The fate, distribution and biological performance of insecticide residues in vegetable crops following seedling treatment

Carrot, cauliflower and radish seedlings raised in sand culture and treated with aqueous suspensions containing chlorfenvinphos, diazinon, iodofenphos or triazophos were planted into the field in 1982 and 1983 to compare the performance against cabbage root fly and carrot fly of these treatments with that of bow-wave applications of granular formulations at sowing. Initial residue concentrations were up to 4100 mg kg^-1 in the seedlings at planting. Thereafter the amounts of insecticides per root system declined. Residue concentrations in mature carrot and radish roots were smaller when plants had been treated as seedlings rather than by bow-wave application. Chlorfenvinphos was the most effective insecticide against both pests. Amounts of insecticide applied in transplanted seedlings were < 5% of the amounts applied by the bow-wave method but short-term control of cabbage root fly on radish was similar. Carrot fly damage was reduced by 60% by some of the seedling treatments after 16 wk in 1982 but in 1983 they were less effective. Pot experiments with chlorfenvinphos showed that most of the insecticide in the seedlings was transferred rapidly into the surrounding soil and it was concluded that the bioactivity resulted mainly from uniform distribution of the released insecticide between and around individual plants.     

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.     

The protection of carrots against carrot fly (Psila rosae) with granular and emulsifiable concentrate formulations of chlorfenvinphos incorporated in gels used for drilling pre germinated seed in a sandy loam

Field experiments were done in a sandy loam in 1979 and 1980 to investigate the performance against carrot fly on carrots of e. c. and granular formulations of chlorfenvinphos incorporated in gels used for drilling pre-germinated seed. With 9·4–66·7 mg a. i./m row, the two formulations performed similarly in a natural hydrocolloid and a mineral colloid gel. Thus the emergence of carrot seedlings 6–7 wk after drilling was similar on plots with untreated gel and those with insecticide-treated gel and, about 6 months after drilling when > 90% of carrots grown without insecticide were damaged by carrot fly larvae, an approximately six-fold increase in dose of both formulations increased the estimated larval mortality from about 70 to 95%. Mean concentrations of residues of total (Z + E) isomers of chlorfenvinphos in harvested carrots treated with 9·4–56·5 mg a. i./m row were50% of the insecticide had been released into both gels.     

Effects of pesticide treatments on the yield of swedes

The effects of insecticide and fungicide applications to swedes (Brassica napus var. napobrassica) were examined at 15 sites in England from 1974 to 1978. Several different pesticide combinations were applied including carbofuran granules at drilling (63 mg a. i./m of row), demeton-S-methyl sprays (0·24 kg a. i./ha) and fluotrimazole sprays (0·18 kg a. i./ha). The best treatments, which varied in different years, gave significantly higher yields than no treatment in 12 out of a total of 15 trials, with varying levels of damage attributable to cabbage root fly (Delia brassicae), aphids (Myzus persicae) and powdery mildew (Erysiphe cruciferarum) in each of the 4 years. In 10 of 12 trials, plots receiving a complete insecticide and fungicide programme yielded on average 40% (range 21–61%) more than untreated plots, mainly through control of root fly and aphids in 1975 and of aphids and mildew in 1976. Aphid damage to swedes was exceptionally severe in both years. Granular formulations of aldicarb, carbofuran, chlorfenvinphos or fonofos used alone to prevent cabbage root fly damage gave significant yield benefits in only 8 of the 15 trials, with least effect in 1977 and 1978 when growing conditions for swedes were good and damage relatively light.     

Chemical control of wheat bulb fly (Delia coarctata) attacking winter wheat in Eastern England, 1969–1981

Dry powder, liquid and microencapsulated formulations of organophosphate and synthetic pyrethroid insecticidal seed treatments were tested as possible alternatives to the standard organochlorine seed treatments for autumn-sown wheat in mineral and organic soils heavily infested with wheat bulb fly eggs and (subsequently) larvae. Retention of insecticides on the seed coat varied from 40% to 120% of the target dose; it was usually good when microencapsulated formulations were used. Chlorfenvinphos, fonofos, isofenphos and triazophos, each applied at 2-0 g a.i./kg seed, were phytotoxic, the symptoms varying from a slight delaying effect upon germination to an adverse effect upon grain yield. Chlorfenvinphos at 0–2 to 2-0 g a.i./kg seed was consistently effective against wheat bulb fly larvae in both mineral and organic soils. Athidathion 0–8 g a.i./kg, carbophenothion 1–2 g a.i./kg, ethion 1–7 g a.i./kg and fonofos (microencapsulated formulations) at 1-0 or 2-0 g a.i./kg were also effective in mineral and organic soils. Of the synthetic pyrethroids tested as seed treatments, permethrin gave excellent results in mineral soils at 1-0 g a.i./kg or in synergised formulations at 0–12 or 0–24 g a.i./kg but was disappointing in organic soils. In a single comparison of seed treatments applied to wheat sown early (14 October) and late (20 November), chlorfenvinphos was effective at both sowing dates whereas athidathion, ethion and pirimiphos-ethyl gave better results in late-sown wheat. A single trial compared deep with shallow sowing of treated seed. Most insecticides performed better on shallow-sown wheat, but chlorfenvinphos was equally effective against the pest at both sowing depths. Most insecticides restricted the numbers of larvae entering host plants but had little or no subsequent effect upon larval survival within attacked shoots. Fonofos and isofenphos, and to a lesser extent chlorfenvinphos, seed treatments additionally killed many larvae within plant shoots.     

Studies on plant growth-regulating substances XLVIII. The effects of3,5-diiodo-4-hydroxybenzoic acid on seedling growth in compact and loose soils

Effects of combinations of insecticides and herbicides on the growth and yield of cauliflower plants (cvs No. 110, Garant and Strong) were determined in two field experiments with seed drilled to give a stand of c. 300000 plants/ha. Granular formulations of chlorfenvinphos or fonofos were applied by the bow-wave method at 2 kg a.i./ha to control cabbage root fly (Delia brassicae). Weeds were successfully controlled with combinations of trifluralin, incorporated into the soil at 0·6 or 1·2 kg a.i./ha before drilling, and propachlor, applied pre-emergence at 2·2 or 4·4 kg a.i./ha. Fonofos, with and without herbicides, significantly lessened (P < 0·01) numbers of seedlings that would survive to harvest. Herbicides and chlorfenvinphos generally did not significantly affect the emergence of healthy seedlings of any cultivar. Combinations of herbicides and chlorfenvinphos were compatible for control of target species. Chlorfenvinphos reduced root damage by at least 50% but did not significantly increase (P > 0·05) the total or marketable weight of curds. Numbers of curds were not usually affected and consistent effects of treatments on maturation periods of the three cultivars were not detected.     

Insecticide granule distribution and the control of Lycoriella auripila (Diptera: Lycoriidae) in mushroom casing material

In laboratory tests the distribution of insecticide in peat–chalk mushroom casing greatly affected the number of adult sciarids which emerged from larvae placed in 50 g samples. Only thionazin markedly reduced emergences when granules were clumped in the centre of the sample of casing. The slope of dosage mortality data for clumped granule treatments was less steep than for mixtures and gave estimated LD₉₅ values of 16300 and 26.8 ppm respectively. Thus, the number of adults which emerged when granules amounting to 6.4 mg of chlorfenvinphos were clumped was 65% of those emerging when only 0.4 mg a.i. was mixed into 50 g casing. However, adults did not emerge when 3.2 mg of the same insecticide was mixed throughout the sample. Increased doses did not, therefore, compensate for inadequate mixing. With 0.2–0.4 mg a.i. chlorfenvinphos mixed through the casing, about three times as many sciarids emerged with the intact granules than when pulverized granules were used. This showed the lack of mobility of this chemical in peat-chalk mixtures and the need for it to be homogeneously incorporated in commercial casing. Pirimiphos-ethyl, diazinon and thionazin also gave improved kills when mixed into the casing rather than clumped. A χ² test of the mortality data suggested a non-linear dosage-mortality relationship for treatments amounting to half the dish. However, LD₉₅ estimates of 37.5 and 62.2 ppm were obtained for mixed and quadrant treatments. Thus, when 3.2 mg chlorfenvinphos was mixed into only half of the volume of casing, the number of adults emerging was only 6% of that from untreated casing. However, larval movement was negligible in untreated casing and this appeared to limit the effectiveness of chlorfenvinphos and pirimiphos-ethyl when they were not evenly distributed throughout the casing. With thionazin and diazinon, mobility of the insecticide appeared to compensate for uneven distribution.     

Chemical control of the cabbage stem flea beetle, Psy Modes chrysocephala, on winter oil-seed rape

In East Anglia, from 1974 to 1976, field experiments were carried out on the chemical control of the cabbage stem flea beetle (PsyModes chrysocephala). Carbofuran, 5% granules, proved an outstanding autumn preventive and mid-winter eradicant treatment under both wet and dry conditions, with 1–5-2-24 kg a.i./ha giving virtually 100% control of larvae. Fonofos and phorate granules at 2–24 kg a.i./ha were also effective. AC 92 100 and thiofanox granules were less extensively tested but both gave good control of P. chrysocephala. Several materials showed little or no activity against the pest. The effective preventive granule treatments were all superior to a standard spray of gamma-HCH.     

Selective effect of the systemic insecticide Phosphamidon on soil,root-surface and leaf-surface fungi

Results of the effect of Phosphamidon on soil, root- and leaf-surface fungi of Vigna sinensis var. azmerly were generally inconsistent. However, there were some consistent ones. Its effect on soil, root- and leaf-surface fungi persisted till after 40 days. In soil the total count was regularly increased after 20 days by the low and medium doses and after 40 days by the high dose. In the rhizosphere, Fusarium was almost consistently activated by the three doses after 5 days of treatment and by the low dose after 20 days. In the rhizoplane, the total count of fungi was lowered by the three doses after 40 days in the two sowings. Alternaria alternata was toxicated by the three doses after several experimental periods of the two sowings in the phyllosphere and phylloplane. When this insecticide was incorporated with the agar medium, it was of no significant effect on the total count of fungi at the low and medium doses but abnormally increased the total count at the high dose. In the liquid medium, the mycelia of the test fungi were not significantly affected except that of Penicillium corylophilum which was significantly retarded by the three doses and Rhizopus stolonifer which was significantly activated by the high dose.     

Effect of crop residue management on the yields of different crops and on soil properties

The effects of chopped (6–9 cm) and unchopped (long) crop residues of wheat (Triticum aestivum L.) and rice (Oryza sativa L.) in corn (Zea mays L.)— wheat and rice-wheat rotations on grain yield and soil properties were investigated in 27 field experiments during 9 years. Experiments on chopped wheat residue involved the treatments of two main plots with residue incorporation at 0 and 4 t/ha before sowing of corn and wheat and having subplots with 0, 40, 80 and 120 kg N/ha. The results obtained for 4 years showed that the incorporation of wheat residue not only improved the soil physicochemical properties but also increased the grain and stover yields of corn significantly. The yield obtained with 80 kg N in conjunction with 4 t/ha chopped wheat residue was identical to that with 120 kg N/ha alone. But the wheat yield was depressed significantly upon the incorporation of wheat residue before the sowing of wheat in all the years of investigation.The experiments on the management of unchopped wheat residue in corn-wheat rotation and of unchopped wheat (6 t/ha) and rice (12 t/ha) residues in rice-wheat rotation, involved three main treatments: physical removal, in-situ incorporation and in-situ burning of residues. Main treatments were tested at 60, 120 and 180 kg N/ha level over 5 years. Irrespective of N application, the residue management treatments had non-significant effects on the succeeding crop yield in all the years. Burning of residue improved the yield by about 0·2 t/ha, whereas residue incorporation did not affect the yield either of corn or rice. On the other hand, the wheat yield was depressed by 0·1–0·2 t/ha in both the rotations.The effect of applied N irrespective of residue management was significant in some years up to the level of 120 kg and in others, 180 kg N/ha.     

An attachment to a tractor-mounted seed-spacing drill for applying granular formulations to small field-plots

Tractor mounted equipment is needed to deliver granular formulations of pesticides accurately to the soil in small-plot trials in a manner comparable to commercial equipment. Inexpensive units incorporating a belt unit mechanism were designed and fitted to a Mk II Stanhay S-870 Precision Seed-Spacing Drill. The individual delivery belts were driven through a continuously-variable reduction gearbox by the main drive shaft of the drill and pre-weighed amounts of granules were placed along the belts. Insecticides and dose patterns could thereby be changed readily from plot to plot. In field assessments of uniform doses of fuller's earth granules delivered to single row, 4·8 and 10·3 m plots, the mean weights recovered were 94–98% of the target doses, S.E.'s being ±2% of the means. When 16-fold, exponentially-increasing doses were delivered, the weights recovered were generally within 10% of the target dose at any point within 0·2 m from the start and 0·3 m from the finish of the plot. The performance of uniform doses of carbofuran (on sand) and chlorfenvinphos (on Spanish Silical) against cabbage root fly on radish in 15 m plots showed that errors in loading were insignificant compared with the variability in pest infestation on the field plots. With doses increasing exponentially by c. 12-fold applied to similar plots, the percentage of carrots or radish undamaged by carrot fly and cabbage root fly increased from 40–60% to 85–99·3%, the relationship between the log-log proportion of undamaged roots and log-dose being linear. The equipment allows free-flowing, granular pesticide products to be applied to small plots of a wide range of row-crops much more accurately than has hitherto been possible. A work rate of 24 plots h^-1 was achieved by a team of two technicians and a tractor driver.     

The influence of climatic conditions around the time of spraying isoproturon on the subsequent injury to barley

Winter barley cv. Igri was grown in pots, either outside under cover, in a glasshouse or under controlled conditions and treated post-emergence with isoproturon. There was a linear relationship between the subsequent weight of plants treated with 2.5 kg a.i./ha and either evaporation from a water surface between 2–7 days post spraying or cumulative temperature between sowing and spraying. The relationship between subsequent weight of plants treated to the foliage only with 5 kg a.i./ha and cumulative temperature between sowing and spraying varied between years 1984–86. The post spraying environment had the major influence on subsequent activity of isoproturon at 2.5 kg a.i./ha applied overall to barley under controlled conditions. There was a greater reduction in CO₂ exchange in plants grown after treatment under high compared to low relative humidity. When isoproturon at 5 kg a.i./ha was applied to barley plants with wet foliage, plants were slower to recover their initial rate of photosynthesis when kept wet for 24 h as compared with 11 h or when allowed to dry after treatment. Photosynthesis was decreased to a lesser extent under the same post spray conditions by 2.5 than by 5 kg a.i./ha and reduction was greater and recovery of photosynthesis slower in plants grown inside compared to outside.     

Activity and residual effect of two formulations of lambdacyhalothrin sprayed on palm leaves to Rhodnius prolixus

The insecticidal activity and residual effect of two formulations of lambdacyhalothrin were evaluated with Rhodnius prolixus; laboratory and field tests were conducted in the State of Chiapas, Mexico. The results indicate that the lethal concentrations of the active ingredient of SC (LC50 = 2.37 and LC90 = 8.5 mg, a.i./m2) were 4-8 times than those with the insecticide WP applied on R. prolixus bugs in palm leaves, a common building material for thatched roofs. Other investigators in South America recommended applying 30 mg a.i./m2 in porous materials; we obtained that the products WP and SC were 3.5 and 16 times more effective on palm leaves. Regarding the evaluation of the residual effects in field spraying, there was up to 15 months persistence after the application of WP in two doses (8.6 mg a.i./m2 and 3.752 mg a.i./m2) with SC. We consider R. prolixus highly susceptible to the employed pyrethroids; they could be used to control this vector in the state of Chiapas, Mexico.     

Effect on radish pests by application of insecticides in a nearby spring oilseed rape field

Chemical control of insect pests is often necessary to ensure high yields of field crops. The aim of the present study was to study whether field pesticide use influences amount of pest damage in neighbouring garden crops. Spring oilseed rape, OSR (Brassica napus L.), was established in Southern Sweden as an example of an agricultural field crop. One half of the OSR field was treated with insecticides to control flea beetles (Phyllotreta spp., Chrysomelidae) and pollen beetle (Meligethes aeneus Fab., Nitidulidae). Radish (Raphanus sativus L.) was used as an example of a common garden crop and it was sown as four replications at three different distances and on four occasions during the season. Care was taken to protect the radish plots from pesticide due to wind drift during applications. Damage to the radish by flea beetle and cabbage root fly (Delia radicum L., Anthomyiidae) along with unspecified leaf damage was recorded. Significantly lower damage by flea beetles was found on cotyledons of radish adjacent to the insecticide treated side of the OSR field compared to the untreated side in radishes from the first sowing. Unspecified damage to true leaves was also less abundant on radishes at the treated side of the OSR field as compared to the untreated side, in all three of the radish harvests analysed. However, radish plot distance from the OSR field did not influence leaf damage. Root fly damage rates in radish did not differ significantly between those adjacent to the treated and untreated sides of the OSR. Damage rates were, however, higher in the radish plots closest to the OSR field in the first sowing, which coincides with the appearance of the first ovipositing females after overwintering as pupae elsewhere. Generally, insecticide treatment in the agricultural field appeared to influence overall damage in the neighbouring garden crop, despite the fact that the garden crop was protected against wind drift of the insecticides during applications.     

Pesta granule trials with Aspergillus alliaceus for the biocontrol of Orobanche spp.

The pathogenic fungus Aspergillus alliaceus has been shown to have potential for the biocontrol of Orobanche spp. (broomrape), a root parasitic plant. The effectiveness of A. alliaceus in reducing Orobanche infection was analysed using pesta granules prepared with different food formulations. The results showed that pesta granules comprising of fungal mycelia/spore mixtures from liquid and solid culture, sclerotia and fungal mycelia reduced Orobanche infection to a greater extent in below ground conditions when applied early and at high doses before crop sowing. In addition, pesta granules eliminated the risk of broomrape contamination within a 0.2–0.3 cm diameter of the granules. The sclerotial pathogenicity of A. alliaceus was compared with those of other fungi reported in other studies. In addition, some morphological and histological studies on the fungal pathogenicity on broomrape plants after infection are presented. The present study reveals the potential of sclerotial A. alliaceus pesta granule applications for long-term broomrape biocontrol under field conditions.     

Use of Avermectins for the Control of Meloidogyne incognita on tomatoes

The efficacy of avermectins B₁ and B₂ for control of Meloidogyne incognita on tomato was studied in pots and field plots for two seasons. Avermectins were applied as granules and liquid in furrows or by low pressure drip irrigation systems, at rates ranging from 0.093 to 0.34 kg a.i./ha, as single or multiple applications. Levels of control comparable to those obtained by oxamyl and aldicarb at 3.36 kg a.i./ha were achieved by the avermectin with only 1/10 the volume of chemicals applied to the environment. Avermectin protection of the roots remained constant throughout the first 5 weeks giving slightly longer protection than oxamyl or aldicarb.     

Dispersion,Dissipation, and Efficacy of Methyl Bromide-Chloropicrin Gas vs. Gel Formulations on Nematodes and Weeds in Tifton Sandy Loam

Dispersion, dissipation, and efficacy of gas and gel formulations of methyl bromidechloropicrin (202, 269, 336, and 403 kg/ha) on nematodes and weeds on tomato were studied in field plots. Concentrations of methyl bromide and chloropicrin 4 hr after soil treatment were greater at a depth of 15 cm than at 30, 45, or 60 cm. The concentrations of both chemicals decreased with lower doses, greater depths, and longer times after application. The gel formulation was more persistent than the gas formulation at both 336 and 403 kg/ha at depths of 30 and 45 cm, especially 24 and 36 hr after chemical application. Plant growth and yield were improved when nematodes and weeds were controlled.     

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.     

The interaction of protectants with EPTC on field bean, and tri-allate on wheat

Protectants (antidotes) were tested for their potential to protect field beans (Vicia faba L.) from EPTC damage, or wheat (Triticum aestivum L.) from triallate damage. For both crops there was considerable variation in the degree of protection shown from similar treatments in different experiments. For field bean, a seed treatment of 1,8-naphthalic anhydride (NA) at 5 mg/g seed gave some protection from EPTC applied pre-planting at 4–8 kg a.i./ha but not in all experiments. NA also caused marked chlorosis of the foliage. N, N-diallyl-2, 2-dichloroacetamide (R25788) at 20 mg/g seed severely damaged field bean in the absence of herbicide but 5 mg/g gave comparable protection from EPTC to that given by NA and did not cause chlorosis. Mixing R25788 with EPTC in the spray tank gave reduced protection. In a single experiment R4115 (chemistry undisclosed) gave some protection against EPTC damage. For wheat, a seed treatment of 5–20 mg/g NA sometimes countered damage from tri-allate applied pre-planting at 1 kg a.i./ha but not generally from higher doses. R25788 sometimes protected from weight loss due to tri-allate at 1 kg a.i./ha but not from damage symptoms, whereas R4115 at 20 mg/g seed alleviated these symptoms but did not prevent weight loss. R25788 at 4 kg a.i./ha mixed in the spray tank with the herbicide partially reduced weight loss and damage symptoms from a dose of 2 kg a.i./ha. Some treatments of R29148 gave complete protection from tri-allate at 1 kg a.i./ha. The results are discussed in the context of the full data from the two series of experiments.     

Effect of Simulated Rainfall on Efficacy and Leaching of Two Formulations of Fenamiphos

Recoverable fenamiphos in the soil and residue in squash following different simulated rainfall treatments after nematicide application were determined in a 2-year study. Efficacy of fenamiphos also was evaluated. Fenamiphos treatments (3 SC and 15 G) were broadcast (6.7 kg a.i./ha) over plots and incorporated into the top 15 cm of soil immediately before planting ''Dixie Hybrid'' squash. Simulated rainfall treatments of 0, 2.5, and 5.0 cm water were applied 1 day after fenamiphos application. Soil samples from 0- to 8-cm, 8- to 15-cm, and 15- to 30-cm soil depths were collected 1 day after the simulated rainfall applications and analyzed for fenamiphos, fenamiphos sulfoxide (FSO), and fenamiphos sulfone (FSO₂). Squash was analyzed for total fenamiphos residue. Greater concentrations of fenamiphos were present in the 0- to 8-cm soil layer following application of 15 G than 3 SC formulation. Simulated rainfall treatments did not alter fenamiphos concentrations in any soil layer (except for the 0- to 8-cm depth in 1992) or concentration of FSO and total fenamiphos residue in the 15- to 30-cm soil layer. Root-gall indices were greater from untreated than most fenamiphos-treated plots, but were not affected by formulations of fenamiphos or simulated rainfall treatments. Concentrations of total residue in squash ranged from 1 to 4 μg FSO₂/g.