A series of aerial applications were made with a helicopter and a biplane to evaluate the feasibility of using aircraft to apply 5 gallons per acre of a water-base spray to southern pine seed orchards. Application parameters were established by a mathematical model which predicts spray coverage. Data obtained on spray deposition at the canopy top and in the tree crown provide a basis for using aircraft to apply pesticides to seed orchards. More spray deposits were found in the upper tree crown than in the lower tree crown. The helicopter achieved higher quantities of deposit in the crown than the biplane. On a percentage basis, however, spray observed at each of the 3 crown levels was comparable in both aircraft. A greater number of spray drops was observed on the slash pine (Pinus elliottii Engelm.) needles than on the Ocala sand pine (Pinus clausa var. clausa (Chapm. Ex Engelm.) Vasey ex Sarg.), suggesting that higher application rates may be required to achieve comparable coverage in densely foliated pines. Under conditions similar to these trials, i.e. aircraft tank mix, drop size, foliage, meteorology, release height, and swath width, one should expect comparable results when treating southern pine seed orchards.
The biological target is becoming increasingly more important in pesticide spray evaluation and to research directed toward improving the safety and effectiveness of pesticides. Various techniques have been used to study the nature of drops which impact and deposit on tree foliage. A few basic techniques are summarized in this paper. Additionally, results are presented on the assessment of drops directly on foliage of slash pine (Pinus elliottii Engelm.) and Ocala sand pine (Pinus clausa [Chapm. ex Engelm.] Vasey ex Sarg. var. clausa). This was one of several techniques used to assess spray coverage from an aerial spray on a project conducted by the United States Department of Agriculture, Forest Service, in cooperation with the Florida Forest Service. Testing was conducted at the Withlacoochee State Seed Orchard, Florida, during February 1980. Results show a greater deposit of spray drops in the upper tree crown than in the lower crown. This was true for both pine species; however, fewer drops per linear length of needle were found on the Ocala sand pine when compared to the slash pine. Zusammenfassung Zur Tröpfchenverteilung auf Kiefernnadeln bei aviochemischen Bekämpfungsmaßnahmen Im Hinblick auf die immer wichtiger werdenden biologischen Aspekte sowie die Erzielung noch gröerer Sicherheit und Wirksamkeit bei der Ausbringung pestizider Sprühmittel wird ein Literaturüberblick über verschiedene Sprühtechniken und ihre Ergebnisse gegeben. Zusätzlich werden die Erfahrungen aus eigenen Versuchen, die in den USA an Pinus elliottii und P. clausa im Februar 1960 durchgeführt wurden, mitgeteilt. Es ergab sich bei beiden Kiefernarten eine größere Ablagemenge an Tröpfchen in der oberen Kronenregion, jedoch waren die Nadeln von Pinus clausa pro Längeneinheit mit einer größeren Zahl Tröpfchen belegt als jene von P. elliottii.
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