is proposed that standard resistant and partially resistant clones be included in all assessment tests. They would act as delineators of resistance classes and would allow easy comparisons to be made between tests whether conducted in glasshouse or field.

Screening for quantitative resistance to the white potato cyst nematode Globodera pallida

SUMMARYThe resistance to Globodera pallida of potatoes bred from Solanum uernei was assessed rapidly in pot tests by counting cysts on the exterior of the root ball. Assessments of resistance made in this way in three consecutive years were reproducible on a ranking basis. There was also a significant agreement in the ranked results of pot and field tests. A more accurate assessment of nematode multiplication rates in the field could be provided by laboratory tests in which temperature, moisture and initial nematode numbers were strictly controlled.

The Influence of Some Environmental and Cultural Conditions On Rearing Populations of Xiphinema and Longidorus1)

Trials were carried out with hand-picked populations of Xiphinema spp. and Longidorus spp. to determine the effect of different environmental and cultural conditions on the nematode multiplication rate. Using Longidorus africanus as a test organism, a four-fold population increase within 5 months was recorded in polyethylene bottles as compared with that in clay pots; population build-up of L. africanus, Xiphinema brevicolle, X. diversicaudatum, X. index, and X. italiae in polyethylene bottles was quicker in a heavy than in a light soil. The increased multiplication rates were attributed to the smaller moisture fluctuations in the polyethylene containers and the heavier soil. Population build-up of X. brevicolle, X. index, X. italiae and L. brevicaudatus was quicker, and the duration of their life cycles was shorter, with increasing temperature levels between 16 and 28°C. Soil drenches with a nutrient solution at a normally recommended concentration were found to suppress drastically populations of L. africanus, while foliar sprays with a number of pesticides had no adverse effect. Attempts to introduce a single plant variety as a standard host in cultures of Xiphinema and Longidorus spp. were unsuccessful. Among the nematodes successfully cultured to date, the Longidorus spp. appear to have a shorter life cycle than the Xiphinema spp. X. mediterraneum and all the bisexual species of the two genera tested so far, have failed to thrive well in artificial cultures.