Pesticide Groups

Provides a coordinated crop protection industry response to the development of resistance in insect and mite pests. During the last decade, IRAC has formed several international working gi oups to provide practical solutions to mite and insect resistance problems within major crops and pesticide groups. 

Another important result of the appearance of resistant target species is the increase in the number of pesticides to which pests acquire resistance. Resistance develops to all the pesticide groups used (Table 5.2). 

Table 5.2. Pesticide groups to which agricultural pests have become resistant [1]...

Table 5.5 Application index of different pesticide groups and growth regulators used in Germany, calculated within the project Neptun 2000 (Rot berg et al. 2002)...

Why is the plant growth regulator market the least commercially important of the four major pesticide groups ... 

Pesticides Group Acute Oral LD50 (mg/kg) Rat Acute Dermal LD50 (mg/kg) RafVRabbift Acute Inhalation LD50 (mg/L air) Rat... 

Unlike other pesticide groups such as the insecticides or fungicides, herbicides now encompass a very wide range of structural types (Fig. 1). Aliphatic, aromatic, and heterocyclic systems a variety of common and less common functional groups... 

Dr G. Vaagt, Pesticide Group, Plant Production and Protection Division, FAO, Rome, Italy... 

Repea ted expos ure to a pesticide, a pesticide group, or a combination of pesticides over a long period of time. 

Herbicide resistance is currently less of a problem than with the other pesticide groups, although, once it occurs, the effects are profound. Instead, the major interest centres around the control of off-target drift (i.e. application issues), specificity and the use (and side-effects) of certain herbicides with genetically modified crops. The examples listed in Table 8.1 indicate the continuing importance of pre-1980 molecules. For instance, glyphosate has become the most important herbicide, with its recent fall in price, broad spectrum of efficacy, low mammalian toxicity and (where GM crops are acceptable) its compatibility with Roundup ready crops. 

Of the 19 pesticides grouped in Table II, all were negative in five Phase I bioassays and the Phase 2 bioassays performed. These compounds included insecticides (I), fungicides (F), and herbicides (H). Malath ion, parathion, pentachloronitrobenzene (PCNB), and phorate were also negative for heritable chromosomal effects in the mouse dominant lethal test. The six compounds grouped in Table III that were positive in three or more bioassays were acephate, captan, demeton, folpet, monocrotophos, and trichlorfon. Positive results were seen for demeton in all in vitro tests in Phase 1 and Phase 2. Folpet and captan were positive in all Phase 1 and all Phase 2 in vitro assays except the test for unscheduled DNA synthesis in WI-38 cells. Trichlorfon was positive in all Phase 1 and Phase 2 in vitro tests, with the exclusion of relative toxicity tests with E coli and subtiI is. 

FIGURE 15.20 PCB chromatograms by GCECD using pattern recognition (a) Aroclor 1260 standard at 0.5 ng/ xL (b) Aroclor 1260 contaminated soil see Table 15.17 for instrumental conditions (courtesy of Lancaster Laboratories, Pesticide Group). 

FIGURE 15.21 Organophosphorus pesticides using dual columns and the NPD. Conditions injector 275°C carrier gas, hydrogen at approximately 4-5 mL/min through each column, CLPl and CLP2 see Table 15.17 oven, 120°C for 1.0 min, and ramp to 270°C at 9°C/min, and hold for 13 min. (Courtesy of Lancaster Laboratories, Pesticide Group). 

Of the field and laboratory air studies that have been performed, sunlight-induced chemical oxidations and photochemical reaction pathways usually render pesticide residues less toxic, more polar, and more susceptible to being washed-out of the air mass (J1,12,13,14,15), Field and laboratory atmospheric pesticide fate studies have also reported the formation of photooxidation products that can have equal or higher toxicity and/or greater environmental persistence than the parent pesticide 16,17,18,19), Because of the limited number of atten ted atmospheric fate studies, there remains a substantial degree of uncertainty in regards to the mechanistic behavior and possible fate of many pesticide groups that can reside in the lower atmosphere. 

The insecticide BHC (benzene hexachloride. Lindane) is also produced by the chlorination of benzene, but under conditions which favour chlorine addition not substitution, using U.V. light as a catalyst. It is not an aromatic compound at all, but a saturated hexachlorocyclohexane. The fact that it has properties which are similar to those of hexachlorobenzene, and that it is detected by the same analytical methods for the chlorinated pesticide group, often causes confusion. 

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