Population Dynamics Of Diamondback Moth Research Articles

Management and population dynamics of diamondback moth (Plutella xylostella): planting regimes, crop hygiene, biological control and timing of interventions.

Using an age-structured process-based simulation model for diamondback moth (DBM), we model the population dynamics of this major Brassica pest using the cropping practices and climate of Guangdong, China. The model simulates two interacting sub-populations (demes), each representing a short season crop. The simulated DBM abundance, and hence pest problems, depend on planting regime, crop hygiene and biological control. A continuous supply of hosts, a low proportion of crop harvested and long residue times between harvest and replanting each exacerbate pest levels. Biological control provided by a larval parasitoid can reduce pest problems, but not eliminate them when climate is suitable for DBM and under certain planting practices. The classic Integrated Pest Management (IPM) method of insecticide application, when pest threshold is reached, proved effective and halved the number of insecticide sprays when compared with the typical practice of weekly insecticide application.

Lethal and Sublethal Effects of Cantharidin on Development and Reproduction of Plutella xylostella (Lepidoptera: Plutellidae).

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a major pest of cruciferous vegetables throughout the world. Cantharidin, a natural toxin isolated from beetles in the families Meloidae and Oedemeridae, has been reported to be toxic to some pests, including the diamondback moth. However, the effects of cantharidin, especially its sublethal effects on development and reproduction of diamondback moth, are less known. In this study, we investigated the sublethal effects of cantharidin at LC2 (0.41 mg liter(-1)), LC10 (1.33 mg liter(-1)), LC25 (3.38 mg liter(-1)), and LC50 (9.53 mg liter(-1)) on development and reproduction parameters of two consecutive diamondback moth generations. The results indicated that cantharidin reduced population growth by decreasing its pupation rate, pupal weight, and adult emergence, and by delaying its development. Furthermore, the duration of the female preoviposition period increased, while the oviposition and postoviposition periods, fecundity, and survival rates of the offspring decreased. The peaks of age-specific fecundity in LC10, LC25, and LC50 treatment groups lagged behind the control group. The mean values of the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were significantly lower than those of the control, and the mean generation time (T) was prolonged. The present study demonstrates that cantharidin exhibits significant adverse effects on the population dynamics of diamondback moth, leading to fitness disadvantages.

A single hot event that does not affect survival but decreases reproduction in the diamondback moth, Plutella xylostella.

Extremely hot events (usually involving a few hours at extreme high temperatures in summer) are expected to increase in frequency in temperate regions under global warming. The impact of these events is generally overlooked in insect population prediction, since they are unlikely to cause widespread mortality, however reproduction may be affected by them. In this study, we examined such stress effects in the diamondback moth, Plutella xylostella. We simulated a single extreme hot day (maximum of 40°C lasting for 3, 4 or 5 h) increasingly experienced under field conditions. This event had no detrimental effects on immediate mortality, copulation duration, mating success, longevity or lifetime fecundity, but stressed females produced 21% (after 3 or 4 h) fewer hatched eggs because of a decline in the number and hatching success of eggs laid on the first two days. These negative effects on reproduction were no longer evident in the following days. Male heat exposure led to a similar but smaller effect on fertile egg production, and exposure extended pre-mating period in both sexes. Our results indicate that a single hot day can have detrimental effects on reproduction, particularly through maternal effects on egg hatching, and thereby influence the population dynamics of diamondback moth.

Effects of larval density on growth, development and reproduction of diamondback moth (DBM), Plutella xylostella

为明确小菜蛾幼虫密度对其种群增长的影响, 在室内条件下[温度(22±1) ℃, RH 70%~80%, 光周期 12L∶12D]对不同幼虫密度[1头·皿^-1、10头·皿^-1、20头·皿^-1、30头·皿^-1、40头·皿^-1(直径为9 cm)]饲养的小菜蛾生长发育及繁殖进行了研究。结果表明, 幼虫密度对小菜蛾幼虫、蛹的发育历期和存活率、蛹重及成虫生殖等有显著影响。幼虫和蛹历期均以10头·皿^-1处理最短, 且随幼虫密度增加而显著延长。幼虫至蛹的存活率以10头·皿^-1、20头·皿^-1处理较高, 显著高于1头·皿^-1和40头·皿^-1处理。蛹重以1头·皿^-1处理最重, 并随幼虫密度的增加而显著变轻。不同幼虫密度下羽化的成虫畸形率差异显著, 以10头·皿^-1处理最低, 其余随幼虫密度的增加而升高。成虫产卵量以1头·皿^-1处理最高, 随着幼虫密度增加, 产卵量逐渐下降。雌、雄蛾寿命分别以40头·皿^-1、10头·皿^-1处理最长, 密度过高时或过低雌雄蛾寿命显著缩短。生命表分析表明, 幼虫密度对小菜蛾种群增长指数影响显著, 以10头·皿^-1处理种群增长指数最高, 幼虫密度过高或过低, 种群增长指数下降。因此, 幼虫密度是影响小菜蛾种群增长的重要因子之一。

Analysis of population dynamics of diamondback moth, (Plutella xylostella (Lepidoptera: Plutellidae)) at two sites in central Ethiopia, with particular reference to parasitism

Change in diamondback moth (DBM) (Plutella xylostella L.) numbers and level of parasitism on head cabbage (Brassica oleracea var. capitata) was monitored for two seasons in two different agroecological zones representing the highland and lowland brassica-producing areas of central Ethiopia in 2001 and 2002. Two to three generations in the highland site and three to five generations in the lowland site per cabbage growing season were observed. Three parasitoids were recorded at both locations. These were Oomyzus sokolowskii (Kurdjumov) (Hymenoptera: Eulophidae), Diadegma sp. (Hymenoptera: Ichneumonidae), and Apanteles sp. (Hymenoptera: Braconidae). Diadegma sp. was the dominant parasitoid at the highland site and O. sokolowskii was dominant at the lowland site. Rainfall and maximum temperature significantly influenced DBM numbers and parasitoid activity at the highland experimental site.

Impact of Intraplot Mixtures of Toxic and Nontoxic Plants on Population Dynamics of Diamondback Moth (Lepidoptera: Plutellidae) and Its Natural Enemies

Studies were conducted in 1993 and 1994 to investigate the effects of intraplot mixtures of toxic (with Bacillus thuringiensis Berliner) and nontoxic plants on population dynamics of diamondback moth, Plutella xylostella (L.), and its natural enemies. In 1993, diamondback moth densities in all plots (mixed and nonmixed) declined after generation 2, apparently because of poor plant quality. In 1994, mixed plots with 83.3% toxic and 16.7% nontoxic plants caused diamondback moth densities on nontoxic plants to decline after 2 generations, whereas population densities in plots of 100% nontoxic plants continued to rise. Diamondback moth, Plutella xylostella (L.), dynamics in plots with 50% toxic plants were intermediate compared with dynamics in the other treatment plots. Percentage of parasitism by the parasitoid Diadegmo insulare Cresson was not significantly different between mixed and nonmixed plots. Incidence of the 4 most abundant diamondback moth predators was not different in mixed and nonmixed plots, nor was there a difference in numbers of predators on toxic versus nontoxic plants. These data suggest that intrafield mixtures could serve to decrease density of a target pest such as the diamondback moth, while not adversely affecting natural enemies.