Mite Counts Research Articles

Control of Citrus Red Mite on Lemons, 1982

Abstract Two newer materials were compared with Vendex and Kelthane for control of the citrus red mite on lemons. Each treatment consisted of one-tree plots replicated four times. Applications were made 22 Mar. with a John Bean Sprayer using a hand-gun at 300 lb/in2, ca. 3 gal per tree (180 gal/acre). Mite counts were made in the grove with the aid of a 20X magnifying lens 3, 10, 14, and 21 days after spraying.

Control of Green Peach Aphid, Peach Twig Borer, 1983

Abstract Peach orchards ca. 2 miles apart were selected for these tests. They had been unsprayed for several years. Orchard #1 contained several peach varieties including Early Red Haven and Elberta. Orchard #2 contained predominantly J. H. Hale with some Elberta mixed in. Five single-tree replicates per treatment were used in a randomized block design. A single prebloom treatment was applied 31 Mar. All treatments were sprayed to the point of drip (400 to 500 gal/acre) with handguns at 400 to 500 lb/in2. Efficacy evaluations for green peach aphid and peach twig borer were made 9 May and 21 Jun. Total number of aphid colonies and wilted terminals were counted per tree. Mite counts were made by collecting 25 leaves per tree in the field. Samples were returned to the laboratory, brushed and counted under a binocular microscope.

Lygus Bug Control on Cotton, 1983

Abstract Two applications of insecticides for lygus bug control were made on Acala SJ-2 cotton planted 16 April at the Univ. of California West Side Field St. (Five Points, Fresno County, Calif.). Individual plots were 24 rows wide (40-in centers) and 150 ft long, replicated four tmes in a randomized complete block design. All treatments were made with a high clearance ground sprayer (Hagie 470) equipped with drop booms, through five nozzles per row delivering 25 gal/acre at 40 lb/in2 . Application dates were 2 to 3 Aug. and 29 to 30 Aug. (Zectran at 0.25 lb (AI)/acre was not retreated). On 17 Aug. an application of Comite 6.5E at 1.4 lb (AI)/acre was made toan eight-row subplot in each plot; insect and mite counts were not made in these subplots although yield was recorded. Sweep net (lygus bugs) and D-Vac (lygus bugs and predators) samples were taken 1, 6, 14, 21, 30, and 35 days posttreatment. Spider mite counts were made on 17 Aug. and 1 Sept. by sampling 100 mainstem leaves (eighth unfolded leaf below terminal) per treatment (25 per replicate) and processing through a sodium hypochlorite wash system. Yields were determined by mechanical harvest of the center four rows of each subplot. Sweep net samples 1 day pretreatment averaged 22.5 L. hesperus per 50 net sweeps.

Effect of Materials Applied for Control of Citrus Thrips on Citrus Red Mite Populations, 1983

Abstract Materials were applied in Field 12 of the Lindcove Field Station (Exeter, Calif.) at petal fall (18-19 May) for control of citrus thrips, using a Hardie hand-gun and John Bean sprayer at 500 lb/in2, outside coverage and approximately 200 gal/acre. Four tree plots were used with three replicates per material. Naked-eye counts of adult female mites on 32 leaves per tree (two, four-leaf terminals per quadrant) were made. Counts were discontinued at mite levels in excess of 6.25 per leaf.

Citrus Red Mite Pesticide Efficacy Tests in the San Joaquin Valley, 1983

Abstract Acaracids were tested for control of citrus red mite populations in two tests in the San Juaquin valley, near Ivanhoe, Calif, and at the Lindcove Field Station, near Exeter, Calif, respectively. In Test 1, materials were applied at 100 gal-acre using an FMC 267 speed sprayer driven at 2 mph. Each material was applied to a 2-acre plot with 10 trees chosen initially at random from the plot and monitored on each sample date. In Test 2, materials were applied using a Hardie hand gun and John Bean sprayer at 500 lb/in2 thorough distribution coverage at approximately 15 gal per tree with six single-tree replicates per material. For both tests, naked-eye counts of adult female mites on 32 leaves per tree (two, four-leaf terminals per quadrant) were made.

Apple, European Red Mite, Screening for Resistance to Acaricides, 1983

Abstract Susceptibility of 14 populations of ERM to Plictran, Kelthane, and Omite was assayed in the laboratory using a foliage dip test. A field test was conducted in two orchards to determine whether laboratory tests would predict field performance. In laboratory test bouquets of terminals were collected in each orchard within 3 days of the test, placed in 5 gal pails of water and brought back to the laboratory. Foliage from all orchards except Cream Ridge carried residues of previous acaricide applications. Terminals were pruned to shoots of five to eight leaves; each shoot was considered a replicate. Six to 10 replicates were used for each dosage per orchard. Shoots were dipped for 3 sec in a suspension of the test acaricide, then placed in an Erlenmeyer flask of water. Counts of live motile mites were made after 72 h, except for one test with CG 121633 (96 h), and Vendex (120 h). Control shoots were dipped in water containing a drop of (B-1956). The effect of treatment is expressed as % reduction in number of live mites on treated foliage compared to controls. Higher dosages were equivalent to field rates for acaricides, and lower rates were 0.25 field rates. Field tests were conducted at 2 locations, the Rutgers Tree Fruit Research Center at Cream Ridge, N.J. Treatments were applied (Hurff) at Monroeville, N.J. Treatments were applied to single-tree plots of a spur-type Red Delicious with four replicates per treatment. Trees were sprayed to runoff, using a hydraulic sprayer equipped with a handgun. Treatments were applied on 28 Jul. at Cream Ridge and 5 Aug. at Hurff’s and counts were made after 72 h. Mite population estimates were made by randomly picking 10 leaves per replicate and counting mobile mites.

Citrus Red Mite Pesticide Efficacy Tests in Riverside, 1983

Abstract Acaricides were tested for control of citrus red mite populations in 2 tests in Riverside, Calif. A randomized block design was used with 4 single-tree replicates per treatment. Materials were applied using a Hardie hand-gun (single nozzle, no. 8 disk) at 450 lb/in2, (ca. 1200 gal/acre; 12 gal per tree) using a John Bean sprayer. Naked-eye counts of adult female mites on 32 leaves per tree (two four-leaf terminals per quadrant, top surface only) were made.

Tests with San 547A and San 548A for Mite Control, 1983

Abstract Treatments were randomized and replicated four times on single-tree plots in a 20-year-old grapefruit orchard (30 by 25 ft spacing). Treatments were made Sept. 9 using a PTO-driven Meyers Sprayer with speed, nozzling and pressure adjusted to apply a spray volume of 125 gal/acre. Twelve fruits were selected at random in each treated tree, and utilizing a 10X handlens all CRM were counted in two, 1 cm2 lens fields per fruit. TCM were monitored by randomly collecting 12 leaves per treated tree, processing them through a mite brushing machine and counting all TCM motiles under a binocular microscope.

Apple, Test of Acaricides, 1983

Abstract Experimental sprays were applied to runoff to single-tree plots in a randomized block design with two replicates of ‘Golden Delicious’ and two ‘Red Delicious’, both spur-type trees. Experimental sprays were applied with a spraygun from a truck-mounted John Bean sprayer equipped with a 35 gal/m pump. Spray dates were as follows: 29 Apr. (all UC-81341 treatments only), 16 and 28 June, 22 Jul., and 3 Aug. General purpose sprays of Captan 50W, Topsin M, Guthion 50W, and Sevin 50W were applied at ca. 2-week intervals throughout the summer. Average temperatures were: May 57°F, Jun. 68°F, Jul. 74°F, and Aug. 72°F. Rainfall in inches totaled: May 4.98, Jun. 4.42, Jul. 0.83, and Aug. 2.01. Effectiveness of test materials on European red mite was evaluated by making counts of mites from random samples of 25 leaves per tree, 100 leaves per treatment on several dates. Mite population pressure was heavy throughout the season. Russeting of ‘Golden Delicious’ apples was determined by scoring a random sample of 30 apples per replicate, 60 apples per treatment. Fruits were rated as no russeting (1), light russeting (2), moderate russeting (3), and severe russeting (4). Possible ranges were: russeting, none to light 30-60 , light to moderate 60-90, and moderate to severe 90-120.

Apple; Mite Control, 1983

Abstract Two experimental chemicals, dicofol, and water were applied to apples on M-26 root stock for control of the twospotted spider mite. Chemicals were compared with each other and with water (check) to determine their effectiveness 1 day and 1 week after treatment. There were 4 replicates in a randomized block design. Each replicate consisted of three rows with four trees in each row. Two blocks with eight replicates in each block were adjacent to each other, separated by a buffer row of ‘Golden Delicious’ apples. All treatments were applied with a tractor mounted Kinkelder Model P-100 air-blast sprayer at 48 gal/acre on 12 July. Mites were counted one day before treatment (11 July), and one day (13 July) and one week (19 July) after treatment. Ten leaves were removed from each of four trees per replicate for each evaluation. Mites were removed from leaves with a Burney mite-brushing machine, placed on a circular glass grid plate, and counted under a dissecting scope. Pretreatment mite counts were used as a standard to determine the percentage of mortality in each plot 1 and 7 days after treatment.

Resistance of Cotton, Gossypium hirsutum L., to Natural Field Populations of Twospotted Spider Mites (Acari: Tetranychidae)1

Natural populations of twospotted spider mites, Tetranychus urticae Koch., infested cotton, Gossypium hirsutum L., in genetic studies in 1980 at three locations near Stoneville, Miss. There were significant differences in spider mite numbers between genotypes. The phenotyphic ranges in spider mite counts per 6.5 cm2 of leaf surface were: test I, 3.9 to 1.4; test II, 12.3 to 6.4; and test III, 4.9 to 3.7. Genotypes developed in the Mississippi delta had the lowest populations of spider mites. Cottons which tended to have high population numbers were Camd-E, Coker 76-118, MO 311, MO 73-1203, UGA 220, TH 149, Delcot, and Coker 201. Okra-leaf cotton had significantly fewer spider mites than frego bract, smoothleaf (Sm2), nectariless, glandless, and normal isolines. Correlation analyses of interest in test I were: spider mites with yield, percent first harvest, and yield first harvest, r = −0.55\*,0.58\*, and 0.25, respectively. In test II, correlations were: r = −0.47*, 0.66** and −0.07, respectively, for yield, percent first harvest, and yield first harvest. Yield data were not obtained from test III.

House-dust mites and absolute indoor humidity.

The concentration of house-dust mites (Dermatophagoides spp.) was investigated for four seasons in three locations in each of 50 Danish apartments. Simultaneously the absolute humidity was recorded and the previously known correlation between mite counts and indoor humidity was confirmed. It appeared, however, that apartments which had a low absolute indoor humidity in the winter period (due to low household load of water vapour) did not contain noticeable concentrations of house-dust mites in the summer and autumn despite the fact that the indoor absolute humidity in these apartments could be high enough to allow for a high peak-population of mites. Because of this it is suggested that in a temperate climate avoidance measures against house-dust mites should be supplemented at least by a drying out period in the winter, when this process is convenient to perform because of the low outdoor absolute humidity.

Practical Application of the Stable Age Distribution: Analysis of a Tetranychid Mite (Acari: Tetranychidae) Population Outbreak

Stage-structured counts of tetranychid mites (eggs, immatures, and adults) on 360 whole cotton plants were made during a single growing season in California, These counts were analyzed by using their departure from a stable stage distribution (65% eggs, 25% immatures, and 10% adults) implied by the birth and death rates from a previous life history study of the twospotted spider mite. By using these stable distributions as base lines for analysis, several questions were addressed, including: (1) What was the possible influence of migration on age structure? (2) How did the birth and death rates in the field populations compare with those determined in the laboratory? and (3) How did birth and death rates differ among the three growth phases? It is concluded that in general the stable age distribution is useful in demographic field studies because it focuses attention on age structure, any observed departure from it demands an explanation, and any explanation must take into account collective changes in proportions of stages intercoupled with commensurate shifts in growth rate.

Apple, Test of Acaricides, 1982

Abstract Experimental sprays were applied to run-off to single-tree plots in a randomized block design with 2 replicates of Golden Delicious and 2 Red Delicious, both spur-type trees. Experimental sprays were applied with a spraygun from a truck-mounted hydraulic sprayer. Spray dates were as follows: Apr 29 (Tranide treatment); Jun 8 (all treatments except Tranide); Jun 18 (all treatments except Tranide); and Jul 23 (all treatments except Tranide). General purpose sprays of Captan 50W, Guthion 5QW and Sevin 50W were applied at intervals of ca. 2 weeks throughout the summer. Average temperatures were: May 66 F, June 67 F, Jul 78° F, and Aug 74 F. Rainfall in inches totaled: May 2.45, Jun 6.65, Jul 3.00, and Aug 1.80. Effectiveness of test materials on European red mite was evaluated by several counts of mites on random samples of 25 leaves/tree, 100 leaves/treatment. Mite population pressure was heavy throughout the season. Russeting of Golden Delicious apples was determined by scoring a random sample of 30 apples/replicate, 60 apples/treatment. Fruits were rated as no russeting (1), light russeting (2), moderate russeting (3), and severe russeting (4). Possible ranges were: russeting, none to light 30-60, light to moderate 60-90, and moderate to severe 90-120. All treatments provided good to excellent control of the European red mite except the Tranide treatment and the low rate of NC-21314. The half-rate combination of Carzol plus Plictran gave longer residual control than Carzol alone. Starting with the first treatment, average russet ratings in order are as follows: 98, 100, 98, 88, 101, 99, 108, 94, 98, 110, and 113.

Citrus Red Mite Pesticide Efficacy Tests in California, 1982

Abstract Acaracides were tested for control of citrus red mite populations on 12-year-old lemon trees (21 ft × 21 ft spacing, EW rows) located in Riverside, CA. A randomized block design was used with 8 single-tree replicates per treatment. Treatments were applied May 13 with a Hardie hand-gun (single nozzle, no. 8 disc) at 450 psi (ca 1200 gal per acre, 12 gal per tree) using a John Bean sprayer. Naked-eye counts of adult female mites on 32 leaves per tree (two 4-leaf terminals per quadrant, top surface only) were made.

Altitude and house dust mites

The effects of altitude on house dust mites (one of the allergenic components of house dust) and the synthesis of anti-acari IgE antibodies were studied. Flotation extraction, counting, and identification of mites were performed each season for 1 yr on 218 mattress-dust samples taken from the Briancon region in the Alps, 900 to 3170 meters in altitude. Of the total dust samples, 41 were repeatedly positive and 177 repeatedly negative. The percentage of positive samples and the concentration of mites varied inversely with the altitude (40% positive with seven mites per 100 mg of dust at 900 to 1100 m, 14% and 4/100 mg at 1200 to 1350 m, 6% and 2/100 mg at 1400 to 1600 m, and 0% at higher altitudes). Species did not vary with altitude ( Dermatophagoides pteronyssinus 17%, Euroglyphus maynei 51%). In contrast, on the plain we found 80% of 77 dust samples positive (88 mites/100 mg of dust, 65% D. pteronyssinus ), with the peak in autumn. Total and specific IgE were measured initially and every 3 mo in 42 asthmatic children with positive skin tests to D. pteronyssinus and subjected to a 9-mo stay in Briancon (the highest city in Europe, 1365 m altitude). Geometric mean of initial total IgE (1047 U/ml) dropped to 40% (p≤0.001); specific IgE to D. pteronyssinus also fell. The value of climate change as a therapeutic modality in asthma is not supported by convincing data but may be attributed in some cases to removal of antigenic stimulation. The decrease in the number of mites and in IgE levels at higher altitudes supports this hypothesis.

Pedigree Analysis of Apple Clones with Differences in Preference to European Red Mite, Panonychus ulmi (Koch)1

Abstract Selections of apple (Malus domestica Borkh.) of known parentage were exposed in a greenhouse to artificial infestations of European red mite. The clones PRI 95356, N.J. 70, PRI 123056, and PRI 159155 and ‘Vista Bella9, were the least preferred (P = 5%); mite counts per leaf and per cm2 of leaf area were highly correlated even though the leaf area varied within and between selections. There was no evidence that any parent in the pedigrees contributed to ERM resistance based on an analysis of the association of mite numbers for the 4th and 5th week after infestation and the expected frequency of genetic contribution from various parents in the pedigree.

Apple, Test of Acaricides, 1981

Abstract Experimental sprays were applied to runoff to single-tree plots in a randomized block design with 2 replicates of Golden Delicious and 2 Red Delicious, both spur-type trees. Experimental sprays were applied with a spraygun from a truck-mounted John Bean sprayer equipped with a 35 gpm pump. Spray dates were as follows: Apr 20 (first UC-55248 treatment, no Kelthane); May 8 (second UC-55248 treatment); Jun 11 (all treatments except UC-55248); Jun 23 (all treatments, third UC-55248 treatment at high rate). General purpose sprays of Captan 50W, Guthion 50W and Sevin 50W were applied at ca intervals of 2 weeks throughout the summer. Average temperatures were: May 59.9 F, Jun 69.9°F, Jul 73.2 F and Aug 70.0°F. Rainfall in inches averaged: May 3.17, Jun 4.11, Jul 2.79 and Aug 4.08. Effectiveness of the test materials on the European red mite was evaluated by making several counts of mites on random samples of 25 leaves/tree, 100 leaves/treatment. Mite population pressure was heavy throughout the season. Russeting of Golden Delicious apples was determined by scoring a random sample of 30 apples/replicate, 60 apples, treatment. Fruits were rated as no russeting (1), light russeting (2), moderate russeting (3), and severe russeting (4). Possible ranges were: russeting, none to light 30-60, light to moderate 60-90, and moderate to severe 90-120.

Evaluation of Acaricides for Control of Citrus Red Mite on Lemons, 1981

Abstract This experiment involved efficacy of the citrus red mite on lemons at Yuman, AZ. Experimental compounds were compared to Kelthane, a current standard acaricide for control of citrus mites in AZ. A randomized block design was utilized with 1-tree plots and 4 replicates. Test materials were applied with a hand-gun from a John Bean Sprayer operating at 300 psi and a rate of 150 gpa (2.5 gal/tree) on Mar 30. Mite counts were made from 25 leaves/plot, selected at random. Leaves were brought into the laboratory and processed through a mite washer and separator appratus adapted from a Schriven and McMurty design.

Control of Spider Mites on Cotton, 1981

Abstract Acaracides were applied to Acala SJ-2 cotton planted Apr 5 near Five Points, CA in rows spaced at 40 inches. Individual plots were 8 rows wide and 100 ft long. Treatments were replicated 6 times in a randomized complete block design and applied Jul 14. On Aug 28 Mitac was reapplied to the 0.25 + 0.25 lb ai/acre treatment. Applications were made by high clearance sprayer equipped with drop booms using 5 solid cone nozzles per row delivering 47 gal/acre at 40 psi. Mainstem leaves (fifth unfolded leaf below mainstem terminal) were sampled on 4 post-treatment dates and processed through a sodium hypochlorite wash system. Counts were made of all active stages of the Tetranychid complex; only adult female counts are reported as they represent a consistent proportion of the total population. Mite counts were transformed by x + 0.5 for statistical analysis. Yield was determined by mechanically harvesting the 4 center rows of each plot on Oct 9.