Evaluation of Organophosphate and Pyrethroid Insecticides for Control of Asian Citrus Psyllid and Citrus Leafminer on Oranges, Summer, 2014 *

ACP is the key pest of Florida citrus due to its role as vector of greening disease or “huanglongbing.” Feeding damage from CLM larvae facilitates spread of citrus canker caused by Xanthomonas axonopodis pv. citri . Both pests feed on young flush and are also damaging in their own right. Therefore, effective insecticides are needed. The experimental block at a commercial grove near Labelle, FL, consisted of 12-yr-old sweet orange “Hamlin” orange trees planted at a density of 132 trees/acre. Seven treatments and an untreated check were randomly distributed in an RCBD with four replicates in five-tree plots over four rows with one untreated buffer row between treated rows and one untreated buffer tree between plots within a row. Treatments were applied on 24 June to both sides of the trees using a Durand Wayland AF100-32 air blast speed sprayer operating at 1.9 mph and 350 psi equipped with four John Bean ceramic nozzles # 4, 4, 4, 2.5 with three, two, one, and one whirl plates, respectively, delivering 100 gpa. Ten randomly selected shoots per plot were collected and examined under a stereomicroscope in the laboratory to count ACP nymphs and three fully expanded leaves on each shoot were examined to count CLM larvae. Density of ACP adults was assessed using a stem tap sampling method whereby a randomly chosen branch was struck three times with a short length of PVC pipe and individuals falling on a white clipboard placed underneath were counted. Four tap samples, one on each side of the canopy were conducted per tree on three central trees per plot. Data were subjected to analysis of variance and means separated using LSD ( P  = 0.05) are presented.

All treatments provided significant reduction in ACP nymphs compared with the check through 20 DAT although the Malathion treatment was less effective than the other treatments ( Table 1 ). Significant reduction in adults was observed in all treatments through 43 DAT except Malathion which was not significantly different from the check on any sample date and Imidan + Dyne-Amic seven DAT. The 16 oz/ac rate of Malathion is too low. There was no significant effect of rate or surfactant with Imidan against ACP adults but the low rate and the higher rate + Dyne-Amic did seem to control CLM although strangely enough the high rate by itself did not. No phytotoxicity was observed.

Author notes