Foliar Insecticide Treatments Research Articles

Insecticide Use in Bt and Non-Bt Field Corn in the Western Corn Belt: As Reported by Crop Consultants in a Mail Survey

The use of foliar insecticides to control arthropod pests in corn is reported to be more extensive in the western high plains (western Kansas and Nebraska and bordering areas) than in the Midwest corn belt. Recently, the extent of insecticide use has become an important matter because the U.S. Environmental Protection Agency (EPA) has implemented the high-dose–refuge strategy for insect resistance management (IRM) to delay the development of resistance to transgenic corn in the European corn borer, Ostrinia nubilalis (Hubner). The use of foliar insecticide applications could reduce the effectiveness of the refuge for the IRM strategy. To get better data on this matter, we developed a crop consultant survey to collect information on insecticide use on Bt and non-Bt corn in Kansas and Nebraska. Data were compiled according to three agronomic regions within these two states based on different agricultural practices and insect complexes (southwest, west, and east). The consultants reported that during the early-whorl stage, relatively few corn acres were treated with foliar insecticides (≤14.2%) in any of the three regions, and the trends suggested that non-Bt corn received slightly more insecticide than did Bt corn. The consultants also reported that during late-whorl stage, the dryland corn acres also received fewer foliar insecticide treatments (≤12.4%) and again, non-Bt corn received slightly more treatment than did Bt corn. However, the consultants reported that during the late-whorl stage, irrigated corn received considerable foliar insecticide treatment, particularly in the southwest region: 66% in the non-Bt corn and 40% in the Bt corn. They also reported that 34% and 31% of these treated acreages received two treatments for pests, such as southwestern corn borer, Diatraea grandiosella Dyar, and spider mites, Tetranychidae (which are not as important in the other regions), in addition to treatments for European corn borers and western corn rootworm, Diabrotica virgifera virgifera LeConte (which are present in all three regions). The difference in insecticide use between non-Bt and Bt corn was 26, 6, and 19% in the southwest, west, and east regions (respectively) during 2002, and 20, 12, and 12% in the respective regions during the previous 5 yr. This level of treatment differential between Bt and non-Bt could potentially reduce the time to resistance in the European corn borer from 30 yr to 18 yr based on modeling projections with similar assumptions. These data also document that the use of insecticides is lower in Bt corn than in non-Bt corn, making this one of the first surveys to document a reduction in the use of foliar insecticides in Bt corn as compared with non-Bt corn.

Evaluation of Foliar Treatments for Potato Leafhopper on Alfalfa, 1997

Abstract A study to evaluate the efficacy of 9 foliar insecticide treatments to control PLH was conducted on the second cutting of alfalfa at the OARDC Western Branch Station near South Charleston, OH. Plots were 20 X 50 ft with four replications in a RCBD. Treatments were applied 25 Jul with a custom-built sprayer having a boom length of 10 ft and TeeJet 8002 nozzles spaced at 15-inch intervals. The system was calibrated to deliver 25 gpa at 35 psi at a tractor speed of 3 mph. Abundance of PLH adults and nymphs were estimated prior to treatment and at 7, 14, and 20 DAT by taking 10 pendulum sweeps per plot. Alfalfa stand heights were recorded prior to treatment and at 20 DAT to determine stand growth per treatment

Controlling Tobacco Aphids on Flue-Cured Tobacco, 1996

Abstract Flue-cured tobacco, variety K-326, was transplanted on 10 Apr at the Georgia Coastal Plain Experiment Station Bowen Farm. Production practices were used according to Georgia Cooperative Extension Service guidelines and included a preplant tank mixture of Tillam and Devrinol for weed control, Ridomil for blue mold control, and Nemacur for nematode suppression. Fertilizer (6-6-18) was applied in a split application at a rate of 1000 pounds of acre. Plots 2 rows wide (44-inch row spacing) by 20 ft long were arranged in a RCBD with 4 replications. Plots were separated on each side with one fallow border row and on each end with a 6 ft wide alley. Two Orthene attransplant treatments were applied in the transplant water at transplanting. On 30 May, 9 foliar insecticide treatments were applied using a CO2-powered backpack sprayer equipped with three TX-12 nozzles directed over a single row, delivering 24.5 gpa at 40 psi. The number of live aphids on plants 2, 4 and 6 of the second row was recorded from each plot prior to treatment (Pre-t) and 4,7,14 and 21 days after treatment (DAT). Plants 2-11 on the second row were harvested on 21 Jun and cured weights determined by factoring out the moisture content. All data were subjected to analysis of variance and the means were separated using Duncan’s multiple range test (P = 0.05).

Tobacco Aphid Control in Flue-Cured Tobacco, 1996

Abstract Flue-cured tobacco, variety K-326, was transplanted on 11 Apr 1996 at the Georgia Coastal Plain Experiment Station Entomology Farm. Production practices were used according to Georgia Cooperative Extension Service guidelines and included a preplant tank mixture of Tillam and Devrinol for weed control, Ridomil for blue mold control, Lorsban for soil insect control, and Nemacur for nematode suppression. Fertilizer (6-6-18) was applied in a split application at a rate of 1000 pounds/acre. Plots two rows wide (36 inch row spacing) by 20 ft long were arranged in a randomized complete block design with four replications. Plots were separated on each side with one un-treated border row and on each end with an alley 6 ft wide. Two Orthene at transplant treatments were applied in the transplant water at transplanting. On 27 May, 4 foliar insecticide treatments were applied using a CO2-powered backpack sprayer equipped with 3 TX-12 nozzles directed over a single row, delivering 29.9 gpa at 40 psi. The number of live aphids on plants 2, 4 and 6 of the left hand row was recorded from each plot prior to treatment (Pre-t) and 4,7 and 14 days after treatment (DAT). All plants were harvested on 17 Jun and 25 Jun, then weighed. All data were subjected to analysis of variance and the means were separated using Duncan’s multiple range test (P = 0.05).

Control of Lepidopterous Insects on Cabbage, 1996

Abstract Fourteen foliar insecticide treatments were compared with an untreated check for control of insects on cabbage at the University of Tennessee Plateau Experiment Station, Crossville, TN. Fertilization consisted of 500 lb/A of 10-10-10 applied broadcast and disk incorporated 29 Apr. Greenhouse-grown plants were transplanted 29 Apr. Weed control consisted of Treflan at 0.75 lb Al/acre applied PPI on 29 Apr, cultivation on 20 May, and Lentogran at 0.9 lb Al/acre post emergence on 6 Jun. Treatment plots consisted of 3 rows, each row being 3 ft wide and 10 ft long with 10 plants. Fifteen treatments were arranged in a RCB design with 4 replications. CS 7 at 0.25% v/v was added to Aphistar and Confirm. Treatments were applied on 13, 20, 27 Jun, and 3 Jul using backpack carbon dioxide powered hand sprayers. Spray volume was 80 gpa of finished spray. Treatments were evaluated by rating the percent of foliage damage. Marketable yields were recorded 29 Jul.

Control of Squash Bug on Watermelon, 1996

Abstract Watermelon, ‘Sangria’, was direct seeded in May ‘96 at the Lane AREC, Lane. OK. The experimental design was a RCB with 4 replicates and 15 treatments. Plots were one bed wide, 9 ft, by 50 ft long with 10 ft alleys between plots Foliar insecticide treatments were applied with a tractor mounted sprayer that broadcast a 72 inch spray swath over the plots using 4 nozzles (TXVS261 delivering 41 gal/acre at 42 psi. Furadan and Admire were applied with a tractor mounted sprayer at planting. Plots were treated on 15 and 22 Aug. Squash bug populations were surveyed on 26 Aug by counting total number of bugs (adults and nymphs) in 0.5 sq yd area in each plot.

Evaluation of Foliar Treatments for Potato Leafhopper on Alfalfa, 1996

Abstract A study to evaluate the efficacy of 5 foliar insecticide treatments to control PLH was conducted on second cutting alfalfa at the OARDC Western Branch Station near South Charleston, OH. Plots were 30 X 50 ft with four replications in a RCBD. Treatments were applied 21 Jun with a custom built sprayer having a boom length of 15 ft and flat spray tip nozzles (TeeJet 8003VS) mounted at 15 inch intervals. The system was calibrated to deliver 25 gpa at 35 psi at a tractor speed of 3 mph. Abundance of PLH adults and nymphs was estimated prior to treatment and 7, 14 and 21 DAT by taking 10 pendulum sweeps per plot. Alfalfa stem length was recorded prior to treatment and at 21 DAT to determine stem growth per treatment. Dry weight yield was determined from harvest of two 3.5 ft X 50 ft swaths taken with a custom built plot harvester with a flail cutter.

Lmidacloprid Formulation and Soil Placement Effects on Colonization by Sweetpotato Whitefly (Homoptera: Aleyrodidae): Head Size and Incidence of Chlorosis in Lettuce

The effects of imidacloprid formulation and soil placement on colonization by sweetpotato whitefly, Bemisia tabaci (Gennadius), at 3 plant growth stages of lettuce, Lactuca sativa L., were evaluated in experimental and commercial lettuce plots in 1993–1994. We also evaluated the effects of imidacloprid treatments on yield response and incidence of chlorosis associated with sweetpotato whitefly control. Imidacloprid placement had a significant effect on sweetpotato whitefly colonization in lettuce throughout the experimental period. Sweetpotato whitefly densities on lettuce varied at each plant stage relative to depth of placement within the lettuce seed bed. Applications made to the soil surface and at 4.0-cm subseed furrow, followed by irrigation, provided the most consistent control of sweetpotato whitefly nymphs in small plots and in on-farm lettuce plots. These imidacloprid soil treatments also prevented reductions in head size and incidence of leaf chlorosis associated with sweetpotato whitefly colonization in lettuce. Our data suggest that incorporation of imidacloprid into the upper 3-4 cm of soil below the seed furrow is optimal for absorption and translocation by lettuce roots. Imidacloprid soil treatments may provide a more environmentally suitable and effective alternative to control of sweetpotato whiteflies in lettuce than is currently possible with foliar insecticide treatments.

Alfalfa Weevil Control In Ohio, 1995

Abstract A test to evaluate the efficacy of 4 foliar insecticide treatments for control of AW was conducted on first cutting alfalfa at the OARDC Western Branch Station near South Charleston. Plots were 30 X 50 ft with 4 replications in a RCBD. Treatments were applied on 13 May with a custom built sprayer having a boom length of 15 ft and flat spray tip nozzles (TeeJet 8003VS) mounted at 15 inch intervals. The system was calibrated to deliver 32.8 gpa at 30 psi at a tractor speed of 3.5 mph. Abundance of AW larvae was estimated prior to treatment and 3, 7 and 14 DAT by collecting 20 stems per plot, shaking the stem samples in a bucket, and counting the number of larvae collected in the bucket.

Alfalfa Weevil Control In Ohio, 1995

Abstract A test to evaluate the efficacy of 4 foliar insecticide treatments for control of AW was conducted on first cutting alfalfa at the OARDC Western Branch Station near South Charleston. Plots were 30 X 50 ft with 4 replications in a RCBD. Treatments were applied on 13 May with a custom built sprayer having a boom length of 15 ft and flat spray tip nozzles (TeeJet 8003VS) mounted at 15 inch intervals. The system was calibrated to deliver 32.8 gpa at 30 psi at a tractor speed of 3.5 mph. Abundance of AW larvae was estimated prior to treatment and 3, 7 and 14 DAT by collecting 20 stems per plot, shaking the stem samples in a bucket, and counting the number of larvae collected in the bucket.

Potato Leafhopper Control in Alfalfa, 1994

Abstract Five insecticides were evaluated for PLH control in a first yr stand of ‘Arrow’ alfalfa located in Montgomery Co., VA in 1994. Plots of 24 × 40 ft were arranged in a RCBD with four replications. A pre-treatment estimate of PLH density was made on 1 Jul. Counts of PLH were made from 4 sets of 10 pendulum sweeps of a 15 inch diam sweep net taken arbitrarily across the field. On 1 Jul, after completing the pre-treatment estimate, foliar insecticide treatments were applied using a CO2 backpack sprayer, delivering 20 gal per acre at 40 psi. Post-treatment estimates of combined PLH nymphs and adults per 10 sweeps were made in all plots on 5, 8, 12, 16, and 22 Jul. Alfalfa stem heights also were determined in all plots on 16 and 22 Jul. Treatment yields were determined at 12% bloom on 28 Jul from 60 ft2 swaths taken from each plot using a sickle-bar mower. Freshly mowed alfalfa was raked into a pile and weighed using a milk scale to determine the wet wt. A 2.2-lb subsample of alfalfa was removed from each plot and dried at 130 to 140°F for 48 h to determine percent dry matter. A two-way ANOVA with Fisher’s protected LSD was used to analyze differences among treatments in PLH sweep net counts (after [x + 0.5]1/2 transformation), stem ht, and dry matter yield for each sample date.

Experimental Foliar Treatments for Control of Tobacco Thrips in Peanut, 1993

Abstract Efficacy of foliar insecticide treatments was evaluated against TT injury in Virginia-type peanut in Suffolk, VA. Peanuts were planted 7 May with 36-inch row spacing. Foliar treatments were applied twice, at late ground cracking (LGC) about 4 wk after planting (2 Jun) and again at early postemergence (EPO) about 6 wk after planting (15 Jun). Treatments were applied as a 12-inch band over the row with a CO2-pressurized backpack sprayer calibrated to deliver 17 gal formulation per acre at 22 psi through one 8004E flat fan nozzle per row. A seed treatment (Hopper box) was included in 2 treatments. Product and seed was layered and gently mixed in the planter box just before planting. Aldicarb (Temik 15GF) was applied to 1 treatment into the seed furrow (IF) at planting as a standard for comparison. A RCBD was used with 4 replicates; plots were 4 rows × 40 ft. Metam-sodium (Vapam at 10 gal per acre) was applied to the entire test 2 wk before planting 6 to 8 inches below the soil surface with a single chisel shank centered in front of a Tilrowvator with Virginia-type bedshapers. Beds were 24 inches wide and 4 inches tall. Treatments were evaluated by determining plant injury based on a 0-10 scale where 0 = no TT injured leaves and 10 = 100 percent injured leaves. Yield was based on digging, combining, drying and weighing peanuts from the 2 center rows (80 row ft) of each plot. Data were analyzed using ANOVA and LSD procedures.

Experimental Foliar Treatments for Control of Tobacco Thrips in Peanut, 1992:

Abstract Efficacy of foliar insecticide treatments was evaluated against TT injury in Virginia-type peanut in Suffolk, VA. Peanuts were planted 4 May with 36-inch row spacing. Foliar treatments were applied 2 x, either broadcast at late ground cracking and again at early postemergence (broadcast, LGC + EPO), or banded at late ground cracking and again at early postemergence (band, LGC + EPO). The late ground cracking treatments were applied about 4 wk (2 Jun) after planting and the early postemergence treatments were applied about 7 wk (24 Jun) after planting. Broadcast treatments were applied with a CO2 pressurized backpack sprayer calibrated to deliver 20 gal/acre at 17 psi through 8003 VS flat fan nozzles spaced 18 inches apart on the spray boom. Band treatments were applied in a 12-inch band over the row with a CO2 pressurized backpack sprayer calibrated to deliver 17 gal/acre at 22 psi through 1,8004 E flat fan nozzle per row. A RCB experimental design was used with 4 replicates; plots were 4 rows by 35 ft. Treatments were evaluated by determining plant injury based on a 0-10 scale where 0 = no TT injured leaves and 10 = 100 percent injured leaves. Data were analyzed using ANOVA and LSD procedures.

Foliar Treatments for Control of Tobacco Thrips in Peanut, 1991

Abstract Efficacy of single (band, late crack) and double (band, late crack plus band, post) foliar insecticide treatments was evaluated for control of TT injury in Virginia-type peanut. Peanuts were planted 9 May with 36-inch row spacing. Band, late cracking time treatments were applied about 2 weeks after planting (24 May) and band, post treatments about 4 weeks after planting (6 Jun), both in a 12 to 14-inch band over the row with a COa pressurized backpack sprayer calibrated to deliver 17 gal/acre at 22 psi through one 8004E nozzle per row. Temik 15 G was applied in-furrow at planting as a treatment standard. A randomized complete block experimental design was used with 4 replicates; plots were 4 rows × 30 ft. Treatments were evaluated by determining plant injury based on a 0-10 scale where 0 = noTT injured leaves and 10 = 100% leaves injured. Data were analyzed using ANOVA and LSD procedures.

Control of Leafminers on Cantaloupe, 1991

Abstract Cantaloupes were direct seeded into “Yuma Beds” on 18 Mar. Plants were thinned at 12 inch intervals on 5 Apr. Plots consisted of six 60-ft long beds spaced 80 inches apart and bordered on each side by an untreated bed, arranged in a completely randomized block design with 5 replicates. Applications were made on 23 Apr, 6, 20, 25 May, and 3 Jun. Foliar insecticide treatments were applied with a tractor-mounted boom sprayer (4 nozzles/bed spaced 12 inches apart) operated at 60 psi, delivering 25 gal/acre. Spreader-sticker (Raincoat) was included in all spray treatments at a rate of 6 oz/acre. Plots were sampled on 15, 22, 30 May, and 6 Jun. Samples consisted of 20 leaves collected from the center two rows of each replicate. Leaves Were taken to the laboratory, and the numbers of live and parasitized leafminer larvae present were recorded for each plot. Data were analyzed for treatment differences using ANOVA and Ryan’s Q-test (Proc GLM).

Controlling Tobacco Insect Pests with Transplant and Foliar Insecticide Treatments, 1991

Abstract Flue-cured tobacco, 'CV K-326', was transplanted on 12 Apr at the Coastal Plain Experiment Station Bowen Farm in Tift County, GA. Production practices were carried out according to Georgia Cooperative Extension Service recommendations. A pre-plant incorporated tank mix of the following was applied; Tillam and Devrinol for weed control, Ridomil for blue mold control, and Nemacur for nematode suppression. Fertilizer (6-6-18) was applied at a rate of 1000 lb/acre in a split application. Prior to planting, plots 4 rows wide (44 inch row spacing) by 20 ft long were arranged in a randomized complete block design with 4 replications. Six transplant insecticide treatments were applied at planting and included NTN 33893 in the transplant water, NTN 33893 as a foliar spray after transplant, Orthene in the transplant water, Orthene as a foliar spray after transplant, Temik in a 6-inch band to the side of the row and incorporated after transplant, and Furadan in an incorporated band after transplant. Also, Orthene was foliar-applied at 2 and 4 wk after transplant. The eighth treatment was an untreated control. Transplant water treatments were applied at a rate of 4 oz of form per plant. Foliar sprays were applied with a CO2-powered backpack sprayer equipped with 3, TX-12 nozzles directed over the row, delivering 22 gal of form/acre at 35 psi. Granular materials were applied with a Gandy applicator as sidedress applications in a 6-inch band to the right of the row and lightly incorporated. The center 2 rows of each plot were treated with an untreated border row on each side. All plots were separated on each end with an alley 4 ft wide. The number of live aphids and thrips was recorded on plants 2, 4, and 6 of row 2 of each plot 10, 21, 40, and 70 days after transplant. Also, the number of budworms and hornworms per 10 plants was recorded on these same sampling dates. Aphid damage ratings were taken on 27 Jun from each of the 10 plants in row 2 that were being used to determine yield estimates. Damage scores ranged from 0 (no visible aphid injury) to 10 (all upper leaves essentially covered with aphid injury, honeydew, and sooty mold). Also on 27 Jun each of the 10 plants were visually rated for percent defoliation. Between mid-Jun and late Jul each plot was harvested (4 primings) and cured. All data were subjected to ANOVA and Duncan's multiple range test (P = 0.05).

Effect of Treatment Regimen on Control of Heliothis virescens and Helicoverpa zea (Lepidoptera: Noctuidae) on Cotton

Four foliar insecticide treatments ([All/ha), cypermethrin (0.067 kg), Bacillus thuringiensis subsp. kurstaki (Berliner) (29.6 billion International Units [BlUl), amitraz (0.14 kg), and B. thuringiensis + amitraz (29.6 BIU + 0.14 kg), were evaluated for influence on economic returns and for efficacy against the tobacco bud worm-boll worm complex, Heliothis virescens (F.) and Helicoverpa zea (Boddie), on cotton, Gossypium hirsutum L., at Florence, S.c., in 1988 and 1989. Each treatment was applied at regimens of scheduled applications (every 2-7 d, season-long), a threshold of five eggs per 100 plants, and a threshold of six larvae per 100 plants. Both years were characterized by low tobacco bud worm-boll worm population densities during June and early July followed by sharp increases in mid-July. Cotton flea hopper, Pseudatomoscelis seriatus (Reuter), densities did not exceed 1 per 10 plants. Cypermethrin and B. thuringiensis were the most effective and least effective treatments, respectively. Differences among treatment regimens for each insecticide usually were nonsignificant, but the efficacy of B. thuringiensis + amitraz was significantly reduced in 1988 when treatments were delayed until the larval threshold was reached. Economic returns were greater for the egg and larval thresholds than for the scheduled regimen. The low population densities of H. virescens, H. zea , and cotton flea hoppers before mid-July had no apparent effect on yields, and 15-17 season-long scheduled insecticide applications beginning in mid-June offered no advantage compared with five to eight applications (larval threshold) beginning in July.

Insecticide Trials on Cucumber, 1987:

Abstract Cucumbers were planted 26 Aug. The plants were grown on trellises in rows 5 ft apart. Black plastic mulch was laid on all rows. The design of the experiment was a split-plot. To determine whether A. similis could be controlled with insecticides applied in the soil, granular Diazinon was applied to half the rows; the other half were untreated. The soil type was a Guam clay, a shallow clay soil over limestone. The soil temperature was 29°C. Each row was then split into four foliar insecticide treatments. Foliar insecticides were applied with a Solo backpack sprayer, and approximately 150 gal water was sprayed per acre. Each treatment was replicated 4 times. Foliar treatments were applied weekly, beginning 16 Sep. A. similis were counted by walking along the rows and counting all adults visible on the foliage. D. indica numbers were estimated by counting the number of caterpillars per leaf on each of 10 mature leaves/subplot. Thrips and aphids were counted by picking 10 mature leaves per subplot and bringing them in bags to the laboratory where they could be counted under a binocular microscope.

Control of Armyworm and Cutworms, 1987

Abstract Five insecticides were evaluated at 2 sites in southwestern Virginia (Montgomery and Giles Counties) for control of larvae of armyworm and of various cutworms in no-till field corn after a pre-emergence tank mix of recommended herbicides and liquid nitrogen had been applied. Plots were established in a randomized complete block design with 4 replicates. Each plot was 4 rows wide and 50 ft long. For each of 4 of the treatments, the insecticides were impregnated on 25 lb of fertilizer (Green Grass general purpose lawn and garden fertilizer, 0-17-35, with boron) and spread by hand evenly throughout the plot. For each of these 4 treatments, the requisite amount of insecticide was first dissolved in 500 ml water, then sprayed onto the fertilizer with a hand-held mister as the fertilizer turned in a cement mixer. The damp fertilizer was then spread out on plastic sheets to dry for 1 d in the sun. The control for this group of impregnated treatments consisted of 25 lb of the fertilizer, also spread by hand. A compressed-air sprayer with 2 fan nozzles (Teejet 80034) delivering 16 gal/acre at 30 psi was used to make the foliar insecticide treatments. To ensure uniform coverage by the spray, 4 adjacent swaths of the insecticide, each approximately 3 ft wide, were applied over each plot. The control of this latter group of sprayed treatments was left untouched. The corn plants in the center 30 ft of the 2 center rows of each plot were counted about a month after planting, and the plants damaged by larvae caterpillars in the same area were counted in mid-summer. Ensilage yields were determined at harvest by cutting all the stalks from the same 60 row-ft for which plants were counted and damage was surveyed, then weighing these stalks using a sling swung from milk scales attached to a portable tripod. Damage and yield data were subjected to ANOVA. In Montgomery ‘3233 Pioneer’ field corn was planted in 38-inch-wide rows 11 May to corn stubble without cover, and the tank mix (paraquat, citrazine, simazine, and metachlor) was applied the same day. Insecticides were applied 13 May. Plants were counted 15 Jun, damaged plants were counted 18 Jun, and yields were determined 9-12 Sep. In Giles, ‘789 DeKalb’ field corn was planted in 36-inch-wide rows 15 May over a winter cover crop of rye, and the tank mix (paraquat, atrazine, and bicep) was applied the same day. Insecticides were applied 20 May. Total plants and damaged plants were counted 11 Jun, and yields were determined 16-17 Sep.

Economic Injury Levels and Economic Thresholds for Cereal Aphids (Homoptera: Aphididae) on Spring-planted Wheat

Foliar insecticide treatments were applied at various stages of plant growth to control natural infestations of two cereal aphids, the English grain aphid, Sitobion avenae (F.), and the rose-grass aphid, Metopolophium dirhodum (Walker), in field plots of spring wheat. Yield increases of 2.7 t/ha (36.5%) and 1.2 t/ha (29.3%) were obtained when sprays were applied at flowering in 1984 and 1985, respectively. Lower but significant yield increases were also obtained when sprays were applied at the milky ripe and early dough stages. Depending on the cost of chemical treatment and price received per kilogram of wheat, the economic injury level was calculated to be 15 and 10 aphids per tiller in 1984 and 1985, respectively. Based on the plant growth stage and the rate of aphid population growth, economic thresholds were calculated to be 2–4 aphids per tiller at flowering, 6–10 aphids per tiller up to the milky ripe stage, and 10 or more aphids per tiller from the milky ripe to medium-dough stage. After the medium-dough stage, treatment cannot be justified.