Aphid Counts Research Articles

Apple, Insect and Mite Control, 1986

Abstract Test materials were applied to 20- to 30-year-old apple trees at Monmouth, Maine, as dilute sprays using a hand gun and a hydraulic sprayer operating at 250 psi at 350 (Test 1) to 400 gal/acre. Trees were sprayed on 10 May (prepink, PP), 28 May (petal fall, PF), 12 Jun (first cover, IC), 24 Jun (second cover, 2C), 7-8 Jul (third cover, 3C), 22-24 Jul (fourth cover, 4C), 5 Aug (fifth cover, 5C), 20-21 Aug (sixth cover, 6C), as noted in the table. The fungicide program consisted of Difolatan 4F (5 qt/100) on 25 Apr (quarter-inch green), Captan 80W (1 lb) plus Benlate 50W (4 oz) on 21 May (bloom) and with Funginex 1.6EC (13 oz) on 26 May and Polyram 80W (2 lb) which was mixed with each insecticide treatment at each spray date. There were 4 single tree replicates for each treatment. A randomized complete block design was used with 2 ‘Mcintosh’ and 2 ‘Cortland’ cultivars in Test 1 and 4 ‘Mcintosh’ in Test 2. Except for test trees, the orchards were not sprayed with insecticides or acaricides. On 28 Aug, about 450 apples were picked from the 4 trees of each treatment and examined on 6 Sep for external egg punctures (AM), egg-laying scars (PC), and typical feeding injuries (CM, LAW, and TPB). ERM were counted on 25 leaves collected at chest-height around the periphery of each tree. Leaves were brought into the laboratory and brushed onto glass plates coated with a Tween 20 and alcohol mixture; mites were counted the same day. Aphid counts were based on 10 randomly selected vegetative terminals around each tree. Numbers of live aphids on the distal 4 unfurled and 1 furled leaves and on the stem included by these leaves were recorded on 23 Jul (Test 1). Although May was fairly warm and wet, the rest of the season was cool and wet, especially the first half of Aug (4.8 inches rain). At least a trace of rain was recorded for over half the days during the season.

Spidermite and Aphid Control in Chemical Trials on Strawberries, 1986

Abstract Parker’ strawberries were transplanted early Nov ‘85 into drip-irrigated, double-row raised beds. Beds were mulched with clear plastic approximately 1 wk following transplanting. Treatments were arranged in a randomized complete block design with 4 replicates of each treatment. Each replicate consisted of 2 sub-beds (2 rows by 30 ft). Insecticides were applied on 5 and 19 Mar, 2, 16, and 30 Apr, 14 and 28 May. As foliage height and density increased, nozzles varied from 2-4/row and carrier was 100 gal/acre. Disc-type nozzles incorporated D-2 or D-3 orifice discs, #23 cores, and 50 mesh screens. All treatments except avermectin Bi included 0.04% spreader-sticker (Leaf Act 80A). Spidermite population evaluation was based on percentage of plants infested on the highest trifoliate on each plant for 5 plants/replicate every week (20/treatments/wk). Data were collected weekly from 11 Mar through 2 Jun. Aphid counts were collected at the same time as the spidermite data, but percentage of plants infested was based on the presence or absence of aphids on the oldest trifoliate. Again, 5 randomly selected plants were sampled/replicate every week, yield data were collected by weighing (in grams) and counting all berries from each replicate every week from 11 Mar through 2 Jun.

Insect Control on Flue-Cured Tobacco with Insecticides Applied to the Soil and In the Transplant Water, 1986

Abstract Tobacco was transplanted in a Chesterfield-Mayodan-Bourne sandy loam soil near Blackstone, VA, on 6 May. Experimental plots were arranged in a randomized complete block design replicated 4 times. Plots were 40 ft (24 plants) × 2 rows on 4 ft centers. Transplant water treatments were applied in 200 gal of water/acre (116 ml/plant) using a hand operated transplanter. Temik 15G was applied in a 12-inch band using a Gandy granular applicator mounted or a push-cart. The band application of Standak was made with a CO2-powered backpack sprayer using a single 8004E tip to deliver the Standak in 10 gal finished spray/acre at 30 psi. The band treatments were applied and incorporated with a rotary tiller and by bedding on 30 Apr. Wind speed was 5-10 mpr and temperature was 85-90 degrees F at time of application. Insect counts were made once every 1-2 weeks from mid-May through Aug. On the first 2 dates flea beetle feeding holes were counted on the most damaged leaf of 10 plants/plot. Green peach aphids were counted on the 4 upper leaves of 10 leaves/plot. Counts of hornworms and the number of leaves destroyed by hornworms were made for 24 plants/plot on 13 and 24 Jun, respectively. Tobacco in 1 row of each plot was harvested and cured for yield determination. Aphid counts were transformed to Log10(counts + 1). Data were analyzed using ANOVA and DMRT. Actual means are presented in the tables.

Aphid Control on Spring Wheat with Foliar Applied Insecticides, 1986

Abstract Owens’ wheat was planted on 23 Apr at the University of Idaho Research and Extension Center, Caldwell, ID in a furrow-irrigated field. Plots were 12 ft by 6 ft in a randomized complete block design with 6 replicates. A 4 ft untreated border was between plots and 6 ft of fallow ground separated blocks. All treatments were applied using a CO pressurized hand sprayer delivering 38 gal water/acre at 35 psi. Capture 2EC at 0.8 lb (AI)/acre was applied on 14 and 20 Jun and 8 Jul to keep a treatment relatively free of aphids. Capture was also applied to one plot on 20 Jun at approximately flowering and another plot at early milk stage, 17 Jul. The remaining treatments were applied 8 Jul. Aphid counts were taken 8, 10, 24, and 29 Jul. Plots were harvested 13 Aug with a small-plot combine which cut a 5 ft swath. No phytotoxicity was noted in any of the plots.

Apple, Insect and Mite Control, 1985

Abstract Test materials were applied to 19- to 29-year-old apple trees at Monmouth, Maine, as dilute sprays using a hand gun and a hydraulic sprayer operating at 250 psi at 300 gal/acre. Trees were sprayed on 16 May (pink, P), 28-29 May (petal fall, PF), 14 Jun (first cover, 1C), 25-26 Jun (second cover, 2C), 9 Jul (third cover, 3C), 23-24 Jul (fourth cover, 4C), 6 Aug (fifth cover, 5C), 20 Aug (sixth cover, 6C), as noted in the table; the Rotacide treatment (3C-9C) was applied only on 9 Jul, 17 Jul, 25 Jul, 2 Aug, 8 Aug, 15 Aug, and 22 Aug. The fungicide program consisted of Difolatan 4F (5 qt/100) on 24-28 Apr and Polyram 80W (2 lb) which was mixed with each insecticide treatment at each spray date; no Polyram mixtures were made with the Rotacide treatment (3C-9C). There were 3-4 single tree applications for each treatment. A randomized complete block design was used with 2 ‘Mcintosh’ and 2 ‘Cortland’ cultivars in Test 1 and 4 ‘Mcintosh’ in Test 2. Except for test trees, the orchards were not sprayed with insecticides. On 28 Aug, 0.5 box of apples was picked from each tree (only 3 trees were sampled in Test 2), and about 520 (Test 1) or 180-370 (Test 2) apples were examinee1 per treatment on 7 to 14 Sep for external egg punctures (AM), egg-laying scars (PC), and typical feeding injuries (CM, LAW, and TPB). ERM were counted on 31 Jul and 15-16 Aug on 25 leaves collected at chest-height around the periphery of each tree. Leaves were brought into the laboratory and brushec onto glass plates coated with a Tween 20 and alcohol mixture; mites were counted the same day. Aphid counts are based on 10 randomly selected vegetative terminals around each tree. Numbers of live aphids on the distal 4 unfurled and 1 furled leaves and on the stem included by these leaves were recorded or 18 Jul and 1 Aug (Test 2). May and Jun were cool, the first half of Jul was wet (3.9 inches rain), and Aug was wetter (3.4 inches rain) and cooler than normal.

Evaluation of Insecticidal Plant Fertilizer Spikes for Aphid Control, 1986

Abstract Young plants at first cutback stage in 6-inch pots of Metro Mix 500 medium were placed in an enclosed greenhouse and inoculated with green peach aphids from a cultured colony in Apr. A concurrent melon aphid infestation was allowed to develop naturally during the trial period. After ca. 7 days, test fertilizer spikes (6g, 1% insecticide, 3-2-2 fert.) were inserted in the soil of each pot. There were 3 replicate pots per treatment. After 3 weeks, counts of all live aphids (both species pooled) were made for each pot.

Control of Arthropod Pests on Cantaloupe, 1986

Abstract ‘Magnum 45’ variety cantaloupe was direct seeded in beds on 2 m centers on 17 Mar at the Texas Agricultural Research and Extension Center, Weslaco, TX. Soil type was a Willacy fine sandy loam. Plants were thinned to 45 cm spacing on 15 Apr. Sixty-eight kg N-32 per ha was applied prior to planting. Pesticide treatments were applied 22 Apr and 6 Jun to single bed, 9 m long plots with a tractor mounted, C02 powered sprayer calibrated to deliver 143 liter/ha (2.8 kg/cm2, 4 TX-4 nozzles, 6.4 kmph). Arthropod populations were monitored by surveying 3 primary vines per plot on 29 Apr and 14 May and recording number of cucumber beetle adults, melon aphids, spider mites, flea beetle adults, leafhopper nymphs and adults, leaves with leaf miner mines, leaves, flowers, and fruit. Melon yield was determined as wt/melon and total wt of melons/plot on 3, 6, 10 and 13 Jun. Aphid and mite counts were transformed by taking the loglO + 1 of counts, due to the aggregated nature of populations of these species.

Arthropod Control and Chemical Phytotoxicity on Strawberries, 1985

Abstract ‘Parker’ strawberries were transplanted 2 Nov ’84 into drip-irrigated, double-row raised beds. Beds were mulched with clear plastic approximately 1 wk following transplanting. Treatments were arranged in a randomized complete block design with 4 replicates of each treatment. Each replicate consisted of 2 sub-beds (17 plants/sub-bed). Insecticides were applied on 29 Mar, 11 and 25 Apr, 9 and 23 May, and 6 and 20 Jun. As foliage height and density increased, nozzles varied from 2-4/row and carrier was 100 gal/acre. Disc-type nozzles incorporated D-2 or D-3 orifice discs, #23 cones, and 50 mesh screens. All treatments included 0.04% spreader-sticker (Leaf Act 80A). Spider mite population evaluation was based on percentage of plants infested on the highest trifoliate on each plant for 10 plants/replicate every wk (40/treatment/wk). Data were collected every other wk from 25 Mar-17 Jun, and again on 25 Jun. Aphid counts were collected at the same time as the spider mite data, but percentage of plants infested was based on the presence or absence of aphids on the oldest trifoliate. Again, 10 randomly selected plants were sampled/replicate every other week. Phytotoxicity was assessed by photosynthesis (PH) and stomatal conductance (RS) measurements made with the LI-COR 6000 on 10, 15 and 26 Apr (13 days after 1st treatment, 4 days after the 2nd treatment, and 1 day after the 3rd treatment, respectively). Yield data were collected (all berries in each replicate) on the same dates as the mite counts.

Early Season Cotton Insect Control, 1984

Abstract ‘Stoneville 825’ variety cotton was planted 10 May on a Grenada silt loam at the West Tenn. Exp. Stn., Jackson, TN. One-row plots (40-inch spacing) were 30 ft long. Treatments were replicated 6 times in a randomized complete block design. All seed was commercially treated with 2 fungicides. Ten pounds of Terraclor Super-X per acre was applied in-furrow. Foliar sprays were applied 4 Jun at 4.6 gal of spray per acre (3 mph, 40 psi) with a hand-held CO2 pressurized B&G spray system. Pre- and posttreatment thrips and aphid counts were made by pulling 4 seedling plants from each row and placing these in a pt jar. The jars were returned to the laboratory where the plants were beaten over a large funnel. Insects were collected under the funnel in 70% alcohol. Posttreatment counts were made 11 Jun.

Aphid Control on Louisiana Pecans, 1984

Abstract The study was conducted on mature ‘Stuart’ trees at the LSU Pecan Research-Extension Station, Shreveport, Louisiana. A randomized block design was used consisting of 3 blocks, with 1 tree per treatment, per block. Pretreatment counts were made on 26 Jul. Applications of foliar applied materials were made on 27 Jul, using an FMC 957 speed sprayer delivering 30 gal of finished material per tree. Aphid counts were made on 30 Jul. Sampling consisted of counting the number of aphids—both nymphs and adults—on 10 compound leaves per tree.

Insect Control on Cabbage, 1985

Abstract ‘Greenback’ cabbage seedlings were transplanted on 7 Mar at the University of California’s South Coast Field Station in Santa Ana, California. Experimental plots were 4 rows wide (40 inch centers) by 36 ft long separated by a 3-ft buffer. The cabbage transplants were sprinkler irrigated for 2 wk, and drip irrigated thereafter (water pH 7.2-7.5). Treatments were replicated 4 times in a randomized complete block design. Alternate week applications were initiated when transplants were 2 wk of age. Application dates included 21 Mar, 4 and 18, Apr and 2 and 16 May. A tractor-mounted boom sprayer was operated at 100 psi. As plant height and foliage density increased, nozzles varied from 1-6 per row and carrier (water) increased from 50 gal/acre (21 Mar-4 Apr) to 100 gal/acre (18 Apr on). Disk type cone nozzles incorporated D 1-3 disks, #23 or 25 cores and 50 mesh screens. All treatments included 0.04% spreader-sticker (Leaf Act 80A). Evaluation of Lepidoptera populations was based on no. of larvae/plant found on 10 plants/replicate (40 per treatment) from the center 2 rows of each replicate every week. The diamondback moth, and cabbage looper, were recorded separately. Aphid counts were indexed as follows: 1 = 0-10, 2 = 11-25, 3= 26-50, 4 = 51 +. Because of high initial densities, and the rapid movement of alate aphids between plots, index values approaching one can be considered good.

Irish Potato, Control of Potato Infesting Aphids, 1985

Abstract The foliar and systemic experiments were randomized complete block designs with 6 replicates each and were conducted at Presque Isle, ME on land that was in clover in 1984. The planting dates were 21 May ’85 for the systemic experiment and 22 May, for the foliar experiment. In each experiment the 3-m space between blocks and the 1.4-m space between columns and at the sides and ends of the experiments were sown to oats after planting. Each plot consisted of 4 rows of potatoes 0.9 m apart and 15.0 m long. The healthy Katahdin seed pieces ca. 75 g each were planted with a tractor-pulled, assisted-feed planter. Fertilizer and hilling practices were normal for the area. Late blight was controlled by 7 foliar applications of Dithane M-45 (1681 g/ha weeks of 8 and 15 Jul, 2242 g/ha weeks of 22, 29 Jul, 12, 19 and 26 Aug) and 1 application of Ridomil 2E (1.17 1/ha 31 Jul). Soil applications of insecticides were made with a modified Gandy applicator just prior to planting or as a sidedressing after emergence. Foliar insecticide applications were made with a Century boom sprayer, 3 nozzles per row at 7.0 kg/cm2 pressure and 1.2 kl/ha. Numbers of aphids (by species) were counted on top, middle, and bottom leaves of 25 plants in the middle rows of each plot. When dates of count and application were the same, aphid counts were made prior to applications of the insecticide. Analyses of variance were calculated following transformation of the data using log10(x + 1). Means of the total number of wingless aphids were compared using DMRT and then reconverted. The soil was classified as Caribou Loam, pH 5.2. Total monthly rain fall for Jun, Jul, and Aug was respectively 11.2, 13.8 and 6.1 cm. The average temperature for each of the same 3 months was 15.6, 19.5 and 17.2°C.

Control of the Spotted Alfalfa Aphid and Pea Aphid with Foliar Sprays in Idaho, 1985

Abstract Insecticide treatments were applied to 8 inch high alfalfa near Kimberly, ID, on 6 Aug ’85. Plots were 24 ft × 24 ft, with 4 replications arranged in a randomized complete block design. Sprays were applied with a CO2 back-pack sprayer at 25 psi delvering 50 gal water/acre. Aphid counts were made with a 15-inch diam sweep net taking 5 (90°) sweeps per plot.

Apple, Large Block Chemical Control of Codling Moth, 1985

Abstract Two insecticides were evaluated for their ability to provide seasonal control of the codling moth. A 25-year-old apple orchard with under-tree irrigation was used for this test. All materials were applied in a dilute spray at 400 gal per acre using a Bean airblast sprayer. Two applications were made against first generation of codling moth. The first Dimilin application was timed to coincide with beginning of oviposition or 75 degree days (9 May) after first moth detection in pheromone traps. The second application was applied 21 days following the first (1 Jun). The first application of Guthion was timed to coincide with predicted 3% egg hatch or 250 degree days (23 May) following first moth flight as detected in pheromone traps. The second cover was applied 21 days following the first (13 Jun). One application was made against second generation. Dimilin was applied at 1000 degree days (8 Jul) following first moth while Guthion was applied at 1650 degree days (23 Jul) after first moth. After first generation all fruit from 25 trees in each block were examined and the number of injured apples recorded. Following second generation 100 fruit on 25 trees were examined and the number of injured fruit recorded. Mites were sampled bi-weekly beginning in mid-Jun. Fifty leaves were selected at random (5 leaves/tree) from trees within each test block, brushed and counted in the laboratory. Aphid counts were taken on 13 Sep. Relative density of green apple aphid (GAA) was estimated by counting infested terminals out of 50 from each of 10 trees selected at random from each block. Density of woolly apple aphid (WAA) was estimated by selecting 10 vegetative shoots from the center of each of 10 trees per block. Active WAA colonies on each shoot were counted. Density of white apple leafhopper (WALH) was estimated by counting leafhoppers observed on 25 leaves per tree from each of 10 trees per block.

Corn Root Aphid-Nematode Control, 1980

Abstract Experiments were conducted in Phelps County, NE, to evaluate 3 insecticides for reducing corn root aphids and/or nematode damage to corn. Plots were 2 rows (spaced 0.9 m), 10.7 m long arranged in a Latin Square design Experiment 1 was located in an area of the field that had severe stand reduction in 1979. Experiment 2 was in an area that did not have severe stand reduction in 1979. The granular insecticide/nematicides were applied after planting but before corn was emerged with a Noble metering device mounted on a manually operated planter press wheel to give an 18-cm band over the planted furrow. Pretreatment and posttreatment nematode soil samples were taken with a 2.5 × 20-cm soil probe. Corn root aphids are transported from plant to plant by ants (Lasius neoniger Emery). To prevent disrupting the experiment by digging plants and counting aphids, insect control was based on number of active anthills/row. Yields were determined by hand harvest.

Irish Potato, Control of Potato Infesting Aphids, 1984

Abstract The foliar and systemic experiments were randomized complete block designs with 6 replicates each and were conducted at Presque Isle, Maine on land that was in clover in 1983. The planting dates were 22 May, 1984 for the systemic experiment and 23 May, for the foliar experiment. In each experiment the 3.0-m space between blocks and the 1.4-m space between columns and at the sides and ends of the experiments were sown to oats after planting. Each plot consisted of 4 rows of potatoes 0.9 m apart and 15.0 m long. The healthy Katahdin seed pieces ca. 75 g each were planted with a tractor pulled assisted feed planter. Fertilizer and hilling practices were normal for the area. Late blight was controlled by 8 foliar applications of Diathane M-45 (1681 g/ha weeks of 9 and 16 Jul, 2242 g/ha weeks of 23, 30 Jul, 6, 13, 20 and 27 Aug). Soil applications of insecticides were made with a modified Gandy applicator just prior to planting or as a sidedressing after emergence. Foliar insecticide applications were made with a Century boom sprayer, 3 nozzles per row at 7.0 kg/cm2 pressure and 1.2 kl/ha. Numbers of aphids (by species) were counted on top, middle, and bottom leaves of 25 plants in the middle rows of each plot. When dates of count and application were the same, aphid counts were made prior to applications of the insecticide. Analyses of variance were calculated following transformation of the raw data using log10(x + 1). Means of the total number of wingless aphids were compared using DMRT and then reconverted. The soil was classified as Caribou Loam, pH 5.2. Total monthly rainfall for Jun, Jul, and Aug was respectively 15.52, 13.74 and 7.26 cm. The average temp for each of the same 3 months was 15.6, 20.0 and 19.7°C.

Apple, Insect and Mite Control, 1984

Abstract Test materials were applied to 28-year-old apple trees at Monmouth, Maine, as dilute sprays using a hand gun and a hydraulic sprayer operating at 250 psi at 300 gal/acre. Trees were sprayed on 17 May (pre-pink), 3 Jun (petal fall), 16 Jun (first cover), 27 Jun (second cover), 11 Jul (third cover), 26 Jul (fourth cover), 8 Aug (fifth cover), 20 Aug (sixth cover). Materials were applied on dates as noted in table. The fungicide program consisted of Difolatan 4F (5 qt/100 gal) on 29 Apr, Phygon 50W (0.5 lb) on 1 Jun, Polyram 80W (2 lb) and Amid-Thin W (12 ppm) on 13 Jun, and Cyprex 65W (0.75 lb) on 29 Jun and 3 Jul. In addition, Polyram 80W (2 lb) was mixed with each insecticide treatment at each of the first 5 post-bloom sprays, and Captan 80W (1 lb) was mixed at the last 2 cover sprays. There were 4 single-tree replications for each treatment. A randomized complete block design was used, with 2 ‘Mcintosh’ and 2 ‘Cortland’ cultivars per treatment. Except for test trees, the orchard was not sprayed with insecticides. On 30 Aug, 0.5 box of apples was picked from each tree, and about 490 apples were examined per treatment on 9 to 15 Sep for external egg punctures (AM) egg-laying scars (PC), and typical feeding injuries (CM and LAW). ERM were counted on 3 dates from 19 Jul to 17 Aug on 25 leaves collected at chest-height around the periphery of each tree. Leaves were brought into the laboratory and brushed onto glass plates coated with a Tween 20 and alcohol mixture; mites were counted the same day. Aphid counts are based on 5 randomly selected vegetative terminals around each tree. Numbers of live aphids on the distal 4 unfurled and 1 furled leaves and on the stem included by these leaves were recorded on 9 and 17 Jul. Jul and Aug were relatively dry (1.8 and 1.5 inches rain, respectively); Aug was also warm.

Aphid Control in Irrigated Spring Wheat, Washington, 1984

Abstract Eight insecticides were evaluated to determine their efficacy in controlling grain aphids. Insecticides were applied 9 Jul ‘84 to wheat (early dough stage of growth) grown on the Washington State University, Irrigated Agriculture Research and Extension Center, Prosser, WA. Pretreatment aphid count averaged 31.1/plant, 9 Jul ‘84. Treatments were applied with a hand-held sprayer calibrated to deliver 43 gpa at 40 psi. Plots were 3 x 25 ft, replicated 4 times in a randomized complete block design. Treatments were evaluated on the total aphids present per 5 randomly selected wheat heads from each plot at several posttreatment intervals.

Synthetic Pyrethroids for Aphid Control on Potatoes, 1982

Abstract Potatoes were planted on 20 Apr in Ritzville silt loam soil (Mesic Calidirothic Haploxerolls) pH 6.2, and organic matter 1.6% at Yakima, WA. The experimental insecticides were applied to the foliage of potatoes with a 2-row, 4-flat fan nozzle, portable boom CO2 powered sprayer at 50 PSI in 50 gal of water per acre on 15 Jun ’82. The plots were 2 rows (34 inch) wide and 25 ft long. The treatments were replicated 4 times in a randomized complete block design. The potato crop was sprinkler irrigated on 13 Jun, before the insecticide application, and on 25 Jun, after the 10-day aphid count. The normal irrigation cycle was on a 5 to 7-day interval. Twenty compound potato leaves were collected from the lower 2/3 of the plants from each plot and the number of green peach aphids (GPA) on the leaves were counted on 18, 22, 25 and 29 Jun; or 3, 7, 10 and 14 days posttreatment.

Foliar Sprays for Control of Aphids on Potatoes, 1983

Abstract ‘Russet Burbank’ potatoes were plantd on 13 Apr., in Ritzville silt loam soil (Mesic Calciorthidic Haploxerolls) pH 6.2 and organic matter 1.6% at Yakima, Wash. The insecticides were applied with a two-row, four nozzle (TeeJet AI 80015) portable boom CO2-powered sprayer at 50 lb/in2 in 50 gal of water per acre on 9 June. Each plot was two rows (34-in. row spacing) wide and 19 ft long. Each treatment was replicated four times in a randomized complete block design. The potato crop was sprinkler irrigated with 0.75 acre-inch applied at 5- to 7-day intervals, except the plots were irrigated on 8 June before treatment then on 16 June after the aphid counts. Twenty compound potato leaves were collected from the lower two-thirds of the plants on 10, 13, 16, and 24 June. The number of green peach aphids on the leaves were counted. The data were analyzed as a split-plot in time over the four counting dates.