Mean Number Of Aphids Research Articles

LIFE TABLE ATTRIBUTES AND FEEDING EFFICIENCY OF OENOPIA SAUZETI (MULSANT) (COLEOPTERA: COCCINELLIDAE) FED ON APHID (APHIS GOSSYPII)

Ladybird beetles are play vital role in agroecosystem due to successful and efficient feeding behavior against aphids, the present research experiment was carried to find out the life history and feeding efficacy of oenopiasauzetifed on Aphis gossypii,at the laboratory of Biological Control, integrated pest management programme (IPMP), National Agriculture Research Centre (NARC), Islamabad. The results of the experiment revealed that the mean developmental time of immature stage 3rd and 4th instar have a significant difference with 3.72±0.11 and 3.87±0.036 days, while the egg to adult emergence was 39±0.35 days. The longevity has significant difference in male and female with the higher values at female 34.0 days. Similarly, the feeding efficiency was maximum in O. sauzeti females which feeds on 2227.1 mean number of Aphis gossypii, while the (409.25±1.42) mean numbers of aphids were consumed by larva. The maximum aphid consumption was observed at 4th instar larva (198.98±0.51 aphid) followed by 3rd instar larva (128.57±0.59 aphid). The mean oviposition time of O. sauzetion A. gossypii was recorded as 21.36 days and average eggs laid female-1 day-1 was 20.53, while the total laid eggs given by a female were 253.60. The apparent mortality (100qx) was maximum at egg stage (24) and the mortality survival ratio (MSR) was highest at pupal stage (0.53), similarly, the indispensable mortality (IM) was also observed high at pupal stage. The maximum survival fraction (Sx) was observed at the 4th larval stage (0.91) and the maximum life expectancy (ex) was observed at 1st larval instar (4.51) days. The total killer power (k-value) of the O. sauzetifor the complete generation was 0.49. This will help to develop an ecofriendly managing approach for the minimizing the aphids infestationin economical important crops.

Soybean aphid infestation and crop yield in relation to cultivar, foliar insecticide, and insecticidal seed treatment in South Dakota

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), remains an important pest of soybean, Glycine max (L.) Merr., in areas of the Midwestern United States and southern Canada. Options for managing soybean aphid are currently limited to insecticides and aphid-resistant varieties. Farmers commonly employ a prophylactic treatment of soybean seed with a neonicotinoid insecticide such as thiamethoxam and often a remedial, late-season application of foliar insecticides such as the pyrethroid, λ-cyhalothrin. Environmental concerns about detrimental side effects of neonicotinoids and the substantiation of pyrethroid resistance in field populations of soybean aphid have strengthened the case for planting aphid-resistant soybean cultivars. We conducted a three-year field study in eastern South Dakota, United States, that evaluated commercially-available active substances and enhanced plant materials for soybean aphid management that included a thiamethoxam seed treatment, spray application of λ-cyhalothrin, and an aphid-resistant soybean cultivar containing a pyramid of the Rag1 and Rag2 aphid-resistance genes. Soybean aphid infestations had sustained, economically injurious levels in 2015, but not the other two years. The three management tactics independently reduced soybean aphid population densities. Thiamethoxam and the resistant cultivar suppressed cumulative aphid-days (CAD) in all three years, whereas the λ-cyhalothrin spray decreased CAD in 2015 and 2017. By far, the resistant cultivar had the greatest impact on soybean aphid populations, reducing CAD by 28- to 150-fold year−1, with mean numbers of aphids much less than 100 soybean aphids plant−1. Thiamethoxam seed treatment reduced CAD by 1.7- to 3.5-fold year−1, and λ-cyhalothrin reduced it from 2.0- to 5.6-fold year−1. Soybean yield was not affected by treatments in 2015. Yield was greater for the susceptible than for the resistant cultivar in 2016, and yield was greater for plots without foliar insecticide in 2017. Implications for the use of these management tactics against soybean aphid are discussed.

Resistance and tolerance of ten carrot cultivars to the hawthorn-carrot aphid, Dysaphis crataegi Kalt., in Poland.

Damage caused to cultivated carrots by the hawthorn-carrot aphid, Dysaphis crataegi Kalt. (Hemiptera: Aphididae) is one of the factors limiting carrot production in Poland. Planting resistant and tolerant cultivars could reduce yield losses due to the damage caused by this pest. This study was conducted to evaluate the resistance and/or tolerance of 10 carrot genotypes to hawthorn-carrot aphid. Their field resistance was determined under field conditions based on five indicators, namely, mean number of alates (migrants) per plant and mean percentage of plants colonized by them, mean seasonal number of aphids per plant, mean number of aphids per plant and mean percentage of infested plants at peak abundance. Antibiosis experiments were conducted under laboratory conditions and pre-reproductive, reproductive time, fertility, and demographic parameters, represented by the net reproduction rate (Ro), intrinsic rate of increase (rm) and mean generation time (T), were calculated. Five cultivars, Afro F1, Nipomo F1, Samba F1, White Satin F1, and Yellowstone showed field resistance. Antibiosis experiments revealed significant differences among the carrot cultivars in the length of the reproductive period, female fecundity in the time equal to the pre-reproduction time, and total progeny of hawthorn-carrot aphid. The intrinsic rate of natural increase (rm) for apterous aphids varied significantly, ranging between 0.181 (Nipomo F1) and 0.343 females/female/day (White Satin F1). Additionally, the estimated net reproductive rate (R0) was the lowest on Nipomo F1, and this genotype was determined to be resistant. Our results suggest that a very high density of trichomes on the leaf petioles (71.94 trichomes/cm2) could adversely affect the feeding, bionomy, and demographic parameters of hawthorn-carrot aphid on the cultivar Nipomo F1. In addition, Napa F1 and Kongo F1 demonstrated high tolerance. Considering all the results collectively, four genotypes, Afro F1, Kongo F1, Napa F1 and Nipomo F1, were relatively resistant/tolerant to the hawthorn-carrot aphid.

Influence of Trap Crops on Tomato and Squash Insect Pests

Influence of Trap Crops on Tomato and Squash Insect Pests

Management of mustard aphid, Lipaphis erysimi Kalt on mustard crop

Field experiment was conducted during rabi season of 2014 to study the management strategies against aphid, Lipahis erysemi on mustard crop in two villages of Gopalganj district of Bihar. The present experiment comprising ten treatments was laid out in randomised block design with three replications. The results showed that all the insecticidal treatments were significantly superior to untreated control in minimising aphid population. In overall the minimum (4.55 and 5.09) mean number of aphids on 10 cm terminal portion of shoots per plant was recorded in treatments clipping of aphid infested twigs and spraying with Anaconda 50 EC (chlorpyriphos 45% + cypermethrin 5%) @ 1.0 ml/l water at 10 days interval and clipping of aphid infested twigs and spraying with polytrin 44 EC (profenophos 40% + cypermethrin 4%) @ 1.0 ml/l water at 10 days interval respectively the two being at par in comparison to the 12.48 in untreated control. Maximum yield of 13.68 and 12.56 q/ha was also recorded in the same two treatments respectively the two being at par as compared to 6.39 q/ha obtained in case of control.

Combining entomopathogenic fungi and parasitoids to control the green peach aphid Myzus persicae

The green peach aphid, Myzus persicae, is a major insect pest worldwide. The parasitoid Aphidius colemani and more recently, the entomopathogenic fungus Lecanicillium muscarium strain KV01 (Mycotal®), have been considered as potential biological control against M. persicae. However, no studies have been carried out on the interaction between L. muscarium and A. colemani against M. persicae. This study, therefore, was conducted to determine the most effective timing of application of this fungal strain in combination with either naturally occurring or introduced parasitoids to control Myzus persicae in the laboratory and controlled field environments. In the laboratory, mummification, emergence of parasitoid adults from mummified aphids and female sex ratio of the emerging adults, were not affected when the fungus was applied 6 or 7days after the parasitoids were added, compared with treatment with A. colemani only. Although a 40% reduction in the female sex ratio of emerging parasitoid adults was recorded when fungi applied 3days after the parasitoids were added, fungal application had no significant effect on longevity and fecundity of the female A. colemani F1 generation that emerged from fungus-treated aphids. In the semi-field experiment, the mean number of aphids per leaf was significantly lower in the treatment involving A. colemani in combination with L. muscarium than those with A. colemani alone. However, aphid reduction in the treatments involving naturally occurring parasitoids alone and those in combination with L. muscarium was not significantly different. This study suggests that it is possible to combine L. muscarium with A. colemani to increase the level of aphid control. A more detailed knowledge of the effects of naturally occurring parasitoids on pest control and their interaction with other biological control agents will help to develop environmentally sound crop management strategies with reduced insecticide applications.

Dispersion patterns and sampling plans for the pea aphid, Acyrthosiphon pisum (Harris), on grass pea, Lathyrus sativus L.

From 2009/2010 to 2010/2011, flight patterns and spatial distribution of pea aphids were studied in northwestern Ethiopia. Yellow traps were used and legume fields sampled. Trap catches varied between years (lower in 2009/2010 than in 2010/2011), locations and months in the growing season. At Woreta, peaks were observed in January (20–70 per trap) and at Wondata in October and November (60–80 per trap). Also, pea aphid numbers were more on fallow land than on other land-use systems (a maximum of 41,000 in December 2010/2011 and 25,000 in January 2009/2010 per 100 plants). Taylor's power law coefficients, i.e., b values, were significantly greater than 1 on grass peas planted after fallow; the corresponding r2 values ranged between 0.87 and 0.94. Coefficients were inconsistent on grass peas planted after teff and undersown in maize. The optimum sample size n (number of yellow traps) required in relation to the mean densities of the pea aphid was more or less the same for the three levels of accuracy (D = 0.2, 0.3 and 0.5). At D = 0.5, numerical sample size curves showed 10 traps as mean number of aphids per trap approached 4 or 5, which is practical and affordable. Some additional work at more locations may be required to validate these sampling plans before wider use.

Mating or ovipositing? A crucial decision in the life history of the cabbage aphid parasitoid Diaeretiella rapae (M’Intosh)

1. The reproductive fitness of a parasitoid depends on its mating and ovipositing success. Virgin haplodiploid females can reproduce, but produce only males, and may diminish fitness by producing more male offspring than required. Therefore, females must decide on whether to mate or oviposit first. 2. This study was conducted to assess the mating versus ovipositing decision and its impact on the reproductive fitness of Diaeretiella rapae (Hymenoptera: Aphididae), an endoparasitoid of the cabbage aphid Brevicoryne brassicae (Hemiptera: Aphididae). 3. When newly emerged females were given a choice between mating and ovipositing, about 62% of D. rapae females preferred to mate before ovipositing. Those females who oviposited before mating parasitised only 10% of the available aphids. After mating, females superparasitised their hosts with fertilised eggs, which resulted in a highly female-biased sex ratio in the offspring. 4. Mating success was very high (91%) in the presence of hosts (cabbage aphid nymphs) compared with that in the absence of aphids. However, mating success was not influenced by the quality (size) of the hosts present in the mating arena, despite a parasitoid preference for larger hosts during oviposition. The time between pairing and mating was also shorter in the presence of host aphids. The mean number of aphids parasitised and the parasitism rate were significantly greater after mating.

SamplingAphis glycines(Homoptera: Aphididae) in Soybean Fields in Illinois

The aphid Aphis glycines Matsumura, which was first observed in North America in 2000, is a pest of soybean, Glycine max L., in the United States and southern Canada. This study focused on the distribution and sampling of this aphid at two spatial scales: field and township. We sampled 14 soybean fields in each of two townships in Kendall and Champaign counties in Illinois on four sampling dates during the summers of 2001–2003. Generally, there was little synchrony of population dynamics (increases or decreases) across the fields in either township during the middle of the summers. There was significant field-to-field variability in mean number of aphids per plant. Thus, multiple fields must be sampled to accurately understand the infestation levels in a township. For Kendall Township in all years, drilled soybean fields always had the highest mean density at the second and third sampling dates, but fields with wide rows (0.61–0.76-m widths) had the highest mean density at the fourth date. However, row spacing had no significant influence on the mean density in most of the other analyses of variance. The probability of finding an infested field by mid-July when mean density in the township is less than two aphids per plant is 50% for Kendall County and 11% for Champaign County. Thus, at least two and 14 fields in Kendall and Champaign counties, respectively, must be sampled (50 plants per field) to have at least a 75% chance of finding a new invader in at least one infested field in a township during that period. Variance was related to mean number of aphids per plant, M, in a field by S2 = 6.39911 × M1.71779. This specific form of Taylor’s power law allowed us to calculate the appropriate sample sizes (plants/field) needed to obtain different levels of precision. Regression analysis showed no relationship between aphid density and distance from the field edge over the 50-m transects used in sampling. The relationship between the proportion of infested plants in a field, P, and mean aphid density, M, is represented by P = 1 − exp(−0.195764M). The proportion exceeds 0.99 for mean densities exceeding 24 aphids per plant in a field. Thus, our results suggest that aphids should be counted on 50 plants per field to obtain a reliable estimate of the population.

Comparison of Methods for Monitoring Mindarus abietinus (Homoptera: Aphididae) and Their Potential Damage in Christmas Tree Plantations

The balsam twig aphid, Mindarus abietinus Koch, causes distortion, loss, or both, of needles on balsam fir Christmas trees. Insecticides are often applied for control of twig aphids with little monitoring of population levels or their subsequent damage. This study compared the utility of 2 techniques (beating discs and visual counts of infested shoots) that could easily be used by Christmas tree growers to monitor aphids. A beating technique was better than visual counts for detecting numbers of fundatrices before and during budbreak, whereas visual counts of midcrown infested shoots were more feasible for estimating aphid abundance after budbreak. Sample size analysis indicated that a minimum of 15 trees could be used for either method to estimate mean numbers of fundatrices or mean proportions of potentially infested shoots. Correlation analyses between mean numbers of aphids or proportions of infested shoots and resulting proportions of undamaged shoots were variable with a significant and negative correlation between infested shoots and subsequent undamaged shoots ( r = −0.83). Paired comparisons were also made between selected and nonselected Choose-and-Cut Christmas trees to evaluate public perception of aphid damage. The public did not differentiate between aphid-damaged and undamaged trees, but they did show a preference for larger trees. Our results indicate that growers need to monitor aphids before budbreak and limit insecticide applications to trees with predictable levels of infestation (e.g., 2 or more fundatrices per disc results in ≈50% infested shoots) that will be harvested for shipment rather than grown for Choose-and-Cut.

Shoot‐feeding Aphids Promote Development of Gremmeniella abietina, the Fungal Pathogen Causing Scleroderris Canker Disease in Conifers

AbstractWe tested experimentally whether shoot feeding aphids Cinara pinea (Mordv.) can promote the development of Gremmeniella abietina (Lagerb.) Morelet, a fungus which causes Scleroderris canker disease in conifers. Pine seedlings were infested with aphids at two different times, and subsequently inoculated with conidia of G. abietina at two different times. The degree of infestation was classified into three groups based on the number of aphids/seedling: none, one (low level), and three (high level). Because of parthenogenetic reproduction, the number of aphids increased during the summer, so we also used aphid numbers to explain the development of the symptoms. Necrosis caused by G. abietina was more prevalent in seedlings infested by aphids in June, and inoculated with fungus in July. Expressed as percents of the total length of the shoots, the necrosis had advanced 50%, 70%, and 95% with no, low, and high aphid levels, respectively. Canker formation was significantly greater when G. abietina conidia were inoculated in July, compared to August. In August, there were no statistically significant differences in the intensity of disease between aphid infestation levels, but the mean number of aphids was related to disease intensity. In the spring following infection, seedlings with aphids had more dead and fewer healthy terminal buds compared to seedlings without aphids.

Gaucho as an Aphicide in Spring Barley

Abstract Plots were seeded by small plot drill on 14 May (80 lb/acre) at the USDA-ARS Western Regional Plant Materials Introduction Center at Central Ferry, WA. Gaucho was applied as a seed treatment and Dimethoate was applied 20-days after emergence (DAE) with a CO2-powered backpack sprayer at 20 gpa and 20 psi, with the spray buffered to pH 5.0. Plots were 10 X 30 ft replicated 4 times in a RCB design. The experiment was designed to measure 1) the impact of Russian wheat aphid (and other cereal aphids present) on spring barley yields at economic injury levels; 2) the value of Gaucho as an aphicide in spring barley; and 3) effects of aphid controls on parasitoids of RWA and other species. Treatments were evaluated at 6, 13, 20, 27, 34, 41, 48, and 55-DAE by visual examination for each aphid species per tiller plus number of aphids per tiller, and the mean number of aphids parasitized (Diaeretiella rapae Hymenoptera: Aphidiidae in all cases). The dimethoate treatment was made on 20-DAE (approaching economic injury level) and evaluated on 6-DAT (27-DAE) and 13-DAT (34-DAE) as well as on all other DAE dates. At crop maturity, yield was calculated from m2 samples from each replicate to provide mean tons/acre for each treatment. Data were analyzed by ANOVA (P = 0.05; LSD).

Efficacy of Systemic Aphicides for Control of Melon Aphid on Cantaloupe, 1993

Abstract Two greenhouse trials were conducted sequentially to evaluate rates of systemic aphicides for control of melon aphid on cantaloupe. Methods of both trials were the same with the exceptions of the cultivars used, number of replicates and sample intervals. In the first trial, ‘Top Mark’ cantaloupe were planted 16 Aug and arranged in a RCB design with 4 replications. In the second trial, ‘Perlita’ cantaloupe were planted 4 Oct and arranged in a RCB with 3 replications. In both trials, cantaloupe were seeded in 6-inch pots with Metro Mix® Redi Earth growing medium (40-50% peat moss; 50-60% medium vermiculite), thinned to 1 plant per pot when plants reached the 1st true leaf stage, and maintained in a greenhouse at 65°F a 85°F during the trial. Untreated cantaloupe and watermelon plants colonized with melon aphid were interspaced between treated plants as an infestation source during the trial. A general purpose fertilizer was applied at the recommended greenhouse rate, triadimefon was misted over plants with a spray bottle at the recommended rate for powdery mildew control, and plants were irrigated as needed by adding water to plastic trays used to hold each pot. All treatments were applied as a soil drench around the base of each plant after pretreatment counts. Four oz total volume was used for each treatment and the untreated control received 4 oz of water alone. The total number of aphids were counted on three leaves per plant, and each leaf was marked and resampled 3 (1st trial); 4, 6, 8, and 10 DAT (2nd trial). Linear regression analysis was used to determine relationships between aphicide rate and mean number of aphids per leaf. Data were analyzed for treatment differences using analysis of variance and means were separated with Ryan-Einot-Gabriel-Welsch multiple range tests (P ≤ 0.10).

Response of Melon Aphid to Rates of Admire and CGA 215944 on Watermelon, 1993

Abstract ‘All Sweet’ watermelon were seeded in 4-inch pots with Metro Mix® Redi Earth growing medium (40-50% peat moss; 50-60% medium vermiculite) on 18 Jun and maintained in a greenhouse at 65°F a 85°F during the trial. Plants were placed outside the greenhouse two weeks prior to treatment to allow natural colonization by melon aphids. Forty-four plants of uniform size and initial aphid numbers were selected for use in the study. Plants were transplanted into 6-inch pots and returned to the greenhouse. Peters general purpose fertilizer was applied at the recommended greenhouse rate on 22 Jul and plants were irrigated as needed by adding water to plastic trays used to hold each pot. All treatments were replicated 4 times in a RBC block design. Eleven treatments, five serial dilutions of two aphicides and an untreated control, were applied as a soil drench around the base of each plant on 27 Jul after pretreatment counts. Four oz total volume was used for each treatment and the untreated control received 4 oz of water alone. The total number of melon aphids was counted on 3 leaves per plant 6, 10, and 14 DAT. Linear regression analysis was used to determine relationships between aphicide rate and mean number of aphids per leaf. Analyses of variance were used to distinguish differences in aphid numbers and among aphicide rates. Means were separated with Ryan-Einot-Gabriel-Welsch multiple range tests (P ≤ 0.10).

Binomial Sequential Sampling Methods for Cereal Aphids in Small Grains

Seventy-one samples of 200 to 400 tillers each were taken from small grain fields. An equation used to relate the proportion of infested tillers to the mean number of aphids per tiller fit the data well ( r 2 = 0.98). Although the equation was developed from pooled counts of four species of cereal aphids ( Schizaphis graminum (Rondani), Sitobion avenae (F.), Rhopalosiphum padi (L.), and R. maidis (Fitch)), it described the relationship between the proportion of infested tillers and mean number of aphids per tiller adequately for each species individually. When predictions from the equation were compared with independent data, the predicted and actual numbers of aphids per tiller were similar. Required sample sizes for estimation of the mean number of aphids per tiller with fixed average levels of precision (standard error /mean) were determined. Required sample sizes to achieve a precision level of 0.15 ranged from a low of approximately 110 tillers for intermediate aphid populations to >500 tillers for low and high aphid populations. A truncated sequential sampling plan was developed. Using this plan, from 25 to 100 tillers are inspected for the presence or absence of cereal aphids. The average number of tillers inspected to arrive at a control decision ranged from 25 to 76 tillers depending on aphid population density. The frequency of decision errors was high (approximately 0.9) for populations near the action threshold (12.5 aphids/tiller), but was otherwise acceptable.

Field evaluation of citrus germplasm for resistance to the black aphid, Toxoptera aurantii (Boy.) Under tropical humid south Indian conditions

Studies on relative susceptibility of 78 citrus varieties/hybrids to the incidence of black citrus aphid, T. aurantii under tropical humid conditions in south India revealed that none of the varieties was completely free from aphid incidence. The varieties Nagpur Mandarin and Ikeda Unshiu among mandarins; Longsport Valencia, Campbell Valencia and Washington Navel among sweet oranges; and Carrizo Citrange a hybrid and Dessert Orange, Eureka Lemon, Grape Fruit Pink and Jatti Khatti, among acid citrus group, recorded significantly least mean number of aphids per flush and can be effectively used in breeding programmes.

Insecticides and Combinations for Control of Green Peach Aphid, 1986

Abstract Aphids from a greenhouse colony were introduced onto greenhouse-grown, vegetative, potted mums in Jan. All plants were initially pruned to equal height and six leaves. Two foliar sprays, 3 days apart were applied to runoff with hand-held mist bottles. Efficacy evaluations on both lower canopy leaves and 3-inch terminal shoots were based on the mean number of aphids per replicate pot, with 3 samples summed to comprise each replicate, and 4 replicate pots per treatment.

Aphid Control on Louisiana Pecans, 1983

Abstract The study was conducted on mature Stuart pecan trees, approximately 60 ft. tall, in south Bossier City, Bossier Parish, La. A randomized block design composed of three blocks, with one tree per treatment, per block, was used. Nine treatments were evaluated. Insecticides were applied 17 Aug. with an FMC 957 speed sprayer, calibrated to deliver approximately 30 gal of finished material per tree. At the time of application the mean number of aphids per leaf exceeded the threshold of 10 aphids per leaf. Four hours after treatments were made 0.15 in. of rain fell, this was followed by another .1 in. of rain 24 h later. Sampling was conducted on 19 Aug. and consisted of counting the aphids on 10 randomly selected compound leaves per tree. Data were subjected to analysis of variance.

Sequential Plans for Sampling Aphids on Sugar Beets in Kern County, California

An efficient sampling plan, to aid in the timing of treatments, is essential to the development of a practical insecticidal program for possible, use in the control of Myzus persicae (Sulzer), the major vector of the beet yellows viruses. Sequential sampling, in which decisions are made upon the accumulated results of each unit sampled, in many eases can save both time and money. Although the tendency of aphids to colonize individual plants leads to what is known as over-dispersed, or contagious, distributions, critical population levels (assumed to be approximately one aphid per plant) are reached before 100% of the plants are infested. This fact permits the use of sequential sampling plans based upon either the mean number of aphids per plant or the number of plants found to be infested. In situations of very light or very heavy populations the use of a sequential sampling plan should allow rapid decisions to be made as to whether critical population levels have been reached.