Monday, July 6, 2020

Tarnished Plant Bug Alert for Cotton

Due to abundant rainfall over most of the state in recent weeks, the migration of adult plant bugs from wild host (daisy fleabane) has been slow and extended over several weeks. This makes it difficult to make treatment decisions since the adult numbers may be below threshold level (8 per 100 sweeps) for several consecutive weeks. It is for this reason that we also use a pinhead square retention count (need 80% retention) in making treatment decisions. It is possible that a sub-threshold number for consecutive weeks will do economic damage. Large farmers spread over a wide geographical area (multiple counties) do not have the ability to treat individual fields on a particular day. As the result, when PGR and boron applications are being made, a plant bug insecticide is included.

               Plant bugs tend to go to the earliest planted cotton first. As we move through July, all fields will eventually reach the blooming stage. When cotton reaches the blooming stage, we will begin to find immature plant bugs that have hatched from the eggs that were deposited by the adults that migrated from wild host. In blooming cotton, we can no longer use the pinhead square loss in making treatment decisions. Immature plant bugs move deeper into the canopy and feed on large squares, which results in damaged “dirty” blooms. The treatment threshold for these immature plant bugs is 3 per 5 row feet using a black drop or shake cloth. The product Diamond is a great plant bug suppression tool when immatures occur at threshold level in blooming cotton. Diamond at 6 to 9 oz. per acre will give 2-3 weeks control of immatures. Diamond can be mixed with an insecticide such as Bidrin, Centric, imidacloprid (Admire Pro or generic), pyrethroid or Transform. The number of adult plant bugs usually begins to decline (natural mortality) after first bloom as the immatures increase. In fields where plant bugs go uncontrolled for weeks, the immatures eventually reach the adult stage. If this situation is allowed to develop, a field may have plant bug populations that include all life stages from eggs in plant stems, immatures to adults. When this situation is allowed to develop into an imbedded population, multiple applications on a schedule are required to being plant bugs under control. It should be noted that clouded plant bugs have made up part of the plant bug population since mid-June. Damage, treatment thresholds and controls remain the same for both plant bug species.

Clouded Plant Bug Immature

Clouded Plant Bug adult