SPRAY APPLICATIONS OF INSECTICIDES TO CONTROL ASIAN CITRUS PSYLLID AND CITRUS LEAFMINER ON ORANGE, 2007

Feeding of nymphs and adults of ACP causes distortion of young citrus leaves and can result in acquisition and transmission of the bacterium Candidatus Liberibacter asiaticus responsible for the citrus greening or huanglongbing disease. Feeding by the CLM larvae damages the leaf and exposes it to infection by the bacterium Xanthomonas citri responsible for the citrus canker disease. Therefore, both pests need to be controlled to reduce spread of these diseases. The experimental block at the Southwest Florida Research and Education Center (SWFREC), Immokalee, Florida consisted of 12-yr-old sweet orange Citrus sinensis (L) Osbeck ‘Valencia’ trees planted on double-row raised beds at a density of 132 trees/acre. Trees were irrigated by micro-sprinklers and subjected to conventional cultural practices. Bed sides of the trees were pruned with a tractor-mounted box blade mower to induce new flush and encourage psyllid infestation. Fourteen treatments and an untreated check were randomly distributed across 4 replicates in 30 rows that included a buffer row between each treated row. Treated rows consisted of 20 trees divided into four plots of 5 trees each. Treatments were applied on 22 Jun 2007 to the bed side of the trees using a tractor mounted hydraulic sprayer operating at a pressure of 150 psi with an array of fifteen ATR-80 ceramic hollow cone nozzles directed at the tree on 3, 5 foot booms to deliver 66 gpa at a tractor speed of 1.5 mph. A pre-treatment sampling was conducted on 20 Jun and treatment evaluations were made 3, 10, 17, and 24 DAT on 15 Jun and 2, 9, and 16 Jul, respectively. One and three trees were observed per plot for pre and post treatment samplings, respectively. Adult ACP density was estimated on each of 3 trees by counting the number of insects falling on a clipboard covered with an 8 1⁄2 × 11 inch white paper sheet placed under randomly chosen branches which were then tapped 3 times with the hand. Ten randomly selected shoots were examined and the number infested with ACP eggs or nymphs recorded. The infestation on each shoot was rated for the presence of ACP stages on a 0 to 3 scale: 0 = none, 1 = eggs and first instars, 2 = second and third instars, 3 = fourth and fifth instars. One infested flush was collected and examined in the laboratory under a microscope to count eggs and live and dead instars of ACP. The number of larvae and adults of four predatory coccinellid species were recorded during a one min observation on each tree. A well developed shoot with pale green leaves was randomly selected from each sample tree and all live CLM larvae were counted on five expanded leaves. All data were subjected to ANOVA to evaluate treatment effects on ACP, CLM, and lady beetle numbers and means were separated using LSD (P = 0.05). Numbers of ladybeetles were combined over all dates and transformed by log(x + 1) prior to analysis. Only the reported variables were evaluated on any specific date.