Nighttime Aerial Sprays for Control of Crepuscular Biting Midges in South Carolina

ABSTRACT Nighttime aerial spray applications with naled were conducted to evaluate their efficacy in controlling crepuscular biting midges (Culicoides spp.) in South Carolina, using a US Air Force C-130. Local populations of Culicoides spp. were monitored before and after the sprays with Mosquito Magnet traps to assess the efficacy of postsunset applications. Biting midge populations were consistently decreased by the aerial spray applications in this study. This indicates that nighttime sprays can be used to control these pests, even when their peak flight activity is focused around sunset.

Concentrated lowvolume aerial sprays to improve spray distribution in large avocado trees

The avocado industry has comprehensive guidelines for groundbased spray application to avocado orchards but there are no current guidelines for aerial spray applications Helicopterapplied deposits from a dilute spray application (600 litres/ha) of copper on a commercial Hass avocado orchard (12 m tall trees) were compared with twotimes (300 litres/ha) and threetimes (200 litres/ha) concentrate sprays with addition of varying rates of the superspreader adjuvant DuWett Tartrazine dye was included as a deposit tracer Concentrate sprays with adjuvant addition consistently gave higher spray deposits on difficulttowet fruit than the dilute aerial spray Deposits on fruit in all canopy zones were increased with concentrate sprays but particularly in the upper lower and outer canopy zones On foliage concentrate sprays with adjuvant addition gave similar spray deposits to the dilute spray Leaves in mid and inner canopy zones tended to be less well targeted by concentrate sprays This must be considered if targeting dense trees with aerial sprays

Airblast Application of Copper Fungicide to Grapefruit Does Not Affect Windscar

Wind-induced blemishing known as windscar and lesions from the disease melanose (caused by Diaporthe citri) are two of the most important causes of fresh grapefruit (Citrus paradisi) cullage in Florida. Copper hydroxide fungicides are the primary means of controlling melanose, but high air velocities from passing sprayers have been suspected of increasing windscar. In 1998 and 1999, airblast applications of Cu(OH)2 (1.7 kg·ha-1 Cu) were made at a range of early fruit development stages to a fresh grapefruit orchard in the Indian River region of Florida. These applications supplemented aerial sprays of Cu(OH)2 that were made uniformly across the entire experimental site at biweekly intervals beginning near full bloom. During the commercial harvest period fruit were sampled from three regions (interior, upper exterior, and lower exterior) of each treatment tree and were evaluated for percentage of fruit surface covered by windscar and severity of melanose. Airblast applications did not affect windscar in either year, but windscar was significantly greater from the upper exterior of the canopy, which is likely to experience the highest natural wind velocities. From these data, it appears unlikely that airblast applications significantly contribute to windscar of Indian River grapefruit. In 1998, no trees receiving airblast applications had significantly lower melanose incidence than the trees sprayed only via aircraft; however, trees receiving four airblast applications were scored as having higher apparent melanose on exterior samples than trees receiving most other treatments. This is consistent with high levels of Cu injury on these fruit which can superficially resemble melanose. Following treatment in 1999, trees receiving four airblast applications of Cu(OH)2 had significantly lower melanose scores than trees receiving either no or only early airblast applications, but were not significantly different from trees receiving a single spray 5.5 weeks postbloom. A computer model, which estimates Cu levels on fruit based on fruit growth, rainfall, and application parameters, indicated exterior fruit receiving four airblast sprays had >3 μg·cm-2 [Cu] for 40 days in 1998 but only 10 days in 1999, which reflects increased probability of Cu damage in 1998. It appears that aerial application supplemented by airblast merits further study as an economical means of melanose control.

Detection of Chlorothalonil in Dew Water Following Aerial Spray Application and Its Role in the Control of Black Sigatoka in Banana

A standardized bioassay measuring the growth inhibition of Aspergillus niger in vitro allowed the detection of small concentrations (0.1 to 20 μg/ml) of chlorothalonil present in dew water on both the adaxial and abaxial surface of banana leaves in a commercial plantation receiving aerial sprays. Chlorothalonil concentrations detected in dew water on the banana leaf surface were within the range of concentrations required to prevent Mycosphaerella fijiensis (causal agent of black Sigatoka) ascospore germination in laboratory bioassays. When 9-cm-diameter banana leaf disks inoculated with M. fijiensis ascospores were immersed for 4 h in water containing 0.1 to 0.6 μg of chlorothalonil per ml, ascospore germination was inhibited by 96.9%. The EC50 values for inhibition of ascospore germination were between 0.01 and 0.03 μg/ml for chlorothalonil and between 3.2 and 3.7 μg/ml for mancozeb. Following a 4-h exposure to chlorothalonil and mancozeb, and subsequent removal of the fungicides by a washing step, ascospores failed to germinate, indicating that both fungicides are fungicidal to M. fijiensis, not fungistatic. Recovery analysis of chlorothalonil spray droplet deposits and active ingredient on deposition cards in the field during aerial spray applications indicated that detectable fungicide deposition on the abaxial leaf surface occurs only when the banana leaf-target is vertical or nearly so. The significance of this observation in relation to the control of black Sigatoka with protectant fungicides is discussed.

Distribution of Thiabendazole-Resistant Colletotrichum musae Isolates from Guadeloupe Banana Plantations

In Guadeloupe, anthracnose of bananas, caused by Colletotrichum musae, is commonly controlled by postharvest thiabendazole treatments. A survey was conducted in 45 banana packing stations of Guadeloupe to determine the proportion of isolates that were resistant to thiabendazole. Isolates resistant to thiabendazole concentrations of 1 μg/ml (R1), 5 μg/ml (R5), and 50 μg/ml (R50) were detected. Most of the resistant isolates were R1 or R5, and of 1,350 isolates, the proportion of resistant isolates (R1 + R5 + R50) was 23%, ranging from 0 to 70% depending on the location. The presence of resistant isolates was correlated with the exclusive use of benomyl as foliar aerial sprays from 1972 to 1982 to control Sigatoka disease. Isolates resistant to concentrations of 1 and 5 μg/ml were as pathogenic as the susceptible isolates and were not controlled satisfactorily by postharvest thiabendazole treatments. Alternative control measures and the importance of resistance in terms of anthracnose control in Guadeloupe are discussed.

A Southwide Test of Bifenthrin (Capture®) for Cone and Seed Insect Control in Seed Orchards

In 1991, a Southwide study to evaluate the efficacy of bifenthrin (Capture®) for cone and seed insect control was established in six loblolly pine (Pinus taeda L.) and three slash pine (P. elliottii Engelm.) seed orchards. A control (no treatment), Capture® (bifenthrin), and Guthion® (azinphosmethyl) treatments were established in each seed orchard. Five aerial sprays were used to apply the insecticides during the growing season. At each spray Guthion® was applied at 3 lb ai/ac. Capture® was applied at 0.2 lb ai/ac for the first spray and 0.1 lb ai/ac for the other four sprays. Under the conditions of this study, Capture® was as effective in controlling cone and seed insects as the standard operational Guthion® treatment. Insecticide treatment resulted in a 42% and 17% increase in the number of sound seeds produced per conelet for loblolly and slash pine, respectively. Local need registration (24C) exists in several states, and seed orchard managers can currently use Capture® in Alabama, Arkansas, Georgia, Louisiana, Mississippi, Oklahoma, South Carolina and Tennessee. Seed orchard managers in other southern states need to determine if a 24C label is available in their state prior to useage. South. J. Appl. For. 18(1):72-75.