Search

The western maize rootworm, Diabrotica virgifera virgifera (Le Conte) (Insecta: Coleoptera: Chrysomelidae), is the one of the most dangerous maize pest as in the USA and Europe. This invasive species exhibits different feeding behaviours in different ecosystems and geographical areas. Though the immature stages of this pest are relatively stationary, feeding only on the roots of the maize, the adults may migrate considerable distances and feed on different host plants. The aim of the study was to identify the profile of plant chemicals that was attractive to adults and rank their preferences. Using specially constructed cages, the insects were fed with known and potential host plants. The following substances were quantified in samples of plants (3×20) and insects (3×10): glucose, fructose, caffeic acid, quercetin, flavone rutoside, total phenols, antioxidant activity, lutein, zeaxanthin and total carotenoids. We found that only five main species plants were consumed by the insects (Cucurbita pepo, Phaseolus vulgaris, Glycine max, Zea mays and Helianthus annuus). Other plants were consumed; however, the statistical results were not significant. Small-scale investigations, as in this study, are important to better understand the possible adaptations of this insect on a large scale. [ABSTRACT FROM AUTHOR]

Diabrotica virgifera virgifera Le Conte is a species of European importance. In our country, in recent years attention has been directed toward host plants. This paper comes as a response to the question whether there are other plants to ensure their survival and breeding, except maize. The literature mentions that the main host plant for Diabrotica virgifera virgifera species is corn (Zea mays). Several other crops, such as sunflower, winter wheat and clover are mentioned in literature as secondary host plants, but no real damage has been observed in the field. The researches were carried out in doctoral experience installed in experimental area field belonging to USAMVB Resort Timisoara. Experimental lot was founded in May, through studies and experimental techniques and seeding of variants. Experience was conceived through the whole surface sowing experiment, in which was then placed a cage of isolation, each cage, in fact, representing a repetition. Diabrotica virgifera virgifera adults were introduced into each cage after their mass occurrence in maize field. Tracking and measuring their feeding mode and setting the plant organs favorite in terms of percentage of attack were made by regular observations at an interval of 7 days. Plants in cages have been maintained as required by technological growth and development links of sunflower. Following observations found that in three repetitions, all plants analyzed were attacked only in the inflorescence. In conditions of isolation Diabrotica virgifera virgifera Le Conte adults are attracted mainly by sunflower inflorescence parts (petals, pollen). The leaves were not attacked. Towards attack percentage recorded in isolation cages it can be observed that all analyzed sunflower plants showed blossom attack starting at a low 25%, in early August and reaching a very high consumption, 75% by the end of August [ABSTRACT FROM AUTHOR]

Accidentally, in the last year (2010), during monitoring activities by reading of traps installed in maize fields, on other plants than maize were observed numerous individuals adults of Diabrotica virgifera v. Le Conte in a process of intense feeding on leaves and flowers. The researches carried out in western part of Romania, in a small plot of maize grown (in stage silk appeared) in combination with beans and pumpkin (this kind of plots are common). Special attention was drawn to the fact that although there is pheromone traps on maize plant the adult preferred beans leaves and flowers. The studies about the preferences of adult Diabrotica virgifera virgifera Le Conte on different type of host plants was observed in field condition, in cages of isolation. Following the results of these primary data we mention that is important to emphasize attractiveness of Diabrotica virgiferea virgifera Le Conte adults for other plants than maize plants. Is clearly evident the preference of adults for pumpkin (mean of 38.5 individuals/RI, RII, RIII, RIV), followed by maize (32.0 individuals/ RI, RII, RIII, RIV) and beans (29.5 individuals/ RI, RII, RIII, RIV). The number of adults feeding on the flowers, pollen or silk in isolation cage was assigned higher (54 adults/maize, 48 adults/pumpkin and 46 adults/bean) than number of adults feeding on the leaves (14 adults/beans, 12 adults/pumpkin and 6 adults/maize). Taking into consideration the sex ratio, the number of males and females varied from host plant to host plant. After our observations and information from literature regarding other species of genus Diabrotica, we conclude that adults of Diabrotica virgifera virgifera Le Conte could turn to other crops than corn for feeding but also for egg laying. If is happened in natural conditions of beans crop or other potentially host plant then we have to take protection measures by introduction of appropriate crop rotation. Activities were carried out under financially support of the PN-II-ID-PCE- 2007-1/RO project. [ABSTRACT FROM AUTHOR]

Lately, Diabrotica virgifera virgifera Le Conte adults (western corn rootworm) (Coleoptera: Chrysomelidae) extended the range of host plants and also the spreading area in Romania. Though, until recently it was associated only with corn plant (it highlighted the research in Europe) today we can say that this invasive insect, in adult stage, became oligophagous. The current state of research in the field, somewhat restrained, outlines the monitoring aspects of morphology, biology, control and less at plant atractivity. This is the main reason in addressing current topics. Also, if we want to answer the question is Diabrotica virgifera virgifera still considered a dangerous pest from crops of Romania? the answer is definitely positive. The research took place over the course of tho years of study 2011 and 2012. In our studies we used observation cages type I and II (small cages and high cages). Thus for the evaluation of trophic preferences were achieved through the determination of frequency and intensity of attacks on various plants. In the experimental covered setting is obvious attraction towards other than corn comparative with uncovered setting. By far, the preferred were plants from Cucurbitaceae and Leguminosae. According to the observations made on the leaves with the highest average attack occurred at the plants of melon, soybean and beans. The damage done by insects on flowers have highlighted orientation towards plants of sunflower, cucumber and melon. Between variants down to the various plant species in relation to the total number of leaves, flowers, leaves and flowers attacked. Actually, this species invaded the corn crops in western, southern counties, the Nordic and central Romania and damaged few crops. But we supposed that in follow soon will be present throughout the country and the attractiveness of the new plants will grow. [ABSTRACT FROM AUTHOR]