- Most effective means for controlling pink bollworms, bollworms, beet armyworms and fall armyworms is to plant a cotton variety containing Bt genes.
- Many High Plains growers do not plant much Bt cotton.
- Decision depends on how much risk you are willing to take to gain whatever benefit you see by planting a non-Bt variety.
Undoubtedly the most effective means for controlling pink bollworms, bollworms, beet armyworms and fall armyworms is to plant a cotton variety containing Bt genes. These include varieties containing Bollgard 2 and Widestrike technologies.
Depending on the circumstances, a grower may opt not to plant a Bt cotton variety. Reasons for this decision vary but include not wanting to pay the tech fee, no recent history with troublesome worm populations, choosing a non-Bt variety based on desired agronomic characteristics, or resistance to disease or nematodes. Regardless of the reason, many growers do not plant much Bt cotton.
Is the cost of the tech fee worth it? Based on the Seed Cost Comparison Worksheet provided by Plains Cotton Growers, (The 2011 Seed Cost Comparison Worksheet is available here: www.plainscotton.org), and a 52,272 seed/acre seeding rate, the tech fee for Bollgard II is $17.51 per acre alone, but roughly $8.60 when stacked with Flex. Widestrike tech fee is $9.09 per acre.
Depending on the insecticide selection, the cost for treating for bollworms (insecticide + application) runs about $8.00 per acre per application, while armyworms will cost about $13.00 per acre per application. However, when treating for bollworms with a pyrethroid, which is the most common treatment, you stand the chance of flaring aphids and possibly mites. Aphids and mites will usually cost about $7.00 and $18.00 per acre to treat respectively.
Also, there is the “nickel and dime” damage low populations of worms cause. In most years we can get by without treating or may have to make only a single application for bollworms on non-Bt cotton. But there is no guarantee. Additionally, Bt cotton is not immune to caterpillar damage. Although not common on the High Plains, we occasionally encounter fields of Bollgard 2 or Widestrike that require insecticide over-sprays for caterpillar control.
In addition to direct costs associated with spraying for worms in cotton there is the peace of mind factor—getting a good night’s sleep without worry about worms. In essence, it’s all a gamble and depends on how much risk you are willing to take to gain whatever benefit you see by planting a non-Bt variety.