Insect-Pest Management and Control (1969) / Chapter Skim
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PLANT AND ANIMAL RESISTANCE TO INSECTS
PLANT AND ANIMAL RESISTANCE TO INSECTS
Pages 64-99
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From page 64... ...
This difference in resistance among animals is present from birth to old age and does not depend on previous exposure to the pests. HISTORY AND EXAMPLES The ease of insect-pest control by the use of insecticides, at least since 1940, has often resulted in the neglect of a study of host resistance to the pests.
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From page 65... ...
, into the United States, an unnamed resistant variety of wheat, Triticum aestivum Linnaeus, was mentioned in 1785 by an unknown writer in a farm paper. All trace of some of the first varieties reported as resistant to the Hessian fly has apparently been lost, but, in a few cases, selections of wheat bearing the same names were later found to be resistant.
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From page 66... ...
Resistance to grasshoppers occurs more commonly in corn inbreds derived from varieties formerly grown in the western United States, where grasshoppers have long been a feature of the environment, than from those in more eastern parts of the country. (Courtesy of Kansas Agricultural Experiment Station)
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From page 67... ...
More than 20 such fly-resistant wheat varieties are presently recommended by the agricultural experiment stations of the states involved. For the first time a high level of Hessian fly control is available to all wheat-growing farmers at no cost except, perhaps, a small amount for superior seed (Figure 3)
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From page 68... ...
(Courtesy of Kansas Agricultural Experiment Station) common European breeds.
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From page 69... ...
Only one case is known where two components of resistance are governed by a single genetic factor, the H3 gene for Hessian fly resistance in wheat. The chemical resistance factor, 6-methoxybenzoxazolinone (RFA)
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From page 70... ...
Compare with Figure 5. (Courtesy Kansas Agricultural Experiment Station)
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From page 71... ...
. Cody was derived from 22 spotted alfalfa aphidresistant plants found in Buffalo alfalfa.
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From page 72... ...
It is characteristic of a number of insects with chewing mouthparts where the first-instar larvae on resistant plants take only small nibbles. This is true of the Colorado potato beetle on wild potato, Solanum demissum Lindley
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From page 73... ...
Skin thickness has long been suggested as a factor in preference or nonpreference of stable flies, Stomoxys calcitrans (Linnaeus) , and horn flies occurring on Holstein, Ayreshire, Jersey, or Guernsey cattle.
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From page 74... ...
ANTIBIOSIS Abnormal Effects When Insect Feeds on Resistant Plant The resistance component is called antibiosis when an insect feeds on a resistant plant, and one or more abnormal effects occur: (1) Death of first-instar nymphs or larvae has often resulted, so that the differences between resistant and susceptible plants vary from zero infestation on resistant plants to high infestation on susceptible plants.
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From page 75... ...
This restlessness has been commonly observed with aphids caged on resistant plants and with the Colorado potato beetle on resistant potato plants, and it probably occurs with the Hessian fly on resistant wheat plants. In the last case, first-instar larvae normally settle down behind the leaf sheath just above the node, but on resistant plants dead firstinstar larvae or small flaxseed (puparia)
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From page 76... ...
, resistant wheat varieties planted in counties of the eastern half of north central Kansas to Hessian fly infestation, 1949-1965. When the acreage of resistant wheat decreased in 1960, the Hessian fly infestation increased.
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From page 77... ...
In pea aphid resistance in peas, Pisum sativum Linnaeus, lower concentrations of amino acids occur in resistant than in susceptible lines. The silks of certain corn lines resistant to the TABLE 1 Range of Differences in Antibiosis Average Progeny per Insect and Crop3 Female Aphid per Day*
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From page 78... ...
A sixth basis for antibiosis may involve proliferating tissue or increased secretions of resistant plants, such as that causing the death of eggs or young larvae of the boll weevil, Anthonomus grandis Boheman, the melon leaf miner, Liriomyza pictella (Thompson) , pine resin midges, Retinidiplosis spp., and possibly bark beetles, Dendroctonus spp.
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From page 79... ...
Very long tight corn husks may reduce susceptibility to the corn earworm, but to breed for long husks may also mean to breed for short ears, which are sometimes difficult to harvest. Long husks are effective by confining the cannibalistic earworm larvae together so that most are killed, providing more food for the larvae before they reach the ear proper, possibly confining larvae for a longer time on silks deleterious to the larvae, or all three reasons.
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From page 80... ...
TOLERANCE The tolerance component of resistance is present when the plant shows an ability to grow and reproduce itself or to repair injury to a marked degree despite supporting a population approximately equal to that damaging or destroying a susceptible host. This component of resistance differs from the other two components in that it concerns a response of the plant, whereas nonpreference and preference, and antibiosis, require characteristics of the plant and an insect response.
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From page 81... ...
Studies of the relationship between the two aphids -- greenbug and spotted alfalfa aphid, Therioaphis maculata(Buckton) and their resistant and susceptible hosts have indicated that susceptible varieties generally had more free auxins in both quantity and kind than did resistant varieties.
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From page 82... ...
SOIL MOISTURE AND NUTRITION Soil moisture conditions greatly affect tolerance levels in comparisons of susceptible and resistant plants fed on by insects with sucking mouthparts. Under drought conditions, differences between such plants are often more evident.
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From page 83... ...
The reverse temperature relationship has been true of the resistance of alfalfa, Medicago sativa Linnaeus, to the pea aphid and the spotted alfalfa aphid. In both cases a number of clones carrying genetic factors for resistance are more resistant at high than at low temperatures.
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From page 84... ...
The growing of an insect-resistant variety may lead to the natural selection of insect biotypes capable of surviving on the resistant varieties. For early recognition of biological strains, the finding of insects of normal size developing on resistant plants, rather than the usual absence of any development or the presence of small individuals, suggests the beginning of the selection of biotypes that will feed on the resistant plants.
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From page 85... ...
A peculiar biological feature has been found in one case of an insect disease. When European corn borer larvae feed on certain resistant corns, a protozoan disease organism, which the larvae sometimes carry, may be eliminated, possibly by the action of RFA, so that the few larvae surviving on the resistant plants are healthier and hibernate more successfully than the greater number of larvae surviving on the susceptible plants.
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From page 86... ...
As quickly as possible, the entomologist working on insect resistance in plants, for example, should also make himself familiar with breeding procedures and materials in the crop under study, the more important varieties, and particular problems that the plant breeder faces. Moreover, he should understand that unless a new variety, carrying insect resistance, is equal to or better than currently grown varieties in other respects it will not be approved for release; more importantly, it will not be grown by farmers.
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From page 87... ...
, among plants badly injured by the insect in farmer's field, Stafford County, Kansas, May 1959. (Courtesy Kansas Agricultural Experiment Station)
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From page 88... ...
As a matter of policy, all new and improved crop varieties, or animal breeds and hybrids, should be routinely tested for reaction to important pests of the crop or animal before being approved or released to farmers by the agricultural experiment station. Evidence that resistance is genetic comes primarily from a study of progeny of the supposedly resistant host, which are compared, where possible, with standard or susceptible varieties or with the original resistant plant or animal.
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From page 89... ...
Synthetic varieties produced by interpollination of individual resistant plants may also constitute important sources of selection for resistant factors under various environments. If the source of resistance is found in a nonadapted variety in a selfpollinated crop, it becomes necessary to cross the resistant plant with another that is adapted to the conditions under study.
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From page 90... ...
Some information on components of resistance may already be available from observation or may be secured from cage tests that compared results where insects were compelled to feed or oviposit on a single variety, plant, or animal with those in which free choice was available. TESTING PROCEDURES FOR SEGREGATING GENERATIONS Testing procedures for segregating generations of crosses between resistant and susceptible plants are generally similar to those used in the search for resistance.
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From page 91... ...
Advantage should be taken of all available agricultural experiment stations in the known range of the insect pest and in the area of probable adaptation of the new plant variety. RESISTANCE STUDIES BEST MATERIAL FOR STUDY Partly in parallel or following the preceding research, a study of the basis of resistance should be made, even though in either plant- or animal-breeding or insect control, information on the basis of resistance is not essential.
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From page 92... ...
An indirect study involves a search for characteristics responsible for attraction of the insect and for characteristic responses normally shown by the insect in the finding of food materials present in susceptible hosts. A comparison with similar attempted isolations from a large number of hosts or from resistant plants or animals may lead to the location of biochemicals concerned with resistance.
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From page 93... ...
When resistance can be found in an adapted variety, its use for insect control can be as fast as working out a dosage for an existing insecticide. Examples of the time required for development of some insect-resistant varieties from the beginning of a search for resistance or location of a specific source of resistance to the release to farmers are: in Hessian fly resistance in wheat -- Kawvale, 18 years; Pawnee, 29 years; Ponca, 19 years; in spotted aphid resistance in alfalfa-Cody, 5 years (Figure 10)
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From page 94... ...
Techniques for speeding up plant selection and plant-breeding are being constantly improved. BIOTYPES AS LIMITATIONS The presence or selection of insect biotypes able to infest resistant varieties can limit the effectiveness of such varieties.
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From page 95... ...
Other problems may occur as resistant varieties come into more general use. ADVANTAGES AND POTENTIALITIES EFFECT OF RESISTANCE IS CUMULATIVE AND PERSISTENT Possibly the most important advantage of the use of insect-resistant plants in insect-pest control has been that the effect of the resistant variety on the pest population is specific, cumulative, and persistent.
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From page 96... ...
If a fraction of the amount spent on the development and testing of insecticides had been used in the development of insect-resistant varieties, many but not all of our major insect pests of crops might have been controlled or partially controlled by this means. Support for host-plant resistance development has gradually but substantially increased in recent years, as state and federal administrators have reduced emphasis on chemical-control investigations and have stressed noninsecticidal means, including host-plant resistance.
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From page 97... ...
SITUATIONS WHERE INSECT-RESISTANT PLANT VARIETIES ARE MOST USEFUL The use of resistant varieties is most valuable in crops of low value per acre, especially where yields fluctuate greatly because of weather and other intermittent hazards, or under situations where insecticidal control is unknown, unavailable, or too costly. Resistant crop varieties should be of special use in the developing countries where acreages worked by individuals are small and farmers are unfamiliar with the use of insecticides.
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From page 98... ...
1960. The development and performance of Cody alfalfa, a spotted alfalfa aphid resistant variety.
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From page 99... ...
1960a. Breeding plants for resistance to insect pests, pp.
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