Oct. 12, 2017
The US EPA has established time-limited tolerances for residues of insecticide tolfenpyrad in or on dry bulb onion [at 0.09 parts per million (ppm)] and watermelon (at 0.7 ppm), which is effective October 10, 2017. This action is in response to EPA’s granting of emergency exemptions under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authorizing use of the pesticide on dry bulb onion and watermelon. The time-limited tolerances expire on December 31, 2020.
The Texas Department of Agriculture (TDA) stated that an emergency situation required the use of tolfenpyrad on dry bulb onions (Allium cepa) to control onion thrips (Thrips tabaci Lindeman) in the Texas counties of Cameron, Dimmitt, Frio, Hidalgo, Maverick, Starr, Uvalde, Willacy and Zavala.
According to TDA, this year’s exceptionally mild winter and record high heat caused the development of large populations of onion thrips, a principle pest of onions, early in the onion crop cycle. The threshold level for applying pesticides to control thrips in onions is 5 to 25 thrips per plant, and TDA stated that over 100 thrips per plant were observed in Texas’ dry bulb onion fields in early March, 2017.
TDA stated that multiple applications of registered pesticides were not controlling these extreme population levels which can reduce yields and bulb size by as much as 50%. In addition, the transmission of iris yellow spot virus in onions, exclusively vectored by onion thrips, is a concern, and several onion fields have been observed with positive symptoms. TDA stated that this virus severely affects the shipping quality of onions, and can be more devastating than damage from the thrips themselves.
Upon EPA concurrence, TDA allowed the use of tolfenpyrad under the provisions of a crisis exemption beginning on March 17, 2017, and subsequently requested a specific exemption to allow the use of tolfenpyrad in dry bulb onions to continue beyond the 15 days provided by a crisis exemption alone.
Separately, the Hawaii Department of Agriculture (HDA) stated that an emergency developed due to outbreaks of melon thrips in watermelon fields at unusually high levels, (up to 200 thrips per leaf), which registered pesticides were not controlling.
HDA stated that above-average rainfall caused rapid growth of host plants, leading to development of very high levels of melon thrips in areas near watermelon fields. Subsequently, a 6-week drought caused early dry-down of this rainy- season vegetation, prompting massive migrations of melon thrips into neighboring watermelon fields.
HDA stated that the melon thrips infestations have caused stunted vines, foliage discoloration, and in some instances have caused such severe damage that the plants no longer produce fruit. The melon aphid also transmits the tomato spotted wilt virus, which causes silver mottle disease in watermelon, further damaging the plants and causing additional yield losses.
HDA stated that some watermelon acreage was abandoned due to the high level of damage from melon thrips infestations, and that significant yield and economic losses would occur in the remaining watermelon acreage without the requested use of tolfenpyrad. Upon EPA concurrence, HDA allowed the use of tolfenpyrad under the provisions of a crisis exemption, beginning on May 31, 2017, subsequently requesting a specific exemption to allow the use of tolfenpyrad in watermelon to continue beyond the 15 days provided under a crisis exemption alone.