Systemic insecticides applied with

Drummond, R.O. and R.E. Gingrich. 1972. Detection of systemic activity of insecticides applied dermally to white mice infested with larvae of Cuterebra sp. Jour. Econ. Entomol. 65 1211-1212. 

In some areas of West Africa, swollen shoot disease is under control by cutting out infected and suspected trees, the exclusion of areas of mass infection, and chemical control with systemic insecticides. In other areas of Africa, however, the disease continues to spread in spite of the control measures applied. Up to February 1954 (19) a total of 24,632,839 trees had been destroyed. The total number of trees in the Gold Coast alone is estimated at 400,000,000. 

Certain neurotoxicants act by directly influencing the electrical activity of the insect nerve membrane through a specific action at ion-selective channels. These phenomena can be studied using many of the neurobiochemical techniques that have successfully been applied to vertebrate nervous systems. In this study we use the technique of insect synaptosomes in superfusion to examine the interaction of a range of insecticidal agents with ion channels in the nerve terminal by monitoring effects on transmitter release. 

In one new development, activated carbon is employed as a reservoir to maintain vapor and solution concentrations at desired levels. Such action is based on the fact that a substance in the adsorbed state becomes less volatile and less soluble. This behavior has been utilized in applying systemic insecticides. These powerful agents are readily soluble and in strong concentrations, they can damage plant life. Consequently, the total quantity necessary for seasonal protection cannot be applied in a single application that is, not under ordinary conditions. In a suitable mixture with carbon, however, the adsorbed insecticide is released gradually and the concentration in the environment is kept at a safe level. 

The widely used insecticide acaricide vamidothion can be made visible either with 0.5% 2,6-dibromo N>chloro-p-benzoquinoneimine in cyclohexane solution or with palladium chloride. These detection systems were applied in metabolism studies (152). The P=S bond has a catalytic effect on the color development when iodine-azide reaction is applied. The white spots on a yellow background were better evaluated when the plates were sprayed with starch solution. The limit of the detection was in the 0.5-10-pg range (149). Dithiophosphate insecticides give a colored complex with palladium(II) ions, K2PdCl4, with the cleavage of the P-S bond. Carbofos, phtalophos, and phosalone were evaluated by this color reaction combined with spectrophotometry (155). 

Menazon (12.20) a somewhat similar compound, but based on the triazine ring, caused a pleasant surprise because, when applied to the soil, it was taken up by roots and translocated to all parts of the plant. This gave protection from aphids and other sucking insects for up to six weeks. It is still used as a seed-dressing for the early protection of crops (Sherlock, 1962). In horticulture, these systemic insecticides are valuable because no insects can be killed except those that bite the plant, which, lacking a nervous system, escapes all injury. Dimethoate (12.21) is now much used for this purpose. Unselective agents which kill all insects are avoided because they interfere with pollination and contribute to the starvation of field birds. 

Field Studies in Forest Streams. Insecticide treatments The fate and persistence of fenitrothion and aminocarb were studied in 1982 in small headwater trout streams within the Nipisiguit River watershed near Popple Depot, New Brunswick. Three study streams were treated with different insecticide tank mixes, receiving two applications at a 6 to 8 day interval sprayed by Agcat or Agtruck aircraft equipped with Micronair spray emission systems. Each stream later received a point source injection by hand-held sprayer of the same insecticide tank mix which had been previously applied to it from the air. 

Table 6.3 shows penetration rates of four insecticides dimethoate, paraoxon, dieldrin, and DDT, through cockroach cuticle. It is seen that the rates of penetration are inversely related to their partition coefficient in the olive oil-water system. In other words, the compound with the best solubility in water, as indicated by its partition coefficient, moved through the cuticle most rapidly. In this experiment, the insecticides were applied to the cuticle as acetone solutions, and it was suggested by the authors that this may have neutralized or canceled any barrier presented by the epicuticle. Thus, the data indicate the... 

Pyrethrins and synthetic pyrethroids are among the safest of the topically applied ectoparasiticides, because of their selective toxicity for insects (mam-malian-to-insect toxic dose ratio is greater than 1000, compared with 33 for organophosphates and 16 for carbamate insecticides). In contrast to the very wide margin of safety for mammalian species, pyrethroids are toxic to fish. The synergistic action of pyrethrins and piperonyl butoxide (in combination preparations) is due to the inhibition by piperonyl butoxide of the microsomal enzyme system of some arthropods. Preparations of synthetic pyrethroids (permethrin, cypermethrin) often contain a mixture of drug isomers in varying proportions. 

With reference to insecticidal activity, volatility could be seen as either a pos-itive or a negative property. Losses from surfaces could reduce efficacy whereas vapour activity could be beneficial. In terms of environmental fate, loss to air is not considered to be a major issue other than for highly volatile and/or stable molecules. Nevertheless, the volatility of [ CJPBO from plant leaf surfaces was assessed in a laboratory system. PBO as an 80% emulsifiable concentrate was applied to french bean leaves, 0.25 pg a.i, cm"2, which equated to a field rale of 250 g a.i, ha"1, and moist air passed over (he surface at a rate of 1-2 ms 1 for 24 hours. Volatile C was trapped and analysed. Approximately 9% of applied radioactivity, all as [KC)PBO, was volatilized in 24 hours which, under the lest conditions, was comparatively low. 

Biting flies are a serious pest of hogs because both the face fly and house fly transmit hog cholera and these pests breed in tremendous numbers in hog lots. Insecticides are also used to eonlrol the hog louse and hog mites. Fogging with 1.00% pyrethrins synergized with 2.00% PBO is a standard fly treatment in hog operations, and the same formulation can be applied directly to the animals. Other fogging formulations containing 0-50% pyrethrins and 1.00% PBO in a dual-synergist system are also frequently used. 

Similar tests have been conducted with a coleopterous-active MCap product (MYX 1806) targeted against the CPB on potatoes, hi these tests, potato foliar protection and yields were compared for MYX 1806 and its naturally occurring counterpart, Bt variety son diego (M-One insecticide) (Figures 4 and 5). The results confirm that when equivalent toxin rates were applied for each product, the persistence conferred by the MCap system resulted in superior CPB control. Additionally, it was demonstrated that the protected toxin of MYX 1806 could be applied at two thirds the toxin rate, and yet still maintain higher levels of insect control than the full rate delivered by M-One. 

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