 |
Ornamentals and Turf |
Japanese beetles are already emerging this season. It is not quite clear if the wet soil has helped or hurt them.
Casual use of Japanese beetle traps is not enough to measurably suppress a local population. Additionally, Dr. Dan Potter at the University of Kentucky has shown that in an individual yard, if none of the neighbors are using traps, it is sometimes worse to have a trap than not. The problem is that traps are so much better at attracting the beetles than actually catching them that you have more beetles in the vicinity of the trap than inside the trap. This is especially true if the bags are not emptied regularly. Once captured beetles begin to die in the bag, ammonia repels live beetles from entering the trap. However, the pheromone continues "calling" the beetles for a much greater distance than the ammonia repels them. The net result is greater plant damage than would have occurred in the absence of the trap. If you use traps, at least place them away from plants that are to be protected and empty them every day.
Sevin and other insecticides are labeled for Japanese beetles and are effective in controlling adult feeding as long as the residue remains on the plant. It is recommended that people not try to control Japanese beetles on blooms so as not to kill pollinators (and it is against the product labeling). Keep in mind that Sevin may result in spider mite outbreaks (see below). On mite-prone plants, handpicking or neem oil may be a better option although Sevin will provide better control. For more information, see Ornamentals and Turf Insect Note No. 44.
Apparently the temperature has warmed enough for twospotted and related spider mites to start damaging plants. (There may still be some activity of cool season mites such as spruce spider mite and southern red mite, so examine your plants for those, too, before it is too late.)
Spider mites are tiny warm season arthropods that insert their tiny, scissor-like mouthparts into leaves and petals and cause tiny yellow spots to form as they suck out the contents of the plant cells. Daylilies, roses, butterfly bush, some euonymus, and bedding plants are often infested by spider mites during the summer. Because spider mites flair up in dry weather, their control is somewhat difficult. Plants that have wilted slightly are much more susceptible to pesticide injury than turgid plants. Also, plants are much more likely to be burned if pesticides are applied during midday. Plants should be watered thoroughly before spraying them with pesticide and should be sprayed in early morning or late afternoon so that the pesticide residue is dry before the bright noon sun hits it. Horticultural oils and soaps are moderately toxic to spider mites and they are relatively safe for humans. Soaps and oils have virtually no residual activity so both pesticides must be applied two or three times for complete control (about 5 days between sprays). It may be a long season! Horticultural oils have been shown to be less harmful to beneficial predatory mites. For commercial nurseries, Joust gives excellent control of spider mites and mite eggs on trees, shrubs and flowers (except that it is not labeled for use in the greenhouse). It is also compatible with predatory mites, as are Hexygon and Floramite (two other recommended miticides). Other options are Pylon, Ovation, and Avid. The latter product is labeled for spider mites outdoors except on coniferous evergreens.
The current wet weather has created great conditions for snails and slugs. Slugs are often attracted to blossoms and to succulent leaves. They appear to be as sensitive in their sense of smell as humans. Various baits are available at garden centers. Of the baits which are used for slug control, metaldehyde is used most commonly. Deadline is the longest lasting and most resistant to weathering of the metaldehyde formulations according to research by Dr. Mike Parrella at the University of California. The baits usually work better if they are put under some object. (I like when they hide between two bricks and lay flat and still.) Ornamental and Turf Information Note No. 22 provides additional information on slugs and their management. Bill Symondson of the United Kingdom has good information on nonchemical control methods at the following web site: http://www.cf.ac.uk/biosi/research/biodiversity/staff/wocs2.html. Is there a good side to this? Lightning bugs are predaceous on slugs and snails. Perhaps we will have some sparkling nights this summer.
We have received an increasing number of telephone calls regarding moles in lawns. Though moles may eat grubs, their primary food source appears to be earthworms. If you have mole tunnels in your lawn, it is probably due to a healthy lawn and earthworm population rather than a large grub population. Scout for grubs before treating against moles. Despite all the mole chasers, gum, mothball and other home remedies, trapping is the most effective means for reducing mole populations. We have no recommendations for reducing the generally beneficial earthworm populations unless you care to have a low thatch, low organic matter soil and rock-hard clay yard. For more information on the control of moles, see the following web site: http://www.cropsci.ncsu.edu/turffiles/mole&vole/moles&voles.htm.
Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age or disability. North Carolina State University, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
Last modified on June 16, 2003 by Stephen J. Toth, Jr.
