In a 2-yr field study, selective application of a 2.5% (v/v) solution of the ammonium salt of fosamine [ethyl hydrogen(aminocarbonyl)phosphonate] plus 0.5% (v/v) nonionic surfactant to multiflora rose (Rosa multiflora Thunb. # ROSMU) demonstrated leaves to be the major site of uptake for suppressing growth. In greenhouse studies, 14C-fosamine was absorbed in decreasing order by axillary bud, leaf, and stem treatments, respectively. 14C was rapidly translocated throughout multiflora rose plants when applied to leaf, stem, or bud tissue. The highest 14C concentration always occurred at the site of uptake. In a 32-day study, the treated leaf, the treated bud, and treated stem had the highest 14C concentration when 14C-fosamine was leaf, bud, or stem applied, respectively.

Both gibberellic acid and the substituted phthalimide AC-94377 [1-(3-chlorophthalimido)cyclohexanecarboximide] actively promoted germination of dormant seeds in five species out of nine. The species that responded to both compounds included wild oat (Avena fatua L.), wild mustard [Brassica kaber (DC.) L.C. Wheeler], curly dock (Rumex crispus L.), field pennycress (Thlapsi arvense L.) and tansy phacelia (Phacelia tanacetifolia L. Benth.). on a weight-per-weight basis, the ability of AC-94377 to stimulate germination was equal to, or greater than, GA3. The other two substituted phthalimides tested, AC-92803 [2-(3-chlorophthalimido)-2-methyl-2-isobutyl-acetamide] and AC-99524 [1-tetrahydrophthalimido-cyclohexane-carboximide], had either slight or no stimulatory activity.

Applications of the substituted phthalimide growth regulators AC-94377 [1-(3-chlorophthalimido)cyclohexanecarboximide] and AC-99524 [1-tetrahydrophthalimido-cyclohexanecarboximide] to the soil surface stimulated germination and emergence of dormant wild mustard seed (Sinapsis arvensis L. ♯4 SINAR) shallowly planted in soil in greenhouse experiments. Surface applications of AC-94377 enhanced the germination and emergence of dormant wild mustard seed planted 0.6 cm deep in soil from nine locations as the rates were raised from 0.4 to 3.7 kg ai/ha. Surface application of AC-94377 increased emergence rates and also extended the period of wild mustard emergence. Increasing quantities of wheat (Triticum aestivum L.) straw on the soil surface reduced the effect of surface-applied AC-94377 on shallowly buried dormant wild mustard seed. When dormant wild mustard seed were buried 1.3, 2.5, or 3.8 cm deep, surface applications of AC-94377 also stimulated greater emergence than the dormant controls from these depths, strongly suggesting that the compound moved from the surface to the depth of planting.

Two experiments were conducted. The first experiment compared sweet corn tolerance to clopyralid at 0.2 to 1.1 kg ha-1, EF-689 at 0.07 to 0.6 kg ha-1 and 2,4-D at either 0.3 or 0.6 kg ha-1. Sweet corn tolerated all rates of clopyralid. EF-689 at 0.2 kg ha-1 or greater caused stalk curvature, stunting, and yield reductions. Stalk curvature also resulted from 2,4-D, but not stunting or yield reductions. The second experiment determined the effect of sweet corn genotype and growth stage at application on injury from EF-689. Injury was genotype and growth stage dependent. Stalk curvature was most severe from treatments 6 wk after emergence, whereas the greatest stunting was from treatments at 4 wk. ‘Supreme’ had the least and ‘Maple Sweet’ the most stalk curvature.

EPTC (S-ethyl dipropylthiocarbamate) reduces hypocotyl growth of lettuce [Lactuca sativa (L.) ‘Grand Rapids’] seedlings in response to gibberellic acid (GA3) in the lettuce hypocotyl bioassay. Doses of 0.01, 0.1, and 1.0 mM EPTC were effective over a range of gibberellin concentrations. Significant reductions in hypocotyl growth in response to all doses of EPTC and GA3 at 7.68 μg/ml occurred between 12 and 24 h after initial treatment. In a 72-h experiment, pulse treatments of EPTC at 0.01, 0.1, and 1.0 mM plus GA3 at 7.68 μg/ml for only 1 or 2 h at the beginning reduced the subsequent response of the bioassay when plants were transferred to GA3 alone for the remaining 71 or 70 h, respectively. Final hypocotyl growth in GA3 at 7.68 μg/ml was reduced by exposure to EPTC at 0.01, 0.1 and 1.0 mM plus GA3 at any time during the entire 72 h test period. The interaction between EPTC and GA3 was not due to herbicide-induced precipitation nor decomposition of GA3 in the medium. This was demonstrated by separation of [14C]-GA3 in four thin-layer chromatography solvent systems after incubation in the presence or absence of 1.0 mM EPTC for 48 h. Apparently EPTC can reduce the growth response of sensitive species to exogenous gibberellins in addition to its effects on endogenous gibberellin-like substances or gibberellin biosynthesis.

Napropamide [2-(α-naphthoxy)-N,N-diethylpropionamide] is a preemergence herbicide used for the control of most annual grasses and many annual broadleaf weeds. Its influence on the uptake and translocation of N, P, K, Ca, Mg, Cu, Fe, and Zn by four plant species was observed. Napropamide influenced, in some cases dramatically, the uptake and movement of the essential elements, but its influence was not consistent from one type of plant to another.

Dicamba is a herbicide used for the control of broadleaf weeds in wheat. Dicamba, applied within the recommended growth stage interval, reduced the grain yield of Wakefield winter wheat by 95% in a herbicide sensitivity study at Michigan State University. Growers have also reported yield loss when using dicamba on Wakefield. Field and greenhouse experiments were conducted to characterize the response of Wakefield winter wheat to dicamba and to compare this response to that of ‘Harus’ winter wheat, a cultivar that is not considered sensitive to dicamba. This research was conducted to characterize the sensitivity of Wakefield to dicamba and to develop visual methods for detecting sensitivity of wheat cultivars to dicamba. Field experiments confirmed that dicamba affects the number of spikelets and the seed weight of Harus and Wakefield similarly. However, dicamba, applied within the recommended application interval, caused small, shriveled (underdeveloped) seeds to occur in Wakefield in the field and greenhouse. These seeds weighed very little, did not contribute to grain yield, and could not be harvested mechanically. Dicamba reduced the number of fully developed seeds of Wakefield by as much as 62% in the field and 92% in the greenhouse when applied within the recommended application interval. The number of fully developed seeds of Harus was reduced in the field only when dicamba was applied later than the recommended application interval. Decreases in grain yield due to dicamba were caused primarily by decreases in the number of fully developed seeds. Greenhouse experiments indicated that pollen abnormalities were only a minor cause of the development of underdeveloped seeds.

Chemical ripening of sugarcane is an important component to profitable sugar production in the United States as well as other sugarcane industries throughout the world. Harvesting of sugarcane often begins before the sugarcane reaches the desirable maturity level. This is especially true in the Louisiana sugarcane industry where the window for harvesting is limited because of the risk of freezing temperatures encountered in a temperate climate. Research on the application of chemicals, mostly of herbicide origin, to enhance sucrose accumulation (ripening) or limit flowering to conserve stored sucrose has been conducted for more than 60 yr. The only sugarcane ripener currently registered for use in the United States is glyphosate applied before harvest. The herbicide fluazifop is used as the primary ripener of sugarcane in South Africa. The herbicides glyphosate, fluazifop, and sulfometuron-methyl and the growth regulators ethephon and trinexapac-ethyl are registered for use in Brazil. There is a continuing need to evaluate sugarcane ripeners to increase the utility of currently registered ripeners and to find additional ripeners for use by sugarcane industries. The need for alternatives to glyphosate is especially critical before a glyphosate-tolerant sugarcane can be utilized to improve control of problematic weeds.

Germinating seeds of many species, especially those of tropical or subtropical origin, suffer chilling injury when exposed to low but non-freezing temperatures, resulting in poor seedling establishment and reduction in yield. The severity of injury depends upon several factors such as (i) the species or the cultivars involved, (ii) the initial water content of the seed, (iii) the temperature to which seed is exposed, (iv) the duration of chilling exposure and (v) the period during the course of germination when the chilling exposure takes place. The period of imbibition by seeds is the period of sensitivity to the stresses but especially to chilling temperatures. Imbibitional chilling injury is defined as sensitivity to a combination of low seed-water content and imbibition at cold temperature. The mechanism of chilling injury in seeds is different from chilling injury of hydrated tissues and is discussed in relation to the involvement of membranes, respiration, rate of hydration and the concept of discreet moisture levels. Furthermore, the mechanistic and applied aspects of pre-sowing seed treatments for improved germination performance under chilling stress are discussed with an emphasis on hydration-dehydration, osmotic priming and growth regulator treatments.

Once the inoculum of B. cinerea comes into contact with the host and starts to be active in the phyllosphere of a susceptible host tissue, a series of events take place. These events may develop into a process that leads to necrosis of the host, or may end in an arrested infection with minimal damage to the host tissue. Increased susceptibility to the pathogen is associated with factors that enhance ageing of the host tissues, such as the plant hormones ethylene and abscisic acid and elevation of free radical levels in the host tissue. Decreased susceptibility is obtained by inhibiting the production or activity of such factors in the presence of increased levels of plant hormones such as gibberellic acid, and by increasing the calcium content of the cell walls and by scavenging of free radicals in the host tissue. There is evidence for the induction of resistance in hosts affected by B. cinerea. Host tissues challenged by B. cinerea react at the DNA, RNA and protein level and accumulate pathogenicity related proteins, phytoalexins or other phenolic compounds. Deposition of polymers in cell walls and lignification have also been recorded in various hosts. The role of each of these factors in relation to protection is not clear. Moreover, some of the phenomena may occur too late to protect the host tissue against infection. Although the inhibition of specific proteins such as polygalacturonases has been suggested as a mechanism by which to inhibit disease, it is unlikely that the inhibition of one enzyme, would lead to significant restriction of infection. However, simultaneous inhibition of several hydrolytic enzymes produced by the pathogen should result in disease suppression. Possibilities of reducing the susceptibility of hosts or arresting further development of localized infections are discussed.

The biological effects of six insect growth regulators (IGRs) AI3-37634-c, AI3-36877-b, AI3-37603-b, AI3-36807-b, AI3-37837-a and AI3-36809-a against immature stages and adults of Aedes aegypti have been evaluated. According to IC50 values obtained (concentration to inhibit the emergence of 50% of adults), AI3-36809-a (0.02μg/ml) proved to be the most effective compound, followed by AI3-37603-b (0.04μg/ml), AI3-37837-a (0.11μg/ml), AI3-36807-b (0.17 μg/ml), AI3-37634-C (0.48 μg/ml) and AI3-36877-b (1.4 μg/ml), respectively. The results showed also that the duration of the fourth instar larvae of A. aegypti was prolonged when these larvae were exposed to the effective concentrations of the above compounds.

Apart from delayed lethal action, possible effect of the compounds tested on the basal follicle numbers developed by females of A. aegypti which survived after larval treatment with IC50 of the above-mentioned compounds has been considered. Generally, the results indicate that the females treated have more follicles than the untreated ones of similar age and grown under identical conditions.