State of the Art of Host Plant Resistance to Insects in Cotton

Johnie N. Jenkins, W.L. Parrott, and J.C. McCarty


 
ABSTRACT

A major change has occurred in the past 10 years in cotton cultivars. Cotton production will see additional and major changes during the decade of the 90's. We predict that less pesticide will be used in cotton production and integrated pest management will become more important for those who stay in cotton production. Unfortunately, the cultivars available today are not being used by producers in many areas of the cotton belt in a way to achieve their full potential. Cotton cultivars should be the foundation upon which crop management is developed. Each of the components of crop management, of which insect management is one component, is impacted greatly by the choice of cultivar. There is a great need to optimize crop management and insect control on the present cultivars. Until we learn to do this on a consistent basis we are not going to realize the potential of current or future cultivars.

Modern cultivars produce 2 to 3 times as much lint on the first 3 fruiting branches as cultivars of a decade ago. This affects crop management throughout the season. The nectariless trait is available in the cultivar Stoneville 907 and in the germplasm line MD 51. Each yielded slightly less than the top cultivars in the Mississippi State yield trials in 1990. Each will provide a significant level of resistance to the plant bug complex. Plant bug resistance is also available in several germplasm lines that are not nectariless.

The germplasm WC 12 NL is nectariless okra leaf and was developed by F.D. Wilson. It has shown significant resistance to pink bollworm and the nectariless trait should also increase its resistance to lygus. It required 41% fewer insecticide applications, which were started 21 days later and terminated 10 days earlier than those on Deltapine 61. Seed damage by pink bollworm was 36% less and yield was 12% more than Deltapine 61.

There have been 25 germplasms registered and released that are resistant to Heliothis spp. None of these are at the cultivar stage of development, although many are close in yield. F2 hybrids between resistant germplasms and cultivars may offer a way to use the present Heliothis resistant germplasms in a very short time and with a minimum of breeding. Stoneville 69132 is a germplasm that is at the strain stage of evaluation. It carries a useful level of resistance to tobacco budworm. A germplasm developed by Jack Jones, LA HGFN 850082, is high in gossypol, and is frego bract and nectariless. It is very resistant to tobacco budworm and is very high in yield. In 1990 with TBW applied and not controlled it yielded more than DES 19 or DPL 50 with TBW controlled.

Genetically engineered cottons containing the B.t. gene showed good resistance to TBW in 1990. This means of achieving insect resistance appears very promising. If F2 hybrids prove to be an effective means of achieving resistance to TBW, one could use the cultivar with the B.t. resistance as one parent and a conventionally developed resistant line as the other parent to produce hybrids that would provide two types of resistance to TBW which should delay the development of resistant biotypes to either type of resistance mechanism.

Pest management of the 90's can benefit greatly by developing on the foundation of the current and future cultivars. To do this all parties involved must realize that the cultivars can make a major contribution to the management of insects; however, to realize this potential all involved must understand how these cultivars fruit and manage them in a manner to allow them to achieve their optimum potential.



Reprinted from 1991 Proceedings Beltwide Cotton Conferences pp. 627 - 633
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998