Friday, May 31, 2013

Plant Bug Surveys in Wild Hosts

Historically, years of abundant spring rainfall resulting in delayed cotton planting have been some of our highest plant bug damage years.

Plant bug damage can be more pronounced when the migration of adults from wild host plants occurs prior to or about the time cotton is setting the first pinhead squares (6th to 8th true leaf). One reason for this is that when adult plant bugs feed on pre square cotton they feed in the terminal or growing tip. This feeding can disrupt the physiology of the plant causing abnormal growth (crazy cotton). This abnormal growth can delay fruiting for several weeks.
On May 20, I surveyed one of the primary spring host plants (daisy fleabane) for tarnished plant bugs in Alabama. On that date in Henry County (southeast Alabama) I found that about one-half of the plant bug population was dark (older) adults about ready to migrate to a new host. In past years, cotton is about the only host that is attractive at this time of the spring. Most wild spring hosts are now drying down. The remaining one-half of the population on May 20 were immatures of all stages. This means that the migration to cotton could be extended for a several week period which is common in wet springs.
On May 30, I made a second survey in the same area and found fewer immatures but more light colored younger adults. This may indicate that the older adults have moved to a new host already and some of the immatures are now young adults. I made a second survey on daisy fleabane on May 30 about 80-90 miles farther north than the first one. In this survey I found that they majority of the population was still immature. The fleabane was still greener and fresher at this location which means the plant bug population was in perfect sync with the host plants.
Only time will tell what this means in 2013. However, scouts, consultants and field men should be alert for the presence of adult plant bugs in cotton, and specifically late planted cotton, in the next 10-30 days.

Thursday, May 30, 2013

Updates for Week of May 26th

Kudzu Bug adults depositing eggs in April planted soybeans in Barbour Co. (Eufala) on 5/28/13. Will wait for hatch to assess treatment needs.

Low level of cotton fleahoppers infesting 6-7 true leaf cotton at Prattville, AL.

Some controls still going out for adult grasshoppers in Central, AL. Stand loss detected from GH feeding on stems at or above soil line.

Mid May or later planted cotton with seed treatments should not need foliar thrips spray due to rapid growth of the plants.

Thursday, May 23, 2013

Cotton Growing and Thrip and Grasshopper Treatments

Some of the April planted cotton is finally beginning to grow since the nights have become warmer. April 17 planted cotton at Prattville, AL now has 4-6 true leaves and is about 5 inches high. Thrips pressure is still heavy enough to cause a moderate level of visible injury to true leaves when no foliar insecticide was applied. Most cotton planted in April 2013 definitely needed a foliar spray at the 1-2 true leaf stage. Plants that emerged after May 15 likely will not need this foliar application.

I have had several calls this week about making a combination spray to target thrips and grasshoppers as an over the top herbicide is applied. My comment was positive to do this but realizing that some of the grasshopper population is now adults and will be difficult to control without going to the highest labeled rates of whatever insecticides are applied. I suggest staying with a lower rate and just targeting the thrips and immature grasshoppers.
I will come back in a few days to look ahead at out next potential cotton insect – tarnished plant bug. It has been my experience that wet springs, with delayed planting, have the potential to be bad plant bug years.

Wednesday, May 15, 2013

Thrips and Cotton Update

A lot of cotton has been planted this week (May 13-17). This is the first time many areas have been dry enough since early April. However, believe it or not, much of central Alabama missed rains in the last weather front and it is already too dry for seed to germinate.

Cotton that has emerged has not made much growth to this point. Cloudy weather, cool nights and a moderate number of thrips has severely hampered seedling growth. Based on my observations from monitoring four thrips research trials, I would suggest that the cooler than normal temperatures, especially at night, has done more to prevent seedling plant growth than has thrips injury.
Thrips numbers have not been abnormally high. In fact, it does not appear that the mass movement of thrips from grains and other wild host plants have occurred yet. Thrips damage is moderate to heavy primarily due to the fact that plants are not growing due to cool nights.
Cotton planted this week (May 13-17) should have better growing conditions and grow off rapidly. If that is the case, thrips injury will be minimal in spite of thrips numbers.
I would suggest that cotton emerging after May 20 will not need a foliar spray to supplement seed treatments. My thrips trials planted on April 10 did not emerge and put on a true leaf until more than 21 days after planting. In this situation, much of the thrips control provided by the seed treatments had dropped considerably before a true leaf even emerged.

The bottom line is that growing conditions, moisture and temperature are more important than thrips numbers or the type of thrips control a grower chooses.

No seed treatment and no foliar spray. Plant date 4/10/13.

Seed treatment and foliar spray. Plant date 4/10/13.