`Dancy' tangerines (Citrus reticulata Blanco) were harvested after color break and exposed to high-temperature forced air (HTFA) at 45C for 3.5 or 4 h to kill Mexican fruit fly [Anastrepha ludens (Loew)] larvae. Heat-treated and control fruit were stored subsequently for 2 weeks at 4C. Tangerines harvested after color break (naturally degreened) tolerated exposure to HTFA in a similar fashion as tangerines harvested before color break and degreened by postharvest exposure to ethylene. Titratable acidity (TA) was significantly lower after heat treatments. Flavor, soluble solids concentration, external appearance, incidence of decay, percent juice yield, percent weight change, and flavedo color of heat-treated fruit were not different from nonheat-treated, control fruit. Exposure to HTFA is a viable alternative to methyl bromide for disinfestation of `Dancy' tangerine.
Krista C. Shellie and Robert L. Mangan
Jayesh B. Samtani, Gary J. Kling, Hannah M. Mathers, and Luke Case
, and phytotoxicity. Direct spray application of herbicides to containerized plants can result in leaf scorch, chlorosis on leaves and stems, and reduced plant growth ( Adams, 1990 ). As much as 80% of broadcast herbicide may settle into spaces between
Jan van Niekerk, Charl Kotze, Jade North, and Paul Cronje
, winter rainfall, production areas of South Africa that they are experiencing phytotoxic damage to mandarin fruit when they applied phosphonates at late fruit developmental stages, when color development is advanced. As this was the first of the reports of
Ed Stover, Jack Hebb, Ron Sonoda, and Masoud Salyani
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.
Janet C. Cole
Woody plant species were treated in 1995 and 1996 with 0, 1, 2, or 4 lb/acre (0, 1.1, 2.3, or 4.5 kg·ha-1) propazine (a.i.). Species studied in 1995 included rose-of-sharon (Hibiscus syriacus L. `Double Purple'), japanese boxwood (Buxus microphylla Sieb. & Zucc. `Green Mountain'), butterfly bush (Buddleia davidii var. Veitchiana Rehd. `Nanho Purple'), euonymus (Euonymus fortunei var. acutis Hand-Mazz. `Emerald n'Gold'), forsythia (Forsythia ×intermedia Zab. `Lynnwood Gold'), fire thorn (Pyracantha angustifolia Roem. `Gnome'), and japanese spiraea (Spiraea japonica L.f. `Goldflame'). Crape myrtle (Lagerstroemia indica L. `Acoma' and `Zuni') and juniper (Juniperus chinensis L. `Pfitzeriana') were added and euonymus and japanese spiraea were omitted in 1996. In both years, statistical analyses revealed differences in height and visual quality between plants exposed to propazine and control plants of some species; however, differences were inconsistent in that some plants treated with propazine were larger or rated better than control plants while other plants were smaller or of lower quality than their corresponding control plants. In all cases, differences among propazine treatments within each species were <1.2 inches (3 cm) in height while decreases in visual quality compared to control plants were most evident in plants receiving four times the recommended rate of propazine. The horticultural significance of these differences was, therefore, considered small, suggesting that all of the species tested are tolerant to propazine applied at the recommended rate of 1 lb/acre (1.1 kg·ha-1). Chemical names used: 6-chloro-N,N'-bis(1-methylethyl)-1,3,5-triazine-2,4-diamine (propazine).
Vladimir Orbović, Diann Achor, and James P. Syvertsen
. Despite significant antifungal and antibacterial effects of Cu on different crops ( Reil et al., 1974 ; Teviotdale et al., 1997 ), its use has been occasionally problematic because of phytotoxic effects often attributed to inappropriate adjuvants added to
Fulya Baysal-Gurel and Ravi Bika
in ninebark. The objective of this current study was to identify effective sanitizers, biorational products, and fungicides for the successful management of powdery mildew of ninebark. Those products were also evaluated for phytotoxicity on ninebark
Diana R. Cochran and Amy Fulcher
phytotoxicity ( Meijón et al., 2009 ) and be perceived as digressing from sustainable production ( Lütken et al., 2012 ). Plant growth regulators have several modes of action, including branch inducing, chemical pinching (chemicals that suppress apical dominance
Diana R. Cochran, Amy Fulcher, and Guihong Bi
than untreated, 4 = no difference from untreated, 5 = slightly better than untreated, 6 = moderately better than untreated, 7 = significantly better than untreated. Plants were evaluated at 2 and 6 WAT for phytotoxicity symptoms on a 0 to 10 visual
Menahem Edelstein, Daniel Berstein, Moshe Shenker, Hasan Azaizeh, and Meni Ben-Hur
case, high Se contents in the plant tissue can cause growth inhibition, yield reduction, chlorosis, and even plant mortality ( Terry et al., 2000 ). Hurd-Karrer (1937) was the first to describe Se phytotoxicity (snow-white chlorosis) in wheat plants