The efficacy of two applications of several PRE herbicides for extended control of long-stalked phyllanthus and leafflower were evaluated under container nursery conditions at two climatically different sites in Florida. Prodiamine at 4.5 kg ai/ha provided the longest and most consistent reductions in number, percent coverage (visual) of the medium, and dry weight of both species. Ten weeks of excellent PRE control (percent medium coverage ≤ 10%; number of weeds reduced by ≥ 70%) of both species was obtained at one site after the first and second applications of prodiamine at 2.2 or 4.5 kg ai/ha; two applications were required at the second site for similar control. Rates of the other herbicides were generally too low for excellent control of both species after one application, the exceptions being dithiopyr at 4.5 kg ai/ha and the preformulated combination of isoxaben and oryzalin (1.1 and 3.4 kg ai/ha, respectively). These herbicides provided good (10% < percent medium coverage ≤ 20%; number of weeds reduced by ≥ 70%) to excellent PRE control of long-stalked phyllanthus after the first and second applications at one site. Percent coverage of the medium by either species in untreated containers was 96 to 100%.

Experiments were conducted over a 3-yr period to determine the rate and frequency of herbicide application needed to control common bermudagrass growing in a tall fescue turf. In Experiment I, fenoxaprop plus ethofumesate applied at 0.2 + 1.7 kg/ha in late April and repeated at the same rate at 3- to 4-wk intervals for a total of five applications resulted in excellent (≥ 97%) common bermudagrass suppression. The suppression was higher from combination of fenoxaprop and ethofumesate than when fenoxaprop was applied at 0.2 kg/ha in five applications (≤ 67%). In Experiment II, fenoxaprop plus ethofumesate applied at 0.2 +1.7 kg/ha required four applications per year to effectively suppress common bermudagrass (95%) in 1993, but five applications were needed to obtain similar suppression (96%) in 1994. Tifway bermudagrass was not suppressed during 1994 when fenoxaprop plus ethofumesate were applied at 0.2 +1.7 kg/ha in each of five applications (30%). In most instances, fenoxaprop plus ethofumesate applied at 0.2 +1.7 kg/ha caused only slight to moderate (< 30%) injury to tall fescue for 1 to 2 wk after treatment. When injury occurred, it was temporary as the turf fully recovered within 2 to 3 wk after treatment. An exception occurred in early July 1992 when fenoxaprop plus ethofumesate caused 44% injury to tall fescue after the four applications.

The tolerance of four established seeded common bermudagrass types to PRE and POST herbicides was evaluated. Pendimethalin at 3.4 kg ai/ha, oryzalin at 3.4 kg ai/ha, and dithiopyr at 0.8 kg ai/ha suppressed the quality of bermudagrass 8 to 16% more than oxadiazon at 4.5 kg ai/ha and prodiamine at 0.8 kg ai/ha. When interactions of PRE herbicide by bermudagrass cultivars occurred, oxadiazon, prodiamine, and pendimethalin suppressed the quality of ‘common’ and ‘Sahara’ 18 to 20% more than ‘Tropica’; oryzalin suppressed the quality of common and Sahara 11 to 18% more than Tropica; and dithiopyr suppressed the quality of common and Sahara 9% more than Tropic and ‘Cheyenne.’ The quality of Cheyenne treated with either oxadiazon, prodiamine, or pendimethalin was generally intermediate to the other cultivars. When POST herbicides by bermudagrass cultivar interactions occurred, MSMA plus metribuzin applied at 2.2 + 0.1 kg ai/ha injured common and Sahara an average of 10 to 12% higher than Tropica during 1993 and 1994. Diclofop applied at 1.1 kg ai/ha and dicamba applied at 0.6 kg ae/ha injured common 9 to 12% higher than Tropica. There was no difference in injury to cultivars when treated with 2,4-D plus mecoprop plus dicamba at 1.1 + 0.6 + 0.1 kg ae/ha. In general, Tropica was affected least by PRE and POST herbicide treatments, while common and Sahara cultivars were affected the most.

Field experiments conducted at three locations in Georgia during 1991 and 1992 evaluated AC 263,222 and imazethapyr rates alone at 18, 36, 54, or 72 g ai/ha and in mixture for a total of 36, 54, or 72 g/ha of herbicide applied early-POST for weed control, peanut injury, and yield. An application of AC 263,222 at 72 g/ha controlled (> 90%) Ipomoea morningglories, sicklepod, smallflower morningglory, and yellow nutsedge in all experiments and coffee senna and Florida beggarweed at Chula in 1991. Bristly starbur was controlled at least 90% with AC 263,222 at 72 g/ha at Tifton in 1991, but less than 62% at Chula in 1991. Imazethapyr applied at 72 g/ha controlled coffee senna, Ipomoea morningglories, and smallflower morningglory at least 85%, but did not control Florida beggarweed or sicklepod and provided inconsistent bristly starbur and yellow nutsedge control. Bristly starbur and yellow nutsedge control was increased with several AC 263,222 plus imazethapyr mixtures. High peanut yields comparable to the standard were indicative of the AC 263,222 rate applied whether alone or in mixture with imazethapyr.

Field studies at three sites in Georgia evaluated broadleaf weed and nutsedge management in peanut with PPI applications of imazethapyr and metolachlor and POST applications of paraquat in mixture with imazethapyr or bentazon. Imazethapyr at 36 g ai/ha applied PPI alone or in mixture with metolachlor at 2750 g ai/ha controlled coffee senna; entireleaf, ivyleaf, pitted, smallflower, and tall morningglories; bristly starbur; and prickly sida better than metolachlor applied PPI. Yellow nutsedge control was generally higher where metolachlor was applied PPI. Postemergence control of the aforementioned species and sicklepod was similar with paraquat plus imazethapyr and paraquat plus bentazon. Peanut yields with paraquat plus imazethapyr and paraquat plus bentazon were similar. With one exception, peanut yields from imazethapyr PPI systems were higher than metolachlor PPI systems when POST herbicides were not used. Inclusion of metolachlor with PPI application of imazethapyr increased yields only at one location.

Field studies were conducted from 1991 through 1993 to compare Weed control, peanut tolerance, yield, and net return from imazethapyr applied alone or in combination with paraquat. Sicklepod and Florida beggarweed were controlled with paraquat early POST followed by a POST application of either paraquat with 2,4-DB or paraquat with 2,4-DB and bentazon. Imazethapyr-based early POST treatments offered no improvement. An early POST application of paraquat with bentazon or imazethapyr was required for maximum control of bristly starbur. Imazethapyr applied alone early POST, with no further treatment, provided optimum yellow nutsedge control. Maximum yield and net return were associated with any paraquat-containing early POST-applied treatment followed by one of the tank mixed POST options.

Field studies were conducted from 1991 through 1994 in several locations of Southern Spain to determine the efficacy of imazapyr as late postemergence application in sunflower for broomrape control and the crop response to this herbicide under weed-free conditions. Single applications of imazapyr at 10 to 15 g/ha on sunflower plants at about the V12 (12 leaves) to V19 (19 leaves) growth stages, infected with broomrape plants at the predominant growth stages “c” (small nodule with shoot bud visible) and “d” (shoot bud and roots well developed), resulted in effective control without damaging the crop. Double applications of imazapyr at 10 + 10 g/ha at about the same crop growth stages V12 to V19, at a time interval of 12 to 14 d between single applications, were also efficacious and well tolerated by the crop. The same herbicide treatments applied to weed-free sunflower did not adversely affect the biomass, head diameter or yield of the crop as compared with the nontreated check. As a result of the low rate of imazapyr required for broomrape control, the herbicide treatments are economical (about $3 to $6/ha), non-residual and not affected by the type of soil texture and rainfall conditions.

Field experiments conducted from 1990 through 1993 evaluated single and sequential applications of various postemergence graminicides for common bermudagrass control in peanut. UBI-1956 at 70 and 100 g/ha applied early POST (EP) or sequentially, controlled common bermudagrass equivalent to fluazifop-P applied EP or sequentially. Clethodim provided variable common bermudagrass control. Clethodim applied EP provided better control than sethoxydim while control from sequential clethodim applications were equivalent to fluazifop-P. Fenoxaprop-ethyl alone failed to control common bermudagrass while the addition of fluazifop-P to fenoxaprop-ethyl improved control at least 22% in two of three years. Quizalofop applied EP and fenoxaprop applied sequentially provided common bermudagrass control equivalent to fluazifop-P. Fenoxaprop-ethyl or sethoxydim applied once or twice controlled common bermudagrass similarly. Peanut yield increases from common bermudagrass control were erratic.

Problems with insecticide resistance have long plagued the field of economic entomology. Genetic, biochemical, and ecological information on insects has been used to develop strategies to slow the rate of insecticide resistance evolution. Documented cases of herbicide resistance have increased dramatically over the past 10 yr. This paper compares some aspects of insect and weed biology that can be used in determining whether or not resistance management strategies developed for insects are likely to be useful in combating herbicide resistance. Differences between insects and weeds in terms of genetic architecture, mating systems, and population structure lead to differences in the expected efficacy of some resistance management strategies. Because of the localized population structure of some weeds, it may be easier to get farmers to participate in herbicide resistance management programs and avoid a “tragedy of the commons.” A review of the herbicide resistance literature reveals a number of areas of basic research on ecology and genetics of weeds that could help in designing more appropriate resistance management programs.

Resistance to agricultural fungicides has increaséd dramatically in the past twenty years, following the introduction of systemic fungicides. Disease control failures associated with fungicide resistance have occurred with many classes of fungicides and in many genera of plant-pathogenic fungi. In some cases, resistance evolved extremely rapidly making the chemicals ineffective for disease control only a few years after they were introduced.

The rapid development of resistance to systemic fungicides has led to efforts to develop strategies to avoid or delay the evolution of fungicide resistance in plant pathogen populations. Despite a widespread interest in managing fungicide resistance, very few experimental studies have been performed to elucidate the important factors controlling resistance development. Most fungicide resistance studies have consisted of anecdotal field observations which have rarely been followed up with experimentation. In order to understand what factors affect the evolution of resistance, and to use this information to design effective resistance management strategies, more experimental studies are required.

The first significant cases of herbicide-resistant weed populations were to the triazines in the 1970s. In the last 10 years there has been an increase in the number of weed populations that have become resistant to an array of herbicides. In some of these cases, like rigid ryegrass in Australia, a multitude of resistant biotypes has evolved with different mechanisms of resistance. If the present trend continues, the number of herbicides effective on certain weed species may diminish rapidly. To counteract this trend, industry has organized a number of intercompany working groups to specifically address the development of resistance and to implement plans to manage resistance. University and extension along with industry personnel across the world have begun educating growers on resistance management. However, this effort needs to be intensified to find new solutions for controlling weeds through the use of integrated weed management practices that incorporate new and established herbicides with cultural, mechanical, and biological control methods. The challenge is to develop cost effective, environmentally sustainable programs for weed control while maintaining the present efficiency in food and fiber production so that needs of an ever expanding human population can be met.

In 1753 Linneaus named the genus Potentilla in his Species Plantarum. The common name five finger is used frequently for this group of plants. The genus, in the rose family (Rosaceae), is composed of about 500 north temperate species (50 in North America, 75 European species) of mostly boreal herbs and shrubs. Indeed, Potentilla extends far into arctic regions. However, a few species are south temperate. And although less common, some species are also found in alpine and high mountain regions of the tropics and South America; P. anserinoides Lehm. is a New Zealand native.