Spray scheduling

The great interdependence of public health and agriculture can be no better illustrated than by the problem of insecticide residues in food. Compounds, vehicles, and spraying schedules adapted for insect control must be selected by the agriculturalist in such a way as to ensure an acceptable product at harvest. However, once the product is harvested and offered for human food, it becomes the concern of various public health agencies. The health of the agricultural operator who applied the insecticide is also a matter for medical and public health attention. 

The tests reported were conducted in 1948 on apples growing in the Yakima Valley in the Pacific Northwest and in the Mississippi Valley, to determine the magnitude of parathion and DDT spray residues at harvest. The climates and spray schedules differ markedly in the two areas consequently, spray residues also differ, and are larger in the Mississippi Valley than in the Yakima Valley. 

Spray schedules applied on experimental plots at the Yakima, Wash., and Vincennes, Ind., laboratories of the United States Bureau of Entomology and Plant Quarantine were studied to determine the magnitude of parathion and DDT spray residues at harvest. The parathion sprays were prepared from 25% vet table powder and the DDT sprays from 50% wettable powder, except in one series of tests, when a 25% DDT wettable powder was used. All spray treatments were planned and made by members of the Division of Fruit Insect Investigations. Conventional hydraulic sprayers were used in this work. 

Table IV gives the data from seven plots of Winesap and Rome Beauty apples in the Mississippi Valley. The spray schedules are similar to those used for the plots included in Table III, except that an additional parathion spray was applied on plots 9, 11, 14, and 4 on August 19, and the final harvest sample was taken on October 5. Only on the plot that was sprayed seven times with the 8-ounce strength of parathion (plot 14) did the spray residue at harvest approximate 0.1 p.p.m.

Table VII shows the residues of DDT at harvest in the Mississippi Valley on Jonathan and Starking Delicious apples on which a six-spray schedule was used. All plots except plot 8 were sprayed six times with DDT at 8 ounces to 1 pound per 100 gallons. Plot 8 received only four sprays, three containing 1.5 pounds and one containing 1 pound...

Table VIII shows the residues of DDT at harvest on Rome Beauty and Winesap apples in the Mississippi Valley. The plot treatments are the same as for Jonathan and Starking Delicious apples (Table VII) except that a seven-spray schedule was used. The residues at harvest shown in Table VIII are greater than those in Table VII. A comparison shows that when six cover sprays of DDT are applied without adhesives the harvest residues are approximately 7 p.p.m. or slightly more. If, however, seven cover sprays are applied, the residues may exceed 9 p.p.m. of DDT, unless the concentration is reduced to less than 1 pound of DDT in 100 gallons.

The spray schedules studied in the Yakima Valley included at least three sprays containing not more than 1.25 ounces of parathion in 100 gallons. Harvest residues were less than 0.1 p.p.m. of parathion. 

Spray schedules using 1 pound or less of DDT in 100 gallons in one to four sprays were studied in the Yakima Valley. DDT residues were well below the proposed tolerance of 7 p.p.m. in ail treatments studied. A four-spray schedule with 74 days between the last spray and harvest resulted in a residue of only 3.3 p.p.m. of DDT at harvest. 

Spray schedules with as much as 1.5 pounds of DDT in 100 gallons were studied in the Mississippi Valley. The number of sprays containing DDT was as high as seven, six being applied in most of the treatments. A six-spray schedule in which 1 pound of DDT was used, without any adhesive, resulted in harvest residues approximating or slightly in excess of 7 p.p.m. of DDT. When seven sprays were used DDT residues in some treatments were considerably in excess of 7 p.p.m. 

Using low doses of insecticides—In doing so, plenty of susceptible phenotypes will be spared. The use of reduced application rates is also in line with current IPM programs. In the past, most spray schedules and label directions for insecticide use were found to be overprescribed because of the philosophy of pest eradication (Metcalf, 1980). It is now believed that an insecticide which kills 50% of the insect pest and none of its predators is more valuable than one which kills 95% of insect pests but at the same time eliminates their natural enemies. 

Maltas, Michael. Qrchard Pest Management and Spray Schedule. (Available from North-woods Nursery, 28696 S. Cramer Rd., Molalla, OR 97038.)... 

Controlled release of agrochemicals (e.g., by hydrolysis of a polymeric ester) can offer the advantages of constant level, smaller dose, reduced evaporation loss, lower toxicity, longer life, decreased environmental pollution, and reduced effect on nontarget species by wind or runoff.20 Systemic pesticides are preferred. This ensures protection of the growing tip of the plant. For weed killers, this means that it is not necessary to hit every leaf of the plant with the herbicide. Pesticides are often applied on a spray schedule according to the calendar as a prophylactic measure. Chemical pesticides are used 98% of the time. 

At that time, the spray schedule for the outside was changed to 5-min spraying periods with 1-h breaks between sprayings. The periods between... 

The use of mixtures of fungicide partners without cross resistance is a validated standard tool in resistance management as well as the alternation of non-cross resistant fungicides that is preferably used in longer spray schedules. 

An extensive study of the use of survey traps in the management of the codling moth was carried out in the Rhone Valley and in the vicinity of Paris, France, by Audemard and Milaire (583). They concluded that critical levels of trap catches in conjunction with temperature readings can be used to determine spray schedules. 

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