Friday, May 30, 2008
Size matters when treating for white grubs
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
Or send an e-mail. Answers will be given only in this column. Please don't send pictures or samples.
Recent columns
Q: I live in Canada and I have several questions. But, the most important one is that grubs are in the soil under my lawn. The grass has died in the places that I found the grubs. What can I do?
A: You should first determine whether the grubs present in that soil are actually guilty of eating the grass roots. They could be there because of the decaying organic matter in the soil. Whatever the case, take a sample of the grubs to a local expert in your area for identification and answers.
How deep under the turf roots did you find white grubs and what size are they? This depth is important for the effectiveness of whatever controls are applied. White grub size is important for killing. White grubs smaller than a half-inch die more readily than larger grubs. Here in Roanoke, the annual cycle of white grubs has them coming up to shallower soil depths as our soil warms at this time of year, but the white grubs are large and difficult to control.
Follow control recommendations including timing from local experts. Here in Virginia, turf damaging white grubs can be effectively controlled when a new generation hatches in mid to late summer. Biological controls are slower but can be effective if chemicals are not allowed. Biologicals lethal to white grubs include the pathogenic fungus called Beauvaria bassiana and entomopathogenic nematodes-products with Steinemema riobrave or Heterorhabditis species as the active ingredient. Follow all directions.
Q: Crown Vetch, coming from a neighbor’s yard, is taking over our yard. How do we get rid of it? Ordinary weed controller doesn’t work. Help, please.
A: Spot spray actively growing Crown Vetch in your lawn areas or not close to desirable plants with Roundup to get some control if you want to do this yourself. The Vetch will come back. Note that Roundup will kill most or all green plants whose leaves absorb the active ingredient(s) listed on the label. So, spot spray in late summer (Roanoke time) when grass can be sown in brown areas seven or more days after application.
Or, stop the Crown Vetch invasion by hiring a licensed pesticide applicator who can use a restricted chemical for better Crown Vetch control. Follow instructions for reseeding new grass as needed.
Q: My tomato plant is so heavy with fruit it split one of the stems. How do I patch or fix the stem? Also some of the very small tomatoes are turning red prematurely. What is the cause of this?
A: Fix the split tomato stem by creating a splint around the split section to pull the parts together, and tying the loaded tomato stem to a sturdy stake to support the weight load and prevent further problems. Use flexible materials to wrap tightly around the rigid splint and to tie the heavy tomato stem to its stake, such as old panty hose legs or cloth strips. Do not use plastic strips or wire ties that can constrict the tomato stem as it grows or cut into the stem during windy weather.
Water your tomato plant when the soil feels dry to the touch about an inch under the soil surface and do all things that you can to prevent added stresses to help in the recovery from the split. But, do not apply a complete garden fertilizer containing nitrogen to the tomato plant or encourage rapid growth until mid summer or when some of the tomato leaves become light green.
Small tomatoes turning red prematurely are likely caused by uneven soil moisture, a lack of calcium uptake, insufficient sunlight, and/or too rapid vine growth. Correct these possible problems by regular watering as soon as needed, no more nitrogen fertilizer as suggested above, external application of a calcium supplement product as sold for blossom end rot, and doing what you can to adjacent plants to give your tomato plant more sunshine.
