Chemical Control of Aphid Populations in Cotton Using Hydraulic and Electrostatic Sprayers and Aphid Alarm Pheromone

ABSTRACT
In experimental cotton fields in Lianoverghi, Imathia, Greece in 1995 (cultivar Zeta-2) and Velestino, Magnesia in 1996 (cultivar Corina), experiments comparisons were made between different application methods for chemical control of aphids. There were five treatments in a randomized complete block design in four replications. The treatments were: control, cyhalothrin sprayed with hydraulic or electrostatic sprayer and cyhalothrin with pheromone sprayed with hydraulic or electrostatic sprayer. Observations of the presence of aphids were taken 1-2 days before and 7-8 and 20 days after the applications. The predominant aphid species in both regions was Aphis gossypii Glover. The electrostatic sprayer was more effective than the hydraulic. The presence of the pheromone did not change the efficiency of the insecticide with either method. Both methods were less effective when aphid populations were high. Aphid populations were high in untreated plots 7 days after spraying, but later declined below populations in the treated plots, possibly because of the activity of natural enemies. The electrostatic sprayer was less efficient than the hydraulic when aphid populations were very high and full grown plants formed a continuous canopy.

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Update on the Area-Wide Budworm/Bollworm Management Program with Virus in the United States

ABSTRACT
An area-wide management program with Helicoverpa zea nucleopolyhedrovirus (HzSNPV) has been conducted in the Mississippi Delta to control the first generation of cotton bollworm and tobacco budworm in wild geranium. Results are reported for the 1997 area-wide management program using a lower HzSNPV application rate. The HzSNPV formulation used in this study consisted of GemstarTM LC (Thermo Trilogy, Inc.) diluted in water with an equal volume of cotton seed oil with an emulsifier. Aerial applications of the HzSNPV formulation were applied at a volume of 2.33 liters per ha and with an application rate of 2.5 X 1011 occlusion bodies (OB’s) per ha. Adult emergence, moth numbers and virus stability and activity were monitored to assess the effectiveness of the program. Adult emergence was reduced significantly (82.7%) in naturally-infested enclosure cages treated with the virus. Pheromone trap data suggested that total moth emergence was reduced 47% compared with moth emergence in untreated areas. Wild geranium treated with the virus retained >50% of the original activity 3 days after virus application. Virus mortality was >80% from samples collected randomly immediately after application. A grower-funded program for managing Heliothis/Helicoverpa has been proposed for the Mississippi Delta that would encompass approximately 324,000 ha at an estimated total cost of US$ 1,905,120.

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Use of Pheromones for Pink Bollworm (Pectinophora gossypiella, Saunders) Mating Disruption in Israel

ABSTRACT
Pink bollworm (Pectinophora gossypiella) is one of the major cotton pests of Israel. Until ten years ago the pest appeared mainly in one region, the Beit-Shean valley, but it has spread all over Israel. The number of spray applications against this pest ranges between 1 and 9, mainly organo-phosphates and pyrethroids. Applications start early in the season, disrupting the delicate balance that exists between natural enemies and pests. The result is severe outbreaks of other pest. In the mid-1980s, the Sandoz pheromone product “No Mate” was used for mating disruption. P.B. Rope technology evolved in the Beit Shean valley during the 1990’s. The average number of insecticide sprays declined from 9 to 5. Insecticide applications only commenced in the middle of the season following delayed pink bollworm occurrence and the decline in population intensity. This affected other pest populations. Since 1991 the use of P.B. Ropes and P.B. Rings (AGRISENSE) has increased and during the 1998 season, approximately half the cotton fields are treated with P.B. Ropes. The recommendation in Israel is to administer pheromone Ropes and rings early in the season, prior to appearance of pin-head squares. The initial dosage used to be 500 units (50 mg) per hectare but has been reduced to 250 (40 mg) units per hectare. The application of the pheromones is manual and time consuming. Researchers in Israel are working on a mechanical application method. Pheromones are active for about 2-3 months. Termination of efficacy is difficult to determine. At present, despite difficulties, the American method of pink bollworm oviposition monitoring is under observation.

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Dynamics of Whiteflies and their Enemies in Cotton Fields: Implications for Pest Management

ABSTRACT
The project, entitled “Integrated Pest Management for Cotton” commenced in September 1994 with scientists from four countries, Israel, Egypt, Ethiopia and Zimbabwe co-operating in a joint project funded by the Common Fund for Commodities through the International Cotton Advisory Committee. It seeks to improve the control of honeydew-producing sucking pests, through the use of novel insecticides, natural enemies, better spraying equipment and proper thresholds. Most of the experimentation, especially during the first two years of the project, was carried out in Israel and Egypt. This paper reports some of the more significant findings, with particular emphasis on the importance of natural enemies.

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The Role of Spiders in the Control of Cotton Pests in the Cotton Cropping Systems of Eastern Uganda

ABSTRACT
Work on evaluation of crop mixtures for the management of cotton pests has shown beans to be a suitable intercrop that can augement the numbers of gerneralist predators in the cropping systems of E. Uganda. Incidence of generalist predators in the cotton – bean intercrop shows spiders to be more numerous (57%) as compared to other predators combined (43%). In the cotton- maize intercrop spiders are less numerous (29%) than other predators combined (71%). On cotton bordered by maize the number of spiders is about the same as in the cotton-maize-intercrop. The common predators on cotton bordered by sorghum include 30% spiders. The role of spiders in the regulation of pests in cotton cropping systems is discussed.

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Inhibition of Esterase Mediated Hydrolysis of 1-Naphthyl Butyrate in the B-Biotype Bemesia tabaci (Hemiptera; Aleyroididae) in Australia

ABSTRACT
A colourimetric squash test was used to distinguish between native and B-biotype Bemisia tabaci (Gennadius), for field identification in Australia. This test is based on overproduction of esterase iso-enzymes by B-biotype B. tabaci. This test has occasionally been shown to give a false negative due to organophosphates temporarily binding to esterase enzymes and inhibiting its reaction with an artificial substrate 1-naphthyl butyrate (Byrne and Devonshire, 1991). While it is desirable to have a quick whitefly identification test, it is also important to know if prior treatment with organophosphates will affect the results. Results obtained by polyacrylamide gel electrophoresis demonstrated that the esterase mediated hydrolysis of the artificial substrate 1-naphthyl butyrate is inhibited from 24 to 48 hours after exposure of B-biotype B. tabaci to 0.1% active ingredient organophosphate concentration on exposed leaves. This hinders the ability of the quick identification test to distinguish between resistant B-biotypes and susceptible native B. tabaci if organophosphates were used within 48 hours.

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Pyrethroid Resistance in the Bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in West Africa

ABSTRACT
The sensitivity of bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) to pyrethroids has been monitored in co-operation with CIRAD-CA in research laboratories of National Research Institutes in West and Central Africa for more that ten years. This survey over the last three years, enabled observations of a tendency for resistance to pyrethroids to develop in bollworm. At the same time, loss of efficacy of pyrethroid based sprays has been observed in farmers’ fields in Benin, Burkina Faso, Côte d’Ivoire and Mali. The LD50 recorded in the laboratory on different strains of H. armigera in 1997 and 1998 leads to the factors of resistance varying from 10 to 100 for cypermethrin and deltamethrin. Short term proposals are 1) the implementation of a field survey using the vial test method to learn more about spatial re-partition of the resistant population; b) calendar based spraying programmes with reduced use of pyrethroids; and c) threshold based interventions to control bollworm.

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Quantifying the Organophosphate Resistance of Two Geographically Separate Cotton Aphid Populations by Means of a Polyacrylamide-Gel Electrophoresis (PAGE) Technique

ABSTRACT
Analysis of isoenzymes of different aphid populations showed differences in molecular densities after the addition of different concentrations of an organophosphate. By adding the insecticide, isoenzyme bands of one population get less dense or disappear, while there were minimal changes in the density of the same bands of another geographically separate population. The surplus quantity of active esterase available for binding to the insecticide is represented by a higher density band, possibly reflecting resistance. The technique shows potential to demonstrate resistance of pest populations of red bollworm (Diparopsis castanea), American bollworm (Helicoverpa armigera) and spiny bollworm (Earias spp, probably E. biplaga), the man pests of cotton, against organophosphates. It is a potential tool to quickly monitor resistance on request of the cotton producer.

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Efficacy and Impact of Some Insecticides Used to Control Aphids, Aphis gossypii Glover (Homopters: Aphididae) on Cotton in Uganda, on Predators

ABSTRACT
Representatives of the main insecticide groups currently being used by farmers for the control of the cotton aphid, Aphis gossypii Glover were evaluated . The four insecticides tested were carbosulfan 35 STD (Marshall), cypermethrin 5% E.C. (Ambush), dimethoate 222g/L + chlorpyrifos 278g/L E.C (Salut) and Monocrotophos (Azodrin E.C.). The three foliarly applied insecticides were applied at 5,7,9 and 11weeks after plant emergence (WAE). The fourth insecticide, carbosulfan (Marshall 35) was applied as a seed treatment. Before and after each spray, aphid infestation was assessed and abundance of the major predator species determined. While the protection by the systemic seed dressing did not last beyond five WAE, the most efficacious organophosphorous insecticide (dimethoate 222g/L + chlorpyrifos 278 g/L E.C.) caused the greatest reduction in predator activity. The relative ineffectiveness of cypermethrin 5% against aphids could be due to development of resistance oresulting from its long use. The controversy in insecticide choice for controlling aphids calls for an integrated approach, including cultural and other management options.

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Mechanism of Resistance in Wild Gossypium species to Helicoverpa armigera (Hübner)

ABSTRACT
Eight wild species of Gossypium were evaluated to determine the mechanism of resistance to Helicoverpa armigera (Hübner). Wild species, viz. Gossypium anomalum, G. raimondii, G. harknessii, G. arboreum, G. palmari, G. davidsonii, G. armourianum and G. stocksii and the susceptible control MCU 9 and TCHB 213 were included in the study. Oviposition studies revealed that none of the wild species was preferred for oviposition both under free choice and no choice test. The lowest number of eggs was laid on G. harknessii, G. raimondii, G. stocksii and the largest MCU 9 and TCHB 213. Trichome density did not show linear relationship with oviposition. G. raimondii, G. anomalum, G. davidsonii, G. armourianum and G. stocksii were least preferred for feeding by H. armigera larvae and adversely affected the larval survival, weight gain, pupation, weight and size of the pupae, adult emergence and sex ratio exhibiting antibiotic effect on the growth and development of H. armigera. Tannin, gossypol and total phenols in the leaves and fruiting bodies of wild species were negatively correlated with weight, survival of larvae and pupation of H. armigera.

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