LIFE TABLE AND MALE MATING COMPETITIVENESS OF WILD TYPE AND OF A CHROMOSOME MUTATION STRAIN OF TETRANYCHUS URTICAE IN RELATION TO GENETIC PEST CONTROL

Abstract

Males of Tetranychus urticae Koch (Acarina: Tetranychidae) from a strain, homozygous for a structural chromosome mutation (T) were competed against males from a standard (wild‐type) strain for mating of wild‐type females. The T‐males exhibited only a slight reduction in male mating competitiveness. The debilitating influence of ageing on male mating competitiveness was equal for males of both strains. Life‐table studies on both strains showed that the net reproductive rate (RO) of the T‐strain was 53.3, which was higher than the RO‐value of the standard strain (43.3). This difference was caused by the higher rate of age‐dependent mortality of adult females of the standard strain. Also differences between both strains in the total sex‐ratio were observed; the T‐strain produced significantly fewer males and more females than the standard strain. The mean generation time of both strains was almost equal (14 days). The values of the intrinsic rate of increase (rm) for the T‐strain and the standard strain were 0.286 and 0.273, respectively. The life‐table data correspond well with those published elsewhere on Tetranvchus urtieae The feasibility of T‐strains for application in genetic pest control considering the use of structural chromosome mutations as a “transport mechanism” for conditional lethals is discussed. RESUME ETUDE DE LA TABLE DE VIE ET DE LA COMPÉTITION SEXUELLE ENTRE LIGNÉES DE MǍLES SAUVAGES ET À MUTATION CHROMOSOMALE DE TETRANYCHUS URTICAE EN VUE D'UNE MÉTHODE DE LUTTE GÉNÉTIQUE. Des mǎles de Tetranychus urticae d'une lignée, homozygote pour une mutation chromosomale structurale (T), out été mis en compétition avec des mǎles “sauvages”. Les mǎles T. ne présentaient qu'un léger désavantage dans cette compétition sexuelle. L'effect débilitant de l‘ǎge sur cette compétitivité élait le měme pour les mǎles des deux types. Les tables de vie des deux types ont montré que le taux de multiplication net (RO) de la lignée T était 53,3 soit plus que pour le type sauvage (43,3), Cette différence était due au taux plus élevé de mortalité en fonction de l'ǎge des femelles adultes de la lignée sauvage. Des différences entre les taux sexuels globaux des deux types ont été aussí observées; la lignée T a produit significativement moins de mǎles et plus de femelles que la lignée sauvage. La durée moyenne d'une génération était presque la měme pour les deux lignées (14 jours). Les valeurs du taux intrinsèque d'accroissement (rm) pour les lignées T et sauvage étaient respectivement 0,286 et 0,273. Ces données sur les tables de vie correspondent bienà celles publiées ailleurs pour T. urticae. Les possibilités d'emploi des lignées ***‘I’ pour la lutte génétique, en utilisant les mutations chromosomales structurales comme un “véhicule” de lélaux conditionnels, sont examinées.

Effect of temperature and sperm supply on the reproductive potential ofTetranychus evansi (Acari: Tetranychidae)

“…The increase in the proportion of female offspring produced in the initial part of the oviposition period has also been ,~eported for other tetranychids (Saito and Ueno, 1979;Feldmann, 1981;Sabelis, 1981). Overmeer (1972) reported that the first egg deposited by T. urt~cae tends to be unfertilized, and thus produces a male.…”

Biology of a tydeid mite,Homeopronematus anconai(n. comb.) (Acari: Tydeidae), important in San Joaquin Valley vineyards

“…Most life table studies of Actinedida have been done in the family Tetranychidae, Values of r m for three tetranychid mite species ranged from 0.097 to 0.259 at various temperatures and relative humidities (reviewed in . Feldman (1981) reported r m values of 0.273 and 0.286 for strains of Tetranychus urticae at 28 DC and 70 percent RH, and reported an r m of 0.202 to 0,254 (depending on host plant conditions) in fluctuating temperatures averaging 25°C in 36 to 65 percent RH, In contrast, Laing (1969) reported an r m of only 0.143 for T. urticae in fluctuating temperatures averaging 20.3°C and 55 to 98 percent RH, suggesting that high RH lowers r m in T. urticae. There may be a similar relationship between low temperatures, high humidity, and low r m in H. anconai.…”

“…Values of r, for three tetranychid mite species ranged from 0.097 to 0.259 at various temperatures and relative humidities (reviewed in . Feldman (1981) reported r,values of 0.273 and 0.286 for strains of Tetrarzychus urticae at 28 "C and 70 percent R H , and reported an rm of 0.202 to 0 . 2 5 4 (depending on host plant conditions) in fluctuating temperatures averaging 2 5 "C in 36 to 65 percent RH.…”