Unsprayed Plot Research Articles

Perturbation of Regulated Apple Mites: Immigration and Pesticide Effects on Outbreaks of Panonychus ulmi and Associated Mites (Acari: Tetranychidae, Eriophyidae, Phytoseiidae and Stigmaeidae)

To assess the impact of disturbances on mite populations being regulated at low densities, the phytophagous mites Panonychus ulmi (Koch), Eotetranychus sp., Bryobia rubrioculus Scheuten, and Aculus schlechtendali Nalepa and the predaceous mites Zetzellia mali (Ewing), Amblyseius andersoni Chant, and Typhlodromus pyri Scheuten were sampled during 1996–1997 in 5 apple plots treated with azinphosmethyl (OP) (2 plots), OP + endosulfan (E) (1 plot), or were unsprayed (2 plots) in 1993–1995. P. ulmi had been regulated at very low, but differing densities by predators (OP + E > OP > unsprayed) and the numbers of predator species present were OP + E (1 species), OP (2 species), and unsprayed (3 species) during 1993–1995. During 1996–1997, plots were treated just as in 1993–1995, except that 10 of 20 trees per plot had 150–200 P. ulmi released per tree and all 20 trees of 1 OP and 1 unsprayed plot had esfenvalerate sprayed early in 1996. We expected the peak densities of P. ulmi in 1996–1997 to reflect the earlier densities and the diversities of predators present. Lowest peaks and the shortest outbreaks of P. ulmi in 1996–1997 were expected in the unsprayed plots with 3 predator species and the fewest P. ulmi in 1993–1995; highest peaks and longest outbreaks were expected in the OP + E plot with 1 predator species and the most P. ulmi in 1993–1995. Densities in 1996–1997 supported these expectations, but with strong pesticide effects. With no esfenvalerate use, regulation of P. ulmi was as in 1993–1995, but P. ulmi was 10- to 1,000-fold denser with use of esfenvalerate. With esfenvalerate use and release of P. ulmi , they were most dense in year 1 after treatments and the outbreak lasted 2 yr before predators recovered; with esfenvalerate use and no release of P. ulmi , they were the most dense in year 2 and the oubreak lasted only 1 yr. Outbreaks of A. schlechtendali and B. rubrioculus also occurred in year 2 after esfenvalerate use.

Efficacy and Economics of Management Strategies to Control Anthracnose Fruit Rot in Processing Tomatoes in the Midwest.

Anthracnose (Colletotrichum coccodes) is the major fungal disease affecting processing tomato fruit in the midwestern United States. Currently available disease management strategies evaluated for controlling anthracnose fruit rot (AFR) on processing tomatoes include genetic resistance and the fungicide chlorothalonil applied according to conventional schedules or a disease-forecasting system (Tom-Cast). Experimental field plots were established in West Lafayette, Indiana, and East Lansing, Michigan, in 1993 to 1995. Chlorothalonil was applied every 7, 10, or 14 days or according to Tom-Cast with a threshold of 20 disease severity values, and was not applied to the control. In Michigan, Phytophthora infestans (1993) and C. coccodes (1993 to 1994) caused 91.8% (1993) and 30.7% (1994) fruit rot in the unsprayed plot. In Indiana, C. coccodes caused 69.8% (1993) and 39.0% (1994) AFR in the unsprayed plot. In 1995, Ohio 8245 (Michigan and Indiana), considered to be less prone to anthracnose, and Ohio 7814 were integrated into the conventional and Tom-Cast-prompted spray programs. Cultivar did not affect the incidence of AFR or foliar blight caused by Septoria lycopersici and Alternaria solani in either location. In 1993 and 1994, chlorothalonil applied at 10-day intervals in Indiana resulted in the highest benefit per hectare (BPH) and return per fungicide dollar (RPFD). In 1995, the highest BPH and RPFD resulted from chlorothalonil applied every 14 days to Ohio 8245 (Michigan). Chlorothalonil applied according to the Tom-Cast program resulted in a level of AFR that was generally not statistically different from the 7-day treatment but was high enough to result in crop rejection and high economic loss in 2 of the 3 years the study was conducted. Based on data from this study, it is not commercially feasible to grow processing tomatoes in Michigan and Indiana without chlorothalonil to protect against AFR even when a resistant cultivar is used.

Local density responses of predatory insects of Helicoverpa spp. to a newly developed food supplement 'Envirofeast' in commercial cotton in Australia

Application of supplementary foods to attract, retain and conserve beneficial arthropods in crop systems has been used for several years on crop plants to enhance biological control of pests. The responses of predatory insects of Helicoverpa spp. to sugar and to a mixture of petroleum oil and Kelgum and newly developed food products, Envirofeast and Envirofeast B, were investigated at a commercial, irrigated cotton farm at Auscott in Narrabri in New South Wales from 1992- 94. Individual plots received 8 fortnightly applications of each substance dissolved in water and were compared with a synthetic insecticide-treated and an unsprayed plot. Adult Coccinellidae, Melyridae, Lygaeidae, Nabidae and Chrysopidae responded more positively and numbers increased more throughout the study on plots sprayed with Envirofeast A than all other treatments. In the present of Envirofeast A the predatory insects failed to respond consistently or clearly to either sucrose or a protein supplement spray used in Envirofeast B. The conventional insecticides virtually exterminated the predatory insects. In another experiment in which predatory insects were sampled at varying distances away from the Envirofeast A sprayed and unsprayed plots, predatory insects (but not spiders) were concentrated around the food sprayed plot. This study supports the findings of previous researchers that application of supplementary food can attract and concentrate entomophagous arthropods to enhance biological control of crop pests.

Response ofHelicoverpa spp. (Lep.: Noctuidae) and their natural enemies to petroleum spray oil in cotton in Australia

Refined petroleum products have been used since last century for the control of phytophagous arthropod pests. The response ofHelicoverpa spp. and its natural enemies to petroleum oil sprays on cotton was investigated under laboratory choice/no-choice and small plot field conditions at the Australian Cotton Research Institute at Narrabri in New South Wales. In oviposition choice and no-choice tests, petroleum oil sprays suppressed oviposition inHelicoverpa punctigera (Wallengren) but notH. armigera (Hubner) (Lepidoptera: Noctuidae).H. punctigera females laid about seven times as many eggs on the control (water sprayed) cotton plants as on either petroleum oil spray alone or oil mixed with Kelgum. HoweverH. armigera females laid the same number of eggs on both treated and control plants. In field trials, the number of eggs per metre per sample date found on the plots treated with petroleum oil spray was 3.83 compared with 6.29 and 7.82 eggs respectively on plots treated with conventional insecticide sprays and the unsprayed plots. The number of larvae found on plots treated with petroleum oil sprays was 2.9 times higher than the conventional insecticide sprayed plot, however, this was 1.6 times fewer than the unsprayed plot. The cotton yields from plots treated with petroleum oil sprays was 3.70 bales/ha compared with 7.32 and 2.69 bales respectively from the conventional insecticide treated and the unsprayed plots. Petroleum oil sprays had little or no effect on predatory beetles, bugs, lacewings and spiders.

A Food Web Approach to Evaluating the Effect of Insecticide Spraying on Insect Pest Population Dynamics in a Philippine Irrigated Rice Ecosystem

Summary 1. Data from a 645-taxa Philippines-wide food web and multiple regression models were used to predict population fluctuations of insect pests in a rice field. Independent variables of pest models included the biomass of rice plants in the field, the abundance of each pest, and the abundances of five highly correlated enemies of the pest, all as functions of time. 2. To test the ability of the models to reveal effects of insecticide spraying, a rice field at the International Rice Research Institute (IRRI) in the Philippines was divided into deltamethrin-sprayed and unsprayed plots. Data on the abundance of seven pest species (Nephotettix virescens, Recilia dorsalis, Sogatella furcifera, Nilaparvata lugens, Hydrellia philippina, Ne. nigropictus and Cofana spectra) and their natural enemies (predators and parasitoids) were collected during the dry season of 1990. 3. Spraying insecticide disorganized the population dynamics of insect species feeding in the IRRI field. Multiple regression models were less able in the sprayed plot than in the unsprayed plot to forecast the population fluctuations of pest species on the basis of various numbers and combinations of independent variables. For example, current pest abundance, by itself, was a significant predictor of future pest abundance for four of the seven pests (Ne. virescens, R. dorsalis, S. furcifera, H. philippina) in the unsprayed plot, but significant fits were found for only two pests (R. dorsalis, H. philippina) in the insecticide-sprayed plot. 4. In the unsprayed plot, independent variables were significant predictors of future pest abundance in four of seven initial models compared to one of seven models in the sprayed plot. Step-wise removal of independent variables in the models enhanced their forecasting power in both the sprayed and unsprayed plots, but significant models in the unsprayed plot nearly always outnumbered those in the sprayed plot. 5. In the unsprayed plot, Ne. virescens retained five of seven independent variables as significant predictors, compared to four for S. furcifera, three for C. spectra, and one for the remaining four pests. Classical models that contain one or two species as independent variables may not be sufficient to forecast future abundances of some Philippine rice pests in unsprayed and sprayed plots. 6. In general, models that included interaction terms and either the presence or absence of sprays among the independent variables did not improve the forecasting power of models in either the sprayed or unsprayed plot. 7. The methods developed here for studying the impact of spraying on the organization of arthropod communities in rice fields could be applied to other interventions

Sub‐lethal effects of deltamethrin residues on the within‐crop behaviour and distribution of Coccinella septempunctata

AbstractThe behaviour and distribution of adult Coccinella septempunctata L. (Coleoptera: Coccinellidae) were recorded in two plots of winter wheat infested with the cereal aphids Sitobion avenae (F.) and Metopolophium dirhodum (Walk.) (Homoptera: Aphididae). One plot was sprayed with the pyrethroid insecticide deltamethrin at a rate of 6.25 g a.i./ha and the other was left unsprayed. Single ladybird beetles were released sequentially on the ground at the centre of the sprayed and unsprayed plots and their behaviour and position in the crop canopy were recorded at 30 second intervals for a total of 15 min per beetle. Assessments, with fresh beetles, continued for four days after spray application with a total of eighty ladybird beetles observed. The 15 min period was selected to avoid lethal effects and no ladybird beetles were killed or knocked down as a result of exposure to deltamethrin residues during this period. Significant differences were found between the overall behaviour patterns of C. septempunctata in the untreated and deltamethrin treated plots up to three days after the spray application. Ladybird beetles exposed to deltamethrin residues were observed to walk and groom significantly more frequently and to rest significantly less frequently than those in the unsprayed plot. Significant differences were also found between the observed distribution of ladybird beetles in the sprayed and unsprayed crop canopies, with higher numbers of observations towards the bottom of the crop canopy and on the ground in the deltamethrin treated plot than in the untreated plot during the first two days after deltamethrin application. Upon the foliage itself, ladybird beetles were observed significantly more frequently on the abaxial leaf surface in the deltamethrin treated crop compared with the untreated crop. The results are discussed in terms of possible evidence for the repellency of deltamethrin to C. septempunctata and also the implications for integrated pest management of changes in predator behaviour and crop distribution resulting from sub‐lethal uptake of insecticides.

Validation of 'Downcast' in the prediction of sporulation-infection periods of Peronospora destructor in the Lockyer Valley.

The disease forecasting system 'Downcast' was developed in Canada to indicate sporulation-infection periods of Peronospora destructor (Berk.) Caspary in onions. During 1989, observations were made of downy mildew development in trap plants and of disease progress in an unsprayed plot of onions in the Lockyer Valley, Queensland, and related back to predicted sporulation-infection periods using the forecaster. Over 113 days, there were 20 days when sporulation and infection were predicted, and of these 14 occurred during 4 weeks in July and August. Of 16 groups of trap plants exposed in the field, each for 7 days, 7 were subjected to predicted sporulation-infection periods. Two predicted sporulation-infection periods early in the season did not result in infection of trap plants or of plants in the field plot, probably due to absence of inoculum. Subsequently, groups of trap plants exposed in the field during predicted sporulation-infection periods became infected while those exposed when weather was unsuitable remained healthy. 'Downcast' shows promise as a technique for more effective management of disease caused by Peronospora destructor.

POPULATION GROWTH OF THE PEA APHID, ACYRTHOSIPHON PISUM (HARRIS) (HOMOPTERA: APHIDIDAE), AND PLANT RESPONSE TO APHID NUMBERS IN COMMERCIALLY GROWN FIELD PEAS IN MANITOBA

AbstractPea aphids, Acyrthosiphon pisum (Harris), were sampled weekly or biweekly over the summers of 1985 and 1986 in a total of 15 commercial plantings of Century, Trapper, or Triumph field peas across Manitoba. Pea aphid populations rose more quickly in fields of Trapper than in Century or Triumph fields. The owners of all Trapper fields sampled initiated aerial application of insecticide for pea aphid control; at the time of spraying in 1985, plants in Trapper fields had significantly greater numbers of aphids in sweep samples than such samples from Century or Triumph fields. In 1986, Triumph plants supported greater numbers of aphids than Century or Trapper plants. Triumph plants remained green longer than plants of the other cultivais; in 1985 pea aphid numbers on this cultivar were highest on the last date sampled.Yield components were measured in sprayed and unsprayed plots within the commercial fields. When data were averaged for each cultivar, there were no significant differences in yield per area or in 1000 seed weight between sprayed and unsprayed plots. Data indicated that existing economic thresholds are too low for Trapper peas. However, one of the fields of Trapper peas that we sampled had significantly reduced numbers of pods per plant, yield per square metre, and weight of 1000 seeds in the unsprayed plot; this field had the largest population of pea aphids of any field sampled, with aphid numbers peaking at 48.5 ± 9.2 (SE) per plant lip during pod formation and filling. Significant yield losses also occurred in unsprayed plots of a Triumph field, which had a peak aphid population of 4.8 ± 1.6 per plant stem at pod maturation.

Effect of pesticides on spiders occurring on apple and citrus in Israel

Field experiments in an apple orchard and in a citrus grove were carried out to evaluate the effect of four commercial pesticides in common use in Israel against apple and citrus pests, on the spider populations inhabiting the trees. The spider populations on apple were markedly suppressed by the pesticides, the order of toxicity being Talstar (biphenate) >Mavrik (fluvalinate) > Smash (fenpropathrin) > Dursban (chlorpyrifos). When grapefruit trees were treated with carbaryl + formothion, 232 spiders were sampled in the unsprayed plot, 55 days after treatment, as compared with only 11 spiders in the treated plot. Two and 7 days after treatment with chlorobenzilate, the sample from the treated plot numbered 68 and 55 spiders, respectively, as compared with 50 spiders collected 24 h before treatment. In addition, laboratory tests were carried out to determine the susceptibility of the spiderChiracanthium mildei L. Koch to 17 pesticides. When the spiders were exposed to grapefruit leaves which had been dipped 1 h previously for 5 sec in the aqueous emulsions of the pesticides, chlorpyrifos, fenpropathrin, fenvalerate, phosphamidon and biphenate caused 100%, and cypermethrin and fluvalinate 60% mortality, whereas all the other pesticides tested - acaricides, fungicides and herbicides - caused about 10-40% mortality.

Pesticide use on cereal crops and changes in the abundance of butterflies on arable farmland in England

A survey of butterfly numbers on two plots of arable farmland in southern England in 1984 was carried out using the transect method of Pollard et al. (1975). On one plot the field edges were left unsprayed with pesticides (herbicides, fungicides and insecticides) from 1 January and on the other all fields were fully sprayed in accordance with normal farming practice. Sprayed and unsprayed transect sections were paired up according to adjacent field boundary habitat type. A total of 868 butterflies were recorded on the unsprayed plot compared to 297 on the sprayed plot. Of the 17 species recorded on more than one survey section, 13 were significantly more abundant on the unsprayed treatment. Butterfly species whose larval host plants occurred in unsprayed field edges showed slightly larger differences in number between treatments than species less able to breed in weedy cereal crops. The results suggest that pesticide use on cereal crops may reduce butterfly numbers and that arable farmland is a habitat in need of further study for butterfly conservation.

Relating disease progress to cumulative numbers of trapped spores: apple powdery mildew and scab epidemics in sprayed and unsprayed orchard plots

A technique for relating the progress of plant diseases caused by airborne fungal pathogens to cumulative numbers of trapped spores is proposed. The relationship involves two epidemiological parameters—a disease asymptote and the infection efficiency (disease units/spore) of inoculum. The technique was evaluated using data on apple powdery mildew and scab epidemics in sprayed and unsprayed apple orchard plots. For powdery mildew, the observed relationships were close to those proposed in the unsprayed plot, but changed after or during the period of fungicide application in sprayed plots. Parameter estimates gave useful comparative information on the epidemics. The technique was not useful for scab because of the discontinuous patterns of infection.

MBC‐resistente Freilandpopulationen von Pseudocercosporella herpotrichoides in langjährigem Überwachungsversuch

Abstract MBC resistant field populations of Pseudocercosporella herpotrichoides in a long‐term monitoring experiment In, long‐term field experiment, since 1975/1976 winter whaet was grown continuously for eight years. One half of the 1‐ha field was sprayed once a year with carhendazim against eyespot (Pseudocercosporella, herpotrichoides); another application of MBC/TBZ was, after heading. From 1978/1979 seed was treated with MBC also. The other half of the field remained untreated all the time. During the first five years, in the sprayed plot the relative proportion of MBC‐resistant conidia increased steadily, but on a very low level only. During the next three years, however, there was a sharp increase in the level of MBC‐resistance in the sprayed plot. — In the unsprayed plot, at the end of the eight year period the level of MBC‐resistance in the field population of the fungus still was low.

The Effect of Insect Fauna on Growth Mortality and Natality of Broom, Sarothamnus scoparius

Two plots, each of 240 broom, Sarothamnus scoparius seedlings were planted in March 1966. For 11 years, one plot was sprayed 1-3 times a year with a mixture of dimethoate and malathion; the second plot remained untreated. The aim was to reduce the insect fauna and to gauge its impact on the growth, mortality and natality of the broom bushes. The insect fauna was estimated three times per year between 19661968, twice in 1969 and once per year during 1970-1976. Colonization of the plots was rapid and larger populations of insects developed in the unsprayed plot. The unsprayed bushes did not attain full growth; their mortality rate was higher and natality rate lower compared with the sprayed bushes. Aphids and psyllids in particular, aided by Leucoptera spartifoliella, Miridae and Phytodecta olivacea reduced the vigour of the broom bushes. The seed yield of unsprayed broom over the average 10 year life span of a bush was also reduced by 75%.

Economic Management of Late Blight (<i>Phytophthora infestans</i> L.) of Potato in Eastern Tarai of Nepal

Field experiments were carried out at Regional Agriculture Research Station, Tarahara in threeconsecutive years (1997-2000) during winter season to know the economic sprays of differentfungicides to manage late blight disease of potato. Late blight susceptible cultivar of potatoKufri Sindhuri was used for the experiment. Krinoxyl gold (metalaxyl 8% and mancozeb 64%)at the rate of 1.5 g/l, Dithane M- 45 (mancozeb 75%) @ 0.3% and Bordeaux mixture @ 10 gcopper sulfate and 10 g lime/l of water and their different combinations were tested inrandomized complete block design with three replications. Terminal disease severity was thehighest (7.9) on 0-9 scale disease rating in unsprayed check and it was significantly higher thanthose of other fungicides sprays. Plots with three sprays of Dithane M- 45 @ 0.3% recorded thelowest (2.4) terminal disease severity. Disease development was the fastest in the unsprayed plotcompared to all other treatments. Similarly apparent infection rate was the highest in unsprayedtreatment. Area Under the Disease Progress Curve was also the highest in unsprayed plot and itwas significantly higher than those of other treatments. Tuber yield was the lowest (3.93 kg/4.5m2 plot in unsprayed and the highest (6.08 kg), in the plot receiving four sprays of Dithane M-45@ 0.3 % and this was at par with the tuber yield of plots receiving two and three sprays ofDithane M-45. Benefit cost ratio was the highest (1.54) in case of two sprays of Dithane M-45@ 0.3% at 10 days intervals. All others fungicide spays were uneconomical under Eastern Taraicondition.Key words: Eastern Tarai; economic spray; Dithane M-45; late blight management; potatoDOI: 10.3126/narj.v6i0.3365Nepal Agriculture Research Journal Vol.6 2005 pp.57-61

Adverse Effects on Birds of Phosphamidon Applied to a Montana Forest

A field trial of Phosphamidon applied by aircraft in Montana against spruce budworm (Choristoneura fumiferana) had immediate adverse effects on birds. A 5,000-acre block of forested land was sprayed at the rate of 1 pound per acre. Some birds, including blue grouse (Dendragapus obscurus), were killed by the insecticide. Bird activity on the sprayed plot dropped to about one-quarter of the prespray level of activity while it increased on an unsprayed plot. Two sick blue grouse were caught by hand and held in captivity; one died and the other recovered. Analysis of grouse blood samples showed a marked inhibition of cholinesterase activity in the sick birds, followed by return of cholinesterase to normal in the surviving bird. The spruce budworm continues to be one of the most destructive forest insects in North America (U. S. Forest Service 1964:2), and is the object of large-scale aerial spraying. Although DDT has long been the standard insecticide for use against this pest, its hazard to fish (Cope 1961) and the high residues accumulated in the tissues of big game animals from treated forests (Pillmore and Finley 1963) have aroused growing concern. In 1963, the U. S. Forest Service tested several short-lived insecticide formulations of the organophosphate group against the spruce budworm in hopes of finding an effective replacement for DDT. Phosphamidon (2-chloro-2-diethylcarbamoyl-1methylvinyl dimethyl phosphate) was an attractive candidate material because it has a much lower toxicity to fish than DDT and a relatively short residual life. The commercial distributor's assessment of Phosphamidon's possible hazard to wildlife was highly optimistic (Dever and Wessel 1962). Feeding tests at the Patuxent Wildlife Research Center indicated a high toxicity to bobwhite quail (Colinus virginianus) but a much lower toxicity to ring-necked pheasants (Phasianus colchicus) and mallards (Anas platyrhynchos) (DeWitt et al. 1963:88). A field trial of Phosphamidon was conducted on 5,000 acres of Douglas fir (Pseudotsuga menziesii) forest in western Montana in order to test its effectiveness against the spruce budworm and to evaluate its possible hazard to wildlife, particularly birds. Personnel of the U. S. Forest Service, the U. S. Bureau of Sport Fisheries and Wildlife, and the Montana Department of Fish and Game participated in the study. This content downloaded from 207.46.13.176 on Mon, 20 Jun 2016 07:29:48 UTC All use subject to http://about.jstor.org/terms EFFECTS OF PHOSPHAMIDON ON BIRDS * Finley, Jr. 581 I am grateful to Tom T. Terrell, U. S. Forest Service entomologist and Phosphamidon project coordinator, for technical information and help on numerous occasions. The advice and aid of David Scott and Merle Gee in planning the study are much appreciated. Merle L. Richmond's assistance with all phases of the fieldwork was indispensable to the success of the study. Dr. Robert Eng, Thomas Mussehl, Philip South, and Wesley Woodgerd assisted in searches for grouse after the spray application. Robert Greene, manager of the State Game Farm at Warmsprings, kept captive grouse from the study area and took some of the grouse blood samples required. Measurements of blood cholinesterase were made by Charles W. Hall, chemist, of the Denver Wildlife Research Center.

Control of Pecan Nut Casebearer

A review of current literature shows that great progress has been made in the control of pecan insects by the use of insecticides during the past two decades. For example, prior to 1945, the recommended control measure for the pecan nut casebearer Acrobasis caryac Grote, was 13 fluid ounces of 406X0 nicotine sulfate plus 2 quarts summer oil emulsion per 100 gallons water. In 1962 pecan growers had a choice of five different insecticides that were recommended for the control of the nut casebearer. These insecticides were: DDT, EPN, Guthion, malathion and parathion. Each of these materials is much more effective in controlling the nut casebearer than the formerly recommended nicotine sulfate plus oil. Although the above recommended insecticides give effective control of the nut casebearer on pecans as recommended, some materials are expensive and would not be economical to use on a large scale. Work is being continued with these insecticides in an effort to determine whether the amount of material recommended can be reduced, without reducing the effectiveness. Studies are also being made to determine whether the more costly materials can be combined with a less expensive material in such a manner that when applied the spray will be more economical for the grower, yet still give effective control of the casebearer. In the spring of 1962, malathion, parathion and combinations of malathion plus DDT and parathion plus DDT were used in two separate experiments to evaluate and compare their effectiveness as a control for the nut casebearer. In one of these experiments, south of Lloyd, Florida, preliminary tests were also made with four new materials to determine their effectiveness as a control for the first generation nut casebearer larvae. Parathion, malathion, Thiodan, Bayer 37344, Bayer 44646, Ethyl-Methyl Guthion and combinations of parathion plus DDT and malathion plus DDT were applied one time to single tree plots. All treatments were used as sprays and applied with a hydraulic sprayer (Bean Royal 35 MT). Plots were randomized within each block, and blocks were replicated seven times. An unsprayed plot was used as a control. (See Table 1 for formulations and concentrations used.) The second experiment was set up at the Simpson Nursery Company orchard at Monticello to check the effectiveness of malathion and parathion alone and in combination with DDT as used in the first test. The plot design and method of application used in this test were the same as that used in the Lloyd experiment, except plots were replicated only six times. (See Table 2.) The rieasons for using the malathion plus DDT and parathion plus DDT combinations in these separate tests were to evaluate their effectiveness in controlling the nut casebearer, as compared to the malathion and parathion sprays used in the present recommendations for control and to determine whether the malathion plus DDT and parathion plus DDT combinations would cause a build up in aphid and mite populations.