10 Plant Protection Quarterly Vo1.7(1) 1992 The 2000 mL ha" rates of endosulfan and Control of redlegged earth mite Halotydeus destructor methidathion gave mean protection peri­ ods of 33 and 32.5 d, respectively. This on bare earth was significantly greater than the same compounds at 1000 mL ha" (endosulfan David G. James and Karen J. O'Malley, Yanco Agricultural Institute, New 28.5 d, methidathion 24.3 d) (P<0.05) . The 500 mL ha" rate of endosulfan was effec­ South Wales Agriculture and Fisheries, Yanco, New South Wales 2703, tive for a mean period of 24.2d. Tefluthrin Australia. which was only used in one trial gave a protection period of 18 and 22 d at 300 and Summary ec), ehlorpyrifos (50% ec) and tefluthrin 500 mL ha", respectively. Six insecticides were evaluated as bare (10% ec)). These com pounds were se­ Frequent and sometimes heavy rainfall earth treatments to protect emerging lected as the most promising treatments was a fea ture of all trials (Figure I). More crops from Halotydeus destructor. from a larger range evaluated in prelimi­ than 50 mm was recorded during trials 1,3 Endosulfan, methidathion and nary pot trials. Four trials were conducted and 4. In trial 1, 48.5 mm had fallen by tefluthrin provided residual control of consecutively on light loamy soil at the day 12.7 H . destructor for 17-36 days despite Yanco Agricultural Institute in the rainfall of up to 64 mm. Omethoate gave Murrumbidgee Irrigation Area of south­ Discussion control for up to eleven days but ern New South Wales during June-Sep­ These results indicate endosulfan, phosmet and chlorpyrifos were ineffec~ tember 1989. Treatments were applied to methidathion and tefluthrin have consid­ live after six and twelve days, respec­ single 5 x 15 m plots using a tractor drawn erable potential as bare earth treatments tively. boom spray (5 m) with 12 flat fan nozzles. for H. destructor. Residual protection of The sprayer was calibrated to deliver 50 L 3-5 weeks was achieved from appli ca­ Introduction spra y volume per hectare and 10 L was ti ons of endosulfan at 500-2000 m L ha" The redlegged earth mite, Halotydeu, de­ used for each treatment. Three rates of and methidathion at 1000-2000 mL ha·'. structor (Tucker) is a serious pest of win­ endosulfan and methidathion (2000; 1000, This persistence was obtained despite ter field crops and pastures in inland 500 mL ha"), two rates of omethoate (1000 rainfall of up to 64 mm. southern Australia (Wright 1965, Hely et and 150 mL ha"), chlorpyrifos (1000 and Seedling protection from H. destructor is al. 1982, James 1987). Mite activity com­ 300 mL ha"), tefluthrin (500 and 300 mL desirable in winter crops such as canola mences following autumn rains and in ha") and a single rate of phosmet (1000 for up to five weeks following emergence. some years populations reach plague pro­ mL ha") were used. After this time seedlings are generally ro­ portions (e.g., 1980, 1986) and cause se­ Adults of H. destm ctor were introduced bust enough to survive earth mite attack. vere economic loss to crops such as onto the treatment plots by confinement The applica tion of endosulfan or canoia, cereals, peas and lettuce. Pasture within plastic tubes (II cm diameter) in­ methidathion at crop emergence should establishment can be prevented or re­ serted into the soil. Mites were prevented ensure seedling protection for up to five tarded by earth mites and productivity of from escaping by a ring of polybutene weeks with rainfall or longer if little rain established pasture is substantially re­ sticky material smeared on the inside of occurs. Data from pot trials ind icate duced by large populations (Nicholas and the tubes. endosulfan and methidathion at 1(X)O rnL Hardy 1976). An estimated 1000 mites (calculated by ha-I remain effective against H. destructor The successful establishment of winter weighing three replicates of 1000 adult H. for up to five months if not exposed to crops such as lupins or ca nola is difficult destructor and using the mea n weight) rain (James and O'Maliey, unpublished in the presence ,of large earth mite were placed in each tube and three tube observations). The relatively rainfast na­ populations. Current insecticide treat­ replica tes were used on each plot. A small ture of endosulfan and methidathion on ments for H. destn,ctor (e.g., omethoate, leaf of Echimn plantagineum (L) soil is particularly important and pre­ methidathion, aZinphos-ethyl) are effec­ (Paterson's curse) was put into each tube vents the need for additional treatments tive in vegetated situations but perform as food for the mites. Mites were obtained after rain. With current chemical recom­ poorly when applied to the largely bare from weeds and pasture in the Vanco dis­ menda tions for ea rth mite control in earth co nditions of an emerging crop. trict, stored at SoC and used within 48 h of emerging winter crops, multiple spray These compounds have high initial toxic­ collec tion. Mites were introduced to the applications are often necessary particu­ ity to H. destructor (James 1987) but de­ plots after treatment at intervals of 6-14 d larly under showery conditions. grade rapidly on soil and provide little for a period of up to 49 d. Introductions The protection periods estimated in this residual protection. Consequently, a se­ were not made during rainy weather and study for each treatment are considered ries of insecticide applications are often successive releases were made at different to be conservative. In most instances good necessary to protect an emerging crop for locations within plots. Mortality of intro­ control (>80%) was achieved for a up to five weeks following germination. duced mites was assessed in situ after 48 h number of days following the breakdown The occurrence of ra infall foll owing and the presence of live mites signalled of 100% control. In addition, since mite spraying further reduces insecticide effi­ the end of the efficacy period for a treat­ introductions were made at intervals of cacy and exacerbates the problem. ment. Rainfall was measured at the trial 6-14 d, some lack of precision in deter­ This study was conducted to find a bare site. Data were subjected to Analysis of mining protection periods was inevitable. earth insecticide treatment which would Variance and LSD procedures. If a treatment was successful at6d but not provide residual control of H. destrudor 12 d, the effec tive protection period was for up to five weeks following applica­ Results considered ended at 6 d but may have ex­ tion. Three of the six insecticides exa mined tended to 10 d . In this regard it is impor­ (endosulfan, methid athion, tefluthrin) tant to note that although chlorpyrifos Materials and methods provided residual control of H. destructor was ineffective after 12 d in Trial 4, it Six insecticides were evaluated as bare on bare ea rth for 17-36 d (Figure I). probably had some activity within this ea rth treatments for H. destructor Omethoate controlled H. destructor for up period. The persistence of omethoa te (ll (endosulfan (35% ec), methidathion (40% to 11 d but phosmet and chlorpyrifos were d) in Trial 2 was aided by low rainfall (3.3 ec), omethoate (58% eel, phosmet (15% ineffective after 6 and 12 d, respectively. mm). Other work has indicated this com- Plant Protection Quarterly Vo1.7(l) 1992 11

I I 8< ~ w .J • I ~ ~ i g~ i ~ ~ • ~ ~ 25

A B C E K A B C 0 E F

TRIAL 4

0: ! I 0 0 , 0 • w• I ffi I • • i i ~ I• ~ I• ~ ~

ABC 0 E G H J ABC 0 E J K l M TREATMENT TREATMENT Figure. 1. The effect of bare earth insecticide treatments on residual mortality of H. destn/ctar. Horizontal lines 1 indicate times at which mites were introduced to the plots following spraying_ (A endosulfan 2000 mL ha- , B I I I I endosulfan 1000 mL ha- , C endosulfan 500 mL ha- , D methidathion 2000 mL ha- , E methidathion 1000 mL ha- , F I I I methidathion 500 mL ha- , G tefluthrin 500 mL ha- , H tefluthrin 300 mL ha- , I omethoate 1000 mL ha-', J omethoate I 1 150 mL ha-', K phosmet 1000 mL ha-" L chlorpyrifos 1000 mL ha- , M chlorpyrifos 300 mL ha- _ pound is very susceptible to wash off by New South Wales and is therefore the CN.E. (1986). Tefluthrin - a novel rain on bare earth (James and O'MaUey, most economic bare earth trea tment for pyrethroid soil insecticide. Proceedings unpublished observations.) H. destructor. Endosulfan bare earth of the 1986 British Crop Protection Con­ Methidathion is recommended at a rate sprays were used for the first time in 1990 ference - Pests and Diseases 2B-2, 97- of 90 mL ha-I for use against H. destructor in Southern New South Wales to protect 106. on pasture and a variety of winter crops establishing canola crops. Application of Nicholas, DA and Hardy, D.L (1976). (Goodyer 1991). In recent years a higher either 500 or 1000 mL haol at crop emer­ Redlegged earth mite cuts pasture pro­ rate of 200 rnL ha·1 has been recom­ gence resulted in excellent establishment duction. !oumal of Agricllitllre - Westem mended for the control of H. des tructor on of all monitored crops (James and Australia 17,33-4. bare earth following some early data col­ O'Malley, unpublished observations). Wright, WE (1965) . Carbamate and lected by this laboratory (James, unpub­ organophosphorus sprays as alterna­ lished observations). This rate and the 500 Ackllowledgments tives to DDT to control red legged earth mL ha-I rate used in Trial 3 d o not with­ Thanks are extended to Merv Graham for mites (Hnlotydells destructor and stand more than 10 mm of rain without his assistance in the conduct of these tri­ Pentltalells major) . Australian !oumal of losing effect (James and O'Malley, un­ als. This work was partially funded by the Experimental Agriculture and Animal published observations). However, Oilseeds Research Council. Hllsballdry 5,68-74. methidathion applied at 1000 or 2000 mL ha-I dearly resists the leaching effect of References rain for 3-4 weeks. Tefluthrin is a new Goodyer, G.j. (199/). Insect control in synthetic pyrethroid with good activity winter crops 1991. NSW Agriculture against soil insects (Jutsum et aI., 1986). and Fisheries Publication: Agdex 100/ The rates used in this study (300-500 mL 614. I ha - ) provided control for about three Hely, P.C, Pasfield, G_and Gellatley, j.G. weeks. Higher rates may extend this pro­ (1982). 'Insect pests of fruit and vegeta­ tection period but would have little prac­ bles in New South Wales'. (lnkata Press, tical va lue given the current high cost of Melbourne) this compound. james, D.G. (1987). Toxicity of pesticides Unlike methidathion the 500 mL rates to the redlegged ea rth mite, Halotydells of tefluthrin and endosulfan remained ef­ destnlctor. Plant Protection Quarterly 2, fective after rainfall. Endosulfan is cur­ 156-7. rently half the cost of methidathion in Jutsum, A.R., Gordon, R.F.S. and Ruscoe,