Infestation

About: Infestation is a research topic. Over the lifetime, 8308 publications have been published within this topic receiving 82305 citations.

Tuta absoluta -induced plant volatiles: attractiveness towards the generalist predator Macrolophus pygmaeus

Abstract: One of the most damaging insect pests to tomato crops is the tomato leafminer, Tuta absoluta. Current control methods are not efficient at regulating this pest below the economic threshold, leading to the development of new strategies based on its natural enemies. In this study, we evaluated the ability of Macrolophus pygmaeus to discriminate T. absoluta-infested plants versus non-infested tomato plants. We subsequently collected volatile organic chemicals released by tomato plants under different levels of infestation, and identified the associated herbivore-induced plant volatiles (HIPVs). Behavioural assays were conducted in a double-choice olfactometer and flight tunnel. In both systems, M. pygmaeus was significantly attracted towards infested plants. Because distance attraction is likely to be mediated, at least partially, by volatile organic compounds, HIPVs were collected from healthy and infested plants using a dynamic volatile collection system. Volatile chemical profiles vary with the level of infestation; specifically, twice as many chemicals were identified under infestation by 20 T. absoluta larvae compared to healthy plants. A total of 35 compounds were identified, with β-phellandrene, 2-carene, β-caryophyllene, α-pinene and α-phellandrene representing 76–86 % of the total blend. The release of monoterpenes was strongly influenced by the level of caterpillar infestation, while the amount of sesquiterpenes did not vary significantly. We hypothesise that certain HIPVs, most likely monoterpenes, are involved in prey location by M. pygmaeus and have potential to manipulate the natural enemies of T. absoluta to enhance the control of this crop pest.

Host selection and movements of Ixodes ricinus (Acari) larvae on small mammals

Abstract: The clumped distribution of Ixodes ricinus L. larvae in the vegetation causes a highly overdispersed distribution on small mammal hosts. This distribution pattern fits with the negative binomial distribution. Apodemus sylvaticus L. has shorter daily active time and range and hence probably picks up fewer ticks from the vegetation. In spite of this A. sylvaticus carries considerably more ticks than Clethrionomys glareolus Schreb. and Sorex araneus L. in the field. In laboratory experiments, this difference between rodents was even more pronounced. The reason for such differences in infestation is that the ticks do not accept the various host species to the same extent. Thus, of introduced larvae 8% in C. glareolus and 53% in A. sylvaticus succeeded in engorging. In A. sylvaticus the engorged larvae had a higher mean weight than in C. glareolus. In the fur a larger part of the ticks had more directed and faster movements towards their predilection places on the head on A. sylvaticus than on C. glareolus. In S. araneus only a few ticks moved at all. The majority stayed on the spot where they had been placed. The behaviour of the ticks on the host body explains the differences in attachment sites found in the field on different host species.

Distribution of Ixodid Ticks on Cattle in and Around Holeta Town, Ethiopia

Abstract: The study was conducted from October, 2010 to March, 2011 in Holeta and Adaberga dairy farms and their surrounding kebeles in Ethiopia with the objectives of determining the ixodid tick species prevalence in the area, assessing the difference in infestation among the cattle breeds and farming system and evaluating the predilection site of ticks on the host. Out of the total of 1209 cattle examined, 310 (25.64%) were found to be infested by one or more tick species. About 1831 ticks were collected and subjected to genus assignment then they were grouped into four genera; namely Amblyomma, Rhipicephalus, Boophilus and Hyalomma and five species were identified. The relative prevalence of each species was Amblyomma variegatum (45.49%), Rhipicephalus evertsi evertsi (29.29%), Boophilus decoloratus (18.13%), Amblyomma coherence (5.02%) and Hyalomma marginatum rufipes (1.86%). The prevalence of tick infestation was found to be significantly different (P<0.05) among the three breeds with highest prevalence in Local breed (44.96%) than both Cross (15.83%) and Jersey (8.50%) breed. Similarly, tick infestation was significantly (P<0.05) higher in cattle kept under extensive production system (45.40%) than in those kept under semi-intensive (10.06%) farming system. The present information on the common tick species contributes its part in the development of best control strategies of tick and tick borne diseases in the study area.

Progression in field infestation is linked with trapping of coffee berry borer, Hypothenemus hampei (Col., Scolytidae).

Abstract: Phenology of the coffee plant and infestation by coffee berry borer Hypothenemus hampei Ferrari were studied in relation to trapping of adult females in kairomone-baited traps in a coffee plantation in New Caledonia. In a 0.4 ha coffee field, a group of 27 trees located along a transect beginning at an early infestation point was selected. The number of green, red and dry coffee berries, along with the number of larvae, adult males and females per berry was determined monthly from October 1993 to July 1994. Twelve, red multifunnel traps, each baited with a solution of methanol:ethanol (1:1 ratio, a mean solution release rate of 1 g/day) were placed within the coffee field, along the transect, within the selected trees, grouped in four zones named 1–4. Two additional traps were located outside the plantation. The proportion of infested berries increased as berry maturity and harvest date approached, while the infestation rate decreased with distance from the epicentre. Over the 10 months of the study, beetle populations increased and spread from the original infestation point across the different zones, according to distance and availability of berries or appropriate physiological status. Traps near the epicentre caught the largest numbers of beetles. Linear relationship between trap catch and infestation level was demonstrated. Traps placed outside the field approached zero catch. Trap catch was highly influenced by rainfall events, and the highest captures coincided with rapidly declining berry numbers on trees. There are good prospects for management of this insect using traps.