Efficiency of cotton bollworm (Helicoverpa armigera Hübner) control of different Bt cotton varieties in North China

[Background] The cotton bollworm (Helicoverpa armigera) is one of cotton’s most destructive insect pests in terms of yield and quality. Since 1997, China has grown commercially available transgenic Bacillus thuringiensis (Bt) cotton. We aimed to investigate the variation in resistance of transgenic Bt cotton varieties to cotton bollworm in North China.

[Methods] Populations of cotton bollworm were monitored from 2008 to 2015 in environments where Bt cotton was planted adjacent to other non-Bt crops. The study included 197 Bt cotton varieties planted in 42 counties/locations in three provinces (Hebei, Shandong and Henan) of North China, which were evaluated through field investigations, bioassays, and enzyme-linked immunosorbent assays (ELISA).

[Results] The average number of cotton bollworms never exceeded the action threshold (10 larvae per 100 cotton plants), however, their number reached 19.55 per 100 cotton plants in 2011. The ratios of damaged plants to total Bt cotton stem-tips, buds, and bolls was low except in 2010, when the ratios reached 1.82%, 2.09%, and 10.63%, respectively. The results of bioassay showed that the corrected mortality were higher at the second generation cotton bollworm stage than the third and fourth germination stages. Totally, Bt protein content declined sharply at the seedling stage from 2008 to 2015.

[Conclusions] This study indicated that almost all Bt cotton varieties were capable to effectively control the populations of cotton bollworm in North China.

Efficiency of cotton bollworm (Helicoverpa armigera Hübner) control of different Bt cotton varieties in North China
LÜ Limin, LUO Junyu, ZHANG Shuai, YU Qianlin, MA Ligang, LIU Xiaofeng, WANG Chunyi, MA Xiaoyan, MA Yan and CUI Jinjie

Journal of Cotton Research. 2018; 1:4.
https://doi.org/10.1186/s42397-018-0003-0

Seventh ‘Asian Cotton Research and Development Network’ Meeting, 15-17 Sept 2017, Nagpur India.

The Seventh Meeting of the Asian Cotton Research and Development Network was held at Nagpur during 15-17 September 2017. The Indian Society for Cotton Improvement (ISCI), Mumbai hosted the meeting together with the ICAR-CICR (Central Institute for Cotton Research), Nagpur and ICAR-CIRCOT (Central Institute for Research on Cotton Technologies). The main theme of the meeting was PRODUCING QUALITY FIBRE & DOUBLING COTTON FARMERS INCOME. Cotton researchers from public and the private sector participated. Dr. C. D. Mayee, President, Indian Society for Cotton Improvement, was the chairman, of the organizing Committee. The meeting elected Dr. Prashant G. Patil as Chairman of the Network until the next meeting. Eminent cotton experts i.e., Dr. Timorthy Dennehy, Dr Judith Brown, Dr Albert Santos from US; Dr Derek Russell from Australia, Dr Negm from Egypt and several senior research leaders from India and Bangladesh attended the meeting. The proceedings, recommendations, presentations and abstracts of the meeting can be accessed here.

Seventh Meeting of the ACRDN

Proceedings are available

The Seventh Meeting of the Asian Cotton Research and Development Network was held at Nagpur, India during 15-17 September 2017. The Indian Society for Cotton Improvement (ISCI), Mumbai hosted the meeting together with the ICAR-CICR (Central Institute for Cotton Research), Nagpur and ICAR-CIRCOT (Central Institute for Research on Cotton Technologies).

The main theme of the meeting was  “PRODUCING QUALITY FIBRE & DOUBLING COTTON FARMERS INCOME.” Cotton researchers from public and the private sector participated. Dr. C.D. Mayee, President, Indian Society for Cotton Improvement, was the Chairman of the Organizing Committee. The meeting elected Dr. Prashant G. Patil as Chairman of the Network until the next meeting. Eminent cotton experts like Dr. Timorthy Dennehy, Dr Judith Brown, Dr Albert Santos from US; Dr Derek Russell from Australia; Dr Negm from Egypt and several senior research leaders from India and Bangladesh attended the meeting.

The proceedings, recommendations, presentations and abstracts of the meeting are now available at the ICAC website.

An Integrated Cotton Insect Pest Management System for Cotton-wheat Intercropping in North China

Abstract                                                                         Back to Table of contents

The north China cotton region is the largest cotton-producing area in China, with 3.5 million hectares grown to cotton annually, which constitutes 65% of the nation’s total cotton land. Since the 1980s, there has been a rapid expansion of cotton-wheat intercropping, with the double cropped acreage increasing from 0.4 million hectares in 1978 to 2.3 million hectares in 1993, now accounting for 65% of the region’s total cotton area. Because of this dramatic changes in the cropping systems, structures of insect communities and the dynamics of major insect populations have been altered. Thus, new control strategies and techniques must be developed.

During 1990-1993, structures of insect communities, fluctuations of major insect populations and control techniques in cotton-wheat intercropped areas, were studied. Based on these and previous studies, an integrated insect pest management (IPM) system for cotton-wheat intercropping in north China was developed. The IPM system comprised of four sub-systems; the technical, monitoring, decision-making and extension. The technical sub-system was the major component and consisted of a technical strategy and control techniques. The technical strategy was defined as “suppression of early and late season insect pests through bio-ecological regulating techniques and control of those at mid-season by rational application of insecticides”. The control techniques for the early season were habitat modification, cultivation of early maturing cultivars and conservation of beneficials; those for the mid-season were trapping and chemical control; and those for the late season were application of plant growth regulators, removal of insect food sources and application of selective insecticides.

The IPM system was demonstrated and extended areawide in the major cotton producing provinces of Shandong and Henan during 1991-1993, which brought about significant economic, social and ecological benefits.

                                                                                      Back to Table of contents

HOST RESISTANCE TO THE LEAFHOPPER, AMRASCA DEVASTANS (DISTANT) IN COTTON, GOSSYPIUM SPP.

Abstract                                                                         Back to Table of contents

The cotton leafhopper, Amrasca (Empoasca) devastans (Distant) is a key pest on Upland cotton in India and an upsurge of the pest has been noticed in recent years.  The nymphs and adults desap the leaves resulting in hopperburn, drying and shedding of leaves, reduction in plant stand and loss in yield.  The management of this pest is made difficult by the development of resistance to insecticides and resurgence caused by indiscriminate applications of synthetic insecticides.  Among cultivated cottons, Gossypium arboreum and G. herbaceum are resistant to the leafhopper.  Resistance from these species were transferred to G. hirsutum cottons.  Among wild cottons, G. tomentosum, G. armourianum and G. raimondii are resistant to the leafhopper.

Morphology of cotton plays an important role in imparting resistance to leafhopper.  Hairiness of leaf, toughness of leaf veins, thickness of leaf lamina, length and angle of insertion of leaf hair are associated with resistance.  Non-preference for oviposition is because of high concentrations of allomones like tannins and free gossypol.  Non-reducing sugars, tannins, free gossypol and silica are key factors that influence the antixenosis mechanism.  Anti-nutritional factors like total phenols and epicuticular waxes exert significant adverse effects on leafhopper survival and oviposition.  In G. hirsutum, G. tomentosum and G. arboreum varieties, hairiness and leafhopper resistance are governed by a dominant gene.  The available resistance needs to be exploited both by conventional methods and new innovative techniques.  Cumulative resistance derived from diverse gene pools will be more lasting and there is need to identify new genes that govern the resistance.

Conclusions

For cotton farmers, use of leafhopper resistant varieties is economically cheap and reduces the need to use high cost inputs like insecticides. Given the problems associated with reliance on pesticides, the selection of insect resistant varieties is more pressing than ever before.  Even partial resistance may be useful as it may enhance the effect of natural enemies and possibly reduce the need for other control tactics.  Concerted efforts are essential to breed newer varieties as the present day cultivars are of narrow genetic base which would make them vulnerable to other pests and development of biotypes of leafhopper. Cumulative resistance, derived from diverse gene pools will be more lasting and research attempts should be directed in this line. For continued success of host resistance, research programmes should be directed to identify new gene(s) that impart resistance. Chemical ecology which encompasses the role of varieties that influence the host plant-insect interactions should be directed to identify the role of phytochemicals vis-a-vis host selection by leafhopper. Biotechnology, through the use of genetically engineered transgenic plants offers greatest scope and is one of the virgin areas of research with a lot of potential.

                                                                                        Back to Table of contents

PROBLEMS AND PROSPECTS OF MANAGEMENT OF INSECTICIDE RESISTANCE IN HELICOVERPA ARMIGERA (HÜBNER) IN INDIA

Abstract                                                                         Back to Table of contents

Insecticide resistance in Helicoverpa armigera (Hübner) is a major threat to crop production in India.  Critical gaps in the knowledge base for management of resistant H. armigera in India are identified.  The status, need and constraints to utilisation of Insecticide Resistance Management (IRM) technologies such as scouting, resistance monitoring, temporal and spatial restrictions on the use of pesticides, regulation of application rate, application technology and use of biocontrol agents are discussed in relation to conditions prevailing in India.  A simple IRM strategy for improved control of H. armigera in cotton is suggested.  The need for adopting Integrated Pest Management (IPM) in other host H. armigera crops is emphasised.

                                                                                 Back to Table of contents

SYNTHETIC PYRETHROID INDUCED COTTON PLANT LEAF TISSUE MORPHOLOGICAL CHANGES AND INCIDENCE OF BEMISIA TABACI

Abstract                                                                         Back to Table of contents

Trials were conducted during the 1989 and 1990 cotton growing seasons at Parbhani, Maharashtra State, India to study the impact of synthetic pyrethroids on the incidence of the whitefly, Bemisia tabaci (Gennadius).  Treatments consisted of:  (1) five applications of cypermethrin 0.0075%; (2) five applications of fenvalerate 0.016%; (3) five applications of cypermethrin 0.0075% + dimethoate 0.03%; (4) three applications of cypermethrin 0.0075% alternated with two applications of monocrotophos 0.06%; (5) three applications of fenvalerate 0.016% alternated with two applications of monocrotophos 0.06%.  Whitefly adult populations were significantly higher in cypermethrin and fenvalerate treated plots compared to untreated cotton plots.  The leaf anatomical studies indicated a reduction in the thickness of the palisade layer and a change in the cellular pattern of the mesophyll tissue layer.  The data provided a possible reason for higher whitefly adult populations in the synthetic pyrethroid treated plots.

                                                                                 Back to Table of contents

THE USE OF PHEROMONES TO CONTROL THREE SPECIES OF BOLLWORM IN PAKISTAN

Introduction                                                                Back to Table of contents

The pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae) is a major world-wide pest of cotton.  Once the eggs have hatched and the larvae have entered into the bolls it is difficult to control using conventional insecticides.

The spiny bollworm, Earias insulana (Boisduval) (Lepidoptera: Noctuidae), is largely confined to the near and middle Eastern areas of the world, including the Mediterranean; the spotted bollworm, Earias vittella (Fabricius) (Lepidoptera: Noctuidae) is found further East, particularly in the Indian sub-Continent and is a more sporadic and localised pest.  However, in some years it is capable of causing serious reductions in cotton yield.  Unlike the pink bollworm, which as its name implies primarily attacks the cotton bolls, the spiny and spotted bollworms damage all stages of the crop, the pin-squares, flowers and bolls, and can also act as a stem borer in young cotton plants.

Conclusions

There are now two pheromone formulations available with which it is possible to control the three major bollworm pests of cotton in Pakistan.  Trials have demonstrated clearly that larval infestations by these three species can be reduced and yields of seed cotton increased by a single early season application of either of the formulations containing both pheromones.  Numbers of insecticide applications to control secondary pests can also be reduced.  An important consequence of the reduction in the levels of pesticide applied is the increased numbers of beneficial insects present in the pheromone treated areas which contributes to reduced levels of attack by potentially serious pests such as H. armigera and B. tabaci.

Although the materials and techniques are now available, pheromonal control of the Earias spp. is not an economically viable option at the present time due to the current cost of Earias pheromone.  It is hoped that new and cheaper synthetic routes will be developed, as has happened with other pheromones, which will reduce their cost and lead to their eventual commercial use in cotton pest management.  However, acceptance by farmers and decision makers in Pakistan of the benefits of using pheromones to control of  P. gossypiella is expanding and current commercial evaluation of P. gossypiella pheromone formulations is expected to lead to wider availability and increased use.

The use of slow-release pheromone formulations to control cotton bollworm pests will  also provide the opportunity to reduce current levels of pesticide applied to control the cotton pest complex in Pakistan.  If their use is integrated into the cotton pest management recommendations, they will form an important element of a future Insecticide Resistance Management (IRM) strategy.  This could be of considerable benefit in a region where pesticide resistance in cotton pests is an increasing threat to sustainable cotton production.

Although both the pheromone formulations tested can only be applied by hand, this  makes them particularly suitable for use in Pakistan and other developing countries, where agriculture in general and cotton cultivation in particular is labour intensive and a work-force is available with which to apply the formulations.

                                                                                 Back to Table of contents

THAI COTTON GROWERS STILL FAR AWAY FROM IPM: CONTRIBUTION OF SYSTEMS APPROACH TO A BETTER UNDERSTANDING OF FARMERS’ PRACTICES

Abstract                                                                         Back to Table of contents

On-farm surveys have been performed since 1991 in two cotton growing areas in Thailand for three cropping seasons. A systems approach focused on farmers’ technical choices in relation to characteristics of the bio-physical and socio-economic environments as well as the differentiated functioning of their production systems. On-farm experiments aiming at assessing the impact of different pest management practices on the cotton crop have been carried out in the same areas.

Intensive cultivation practices have brought about fundamental transformations of the ecosystems (e.g. evolution of the entomofauna and insect resistance) as well as the farming systems (high input use, dependence on agrochemicals and lint processing industries, spiralling production costs, etc.) all of which has led to a steady reduction in cotton production during the last few years. One key factor identified as a major constraint for cotton production is the inability of farmers to control pests through economically and environmentally sustainable cultivation practices. Although most cotton growers are aware of the “environmentally friendly” techniques promoted by agricultural extension agencies, they are not able to implement them because of constraints imposed by their socio-economic environment. Thus, Integrated Pest Management (IPM) propositions should avoid any standardized set of pest management techniques but should promote an approach utilizing agro-ecological principles and translating them into a socio-economic framework respecting farmers objectives.

Conclusions

Entering the sixth phase of cotton production history will not be an easy enterprise given:  the critical stage which has already been reached in the environment degradation process (Trébuil, 1993); a government policy which supports the textile industry through raw cotton imports at low prices; and alternative agricultural or non-agricultural activities which have emerged in recent years.

However, rapid solutions toward an improved sustainable pest management have to be found before an intolerable situation spreads to other production, especially orchards and vegetable crops. “The systems approach has shown its relevance to deal with the inter-related components of such fragile ecosystems where disasters have occurred because of non-holistic pest management practices in the past. IPM is not a technological package that farmers can adopt if they see their interest, but an approach utilizing agro-ecological principles and translating them into a socio-economic framework respecting farmers objectives” (Teng and Savary, 1992). Recommendations targeted at the various types of farmer should receive good responses as far as the future users have been involved in the successive phases of their elaboration. In the same way, extension personnel and, more widely, all the actors of regional agricultural development should be involved in such research and development processes.

                                                                                 Back to Table of contents

INSECTICIDE RESISTANCE IN HELICOVERPA ARMIGERA (HÜBNER): STATUS AND PROSPECTS FOR ITS MANAGEMENT IN INDIA

Abstract                                                                         Back to Table of contents

Insecticide resistance and concomitant field failures to control the cotton bollworm, Helicoverpa armigera (Hübner) were first recorded in south India in 1987. During the 1992/93 cropping season a discriminating dose technique was used to routinely monitor resistance in four major cotton and pulse growing areas of Andhra Pradesh State. Very high levels of resistance to pyrethroids and significant endosulfan and organophosphate resistance were a feature of all regions monitored  – the intensity of expression being determined by local selection pressure and mixing of populations by windborne migration against a changing background of insecticide use across seasons. Levels of piperonyl butoxide insensitive pyrethroid resistance were higher in the more intensive insecticide use regions. Farmers are applying more frequent and higher doses of insecticides, often as mixtures, in an attempt to control resistant H. armigera, but field failures and economic losses are common. Wide-scale implementation of insecticide resistance management (IRM) rationale, resulting in greater control over the use of insecticides is urgently needed to reduce the resistance selection pressure on conventional insecticides and to conserve susceptibility to newer insecticides and biorationals with novel modes of action. Constraints and prospects for IRM implementation in India are discussed.

                                                                                 Back to Table of contents