Infestation

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

The ecology of the sheep tick, Ixodes ricinus L.; the infestations of hill sheep.

Abstract: In general, female ticks infest the hairy areas of sheep: head and legs; the (comparatively) bare areas: axillary and inguinal; and certain woolled areas: chiefly the short-woolled margins of the hairy and bare areas; they do not attach in the long wool of withers, back, rump and flanks.More female ticks attach on the head than on the axillary region, and more on the axillary than on the inguinal region, obviously on the principle: first come best served.Different tick stages tend to attach in different zones of the same regions; two theories are put forward to account for this.On a hill pasture where the main tick activity occurs in spring only, the average totals of female ticks carried per annum by ewe, hogg and lamb were in the proportions 8:6: 1. Host size is thought to be the chief governing factor.Under existing British hill pastoral conditions, the upper limits to female tick infestation appear to be of the following order: average spring peak total count per ewe reaches 100–150, with extreme individual limit about 300; and about five times as many ticks are carried per ewe over the entire spring season.On heavily infested hill pasture, stocked at one sheep to 1–5 acres, typical flocks feed from 100 to 600 female ticks per acre per annum. The densest sheep stocking results in the highest tick density.For every one female tick, about eight nymphs were fed by sheep in one season.The better the condition of a sheep, the less bare of wool and apparently (to touch and sight only) the more greasy, and the lower the tick infestation.In any age group of sheep on one grazing, there is considerable range in weekly infestation weights but individuals tend to keep their relative positions consistently in this range. Sheep differing markedly in their infestation weights show a remarkable lack of difference in the majority of physical and physiological characteristics of body form and body surface. (Fleece humidity was omitted from study.) Notably, there is no indication of significant differences in fleece greasiness. Apparently only two characteristics go with the lighter infestations in Blackfaced sheep. These are coarser fleece hair and less clearance between fleece tips and ground, having doubtful and minor effects respectively.The most important factor in individual differences of infestation within an age group is very probably individual activity, i.e. the more ground covered in unit time, the more ticks picked up.

Influence of Mahanarva fimbriolata (Stål) (Hemiptera: Cercopidae) injury on the quality of cane juice

Abstract: Mahanarva fimbriolata (Stal) is an important pest in Latin America and causes significant reduction in sugarcane productivity. There is no information regarding the effect of this pest on the quality of cane juice used for sugar and alcohol production. This work aimed at evaluating the quality of sugarcane juice from plants attacked by spittlebugs. The experiment was arranged in a completely randomized design with 15 replications, and comprised two treatments: control and chemical treatment with thiamethoxam. An average of 9.2 +/- 4.44 spittlebug nymphs m-1 were found in the plots prior to insecticide application. Nymphs were counted 18, 35, 55, and 82 days after the initial sampling (december/2003). During the mid growing season (July 2004), the juice was extracted from stalks and analyzed for Brix, Pol, RS, pH, fiber, purity, TRS, dextran, starch, and total phenolic compounds. Stalk yield was also measured. Chemical treatment was efficient in reducing spittlebug population, and elevated both stalk yield and juice pH. The accumulated infestation expressed as insect-days was significantly and negatively correlated to yield, Pol, pH, and purity. The concentration of phenolic compounds increased with pest infestation, while dextran and starch levels were not affected. The infestation of 2.4 and 7.3 nymphs m-1 day-1 caused reductions of 8.3% and 29.8% in yield; 1.9% and 5.8% in Pol; 0.4% and 1.1% in pH and 0.4% and 1.2% in purity, respectively, in comparison to areas where the pest population was extremely low (< 0.1 nymphs m-1).

Development, Reproduction, and Within-Plant Infestation Patterns of Aphis craccivora (Homoptera: Aphididae) on Alfalfa

Abstract: The goal of this research was to describe developmental rates, reproductive rates, and infestation patterns of Aphis craccivora Koch on alfalfa (Medicago sativa L.). All studies were conducted on the susceptible cultivar OK08 using aphids reared from collections made in Oklahoma. To determine thermal requirements for growth of A. craccivora, development from birth to adult was recorded at 7.2, 12.8, 18.3, 23.9, and 29.4 degrees C. The same constant temperature treatments (except for 7.2 degrees C being raised to 8.3 degrees C) were used to assess the influence of temperature on reproductive rates. Within-plant distribution patterns were determined by infesting three stems on each of 24 plants and recording numbers of A. craccivora on leaf blades, petioles, and internodal stems sections at 2-d intervals through 10 d after infestation. Aphid counts were analyzed to determine significant differences among node parts (leaf blades, petioles, and stem sections). The developmental threshold temperature for A. craccivora was calculated to be 7.1 degrees C, and the thermal constant for development from the first instar to reproducing adult was 100 DD ( degrees C). The optimal temperature range for reproduction on alfalfa was 18-24 degrees C, with a mean of 82 nymphs produced per female. From the initial infestation of three apterae per stem, numbers increased to a mean of 510 per stem after 10 d. Plant profiles showed that the greatest numbers of aphids were located in middle and lower portions of the plant canopy. On all sampling dates, the proportion of aphids on internodal stem sections was significantly greater (P < 0.05) than on petioles and leaf blades.