Vol. 51—1997 - NorthEastern Weed Science Society

94
Exploring the Feasibility of Product Performance Testing
Guidelines in Snap Beans
R.R. Bellinder*, J. Kirkwyland, M. Arsenovic, and R.W. Wallace
Dept. of Fruit and Vegetable Science, Cornell University, Ithaca, NY.
The U.. Environmental Protection Agency (EPA) requires pesticide performance data for
benefits a alysis as part of the pesticide registration process. Recently the EPA has made
attempts t standardize procedures used in field studies designed to obtain pesticide
performa ce data. A key component of the proposed Field Test Guidelines is the side-by-side
comparis n of all available pesticide alternatives along with currently practiced cultural and
biological ontrol measures. To determine the potential difficulties involved with following the
proposed uidelines, product performance tests for snap beans were conducted in 1993, 1994,
and 1995. Trifluralin, EPTC, pendimethalin, metolachlor, bentazon, and fomesafen were tested,
individuall ,and in combinations frequently used by growers [e.g. trifluralin + EPTC;
metolachl r (PRE) + fomesafen or bentazon (POSnl Weedy, handweeded, cultivation, and
cultivatio + handweeding treatments were included in all three years. Although growers
commonl cultivate snap beans, in 1993, none of the herbicide treatments were cultivated. In
1994 and 1995, all herbicide treatments were doubled, with the second recieving supplemental
cultivatio on an as-needed basis. Efforts were made to evaluate not only weed control and
yield, but Iso the effect of weediness on harvesting and snap bean quality parameters, as
required y the proposed Guidelines. Redroot pigweed, common lambsquarters, and hairy
galinsoga were the predominant weeds in all three years. Individually, none of the herbicides
adequate controlled all three of the weeds. It was clear that herbicide combinations provided
more co plete control and higher yields. Metolachlor (PRE) followed by either fomesafen or
bentazon (POSn tended to out-perform the other treatments. The use of handweeding as an
alternativ to herbicides in snap beans is cost-prohibitive. Total handweeding required 40 man
hours an cost $238/A. Even the cost of spot-weeding (estimated by growers to cost $50/A)
would sig ificantly reduce the small profit margin ($150/A) currently required by growers for
continue bean production. Cultivation (2X) alone could replace herbicides in snap beans
however, the risks associated with untimely rainfall and large acreages are unacceptable to
growers. Despite the use of mechanical harvesting equipment, it was not possible to determine
differenc s in snap bean quality. While the usefulness to the EPA of comparative data is clear,
the inclu on of all registered products, plus alternatives leads to large and costly experiments
that are ifficult to analyze statistically and therefore difficult to interpret. Traditional measures
of herbici e performance include weed control, phytotoxicity, and yield. Other factors, e.g.
interfere ce with harvesting, weed contamination, and weed seed return to the soil, should be
consider d when evaluating herbicide benefits. The greatest shortcoming with the Guidelines,
however, is the implied assumption that one compound can serve as a replacement for another.
For any 0 herbicides, the spectra of weeds controlled varies, so that often the most effective
control is achieved by a combination of herbicides. Particularly in the production of minor
crops, fo which fewer pesticides are registered, loss of a single compound can severely curtail
the avail ble pest control options.