A common practice in highbush blueberry (Vaccinium corymbosum L.) culture is to use combinations of insecticides and fungicides to reduce the number and cost of pesticide applications. In response to apparent phytotoxicity observed in commercial fields that were treated with combinations of diazinon and captan formulations, phytotoxicity of two formulations of diazinon (Diazinon AG600 and Diazinon 50W) and captan (Captan 80WP and Captec 4L) was investigated on highbush blueberries during 1997 and 1998. Phytotoxicity injury similar to injury observed in commercial fields was reproduced in treatments with diazinon and captan mixtures in all experiments. The Diazinon AG600 and Captec 4L mixture was the most severe and caused significantly more phytotoxic-ity to fruit and leaves than individual treatments of Diazinon AG600, Captec 4L or untreated control. Separation of diazinon and captan applications by 8 h significantly reduced phytotoxicity compared to mixture treatments. Injured fruit and leaves recovered over time and most treatments showed only a mild injury at the time of harvest. Phytotoxicity on fruit and leaves caused by Diazinon AG600 and Captec 4L mixture was significantly affected by application date with the earliest application causing the greatest injury. These data indicate that diazinon and captan mixtures cause phytotoxicity on highbush blueberries and therefore the two should not be applied in combination.
Qiansheng Li, Jianjun Chen, Robert H. Stamps, and Lawrence R. Parsons
. Table 1. A brief genetic background of the eight Dieffenbachia cultivars and their critical chilling temperatures and durations based on visual leaf injury. Plant canopy heights and widths were measured 5 months after potting. The growth
Youbin Zheng, Linping Wang, Diane Feliciano Cayanan, and Mike Dixon
Cu 2+ application, plant growth was significantly reduced by nutrient solutions with Cu 2+ concentration 1.05 mg·L −1 or greater ( Fig. 2 ). These results are consistent with visual leaf injury and SPAD results in which no Cu 2+ treatment effects
Thomas M. Kon, James R. Schupp, Keith S. Yoder, Leon D. Combs, and Melanie A. Schupp
combination of damaged floral tissue and reduced photosynthesis due to leaf injury. In some experiments, ATS caused unacceptable leaf phytotoxicity ( Byers, 1997 ; Embree and Foster, 1999 ), which resulted in reduced fruit growth ( Wertheim, 2000
Diane Feliciano Cayanan, Mike Dixon, Youbin Zheng, and Jennifer Llewellyn
chlorine in the water and potentially resulting in leaf injury. Nonetheless, many of the observed injuries were mild and difficult to detect. Our previous research ( Cayanan et al., 2008b ) indicated that a free chlorine concentration less than 2.5 mg·L −1
Genhua Niu, Denise S. Rodriguez, Lizzie Aguiniga, and Wayne Mackay
. Results After 11 weeks of treatment, L. havardii had leaf injuries at salinity levels 5.7 dS·m −1 or greater. The 7.6 dS·m −1 and 9.4 dS·m −1 salinity treatments had 7% and 0% survival rates, respectively. Plants had similar visual appearance and no
James D. Oster, D.E. Stottlmyer, and M.L. Arpaia
, were less than would be expected to cause leaf injury. There were no significant effects of the AW or F treatments on root length ( Fig. 4 ), or dry weight, in the 0- to 60-cm depth interval. Root length ( Fig. 4 ) decreased rapidly with depth: from
Thomas Graham, Ping Zhang, Youbin Zheng, and Michael A. Dixon
pixel count. The LDI accounts for all damaged tissue, regardless of origin, so the differences evaluated are relative to the control, which was considered to be the baseline. Fig. 1. Representative steps in the image analysis used to quantify leaf injury
R.E. Byers, J.A. Barden, and D.H. Carbaugh
Terbacil applied to whole-spur `Delicious' apple (Malus domestica Borkh.) trees reduced photosynthesis and fruit set. The addition of the surfactant X-77 to terbacil sprays increased fruit thinning and leaf injury. Terbacil sprays applied to leaves only (fruit covered with foil) were as effective as when applied to leaves plus fruit. Dipping fruit alone in a terbacil solution did not cause abscission. Shading trees for 4 days with 92% polypropylene shade material reduced fruit set =50%. Spraying trees with carbaryl reduced fruit set by 25%. The combination of shade + carbaryl spraying reduced fruit set by 89%. Chemical names used: l-naphthalenyl methylcarbamate (carbaryl); 3-tert- butyl-5-chloro-6-methyluracil (terbacil); 2-chloroethylphosphonic acid (ethephon); alkaryl polyoxyethylene alcohols (X-77).
Donald T. Krizek and Roman M. Mirecki
Cellulose diacetate has been widely used in UV-B enhancement studies under field and controlled-environment conditions since the early 1970s to remove wavelengths below ≈290 nm, without any evidence of toxicity effects. However, while conducting UV-B exclusion studies in window boxes covered with cellulose diacetate (CA) or in Plexiglas chambers lined with CA, there was marginal chlorosis and cotyledon epinasty in `Ashley' cucumber, which is normally resistant to elevated UV-B, while seedlings exposed to open sunlight and those grown under polyester (PE) film to exclude UV-B were free of visible injury. These findings suggested that the CA filter itself may be causing toxicity. To test this hypothesis, a UV exclusion study was conducted in which CA or Teflon (T), both UV-B and UV-A transmitting films, were used to cover window boxes in the following four combinations (top/bottom): CA/CA, CA/T,T/CA, and T/T. When CA was used as the bottom filter (CA/CA and T/CA), the plants showed significantly greater leaf injury and a 2- to 3-fold reduction in growth than when T was used as the bottom filter (CA/T and T/T). These findings suggest that toxicity is caused by CA itself rather than by solar UV-B radiation, possibly as a result of outgassing of phthalates known to be used as plasticizers in the manufacture of CA. Further evidence that CA was responsible for leaf injury was provided by a companion study in which T was replaced by PE and damage was still observed, although no significant growth effects of CA position were observed.