Recommended rates of glyphosate for noncultivated areas destroy the aboveground shoots of the perennial plant leafy spurge. However, such applications cause little or no damage to underground adventitious buds (UABs), and thus the plant readily regenerates vegetatively. High concentrations of glyphosate, applied under controlled environmental conditions, have been shown to cause sublethal effects in UABs of leafy spurge that produce stunted and bushy phenotypes in subsequent generations of shoots. We treated leafy spurge plants in the field with glyphosate (0, 1.1, 3.4, or 6.7 kg ai ha−1) to determine its effects on vegetative growth from UABs and on molecular processes. The number of shoots derived from UABs of glyphosate-treated plants was significantly increased compared to controls in subsequent years after application, and new shoots displayed various phenotypical changes, such as stunted and bushy phenotypes. Quantifying the abundance of a selected set of transcripts in UABs of nontreated vs. treated plants (0 vs. 6.7 kg ha−1) indicated that glyphosate impacted molecular processes involved in biosynthesis or signaling of tryptophan or auxin (ARF4, CYP79B2, PIN3, TAA1, TRP6, YUC4), gibberellic acid (GA1/CPS1, GA2/KS), ethylene (ACO1, ACS10), cytokinins (AHP1, AK2, CKX1), and the cell cycle (CDC2A, CDC2B, CYCD3;1). Glyphosate-induced effects on vegetative growth and transcript abundance were persistent for at least 2 yr after treatment. Determining the molecular mechanisms associated with vegetative reproduction in leafy spurge following foliar glyphosate-treatment could identify limiting factors or new targets for manipulation of plant growth and development in perennial weeds.

Tropical African ticks are found on their hosts throughout the year, but at varying infestation levels. These population changes, for most of the time, have been associated with climatic changes. Their development is inversely related to temperature. Several workers reported that development failed for a number of tick species at temperatures below 15°C, suggesting a possible lower temperature threshold for tick development. The upper development limit for most of the tropical rhipicephalids appear to be 37°C.

Ticks are particularly susceptible to attack during lethargic pre-moulting and the weak post-moulting period. Many biological features enable them, however, to survive especially well. They lay numerous eggs and withstand a comparatively wide temperature and humidity range with greater ease. They survive for months or years without food.

Their degree of host specificity varies from genus to genus or within subgroups of various genera. The requirement of two or more kinds of hosts often with divergent habits, limits their distribution to certain faunal areas.

This paper reviews our current knowledge on development and survival of ixodid ticks under tropical field conditions including some laboratory studies.