PERSISTANCE OF LIQUID AND GRANULAR SLOW RELEASE FORMULATIONS OF SOIL APPLIED INSECTICIDES FOR ASIAN CITRUS PSYLLID CONTROL, 2007

Soil application of the systemic insecticide imidacloprid to citrus in Florida is limited by label restrictions to 1 lb (AI)/acre/yr, which is insufficient to provide year-round protection for this pest even on small trees. Therefore, we investigated the feasibility using aldicarb for this purpose or extending the period of control using a slow release formulation of imidacloprid. The trial was conducted at the University of Florida Southwest Research and Education Center in Immokalee, Florida, on 5-yr-old ‘Valencia’ orange trees planted in a 15 × 22 ft spacing in double-row beds separated by a swale and running north-south. A CRB design was used with each plot consisting of 4 trees. Trees were trimmed approximately every two wk throughout the trial to encourage new growth (flushes) and provide a suitable substrate for oviposition and habitat for ACP nymphs. Weeds, debris and leaf litter were removed from beneath each tree prior to application. NUQ 05054 was applied by scattering 1.25 oz (10 lb/acre) in a four ft circle around the base of each tree on 19 Jun 2007. The 1.0 and 2.0 oz per tree Temik applications were made on 10 Jul by placing a weighed amount of product within two, 3 ft furrows approximately 2 ft from the base of the two opposing sides of tree. Furrows were covered with soil after application. Admire Pro was applied on 12 Jul at a rate of 14 oz per acre (0.11 oz/tree) in 16 oz of solution as a drench to bare soil at a radius of 24 inches around the trunk of the tree with an EZ-Dose sprayer with a pressure of 45 psi and a flow rate of 3.7 gpm. Evaluations were conducted on 18 Jul, 2, 16, 29 Aug, 13, 27 Sep, 11, 24 Oct, 8 Nov and 12 Dec when suitable new terminal growth (flush) was available. Ten shoots on each of three trees per plot were examined for the presence/absence of ACP eggs and nymphs. One shoot of each of the three trees was removed on each of the dates listed as well as 24 Jan 2008 and the number and stage of the ACP nymphs were assessed in the laboratory using a stereoscopic microscope. The adults were monitored on each of three trees per plot using a “tap sample”: gently striking the foliage three times with the hand and counting the adults that fell onto an 8 × 11 inch white surface held underneath. The treatment effect was further evaluated by placing an organdy cage on 11 Oct on two branches per tree in each plot after counting all ACP nymphs on each branch. Branches were clipped on 01 Nov and placed in a freezer for 24 h after which adults were removed and counted.