Abstract
Experiments were carried out on potato in Holland in 1951 to investigate the effects of Systox (diethyl 2-(ethylmercapto)ethyl thiophosphate [demeton]) and DDT on the Aphid vectors of leaf-roll and virus Y, their natural enemies and the yield of tubers, and the effect of demeton on the spread of the two viruses [cf. R.A.E., A 43 61], of which the former is of the persistent type and the latter non-persistent. The experimental plots were surrounded and divided from each other by double rows of densely-sown oats, which have been shown to prevent migration between plots. In those treated with demeton, the middle row was planted with tubers from infected plants, and ten rows of virus-free tubers were planted on either side. The plants were sprayed with 0.1 per cent. demeton at about 117 gals, per acre on 25th May, when they first came up, and at about 180 gals. on 7th, 16th and 22nd June, 3rd, 14th and 25th July, and 3rd August. No infected tubers were planted in the DDT plots, and a spray of 0.4 per cent. wettable DDT was applied on llth and 20th June, and 3rd, 13th and 25th July. Control plots were sprayed with water only. Aphid counts, the results of which are shown in tables, were made some 8-9 days after spray applications, by examining 10-50 plants and counting, on one stem, the Aphids on the largest leaf at the bottom, the largest leaf halfway up, and the whole of the apex, including incompletely opened leaves. Of the Aphids observed, only Myzus persicae (Sulz.) and Aphis nasturtii Kalt. were sufficiently numerous to be considered. The demeton-treated plots remained free from Aphids until 29th June, and though large numbers of alates of M. persicae were present from that date until 24th July and reproduced, no second-instar nymphs were found. In a subsidiary test, alates of M. persicae confined with leaves of a plant treated 8-9 days previously all died within 24 hours. Colonisation between treatments, and nymphal development, had therefore been rendered impossible. Spraying the upper surfaces of the leaves with DDT initially reduced the populations of M. persicae and spraying both surfaces did so still further, but populations were ultimately higher on the treated plots than on the controls. The effects of the insecticides on A. nasturtii were similar. One of the control plots was sprayed, with demeton in error on 16th June, and subsequent observations showed that no Aphids survived on the plants until about 12 days later, the effect of this single treatment on the population as a whole being comparable with that of regular intensive spraying with DDT. Counts of natural enemies of the Aphids (Syrphids and Coccinellids) appeared to indicate that they were killed by the demeton treatments, but the authors point out that they could have been affected by them only during the actual spraying period, and furthermore that the density of predators is apparently dependent on the Aphid population, so that a reduction in the latter automatically results in a reduction in oviposition by the former. There was some evidence, however, that the increase in Aphids following treatment with DDT was more directly due to destruction of natural enemies. Counts on 16th July showed that the number of leaves shed per stem was not affected by demeton but was 1.5 when both leaf surfaces were treated with DDT, 2.5 when only the upper surface was treated and 3.5 for no treatment. Both insecticides increased the yield of tubers slightly but significantly. Two tubers from each of the plants (except those used as sources of virus infection) were harvested and planted in 1952 in such a way that two fields resulted in each of which each plant had the same position as the parent plant in the previous year. Each field was repeatedly examined for virus disease, and the results are shown on figures and discussed. If one or both of the resulting plants showed infection it was considered that the parent plant had become infected in 1951. It thus appeared that about 20 per cent. of the plants exposed to leaf-roll and sprayed with demeton had become infected, as compared with 34.1 per cent. in the controls. The distribution of the infected plants was regular throughout the sprayed plots, however, indicating that the treatment had suppressed the influence on adjacent plants of the sources of infection with a persistent virus, whereas in the controls the percentage of plants infected was considerably higher in the first 3-4 rows parallel to the sources of infection than in the other rows (except those near the oat screens, where alates attempting to leave the plots had been prevented from doing so). The percentage of plants infected with leaf-roll in the 4th-8th rows in both demeton-treated and control plots was 18-28, and it is assumed that this represents infection due to Aphids that were already infective when they entered the plots. In the plots that contained the sources of infection with virus Y and were treated with demeton, infection in the other rows averaged 60.4 per cent., ranging from 87 in the row adjacent to the source of infection to 42 in the 8th and 9th rows. When no source was present and the plots were treated with demeton, 16.9 per cent. of the plants became infected, and when a similar plot was sprayed with water (and once, in error, with demeton) the percentage was 13.8. In the last two cases, infection is ascribed to transmission by Aphids carrying the virus when they entered the plots. The validity of the method employed for assessing virus infection is discussed, and it is concluded that the experiments explain the frequently observed absence of correlation between Aphid counts and the incidence of infection. Since the whole of the standing Aphid population was destroyed in the plots sprayed with dciiifton, the infection that occurred must have resulted from immigrant alates. These are highly mobile and usually escape detection by ordinary methods of population assessment. The difference in the spread of leaf-roll and virus Y agrees very well with the theory of persistent and non-persistent viruses [cf. 29 26]. Virus-free Aphids that acquired the leaf-roll virus from plants treated with demeton died too soon to become infective, but those acquiring virus Y became infective long before they died [cf. 43 61]. No known aphicide could much reduce the spread of virus Y by Aphids entering the field. Treatment with demeton will have little effect on virus transmission if there are no sources of infection within the field when the Aphids arrive. In practice, however, these are usually present, since it is seldom possible to remove all infected plants in time, especially those infected with leaf-roll, the symptoms of which do not appear sufficiently early. Spraying the whole field would make it possible to postpone the removal of plants infected with leaf-roll until symptoms become distinct and prevent the dissemination of infected Aphids at the time of removal. As demeton is dangerous to the worker, however, it is suggested that the spray be applied only to infected plants and those suspected of infection, roguing being carried out at a later date. If a dye were added to the spray, the roguing could be done by unskilled persons. (Abstract retrieved from CAB Abstracts by CABI’s permission)
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Claims 17
Claim · model-written summary
Plots sprayed with demeton remained free from aphids until 29th June.
- Taxon
- Potato
Solanum tuberosumt0 - Treatment
- demetone1
- Interactor
- AphidsAphidomorphae1pest
- Outcome
- Aphidse1
- Direction
- free frome1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“The demeton-treated plots remained free from Aphids until 29th June”
Claim · model-written summary
Alates of M. persicae confined with leaves of a plant treated with demeton 8-9 days earlier all died within 24 hours.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- treated 8-9 days previouslye1
- Interactor
- M. persicae
Myzus persicaee1pest - Outcome
- died within 24 hourse1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“alates of M. persicae confined with leaves of a plant treated 8-9 days previously all died within 24 hours”
Claim · model-written summary
DDT spraying initially reduced M. persicae populations, more so when both leaf surfaces were sprayed, but populations were ultimately higher on treated plots than on controls.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- DDTe1
- Interactor
- M. persicaeMyzus persicaee1pest
- Outcome
- populations of M. persicaee1
- Direction
- initially reducede1
- Qualifier
- populations were ultimately higher on the treated plots than on the controlse1
- Comparator
- controlse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“Spraying the upper surfaces of the leaves with DDT initially reduced the populations of M. persicae and spraying both surfaces did so still further, but populations were ultimately higher on the treated plots than on the controls”
Claim · model-written summary
A single accidental demeton spray on a control plot on 16th June left no aphids surviving for about 12 days.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- demeton in error on 16th Junee1
- Interactor
- AphidsAphidomorphae1pest
- Outcome
- no Aphids survivede1
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“One of the control plots was sprayed, with demeton in error on 16th June, and subsequent observations showed that no Aphids survived on the plants until about 12 days later”
Claim · model-written summary
The number of leaves shed per stem was not affected by demeton.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- demetone1
- Outcome
- number of leaves shed per steme1
- Direction
- not affectede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“the number of leaves shed per stem was not affected by demeton”
Claim · model-written summary
When both leaf surfaces were treated with DDT, 1.5 leaves were shed per stem versus 3.5 with no treatment.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- both leaf surfaces were treated with DDTe1
- Outcome
- number of leaves shed per steme1
- Direction
- lowerinferrede1
- Value
- 1.5e1
- Qualifier
- 3.5e1
- Comparator
- no treatmente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“the number of leaves shed per stem was not affected by demeton but was 1.5 when both leaf surfaces were treated with DDT, 2.5 when only the upper surface was treated and 3.5 for no treatment”
Claim · model-written summary
When only the upper leaf surface was treated with DDT, 2.5 leaves were shed per stem versus 3.5 with no treatment.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- only the upper surface was treatede1
- Outcome
- number of leaves shed per steme1
- Direction
- lowerinferrede1
- Value
- 2.5e1
- Qualifier
- 3.5e1
- Comparator
- no treatmente1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“the number of leaves shed per stem was not affected by demeton but was 1.5 when both leaf surfaces were treated with DDT, 2.5 when only the upper surface was treated and 3.5 for no treatment”
Claim · model-written summary
Both demeton and DDT increased tuber yield slightly but significantly.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- Both insecticidese1
- Outcome
- yield of tuberse1
- Direction
- increasede1
- Qualifier
- slightlye1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“Both insecticides increased the yield of tubers slightly but significantly”
Claim · model-written summary
About 20 per cent of potato plants exposed to leaf-roll and sprayed with demeton became infected, versus 34.1 per cent of controls.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- sprayed with demetone1
- Interactor
- leaf-rolle1pathogen
- Outcome
- had become infectede1
- Direction
- lowerinferrede1
- Value
- 20 per cent.e1
- Qualifier
- 34.1 per cent.e1
- Comparator
- controlse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“about 20 per cent. of the plants exposed to leaf-roll and sprayed with demeton had become infected, as compared with 34.1 per cent. in the controls”
Claim · model-written summary
Infected plants were distributed regularly throughout the demeton-sprayed plots.
- Taxon
- PotatoSolanum tuberosumt0
- Outcome
- distribution of the infected plants was regulare1
- Setting
- sprayed plotse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“The distribution of the infected plants was regular throughout the sprayed plots”
Claim · model-written summary
In demeton-treated plots containing virus Y infection sources, infection in the other rows averaged 60.4 per cent.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- treated with demetone1
- Interactor
- virus Ye1pathogen
- Outcome
- infection in the other rowse1
- Value
- 60.4 per cent.e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“In the plots that contained the sources of infection with virus Y and were treated with demeton, infection in the other rows averaged 60.4 per cent.”
Claim · model-written summary
Without an infection source, 16.9 per cent of plants in demeton-treated plots became infected versus 13.8 per cent in a water-sprayed plot.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- treated with demetone1
- Outcome
- plants became infectede1
- Direction
- higherinferrede1
- Value
- 16.9 per cent.e1
- Qualifier
- 13.8e1
- Comparator
- sprayed with watere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“When no source was present and the plots were treated with demeton, 16.9 per cent. of the plants became infected, and when a similar plot was sprayed with water (and once, in error, with demeton) the percentage was 13.8”
Claim · model-written summary
The authors suggest applying the spray only to infected plants and those suspected of infection.
- Taxon
- PotatoSolanum tuberosumt0
- Outcome
- spray be applied only to infected plants and those suspected of infectione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“it is suggested that the spray be applied only to infected plants and those suspected of infection”
Claim · model-written summary
The authors conclude that the experiments explain the frequently observed absence of correlation between aphid counts and the incidence of infection.
- Taxon
- PotatoSolanum tuberosumt0
- Interactor
- Aphide1pest
- Outcome
- incidence of infectione1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“the experiments explain the frequently observed absence of correlation between Aphid counts and the incidence of infection”
Claim · model-written summary
Virus-free aphids that acquired leaf-roll virus from demeton-treated plants died too soon to become infective, whereas those acquiring virus Y became infective long before they died.
- Taxon
- PotatoSolanum tuberosumt0
- Interactor
- AphidsAphidomorphae1pest
- Outcome
- died too soon to become infectivee1
- Qualifier
- those acquiring virus Y became infective long before they diede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“Virus-free Aphids that acquired the leaf-roll virus from plants treated with demeton died too soon to become infective, but those acquiring virus Y became infective long before they died”
Claim · model-written summary
There was some evidence that the aphid increase after DDT treatment was more directly due to destruction of natural enemies.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- DDTe1
- Interactor
- AphidsAphidomorphae1pest
- Outcome
- increase in Aphidse1
- Qualifier
- destruction of natural enemiese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“the increase in Aphids following treatment with DDT was more directly due to destruction of natural enemies”
Claim · model-written summary
Counts appeared to indicate that natural enemies of the aphids (syrphids and coccinellids) were killed by the demeton treatments.
- Taxon
- PotatoSolanum tuberosumt0
- Treatment
- demeton treatmentse1
- Interactor
- Syrphids and Coccinellidse1other
- Outcome
- natural enemies of the Aphidse1
- Direction
- killede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Potato Viruses”
e1“Counts of natural enemies of the Aphids (Syrphids and Coccinellids) appeared to indicate that they were killed by the demeton treatments”
The same questions in other papers
insecticide · yield · Solanum tuberosum (potato)Results differ
21 papers in the same direction as this paper · 9 in the opposite direction · 1 reporting no difference from an alternative
- no effect
- no effect
- no effect
28 papers more in this group
See all 32 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.