Return to top

2. What is XPo?

Answer: XPo is a new product from Eco Soil Systems, Inc. that is effective against all biotypes (annual and perennial) of Poa annua. XPo contains a bacteria (Xanthomonas campestris pv. Poannua) that infects and kills Poa annua without infecting desirable turfgrass species.

Return to top

3. How does XPo work?

Answer: The bacterial agent in XPo (Xanthomonas campestris pv. Poannua) infects the Poa annua plant by entering a wound in the leaf tissue, such as a mowed leaf. Once in the plant, the Xanthomonas bacteria uses nutrients and sugars in the plant as its food source, multiplies in the vascular system (xylem), plugs up the xylem vessels by producing xantham gum and blocks the flow of water and nutrients. The plugging of the xylem causes wilting and death of the Poa plants that is first seen by a stretching (etiolation) and wilting of the leaves, soon followed by death of the infected plant.

Return to top

4. Do environmental conditions affect the activity of XPo?

Answer: As with all biological control agents, environmental conditions will affect performance. Infection and growth of the bacteria occurs best when air temperatures are between 65 and 80 degrees. At temperatures above 85 degrees growth of the Xanthomonas bacteria slows dramatically, infection rates are very low and few injury symptoms are seen on the Poa annua . However, since the expression of the infection (impact of the vascular plugging) occurs best when the Poa annua is under stress, injury and death of Poa annua will occur more rapidly when temperatures are above 80 degrees. The best environmental conditions for optimum performance of XPo is to have infection occur at temperatures between 65 and 80 degrees when Poa annua is actively growing, followed by a period of higher temperatures(above 80) under which the stress from the xylem plugging will kill the plants.

Return to top

5. How long will it take to see effects from XPo?

Answer: The speed of activity is dependent on environmental conditions and will vary. When conditions are optimal for activity, injury to the Poa annua may begin to be seen around two weeks following the first application. The activity will take longer if temperatures are cooler or if the plants are not actively growing due to high temperatures (85 or above), drought stress, or other stresses.

Return to top

6. Does XPo have an impact on bentgrass or other turfgrasses?

Answer: Since XPo activity is specific to Poa annua, there is no effect on bentgrass or other turfgrasses. This is big benefit for XPo over other annual bluegrass management options, which have a tendency to slow down bentgrass growth.

Return to top

7. How should I apply XPo?

Answer: XPo should be applied when the leaf blades are dry. Removal of morning dew by whipping prior to application will improve infection success. The turf should be mowed immediately following XPo application. Cultural practices (such as brushing the turf) which lift the leaf blades into a more upright position prior to mowing will improve infection levels. Effectiveness will be greatly reduced if the spray dries before mowing. Mowing is needed to cause leaf wounding and to allow for movement of the bacteria into the plant.

Return to top

8. Does Recharge have an impact on the performance of XPo?

Answer: Using Recharge on the same green prior to the application of XPo will stimulate root growth of the Poa, and the plants become healthier. As a result it will work against the effect of XPo.

Return to top

9. What time of year should I apply XPo?

Answer: Because of the characteristics of XPo mentioned above, there are certain times of the year when applications will give the best results. A program of early fall applications followed by series of spring applications after air temperatures have reached 65 to 70 degrees are recommended. The fall applications infect the Poa annua and weaken it prior to overwintering. The spring applications infect plants that either germinated and established after the fall applications were made, infect plants that were not infected in the fall and increase the level of infection in sick plants that overwintered. The multiple applications are required to insure that applications are made during a time when environmental conditions are optimal for infection to occur.