Producers may have additional biological pesticides to add to their arsenal of control methods for pests such as corn earworm and cotton bollworm, said a Texas A&M AgriLife Extension Service entomologist in Amarillo.
A producer’s pesticide options may be limited by product cost, effective classes, pest resistance, and the impact of a pesticide on beneficial populations or possible flaring of other pests, said Ed Bynum, so they are always looking for something new to use.
“Toward the end of our growing season this year there was talk of a new insecticide,” he said. “The active ingredient in this product is the nucleopolyhedrovirus, known as NPV, that is being used in Australia. What is interesting is that this ‘new insecticide’ was studied as early as 1960’s and extensively during the 70’s and 80’s as the nuclear polyhedrosis virus.”
Bynum said it was first registered in 1975 by EPA and marketed as Elcar, Biotrol VHZ and Viron/H for Heliothis zea control in beans, corn, lettuce, peanuts, sorghum, soybeans, strawberry, tomato and cotton. Registration for all of these old products has been cancelled.
Now new products of the same NPV are being marketed as Heligen, Helicovex and Gemstar. These products are specific to larval stages of Helicoverpa, also known as corn earworm, cotton bollworm, tomato fruitworm, soybean podworm and sorghum headworm and Heliothis virescens, aka tobacco budworm.
“Producers are inquiring about the effectiveness of these new items on the market,” he said. “We wanted to provide them an outline of the information we have gathered.”
Numerous NPVs have been identified for different lepidopteran insects, but each NPV is specific to a particular insect host or narrow range of hosts, Bynum said.
There is an NPV marketed as Fawligen that is specific to Spodoptera larvae, which are fall armyworm and beet armyworm. Another NPV product, Loopex, is specific to the cabbage looper, Trichoplusia ni. All of the NPV products will not infect other insects or arthropods, including pests and beneficial predators and parasites.
Bynum explained how the products work, saying the larvae feed on NPV-treated plants where the virus infects the cells of the gut lining and begins to replicate throughout other cells in the larva. These infected cells rupture causing the larva to die. Viral particles released from the larval cadaver onto the host leaves can infect healthy larva when they eat on the plant.
“Larval infection and mortality will be dependent on the amount of NPV consumed and the larval size at infection,” he said.
The infection rate is age-dependent, and it may take a few days to a week for larvae to die. Often times dying larvae will climb to the top of the plant.
“One great virtue of NPV insecticides is they target a very narrow pest range, have no direct effect on beneficial insects and offer little disruption to the arthropod complex in the field,” Bynum said.
“These biological insecticides could be an alternative control method when the target pest has developed resistance to other available insecticides,” he said. “However, with any product for controlling a pest, there is a potential with increased exposure for the pest to develop resistance to the product over time, even NPV.”
Bynum said there is no current data on the effectiveness of NPV product applications for control of the above listed pest species with field crops in the Texas High Plains.
“Since we do not have any definitive results, we (AgriLife Extension) are hesitant to suggest the use of these products, but that does not mean that the products could not provide effective control under the right conditions,” he said.
For those interested in trying any of the NPV products, more facts about the products and general guidelines to help obtain optimum results can be found at https://txppipm.blogspot.com/2018/11/insecticidal-virus-products-for-pest.html.
– Kay Ledbetter, Texas A&M University
