Foliar-Applied Insecticides to Control Asian Citrus Psyllid on Orange: Summer, 2017

Asian citrus psyllid (ACP) is the primary insect pest in Florida orange production due to its role as a vector of huanglongbing or citrus greening disease. Intensive management of this insect requires new and diverse modes of action to slow the selection for insecticide resistance. This experiment was conducted at the Southwest Florida Research and Education Center on 7-yr old ‘Hamlin’ trees bud grafted to ‘US-802’ (Citrus grandis × Poncirus trifoliata) planted at a density of 308 trees/acre. Trees were irrigated with microsprinklers, subjected to conventional cultural practices and pruned to induce flush prior to application. Eight treatments and an untreated check were assigned to eight trees per plot, in an RCB design with four replicates in four rows, each separated by an untreated buffer row. Treatments were applied on 26 Jul 2017 using a Durand Wayland AF100-32 air blast speed sprayer operating at 1.9 mph and 300 psi equipped with three #4 John Beane ceramic nozzles delivering 100 gpa. Ten randomly selected shoots per plot were collected at 2, 7, 14, and 21 days after treatment (DAT) and examined using a stereomicroscope in the laboratory to count ACP nymphs and eggs. The density of ACP adults was assessed on six trees per plot using the stem tap sampling method twice on each tree. For each sample, adults were counted on a white plastic clipboard placed under a randomly chosen limb struck three times with a short length of PVC pipe. Data were subjected to ANOVA and means were separated using LSD (P = 0.05).

No significant treatment effect on adult ACP was observed on 28 Jul, whereas significant suppression was observed on 2 Aug with all treatments except BASF 440 alone at 11 oz or Beleaf at 5.6 oz (Table 1). Lowest ACP density of 2 Aug was in plots treated with Sivanto or BAS 440 plus Abba Ultra, although these were not significantly different from Beleaf or Cormoran at either rate. No treatment was statistically different from the check on 9 or 16 Aug.

No suppression of eggs was seen for any treatment throughout the trial (Table 2). Sivanto and BAS 440 plus Abba Ultra resulted in consistently lower nymphal numbers compared with the untreated check throughout the trial. In contrast, fewer nymphs than the check were seen from the BAS 440 treatment only on 2 Aug and from the 2.8- and 4.3-oz rates of Beleaf only on the first two sample dates. An inconsistent effect on nymphs was observed with Beleaf at 5.6 oz, with no significant effect on the first sample date in contrast to the remaining dates sampled. Similarly, Comoran at both rates resulted in fewer nymphs compared with the check on 28 Jul, 2 Aug, and 16 Aug but not on 9 Aug.

No phytotoxicity was observed. This research was supported by industry gifts of pesticide and funds.