| dc.description.abstracteng | Within the last decade, the cabbage whitefly has become a major agricultural pest for Brassica crops, which has influenced the agricultural productivity of cabbage (Brassica oleracea convar. capitata L.) Brussels sprouts (Brassica oleracea var. gemmifera DC.), cauliflower (Brassica oleracea var. botrytis L.), kale (Brassica oleracea var. sabellica L.), kohlrabi (Brassica oleracea var. gongylodes L.), savoy cabbage (Brassica oleracea convar. capitata var. sabauda L.), and broccoli (Brassica oleracea var. italica Plenck). The current population increase of this species could be explained by climate change with warmer winters, increasing cultivated areas of oilseed rape and Brassica cover crops, and the development of insecticide resistant strains of cabbage whitefly. In the past, the cabbage whitefly was known as a non-significant pest of Brassica crops, which is partly why its biology has only been marginally studied. In this respect, exploring the biological parameters of A. proletella is likely to be of great value to understand the population dynamics of this insect species as well as to discover the reasons behind its current outbreak.
The biological parameters of A. proletella on different host plants were examined in a greenhouse experiment to assess their suitability for the cabbage whitefly. The impact of constant and alternating temperature regimes on the major life cycle component of cabbage whitefly were investigated in growth chamber-experiments. The influence of mating history on the population dynamics of this species was also examined and evaluated under different conditions.
1. Various biological traits (fecundity, pre-oviposition period, survival rate, sex ratio) of A. proletella were studied on winter oilseed rape, kale, cabbage, and kohlrabi to assess the suitability of these host plants.
a. A. proletella was more fecund on winter oilseed rape than kale, kohlrabi, and cabbage.
b. Host plants influenced the pre-oviposition period of A. proletella, resulting in shorter pre-oviposition periods on oilseed rape.
c. Survival rate of A. proletella adults was strongly influenced by host plants, which was the lowest on white cabbage.
d. The sex ratio of A. proletella offspring was significantly influenced by the host plant, with the highest female ratio being on kale and winter oilseed rape.
e. Winter oilseed rape was therefore determined to be the most suitable host plant among all those considered.
2. Evaluating the influence of fluctuating temperatures versus their equivalent constant average on reproduction parameters (fecundity, mean daily fecundity, age-specific fecundity, survival rate, sex ratio) of cabbage whitefly.
a. The 23 °C fluctuating temperature regime decreased the survival rate of cabbage whitefly males in comparison to their equivalent constant temperature mean.
b. The 20 °C fluctuating temperature increased the total fecundity of cabbage whitefly females in comparison to their representative constant temperature mean.
c. The pattern of the age-specific fecundity curve under fluctuating temperature regimes differs from those at constant regimes, leading to a higher peak throughout the earlier stages of the lifespan and a sharper decrease as females become older.
d. The temperature regime did not affect the sex ratio of cabbage whitefly.
3. The influence of mating scenarios (life span mated female and male; virgin female and male; short time mated females) on longevity, survival rate, total fecundity, and sex ratio of A. proletella was examined under constant temperature regimes of 20°C. In addition, the first two experiments also evaluated the influence of mating scenarios on the survival rate and oviposition of cabbage whitefly.
a. The total number of eggs of eight day mated females was slightly lower than those of virgin and life span mated females.
b. The mating history did not influence the life span or survival rate of A. proletella females or males.
c. The sex ratio of life span mated females was lower than that of short time (eight day) mated females, whereas virgin females produced purely male offspring.
d. In the greenhouse experiment the mating history did not affect the survival rate and oviposition of the cabbage whitefly.
e. Under fluctuating temperature conditions, the influence of mating scenario was only detectable under the 20 °C fluctuating temperature regime, where the fecundity of eight day mated females was reduced in comparison to the virgin and life span mated females. | de |