Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: Warren E. Shafer x
  • All content x
Clear All Modify Search
Full access

Warren E. Shafer

Free access

Warren E. Shafer, Gregory Clarke, Robert Fritts Jr., and Derek Woolard

ReTain™ is an organic, water-soluble formulation that contains 15% (w/w) of aminoethoxy-vinylglycine (AVG). AVG, a naturally occurring plant growth regulator, competitively inhibits ACC (1-aminocyclopropane-1-carboxylic acid) synthase, the enzyme responsible for the conversion of S-adenosylmethionine (SAM) to ACC, the immediate precursor of ethylene in plants. ReTain has been under commercial development for the past 6 years, which includes U.S. EPA-approved Experimental Use Permit (EUP) programs in 1995 (Shafer et al., 1996, Proc 23rd Annu. PGRSA Mtg., p. 233–234) and 1996. Under the 1996 EUP, ReTain was tested on nearly 4000 acres of apples in 18 states. When used according to label directions (i.e., 50 g AVG/acre applied 4 weeks before anticipated harvest) with a nonionic surfactant, ReTain effectively reduced preharvest drop and generally resulted in fruit of higher quality than untreated (control) or naphthaleneacetic acid (NAA) -treated fruit. ReTain can delay fruit maturity (as indexed by starch conversion) by ≈7 to 10 days. ReTain-treated fruit were typically firmer (by 0.5 to 1.0 lb), produced significantly less ethylene, and maintained notably greater firmness through storage. The incidence and severity of watercore in `Delicious' was significantly reduced by ReTain, as was the frequency of fruit cracking in `Fuji' and `Gala' in several trials. Based on this benefit profile, ReTain can be an effective harvest management tool for apple growers. U.S. EPA approval for the commercial registration of ReTain is anticipated prior to the 1997 use season.

Full access

Leslie K. Lake, Warren E. Shafer, Sheryl K. Reilly, and Russell S. Jones

Plant growth regulators (PGRs) are often used in crop production for specific niche market needs. PGRs are frequently viewed as secondary business opportunities by the private sector, especially when compared to herbicide, insecticide, and/or fungicide markets. Nonetheless, PGRs are regulated by the U.S. Environmental Protection Agency (USEPA), and the additional cost of regulatory compliance as part of commercial development is significant. Of the two broad classes of pesticides regulated by the USEPA, conventional chemicals and biological pesticides (or biopesticides), many PGRs belong to the biopesticide class, specifically the biochemical category. Because of USEPA's responsibility to assure that any pesticide used in commerce will not result in unreasonable adverse effects to humans or the environment, specific data requirements have been established for product registration. Registrants must address each requirement, either by submitting relevant data or a request to waive the requirement, prior to receiving a federal registration. For biochemical PGRs, the acceptability of data or waiver requests, as well as any proposed label uses, are reviewed by the Biopesticides and Pollution Prevention Division (BPPD). The BPPD was formed in 1994 to facilitate the development of biopesticide products. Given the time and expense associated with PGR product development and commercialization, registrants should work closely with the USEPA and other stakeholders to help ensure successful product development.

Free access

Warren E. Shafer, Gregory Clarke, Robert Fritts Jr., Ricardo Menendez, and Derek Woolard

Aminoethoxyvinylglycine (AVG) is a naturally occurring plant growth regulator that was first patented in 1973 (US patent #3,751,459). AVG has been shown to competitively inhibit ACC (1-aminocyclopropane-1-carboxylic acid) synthase (Yu et al., 1979, Arch. Biochem. Biophys. 198:280–286), which is the enzyme responsible for the conversion of S-adenosylmethionine (SAM) to ACC, the immediate precursor of ethylene in plants. Because of this unique mode of action, AVG has been tested over the years on a wide array of plant tissues. Studies on plants of horticultural interest have included cut flowers (e.g., Baker et al., 1977 HortScience 12:38–39), greenhouse crops (e.g., Saltveit and Larson, 1981, J. Amer. Soc. Hort. Sci. 106:156–159), and tree fruits (e.g., Bangerth, 1978, J. Amer. Soc. Hort. Sci. 103:401–403). AVG is currently being developed by Abbott Laboratories for use on apples (e.g., Shafer et al., 1995, Proc. 22nd Annu. PGRSA Mtg, pg 11–15). This presentation: a) briefly reviews prior literature regarding the effects of AVG on apples, b) provides an update on Abbott's commercial development program, and c) outlines some near-term research objectives for the use of AVG on apples.

Free access

Moritz Knoche, Peter D. Petracek, Martin J. Bukovac, and Warren E. Shafer

14C-urea penetration of isolated tomato (Lycopersicon esculentum Mill. cv. `Pik Red') fruit cuticular membranes (CM) was studied as a function of concentration and temperature. There was no significant effect of cuticular wax on urea penetration at 25C, permeances for the CM being 8.4 × 10-10 and dewaxed CM (DCM) 11.1 × 10-10·m·s-1. Time lags were near zero for both CM and DCM. Steady-state diffusion analysis suggests that the relatively low cuticular permeance of urea is due to low partitioning that offsets high diffusivity. Urea flux through the CM and DCM showed ≈1.5- and 1.9-fold increases, respectively, for each 10C increase between 5 and 45C. Urea flux across CM and DCM increased linearly with concentration (10 μm to 1 m) and, thus, was a first-order process.