A significant amount of rainfall fell on the upper coastal bend in the middle of last week, with reports up to 2 inches to 2.5 inches received in the El Campo and Pierce area of Wharton County. In the past few days 1 inch or more has been widely reported.
Blooming cotton can be found across the entire area with most having 8 to 9 nodes above white flower (NAWF). The balance of the cotton in the IPM program is in the bloom/boll stage, so we are continuing to monitor for bollworms, stink bugs, spider mites, aphids, and Creontiades.
Program fields have improved in fruiting this past week and are averaging a more than 85 percent with a few fields below 80 percent. We are also beginning to see more bollworm activity in a few fields in the Crescent and El Toro areas. The big story, however, is the increase of stink bug population levels reported in Jackson County early this week.
Beneficial numbers in cotton are low to moderate with lady beetle adults, big eyed bugs, minute pirate bugs, green lacewings and damsel bugs observed. A handout on identification of beneficial insects can be obtained from our office.
Corn is beginning to mature rapidly in Jackson County and the conventional thinking is that some fields may be ready to harvest within the month. Additionally, I have received a report that numerous moths are being found in soybean fields, which may give rise to pod feeding worms. Grain sorghum, like cotton, is experiencing significant increases in stink bugs, which, depending on the stage of growth, may demand your attention now.
Here’s an overview of pest activity.
Increasing populations of aphids are showing up in many program fields; however, on balance most are below the economic threshold. With the noticeable recent increase, populations can and will rise quickly. Sometimes aphid numbers increase to moderate or heavy levels and then decline for no apparent reason. Although high populations can develop prior to bloom, most economically damaging infestations develop later in the season during the blooming period. Fields should be scouted twice per week since rapid increases in aphid numbers can occur in a short time. A total of 60 leaves divided between the top, middle and lower portion of the plant should be sampled from plants across the field to determine infestation levels.
We continue to find small numbers of Creontiades in Jackson County; however, as of yet no treatable populations have been found or reported. The adults of this plant bug are on-half-inch long, narrow-bodied and light green. This insect goes through five molts or instars (nymphs). The antennae of nymph and adult Creontiades are longer than the length of their body, while the antennae of nymph and adult fleahoppers are approximately half the length of the insect body.
Nymph and adult Creontiades are light to dark green and have red eyes. Young Creontiades nymphs have red stippling on the antennae, but this usually is not observed after the third instar. In addition, Creontiades adults have a reddish band on the pronotum (segment behind the head). Damage from Creontiades species in cotton can be square and small boll loss. A characteristic clear yellow liquid (frass) is often left on the fruiting structure where Creontiades have fed. Squares and small bolls may suffer damage ranging from just surface feeding and boll malformation to complete fruit loss.
While the sweep net method is a good way of sampling for this pest, it does have some flaws. For example you are only able to sample the upper 10 inches of the plant and you are unable to determine if the rest of plant has any populations. A more effective way is to sample with a drop cloth (beat sheet) because you can knock the insects onto the sheet and count them.
I am unsure of an economic threshold for Creontiades using this method. We need more information about this pest regarding best sampling methodologies, economic thresholds, and efficacy of insecticides, not to mention exactly what are they doing to crops such as grain sorghum and soybeans.
Continue to be on the lookout at this time, for bollworms, especially in non-Bt fields. Egg lays are variable across the area with program fields ranging from zero percent to 8 percent. However, damaged squares were between 0 percent and 16 percent and worms, all of which were less than 2 days old, were detected from zero to 6 percent.
In some situations, the combination of damage and worms puts a treatment decision “right on the bubble,” particularly if we have lost beneficials to multiple insecticide treatments for fleahoppers. Also remember that treatment for bollworm eggs alone is not recommended in cotton, because a high percentage of eggs never hatch due to several mortality factors. Big eyed bugs, minute pirate bugs, green lacewing, and damsel bugs are efficient in removing bollworm eggs and small larvae from cotton.
Noticeable levels of stink bugs have been found feeding on squares and bolls in Jackson County and treatable levels have been reported in Brazoria County. As a reminder, feeding on bolls may cause boll shed and/or seed damage, lint staining and yield reductions. When making management decisions on whether to treat for stink bugs the following should be adhered to: Examine 6 row feet of cotton in several locations in the field. At an average of one or more stink bugs per 6 feet of row, feeding can cause excessive loss of squares and small bolls and may stain lint. Additionally, at least 50 small bolls (the diameter of a quarter) should be examined. If 20 percent of the small bolls have evidence of internal feeding (callous growth on internal boll wall and/or stained lint) and stink bugs are present then treatment should be considered.
Stink bugs often are clumped near field margins. Spot treatment provides effective control when this situation exists. Second through fifth instar stink bug nymphs and adults can damage bolls. Fourth and fifth instars can cause the same level of damage as adults.