This article should appeal to a wide range of producers across Alabama. Year 2016 was an interesting year that started with a very wet spring followed by a drought that really started in June with a dramatic reduction in precipitation that lasted 5 months.
Let us look at the climate data from Clanton, an important fruit and vegetable production region of the state, as a general example of what happened last year. After the last big rain event in June 2016, the total rainfall was a mere 3.9 inch from July to November. That was a shortfall of 18.5 inch! This was a very stressful moment for our crop producers and it made us realize the critical nature of our water resources.
Many northern parts of the state had worse rainfall records, and the struggle continues for many farmers in the state.
Unfortunately, insect pests took full advantage of the hot dry summer months that favored shorter development periods and intense migration between crops. In the graphs below, we have summarized the insect pest population fluctuations based on sticky wing insect traps from multiple locations, including Clanton, AL.
Cool wet spring with frequent rainfalls from January through May appeared to delay the activity of several moth species such as corn earworms, loopers, and some armyworm species. However, moth activity significantly increased in peanuts and vegetables once the drought hit us in mid-summer; we noticed the largest spike in the activity of fall armyworm, soybean looper, and the lesser cornstalk borer in August and September.
We generally see a late season migration of fall armyworms (a highly migratory pest!) from hay and pasture fields to vegetable crops – in 2016 this behavior created an extra heavy pressure made worse by the drought that may have affected crop yield. Direct crop scouting in research plots also indicated an unusually high number of armyworms actively feeding in the crops along with soybean loopers.
The lesser cornstalk borer, a major peanut pest, becomes a major issue during drought and our traps removed nearly 5,000 moths in four months – the highest ever on our record. Extreme drought also pushes insects to seek moisture in soil around plants and that can really mess things up for farmers. Caterpillars and pests like the burrower bugs in peanuts (that may enter the soil cracks to escape heat and get moisture) are very difficult to kill with any organic or conventional contact insecticide.
It was also intriguing to find a very prolonged squash vine borer activity in vegetables with nearly three overlapping generations detected over the year. Tobacco budworm moths were detected at 70 to 80 percent of our pest monitoring locations with very high trap catches in north Alabama. Hot dry weather also favored spider mite outbreaks.
Indiscriminate spraying of crops with synthetic pyrethroids can worsen spider mites in peanuts and vegetables by removing beneficial mites from the ecosystem. An aggressive spider mite outbreak is the worse problem than all other pests combined and crop loss in peanuts can be over 30 percent in uncontrolled conditions – so be cautious in developing your IPM plan during stressful weather.
If the dry conditions persist in summer of 2017, then remember these IPM recommendations:
- Plan your irrigation system now and optimize the water delivery system to maximize plant health. Adjust irrigation schedule to reduce plant stress.
- When in doubt, use insect pest monitoring systems such as bucket traps or sticky wing pheromone trap in order to detect pest activity. Caterpillar outbreaks usually occur within 10 days of a spike if dry conditions persist.
- Reduce spraying of synthetic pyrethroid insecticides in drought conditions and look for softer alternatives. Keep good records and compare effectiveness of products over multiple years.
- Incorporate selective insecticides in your spray rotation to reduce dependence on pyrethroids. Selective insecticides are also generally less harmful to beneficial insects compared to wide-action chemistries.
- Reduce unnecessary tilling or mowing around the field edges or within field. Dust from the end of equipment may have spider mites or they may hitch hike on equipment resulting in spider mite ‘hot-spots’. Treat hot-spots intensely instead of spraying entire fields.
Lastly, when in drought, don’t forget to scout using the proper sampling techniques and tools. Producers should check the Alabama Peanut IPM or the Alabama Vegetable IPM website for complete listing of crop scouting manuals. Hay producers are encouraged to contact Dr. Kathy Flanders and refer to her blog article on armyworms. Consult with the agronomy or commercial horticulture regional extension agents for assistance with insect pest identification and to develop site-specific IPM plans.
U.S. Drought Monitor
Insect pest populations fluctuate greatly with temperature and moisture levels. Please check the USDA Drought Monitor regularly and find the condition in your county.