Panonychus citri is a significant pest of Rutaceae plants. Chitin deacetylase is a key gene in chitin metabolism and the insect molting process. In this study, The PcCDA1 and PcCDA2 genes of P. citri were cloned and identified. The expression of PcCDA1 was higher during the egg stage, while PcCDA2 exhibited the highest expression during the larval stage, with their expression levels showing a clear periodicity. Using RNAi technology to silence the expression of the PcCDA1 and PcCDA2 genes in the mite, the results indicated that only 20.85% successfully molted, while the deformity rates were 78.81% and 85.44%, respectively. HE staining and microscopic observation revealed that silencing PcCDA1 and PcCDA2 caused an increase in the epidermal thickness of P. citri by 1.87 μm and 5.706 μm, respectively. Additionally, silencing PcCDA also significantly reduced the relative mRNA expression levels of chitin synthesis genes (PcCHS1 and PcCHS2) and degradation genes (PcCHT1, PcCHT2, and PcCHT4). These results suggest that the PcCDA gene is crucial for normal molting and epidermal development, providing new scientific evidence for molecular target-based green pest control strategies.

Commercially available cabinet sprayers are not well suited for making low volume applications (<30 L/ha) of herbicides to woody forest species that can be up to 1.5 m tall. A simple, inexpensive laboratory sprayer that overcomes some limitations of commercial cabinet sprays can be built from materials readily available at local building and electronic suppliers. The only specialized equipment required is a positive displacement pump and a rotary disk atomizer. The atomizer is attached to the end of a variable height arm mounted on a laboratory cart. A positive displacement pump ensures controlled flow. The operator pushes the cart along a metal rub rail which keeps the cart tracking in a straight line. Travel speed is regulated by the operator following a marker on a clothesline-like loop of fishing line and is driven by a variable-speed drill attached to a variable voltage power supply.

In the late 1930s, European engineers discovered that, for very low flow rates, rotary disk atomizers produced a more definable range of droplet sizes than hydraulic atomizers. In the late 1970s, a cup-like spinning atomizer was developed to apply herbicides at low and ultra-low volumes. Rotary atomizers distribute droplets in a pattern similar to hollow cone nozzles. The droplet trajectory could affect deposits adversely since droplets released horizontally are exposed to wind and other environmental effects longer than hydraulic spray nozzles. Propellers and fans were used to enhance downward movement of droplets without considering that droplet impingement velocity was critical for efficient deposition. In the early 1980s, rotary atomizers were promoted to reduce herbicide rates, but the claims were products of unconfirmed testing. Herbicide efficacy in confirmed research was not influenced by application with the rotary atomizer, but lower carrier rates reduced the amount of water handled during the spraying operation. The cost of the atomizer, more maintenance, and greater care during operation with no decrease in herbicide rates discourage continued use.

Equipment is described that assists experimental work on controlled-drop application techniques. An electronic tachometer measures centrifugal nozzle rotational speeds in the range 0 to 5000 rpm. Speed control is achieved with a simple regulator incorporated in the tractor electrical system. Both devices are also suggested as worthwhile additions to commercial spray rigs.

Acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid} and bentazon [3-(1-methylethyl-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] plus acifluorfen were applied through hydraulic flat-fan nozzles or controlled-droplet applicators (CDA) in water plus surfactant, soybean [Glycine max (L.) Merr.] oil and water emulsions, and soybean oil alone. Except for inadequate weed control with CDA applications at 7 L/ha, method of application did not affect weed control of common cocklebur (Xanthium strumarium L. #3 XANST) or smooth pigweed (Amaranthus hybridus L. # AMACH) at high rates of bentazon plus acifluorfen (560 plus 280 g ai/ha or above). With low rates (280 plus 140 g/ha or less), hydraulic flat-fan nozzles were more effective than CDA applications. Early CDA applications of acifluorfen in an oil carrier at a volume of 9 L/ha were as effective as hydraulic nozzle applications at a carrier volume of 47 L/ha. Later applications resulted in inadequate weed control. Increasing soybean oil concentration from 2.5 to 40% (v/v) in acifluorfen spray mixtures did not significantly increase the phytotoxicity of acifluorfen.