Thrips Damage Research Articles

Control ofThrips tabaci [Thysanoptera: Thripidae] on glasshouse cucumber using large introductions of predatory mitesAmblyseius barkeri [Acarina: Phytoseiidae

The phytoseiid miteAmblyseius barkeri (Hughes) (=Amblyseius mckenziei Sch. & Pr.) was used for biological control ofThrips tabaci Lind. in 7 commercial glasshouses with cucumber (a total of 5780 m2). Predatory mites were introduced 3–4 times in densities ranging from 40 to 300/m2 at each release. In 6 of the 7 glasshouses, control of thrips was satisfactory throughout the growing season. Thrips densities were kept below 15 individuals per leaf. In 1 glasshouse, thrips damage was seen on the fruits at densities of 25 thrips per leaf, but the thrips population was quickly reduced and remained at low densities for the next 3 months.

Thrips Control on Peanuts, North Carolina, 1987

Abstract A field in northern Northampton County was selected to evaluate specific insecticides and nematicides for thrips control. Soil was sandy with only 0.2% organic matter and pH 6.1. Peanuts were planted on 14 May (36 inch rows) with approximately 130 lb seed/acre. Soil temperature was 67°F. Plots were 2 rows wide × 50 ft long, and each plot was separated by 2 buffer rows. Plots were arranged in a randomized complete block design with 4 replicates. Plot ends were separated by a 5-ft barren strip. Peanuts were planted using a Cole planter, and rolling cultivators were used to lightly incorporate band treatments. In-furrow treatments were placed in the furrow with the seed, and band treatments were placed immediately behind the press wheel. Peanuts were otherwise managed under standard agronomic practices. Thrips control was evaluated by determining the abundance of damaged leaflets per plot. Fifty newly-opened leaflets/plot were randomly selected and examined for thrips damage. The number of damaged leaflets was recorded. Sampling was conducted on 3 dates, 4, 10, and 18 Jun. In addition, on 10 Jun, 10 unopened leaflets per plot were opened and examined for thrips and the number of thrips recorded. All data were transformed by × + 0.5.

Insecticides for Suppression of Early-Season Cotton Insect Pests in the Texas Blacklands, 1987

Abstract Cotton was planted 16 Apr on 38-inch row spacings. Five insecticide treatments, 2 partially treated check treatments, and a completely untreated check treatment were compared in a randomized block design with 4 replications. Plots were 10 rows wide × 75 ft long, but only the middle 4 rows were sprayed. Applications were made with a high-clearance, self-propelled ground sprayer using TX-8 hollow cone nozzles calibrated to deliver 8.6 gal/acre. Insecticide treatments (including applications of Bidrin to the fleahopper check plot) were applied 29 Apr and 6 May for thrips and aphid control when cotton was in the seedling stage. Thrips and aphid densities were measured on 4 Apr and 5 and 12 May by examining 15 randomly selected cotton seedlings from each plot. The individual cotton seedlings were picked whole, quickly immersed, and shaken in pint jars of 70% ethanol. The sample jars were taken to the laboratory and numbers of thrips and aphids were counted under a dissecting microscope. Estimates of thrips damage to cotton seedlings were made 12 May when most plants were in the 5th true leaf stage. Ten randomly selected cotton plants were subjectively rated on a scale of 1-4: 1, no visible damage; 2, light damage; 3, moderate damage 4, heavy damage (e.g., terminal destroyed). An additional application of insecticide treatments (including Bidrin for the thrips-aphids check plot) was made 22 May for cotton fleahopper. Fleahopper adult and nymph densities were determined 22 May and 8 Jun from 30 randomly selected plant terminals in each plot using a combination beat bucket/visual inspection method. Cotton fruiting rates were monitored over a 5-week period by taking daily counts (Monday- Friday) of white blooms within a designated 20-ft section of row in each plot. Yield data were collected in a stratified harvest from 2 pickings of cotton from the same 20-ft row section used for counting white blooms. All data were subjected to analysis of variance.

Nectarine, Carzol for Thrips Control, 1987

Abstract The test was conducted in a small block of nectarines (selection 7-738) at Byron, Ga. Control was directed at critical times of flower and fruit development to determine which treatment times were best for effective control. Carzol 90SP at 0.5 lb (AI)/acre was applied at 4 different timing regimens based on previous population distribution patterns in the same orchard location. A randomized complete experimental block design was used. Emphasis was directed at early season and population build-up of flower thrips populations. Thrips sampling began at pink bud and continued each 2 wk until harvest. Fruit samples were taken just following shuck split, and sampling continued each 2 wk until harvest. A total of 360 fruit were examined for thrips damage from each treatment during the entire sampling period.

Susceptibility of Onion Growth Stages to Onion Thrips (Thysanoptera: Thripidae) Damage and Mechanical Defoliation

Interactions between infestations of onion thrips, Thrips tabaci Lindeman, the three growth stages of onion (prebulbing, bulbing, and sizing), and onion yield were investigated in field and greenhouse experiments. Significant negative correlations existed between thrips numbers and yield only during bulbing, although percentage of yield reduction varied considerably between studies. During bulbing stage, a 2–3% yield reduction per 10 thrips was obtained for two field studies. Under greenhouse conditions, 10 thrips per plant resulted in a 7% yield reduction. In an additional study, plants were mechanically defoliated at 0, 30, and 60% levels during the three onion growth stages. This also resulted in yield reduction following damage during bulbing stage.

Chemical Control of Thrips and Aphids on Cotton, 1985

Abstract Cotton was planted 19 Apr on rows spaced 40 inches apart. Caparol was applied premergent at 2.4 lb (AI)/acre on 19 Apr. Plots were arranged in a randomized block design with treatments replicated 4 times. Plots were 8 rows wide and 40 ft long. Blocks were separated by 15 ft of untreated cotton. The study was bordered in front and back by a 25 ft buffer of untreated cotton. Foliar treatments were applied to the inner 4 rows of designated plots. A backpack sprayer calibrated to deliver 5 gal of solution per acre through two HC-4 nozzles per row at 36 psi and 3 mph was used to apply foliar insecticide treatments. Temik treatments were applied to all 8 rows of designated plots. A 2-row Gandy applicator was used to apply Temik treatments at planting. Foliar treatments were applied 1 and 8 May. Density of thrips and aphids were determined 30 Apr, 7 and 13 May. Density levels were assessed by counting thrips (adults and nymphs) and aphids on 15 randomly selected plants per plot. This was accomplished by emersing plants one at a time in a jar containing 75 percent ethyl alcohol. Thrips were easily dislodged but agitation was required to remove aphids. Number of thrips (adults and nymphs) and aphids were determined by counting them under a microscope. Phytotoxicity of the tested insecticides was assessed by counting plant population density in two 13.1-row-foot sections per plot. Thrips damage ratings were made by averaging ratings of 10 plants per plot (5 plants from each 13.1-row-foot section). Plants rated were selected using a random number table. Plants were rated on a scale of 1 (no visible thrips damage) to 7 (terminal destroyed). Damage ratings were made 13 May. Soil samples to determine nematode density were taken 5 Jun. Four subsamples per plot were mixed together and one sample taken from this mixture. Samples were submitted to the Texas Plant Disease Diagnostic Laboratory at College Station, Texas on the Texas A&M University campus for nematode density dertermination. Cotton fruiting rates were assessed by taking square, bloom, and boll counts. The number of squares per 10 plants was counted and recorded for each plot, 5 Jun, about 1 wk into the squaring period. A count of blooms and bolls was made on two 13.1-row-foot sections per plot 27 Jun, 9 days after first bloom. Yield data was gathered from stratified harvest of two 13.1-row-foot sections per plot. All plots were treated with Cygon on 28 May and 4 Jun for control of cotton fleahopper. Cythion RTU was applied 7 and 13 Jun, and 2 Jul for control of boll weevil. Ammo was applied for control of Heliothis spp. 1 and 10 Jul.

Effects of Insecticide and Plant Populations on the Insect Pests and Yield of Common Bean (Phaseolus vulgaris L.)

Effects of four plant populations 100,000, 200,000, 300,000, and 400,000 plants per ha with and without insecticide application on the insect pests and yield of common beans were studied. Incidence and damage of foliar beetle ( Ootheca bennigseni Weise) and flower thrips ( Taeniothrips sjostedti Trybom) were significantly higher in unsprayed plots compared with sprayed plots. Foliar damage was less at 200,000 plants per ha than at other densities. However, thrips counts were not significantly different among the plant populations tested although insect counts increased with increasing plant populations. The unsprayed plots had more flower and pod damage from the pod borers, Maruca testulalis Geyer and Heliothis armigera Hubner. At 200,000 and 300,000 plants per ha, fewer flowers and pods were damaged. The seed yield was significantly higher in plots sprayed with lindane compared with unsprayed plots. The average seed yield in sprayed plots was 1,275 kg/ha. The highest seed yield, pods per plant, seeds per pod, and seed size were obtained at 200,000 plants per ha (1,230 kg/ha). Possible reasons for decrease in seed yield beyond a plant population of 200,000 plants per ha are discussed. A positive correlation between seed yield and pods per plant, seeds per pod, and seed size were found. A negative correlation coefficient was found between seed yield and flower damage and pod damage.

Thrips Control in Peanuts, 1981

Abstract This field test was conducted at the Wiregrass substation in Headland, AL. Eight treatments and an untreated check were replicated 4 times in a randomized complete block design. Each o.f the 0.01 acre plots was 4 rows wide 936 inch row spacing) and 37 ft long. Plots were treated on May 13, 1981. Treatments, applied on May 13, were seed treatments, in furrow at planting applications, and a combination of in-furrow at planting, and sidedress application at the seedling stage. Sidedress applications were made with a tractor-mounted 2 row electric granular applicator. Plots were examined on Jun 12 rated for thrips damage, stand density and insecticide burn. Thrips damage was rated in a 0-5 scale with 0 being no damage and 5 being severe damage. Stand density was measured as the number of plants in 1 yard of row (maximum rating was 10). Burn was rated in a 0-5 scale with 0 equalling no burn and 5 equalling death of the plant.

Thrips Damage and Control in Onions, 1981

Abstract treatments were arranged in a randomized complete block design with 3 replications (blocks). The plots were 6 rows wide and 25 ft long. An untreated row was left as a buffer between treatments. Insecticides were applied on Jul 16, 22, 29; aug 5, 12 and 25 with a tractor-mounted boom sprayer at 30 gpa. Each week 10 randomly selected plants per plot were sampled for numbers of thrips (adults and larvae) present. Spraying was withheld until an average of 5-7 thrips per plant were counted, total weight and mean weight per bulb were taken on Sep 24 for 15 row ft. On Oct 14 an additional 2 middle rows of the plots were harvested, to have a 45 row ft total sample.

Natural Resistance to Thrips Injury in Cotton as Measured by Differential Leaf Area Reduction1

Ten entries of cotton (Gossypium hirsutum L.) were evaluated for 2 years to measure their relative resistance to injury from thrips (Thripidae). Resistance was measured as the percentage of leaf area reduction associated with thrips damage. Leaf area was determined three times at weekly intervals during each year.Pilose (H2) was associated with a high level of resistance to thrips. Other morphological traits such as Okra‐leaf shape (L°), Red plant color (R1), glandless (gl2, gl3), nectariless (ne1, ne2), or smooth leaf (Sm1, Sm2) did not provide the plant with resistance. Significantly less leaf area damage occurred on the pubescent ‘Tamcot SP‐37’ cultivar than on the glabrous ‘Tamcot SP‐21’ cultivar.

Control of the Cowpea Curculio and Thrips, on Southern Peas, Test 1, 1977

Abstract Peas were planted Apr 26‘77. Plots were 4 rows (3 ft spacing), 50-ft long and were replicated 4 X in randomized complete blocks. Soil was a loamy sand and received 8.4 in. rain and 4 in irrigation. The sprays were applied May 24, Jun 17, 20, 24 with a tractor mounted boom, 3 nozzles/row, 50 gal/acre, 50 psi. Thrips damage was evaluated Jun 2 by scoring 10 plants/plot for damage (0 = no damage, 1, 2, 3=light, moderate, severe distortion, resp.). On Jun 27, 25 pods/plot were harvested and examined for cowpea curculio stings on the hull and shelled peas.

Insect Pests of Grain Legumes

A review is presented of the principal arthropod pests of pulse crops in the tropics. The pests are grouped taxonomically but are discussed roughly in the order in which they colonise a crop. Pests of stored legumes are not dealt with, even though in some cases infestation begins in the field. Information is presented on distribution, damage, the life-cycle and control of leafhoppers, aphids, beanflies, beetles, Lepidoptera, thrips and pod-sucking Hemiptera. Future strategies for pest control are discussed

Control of Cotton Thrips by Seed Treatment, 1978

Abstract Five insecticides were evaluated for systemic activity against thrips. Stoneville 213 cottonseed were treated in a laboratory “tumbler” type seed treater on April 24‘78. All seed except the untreated check were also treated with Captan 30 Flowable and Vitavax 30 Flowable Fungicides at the rate of 1.2 oz A.l. each per 100 pounds. Plots were planted May 10‘78 at Custom Ag Service Research Farm, Loraine, Texas. Each treatment was replicated four times with each replication being two rows wide and 25 feet long. Plantings were made with a two row “cone” type planter with exactly 300 seeds being planted per row of each replication. Stand count, thrips count, and thrips damage ratings were made on June 9‘78.

Insecticides for Frankliniella occidentalis and Lygus hesperus on Safflower Plants12

Replicated small plot and aircraft tests on safflower showed that methidathion and oxydemetonmethyl effectively reduced bud damage from feeding by the western flower thrips, Frankliniella occidentalis (Pergande), and Lygus hesperus Knight. Both insecticides at 0.56 kg AI/ha effectively controlled thrips damage and 2 applications (at prebloom and onset of bloom) were superior to one. Methidathion, applied at 0.56 kg and 1.12 kg AI/ha by aircraft, was more effective in controlling populations of L. hespersus than oxydemetonmethyl, and seed yields were significantly better than in the controls for both dosages. Residues of methidathion at 0.56 kg AI/ha after 3 hand or aircraft applications were low, and residues of oxydemethonmethyl after 3 hand applications also were low. Neither of these insecticides are registered for use on safflower.

Interaction of Peanut Variety and Insecticide1,2

Abstract It is generally assumed that insecticide performance is independent of the peanut variety; however, tests conducted for several years indicate insecticide performance is influenced by the peanut variety. The most significant variety-insecticide interaction resulted from systemic insecticides used for control of thrips and leafhoppers on bunch type peanuts. Thimet (phorate) was more effective than Furadan (carbofuran) for thrips control regardless of the peanut variety. Erratic control of thrips and leafhoppers was obtained on bunch, Virginia type peanuts NC Ac 15754, NC Ac 15753, and ‘Shulamit.’ Thimet applied to runner and intermediate growth type peanuts reduced thrips and thrips damage in excess of 90%. Furadan was ineffective against thrips on NC Ac 15754 and gave less than 50% control on Shulamit. Thimet failed to control the potato leafhopper on NC Ac 15753 and Shulamit but gave good control on NC Ac 15754. Furadan which failed to control thrips on NC Ac 15754 gave approximately 50% control of leafhoppers. Furadan which reduced thrips by only 65% on NC Ac 15753 reduced leafhopper damage by 90%. The peanut variety also influenced insecticidal control of the southern corn rootworm. NC Ac 15753 exhibited 2 to 3 times more rootworm damage than ‘Florigiant’ when both peanut varieties were treated with the same rates of insecticides. Diazinon was ineffective against the rootworm on NC Ac 15753 and Mocap performance was significantly reduced when applied on NC Ac 15753. These data indicate the peanut variety should be considered an integral part of an insect control program.

Resistance to Thrips Damage in Cassava1

Part of the germplasm bank of cassava in the Centro Internacional de Agricultura Tropical (CIAT) was evaluated at the end of each of 2 successive dry seasons for resistance to thrips, Frankliniella sp. and Corynothrips stenopterus Will. Clones were classified in 6 resistance groups on the basis of damage symptoms. About 20% of the 1254 clones evaluated showed no symptoms of thrips damage. Thrips damage and the number of thrips present in the terminal buds were related. A strong relationship existed between pubescence of unexpanded leaves and thrips resistance; plants with pubescent leaves were resistant to thrips attack. At flowering, leaf pubescence decreased and thrips susceptibility increased. Resistance was not associated with plantcyanide content. Thrips may cause similar symptoms as viral or mycoplasmic organisms.

Cotton crop environment, growth and yield in the Sudan Gezira: II. The causes of variation in yield from year to year

SUMMARYAt three sites in the Sudan Gezira the variations in seed cotton yields between 1941 and 1961 were due, in the main, to variations in insect pest damage and, at one site only, to a downward trend in soil nitrogen level.At each site seed cotton yield was predetermined by total plant top dry weight before the opening of the first cotton bolls. The cotton crop was sown in August. At Turabi in the northern Gezira and at the Gezira Research Station in the south-central Gezira, variations in plant growth up to early October had little effect on subsequent yield. The yield was determined by growth during October, November and December; the total top dry weight at the end of December was much more important than the pattern of growth by which this weight was attained. At these sites yield was much more closely dependent on the amount of leaf recorded as free from pest and disease damage than on total leaf weight. Damage due to jassid (Empoasca lybica), thrips (Caliothrips spp.) and leaf curl accounted for 69% of the year to year yield variation at Turabi. Damage due to jassid and thrips accounted for 56% of the year-to-year variation at the Gezira Research Station.Severe pest damage was associated with low July plus August rains and high temperatures during the growing season but was not found to be dependent on leaf nitrogen levels.At Hag Abdulla in the southern Gezira, there was a general downward trend in yields over the years as well as variation from year to year consequent on variations in thrips damage. The downward trend inyields was associated with a trend to lower soil nitrate and plant nitrogen levels which resulted in anearlier cessation of leaf growth in recent years than hitherto.Variation in the level of pest attack accounted for 61% of the year-to-year variation in nitrogen response at Turabi, while at Hag Abdulla the response to nitrogen was determined by the deleterious effect of thrips and by a trend to increasing response as natural soil nitrate levels declined.Gezira commercial crop yields were closely correlated with those of the appropriate experimental plots for the years considered (r = 0·859 for the S-type crop, 0·736 for the L-type crop) inspite of some differences in cultural practice. This suggests that the major causes of variation were the same in both cases and that adequate protection against insect pests should do much to prevent the recurrence of seasons of extremely low yield with their serious economic consequences.

Insect Preference for Peanut Varieties1

Fourteen advanced peanut lines (3 market types) had differential damage by some insect species that feed on foliage. By visual rating, leaf damage to Runner and Virginia types by thrips was not significantly different in 1966. However, the damage to both types was significantly greater than that to Spanish types. The same relationship existed in 1965, but differences by plant types were not significantly different. The varieties Starr, Argentine, Spanish Check, and NC-2 possessed some nonpreference to leaf feeding by thrips. Damage from foliage feeding or larval leaf ragging (largely by the corn earworm, Heliothis zea (Boddie) ), was significantly higher in both 1965 and 1966 for Spanish types than for Runner and Virginia types, but the ratings for lines of Runner and Virginia types were not significantly different. Among the varieties, nonpreference, based on ragging, was indicated for Runner Check, Virginia Bunch 67, Florigiant, Fla. Exp. 416, and Ga. 119-20. In both years, Runner and Virginia types significantly outyielded Spanish types on a per-plant basis. Also, correlations between yield and thrips damage and yield and ragging damage by the corn earworm for varieties showed, in both seasons, that yield significantly decreased with increased ragging and increased with an increase in thrips damage. Artificial applications of eggs of the lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), at a level of infestation of 15 eggs per plant per year failed to produce significant differences in percent of damaged pods among plant types or among varieties.

Effect of Flower Thrips on Onion Seed Plants and a Study of Their Control

Feeding injury by the flower thrips, Frankliniella occidentalis (Pergande), to onion seed plants occurs primarly in the flower filaments, causing a premature loss of pollen, and a decrease in pollination and seed set. Microscopic examinations and counts show that about 10 thrips per flower or floret are needed to cause meaningful injury. Thus, an average of 9,000 to 10,000 thrips per seed head would be necessary to cause any economic injury and seed loss, at an average of 900 to 1000 flowers per head. Field investigations of thrips damage were conducted by introducing varying numbers of adults on seed heads enclosed by fine-meshed cloth cages. The highest infestations of nymphs plus adults attained were 1900, 2400, and 3600 per head. These numbers of thrips did not cause any reduction in the seed set, yield, size or viability. Thrips increased pollination and seed set over the controls in all experiments. The addition of pollinators resulted in an increased seed production and viability over that of thrips alone. The presence of fly pollinators and 2 heads per replicate cage proved necessary to obtain adequate seed set in the thrips-damage studies. Three years of experimentation never demonstrated enough thrips per head to cause an economic loss of onion seed. Two and three applications of parathion and diazinon resulted in satisfactory thrips control. These treatments did not increase or decrease seed set or yield but the use of parathion indicated some increase in seed viability. Parathion treatments reduced numbers of bee and fly pollinators for about 3 days when applied during bloom. A single prebloom application of 1/2-1 lb per acre of dimethoate gave outstanding thrips control and no pollinators reduction. Another application during bloom reduced pollinators for up to 10 days. The single dimethoate application resulted in an increase in seed set and yield, which appeared to be in addition to any possible effect on thrips and pollinators, indicating some additional plant response to the chemical.

Onion Thrips (Thrips tabaci Lind.) Infesting Cabbage1

Infestations of thrips, principally Thrips tabaci Lind., but including small numbers of Frankliniella fusca (Hinds), F. tritici (Fitch), F. exigua Hood, and F. tenuicornis (Uzel) have seriously damaged maturing fresh market cabbage in production fields in eastern Iowa. On the basis of trapping records, the thrips apparently migrated from alfalfa and winter wheat where they had attained great numbers which were counted in periodic samplings. The thrips were not controlled by DDT nor, in fact, by other compounds after they had become established within the cabbage head. A series of insecticides were compared in field plots in 1956 and 1957 through a method of visual rating of relative plant damage at harvest. Heptachlor was the most effective in preventing thrips damage. Following a weekly schedule of applications of heptachlor at one-half pound per acre the marketable crop was increased 30% above that of untreated check plots where losses ranged from 36 to 39% of the crop. The problem of thrips damage to cabbage, though not widely recognized is potentially serious.