Volume XXVII No. 11 May 31, 2002 GENERAL SITUATION: Weather conditions continued to be modified from the previous two months of hot and dry conditions. Temperatures were moderated with highs in the upper 80's to mid 90's this week. The relatively lower temperatures accelerated field plant growth of irrigated crops. Dryland crops continued to suffer from dry conditions. Some rain fell in a scattered pattern with the mid-Valley area receiving the most. Insect activity decreased in some areas and increased in others. Rainfed Grain Sorghum Field Day Rio Farms An attached flyer describes the field day event for grain sorghum that will be held at Rio Farms on Tuesday, June 4th. Since the majority of our sorghum is now grown as rainfed (dryland), this field day should provide producers with some interesting information that is current and related to our short water situation. We hope you can attend and look forward to seeing you there. Boll Weevils Increasing Boll weevil punctured squares were reported from a few more fields this week. Most area fields did not have boll weevil activity reported again this week, however. Weevil punctured square counts reported were very low, but were found in more locations including fields along the Rio Grande, north of Mercedes, near Los Indios and in the Delta Lake area. Weather conditions in the last two weeks have favored boll weevil survival, especially in irrigated farm areas. All fields which have had a history of weevil problems should be monitored very closely now since weevils appear to be in the increasing mode. Bollworm Numbers Lower, but Field Conditions Favorable for Survival Bollworm/tobacco budworm activity was on the decline in most fields this week. Some large bollworms were observed in few fields, but most were too large to kill and in small numbers, not justifying any treatment at this time. The potential for another round of egg laying and worm feeding could be close at hand. Growers Valley wide are encouraged to keep alert for new egg lays. The likely hood of an increase in eggs could start at any time in the next few days to a week from now. Moisture from the current weather pattern may have been helping bollworm egg and small larvae survival, just like the boll weevils. Watch for them. Cotton Aphids Bombarded Cotton aphid infestations were much lower in most fields this week. Both insecticide treatments and beneficial insects took their toll on aphids. Large numbers of parasitized aphids (mummies), lady beetle larvae and syrphid fly larvae were reported from many fields this week. Large numbers of aphid parasite adults were observed in many fields and likely means that aphid infestations will not become as large in the next few weeks as they were. Increased numbers of spiders of various species were also observed.

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PEST CAST continued

Silverleaf Whiteflies Like it Hot

Silverleaf whiteflies (SLWF) populations increased this week compared to last week. The slightly increased temperatures this week, (just prior to the rains) compared to last week, probably aided SLWF. One indicator field in the mid-Valley area showed less than 1 adult whitefly per leaf last week. The same field showed an average of around 10 adults per leaf this week. Increasing adult SLWF counts do not necessarily mean that a major infestation of immature SLWF is in the offing. However, experience tells us to be alert to the increasing adult population and continue to examine leaves for immature stages of the pest. Generally, we suggest using the third fully expanded leaf from the top of the cotton plant and gently roll the leaf over to see how many adult SLWF are on the underside. Following that examination, move to the 5th leaf down from the top to determine how many immatures (both eggs and any stages of nymphs) are attached to the underside of that leaf. You should use a hand lens of at least 10 power to examine for the immature stages.

We suggest a range of 5 to 10 adult SLWF of per leaf for a treatment threshold. However, if no immature stages of SLWF are surviving, then keep checking the field(s) to determine if and when any immatures are coming through. Treatments for either adults or immature stages of SLWF must be directed at the pest as much as possible to insure the greatest kill.

Rainfall Can Be Detrimental To SLWF

We strongly encourage scouting anew for SLWF since the rains. Strong winds and rain like we had on Wednesday night can literally knock SLWF adults off the plants and kill them. Recheck fields which may have been close to needing SLWF controls before treating.

Sorghum Midge on the Hunt

Sorghum midge were observed at above treatment threshold in one field near Rangerville this week. Other field reports around the LRGV this week indicated that midge were not being found. Ideal conditions for midge were present in the one observed field in Cameron county. A midge infestation of 1 or more per head during bloom generally is enough to cause economic damage. The midge-infested field was situated across a turn row from an older, maturing field which had bloomed approximately three weeks earlier. Also, johnsongrass was present in a number of other nearby fields and probably contributed to the midge population.

Any sorghum field which is near bloom stage now and was planted near older sorghum which has already finished blooming is a prime target for damaging midge infestations. Any sorghum fields which are just beginning to bloom or will bloom in the next two weeks need careful, routine scouting to determine if midge are in large enough numbers to warrant treatment. Check several locations in each field, not just the edges. Field margins tend to be places where large midge infestations can appear, but many times the midge will not move past the field edges. Just checking the sides of the field can lead to a false decision about midge treatments. Check well into the field proper before concluding the level of midge infestation.

THE INFORMATION GIVEN HEREIN IS FOR EDUCATIONAL PURPOSES ONLY. REFERENCES TO COMMERCIAL PRODUCTS OR TRADE NAMES ARE MADE WITH THE UNDERSTANDING THAT NO DISCRIMINATION IS INTENDED AND NO ENDORSEMENT BY THE COOPERATIVE EXTENSION SERVICE IS IMPLIED.

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Tuesday, June 4th, 2002
Rio Farms Auditorium, Monte Alto
8:30 a.m.
Breakfast tacos served
Registration and Welcome
Dale Murden- General Manager, Rio Farms
Topics

Tour Rainfed Grain Sorghum Variety Study and
Yield Estimate Contest - Prizes Awarded
Andy Scott- Director of Research, Rio Farms
Sorghum Seedsmen Will Be Present to Answer Questions

Grain Sorghum Physiology: Interaction of Moisture and Fertility
Charles Stichler- Extension Agronomist, Uvalde

Update on the Current Cotton and Sorghum Insect Situation
John Norman- Extension IPM Agent, Weslaco

2002 Farm Bill
John Robinson- Extension Economist, Weslaco

This Educational Program is Sponsored by :

Rio Farms, Inc.
Texas Cooperative Extension