Q. We’ve had a terrible problem with flies this summer. Previous summers haven’t been nearly as bad, but we can’t figure out why there are so many right now. How do we keep them away?
Our climate is warm, but also very dry, and the low humidity tends to keep insect populations in check. Occasionally we can experience an increase in humidity, and when that happens, the flies can multiply quickly. Bare ground seems to attract flies as well. Of course, flies are mostly attracted to anything disgusting (garbage, rotting organic material, feces, etc.), so check your surroundings for these conditions first.
Fly control depends on controlling egg-laying and breeding conditions first. In warm weather, the housefly lifecycle moves very quickly (only 7 days from egg to adult fly). When a fly lands on something, it will deposit saliva to liquefy it before using its sponging mouthparts to ingest the partially digested food. This method of feeding means that flies are alarmingly efficient at spreading all sorts of pathogens. For this reason, exclusion from indoor living spaces (especially food preparation areas) should be a primary consideration. Make sure all window screens are intact and keep trash containers away from doors or other points of entry. Fly paper should be used only indoors in areas of low traffic (nobody wants to accidentally walk into a hanging, sticky tape full of dead flies — don’t ask me how I know this). Inverted cone traps are very useful outdoors, but locate them far from seating areas since the attractant is foul-smelling. Pesticides are not recommended since they are not very effective in this case.
Q. My lawn is being taken over by crabgrass. What can I do to get rid of it since it keeps coming back?
Crabgrass is tricky to get rid of since it reproduces both by rooting stems (runners) and seeds. It will form unsightly clumps in lawns and can choke out turf grass. Manual weeding can be tedious, especially for large or well-established infestations, but is still a good starting point. Unfortunately, each plant can produce over 100,00 seeds, so even if you pull out every clump, you’ll have an uphill battle. These seeds aren’t fussy about germination conditions, either, since they will sprout when the soil temperature stays at 55F or above for several consecutive days.
The best way to control crabgrass is to maintain a healthy lawn that is dense enough to choke out sprouting weed seedlings. For more information on proper mowing, fertilization, and irrigation, see ipm.ucanr.edu/home-and-landscape/crabgrass.