Phytotoxicity of Some Organophosphate Insecticides to Oughly with Air Dry, Sieved Soil, to Pro Duce Rates of 37.5, 75 and ISO Mg Aj
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Plant Protection Quarterly VoI.7(1} 1992 23 -------------------------------- ties of each pesticide were shaken thor Phytotoxicity of some organophosphate insecticides to oughly with air dry, sieved soil, to pro duce rates of 37.5, 75 and ISO mg aj. L-' onions and carrots during germination and emergence soil. Each pot constituted one plot. If it is assumed that in a field situation, P.J. Sinclair, New South Wales Agriculture, Horticultural Research and band-in-furrow treatment would treat a Advisory Station, Griffith, New South Wales 2680, Australia. strip 50 mm wide by 20 mm deep, the rates tested would correspond to 37.5, 75 R.J. Neeson and P.A. Williams, New South Wales Agriculture, Agricultural and 150 mg a.i. m" row, or 0.5,1.0 and 2.0 institute, Yanco, New South Wales 2703, Australia. kg a.i. ha" at a row spacing of 75 cm. The low and medium rates are then compara Summary ble to ra tes used in the field by Getzin The phytotoxicity of some commonly phytotoxicity from carbofuran applied to (1973), Thompson et al. (1981) and used insecticides to onions (Allium cepa) onions as a seed dressing. Chlorpyrifos is Goodyer et al. (1989) . and carrots (Daucus carota) during es generally non-phytotoxic at recom Daily counts of emerged seedlings were tablishment was assessed in pot trials. mended rates and methods of application, made at 7 to 18 days and at 21 days after Terbufos, ethoprophos, phoxirn and but some crops are especially sensitive to first watering. These data were used to de carbofuran (all 10% a.L granular fonnu it during the seedling stage or if the termine the total number of seedlings lations) and chlorpyrifos (25% a.i. chemical is applied close to the seed (Spar which emerged ("maximum emergence") wettable powder) were applied at three row et al. 1973). Stapleton et al. (1987) and number of surviving seedlings at the rates in the soil used to cover the seed found ethoprophos (10% a.i. granular) final count ("final emergence") as a per (37.5, 75 and 150 mg a.i. L" soil 20 mm did not cause significant phytotoxicity to centage of seeds sown and to estimate the deep). No treatment significantly carrots when used as a nematicide, how time in days between sowing and 50% of (P>O.Ol) reduced percentage emergence ever the rate in the vicinity of seed was maximum emergence. Visual observa in onions, whereas terbufos, small (1 .35 kg a.i. ha" spread and incorpo tions of phytotoxic effects were recorded ethoprophos and chlorpyrifos reduced rated) and a delay of several weeks oc and an area meter (Ll-COR Model 3100) emergence in ca.rrots. Seedling size 22 curred before planting_ was used to measure the total size of ten and 37 days after sowing of onions was Some chern ica Is currently considered to seedlings sampled 22 days and 37 days significantly reduced by terbufos, have potential for soll use include after sowing. Seedling size was not deter elhoprophos and chlorpyrifos and in car carbofuran, chlorpyrifos, ethoprophos, mined in carrots at the medium and high rots by ethoprophos, carbofuran and phoxim and terbufos. This study reports rates of ethoprophos, as there were too chlorpyrifos. The same treatments also the results of pot trials conducted to de few plants. caused delays in emergence of both termine the phytotoxicity to carrots and The data for each crop were analysed crops. Visible symptoms in cotyledons onions of those chemicals applied to soil by analysis of variance. Square root trans were also observed with phoxim in on at sowing. formation was required for seedling size ions and carbofuran in carrots. data. Materials and methods Introduction Two experiments were conducted concur Results Soil application of insecticides in dose rently in a glasshouse (temperature Onions and carrots differed markedly in proximity to the seed row can control 12-32' C) at Yanco (Lat. 34' 33', Long. their response to insecticide treatment. In various pests of carrots (Dailcils carota) 146' 25') in New South Wales, one with onions (Table 1), percentage emergence and onions (Allium cepa) during germina carrots (cv. Western Red) and one with was not affected sigruficantly (p>0.01) by tion and early growth (e.g., Sparrow et al. onions (cv. Brown Spanish). Three rates any treatment, whereas in carrots (Table 1973, Stevenson 1976, Goodyer et al. 1989) . of terbufos, ethoprophos, phoxim, 2), both maximum and fina l percentage However, phytotoxicity can be a problem carbofuran (all 10% a.i. granules) and emergence were affected (P<O.OI) by all with some chemicals, either by direct chlorpyrifos (25"10 a.i. wettable powder) rates of ethoprophos and high rates of physiological effects (Dalvi and Salunkhe and an untreated control were evaluated chJorpyrifos and terbufos_ 1975) or by interaction with pathogens using completely randomized deSigns, Seedling size of onions, but not ca rrots, (Rawlins 1965). For example, the with three replicates for the insecticide was significantly (P<0.01) affected by organochlorines lindane and aldrin are treatments and nine for the controls. terbufos at the high rate on both sampling known to be phytotoxic when applied as Greater replication of the control was occasions, whereas carbofuran at me a seed dressing to onions (Finlayson used to improve comparisons between dium and high rates affected seedling size 1957). Diazinon has been found to reduce treatments and the control. The placement of carrots but not onions_Phoxim had no establishment of carrots, but its of pots was re-randomized. several times sigruficant (P>0.01) effect on seedling size phytotoxic effects can be counteracted by during the experiments to reduce any ef of either crop. Chlorpyrifos and seed treatment with the fungicide thiram fects of position in the glasshouse. ethoprophos affected seedling size of (Stevenson 1976). Gogeldrie clay topsoil (van Dijk 1961) both crops, but carrots were more se There is little published information re was used for consistency with previous verely affected and did not grow between garding the phytotoxici ty of other field trials (Goodyer et al. 1989), but was the two sam piing occasions. Decreases in carbamate or organophosphate insecti dried before use for 48 hours at 70'C to seedling size from insecticide treatment cides to carrots and onions. Stevenson kill wireworms. Plastic pots 150 mm in di were associated with delays in emer (1976) provided conflicting evidence on ameter (1.3 L) were filled to 60 mm from gence, which were most evident with the phytotoxicity of ca rbofuran to carrots, the top with untreated soil, followed by a chlorpyrifos in carrots. but Thompson et al. (1981) reported carrot 20 mm layer of sieved untrea ted soil to Shrivelling of the cotyledon tips was numbers were not reduced by rates up to provide a uniform seedbed. Fifty seeds observed in carrots treated with 66.7 mg a.i. m" row. Getzin (1973) found were distributed over the surface and cov carbofuran. At all three rates of phoxim, indications that carbofuran at 45.9 mg a.i. ered to a depth of 20 mm with insecticide onion plants exhibited a very distinctive m-I row in onions had increased plant vig treated soil (approximately 0.3 L) . To pre bleaching at the top of the emerging coty our, but Jodko (1988) encountered some pare the treated soil, appropriate guanti- ledon hook. 24 Plant Protection Quarterly VoI.7(1) 1992 Table 1: Effects of various insecticide treabnents on onions during seed Discussion ling establishment. Carbofuran at the rates tested had no sig· nificant effects on onions and the sugges Chemical, rate and % emergence Days to Seedling size tion by Getzin (1973) that it might stimu formulation (mg a.i. 50% of (~[ em' I I0piantsl) late onion seedling growth was not sup IL of covering soil) Maximum Final maximum at 22 37 ported. Carrot emergence percentage was emergence days from sowing not affected by carbofuran, but sensitivity Carbofuran 37.5 95 94 9.6 2.23 3.23 to the chemical in this crop was indicated lOG 75 94 93 9.2 2.35 3.21 . by reduced growth rate and visible symp ISO 94 93 9.2 2.37 3.14 toms: such damage could explain occa sional reports of red. uced emergence wi th Chlorpyrifos 37.5 95 93 9.7 2.16 3.30 the chemical in the field (Stevenson 1973). 25WP 75 95 93 10.3 1.81' 2.79' Chlorpyrifos reduced growth, but did ISO 94 93 11.2' 1.36' 2.42' not affect percentage emergence of onion seedlings. This insecticide is currently Ethoprophos 37.5 90 89 10.5' 1.77' 2.78' used in onions in New South Wales as a lOG 75 94 93 10.7' 1.68' 2.77' seed dressing at a rate of25 ga.i. kg~' seed. 150 89 89 11.8' 0.95' 2.36' At typical sowing rates of 2.5-4.5 kg seed Phoxim 37.5 90 90 9.4 2.60 3.65 ha·', the rate of chlorpyrifos resulting is lOG 75 94 93 9.5 2.42 3.26 62.5-112.5 g a.i. ha·', well below the rates 150 95 95 9.1 2.26 3.31 tested in these trials. Effects of chlorpyrifos on percentage emergence of Terbufos 37.5 97 95 9.2 2.64 3.13 carrots were only Significant at the high 2.23 3.29 lOG 75 88 87 10.3' rate, however the insecticide had severe, 2.90' ISO 82 82 11.0' 1.72' persistent effects on carrot seedling Control 94 90 9.3 2.55 3.55 growth.