1a.Objectives (from AD-416):
Assist development of an expert system for the intelligent sprayers by investigation of top insects and diseases in ornamental nurseries and field experiments to test the new spray system.
1b.Approach (from AD-416):
Literatures and research reports will be reviewed and nursery fields will be surveyed to determine top insects and diseases in ornamental nurseries in Oregon and western states for the development of models to predict top insects and disease pressures; field experiments in three Oregon leading nurseries will be conducted to evaluate performances of new intelligent sprayers to control the top insects and diseases with reduced pesticide rates; educational materials will be delivered through workshops, field demonstrations and grower meetings to teach spray applicators how to use the new spray technologies.
Field efficacy tests were conducted to evaluate the control of aphids and powdery mildew by use of newly developed ultrasonic sensor controlled variable-rate sprayer in a commercial nursery in Oregon. The control efficiency was also compared between the new variable-rate sprayer and a conventional constant-rate sprayer. During the growing season, application rate of the conventional sprayer was 75 to 100 gallon per acre while the variable-rate sprayer used less than 35 gallon per acre. For aphid evaluation, leaves were randomly selected from the top, middle, and bottom of the red oak tree canopy for a total of five leaves each from 10 different trees in each row, and the total number of aphids from both the top and bottom of the leaves were counted. For assessment of powdery mildew, Norway maples were selected and sampled weekly throughout the growing season. The rating system used a visual assessment of percent coverage of powdery mildew mycelia on both sides of the leaves. These field tests were a paired comparison experiment with the randomized block design. Ratings of powdery mildew fungal sporulations on five leaves of each tree were averaged to represent an observation for statistical analysis. Observations of 20 trees in two rows for each rating day were grouped to calculate the mean rating for either a smart or conventional spray treatment. The mean ratings for powdery mildew between the two treatments for each rating day was then analyzed with Fisher’s least significant difference (LSD) multiple comparison test and tested at the 0.05 percent level of significance. The difference between the averaged rating means of the two treatments from the first rating to the last rating during the growing season was also analyzed with the Fisher’s LSD multiple comparison test and was verified with the t-distribution of differences between rating means of two treatments on the same day. Aphid numbers on five leaves of an oak tree on each rating day and during the growing season were similarly analyzed and significant differences between the smart and conventional spray treatments before and after insecticides treatments were determined. Test results demonstrated that there was no significant difference to control aphids or powdery mildew between the conventional and new variable-rate sprayers while the new sprayer used two to three times less chemicals than the conventional sprayer.
This project addresses critical elements for the development of precision sprayer technology envisioned in ARS parent project Objective 1 “Develop precision sprayers that can continuously match canopy characteristics to deliver agrichemicals and bio-products accurately to nursery and fruit crops”.