Spiders Mites, Nematodes, Other Non-Insect Pests
by Bob Bauer
Also known as Two Spotted spider mite or Red Spider. Tetranychus sp. Spider mites are a tiny arachnids (spiderlike creatures with 8 instead of 6 legs), that appear like dust under the leaves. Spider mites have tiny mouthparts modified for piercing individual plant cells and removing the contents. They cause their damage by sucking the sap from the leaves. Their fine micro-webbing can be seen there, as well as sometimes small black spots. Or they can also appear to be pale dots on the surface of the leaves. The tops of the affected leaflets start to turn yellow and brown in a salt and pepper looking pattern. The leaves then get crispy and curl up, obtaining a dull bronze sheen. They then can turn completely brown, die and fall off. They occur during hot, dry weather. They are extremely prolific, producing a new generation every 5 days, so they can multiply very rapidly. They dislike humidity and rain. They are very tiny, less than 1/2 mm, but can be seen with a magnifying glass. As they age and feed, they change color from greenish white to reddish brown. Tapping an infected leaf on a sheet of white paper will produce a scattering of what looks like ground pepper that moves around. More information can be obtained here: Spider Mites and Their Control.
Treatment: They can be controlled by spraying with water, especially on the underside of the leaves. Water spray the plant every 7-10 days to destroy the webs and knock the mites off. They can be preyed upon by ladybug and lacewing larvae, as well as predatory mites. Predatory mites (usually Phytoseiulus spp., Amblyseius spp. or Metaseiulus spp.) can be purchased and released onto infested plants. They are repelled by Dill underplantings and dislike sulpher sprays. Be sure to thoroughly cover the underside of the lower leaves. They are also susceptible to a spraying of insecticidal soap and applications of horticultural oil - (two percent). Mites are very tiny and soaps and oils work by contact only. They can also be controlled with miticides applied 3 times at three day intervals. Be aware that miticides are specialized pesticides and that normal insect pesticides don't work that well. Avid, Kelthane, difocol, ambectin or hexakis are some of brand names of miticides.
'Cricket'
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Rose Problems Page
Nematodes are small soil-inhabiting worms. Several different types of parasitic nematodes damage rose roots. There are good and bad nematodes. Many of them are beneficial to your soil and limit damage caused by other garden pests by feeding on them. Non-beneficial nematodes are only a problem in specific areas and climates. 'Root Knot' Nematodes Meloidogyne hapla are the ones most commonly mentioned as rose pests. These parasitic nematodes suck and drain the fine hairlike rose roots and create knots in the smaller roots limiting the development of the root system. These timy swellings (called galls) appear all over the mass of the rose roots. The roots that are damaged by these nematodes can no longer take up water or fertilizer into the upper parts of the plant. Plants with nematode root damage can be stunted or weak and don't have normal healthy green coloration. They also will not produce new growth very well, and flowers will be sparse. The overall life span of the nematode affected rose will be shortened greatly. Rose lovers in the state of Florida seems to have the worst problems with nematodes. Damage is at its worst in warm sunlit sandy soils that remain moist.
Treatment: Marigolds or Alliums as underplanting are said to repel nematodes. Nematodes can be dealt with by planting nematode-free plants into parts of the garden where nematodes haven't been a problem previously. In soil where nematodes have been a problem before, the soil can be fumigated. The fumigation takes place by the addition of methyl bromide. Some recommendations are for 2 pounds per 100 square feet under a plastic cover. Be aware that not all nematodes are bad. In Florida, many rosarians recommend that you buy only roses that are budded on special nematode resistant root stock varieties. 'Fortuniana' is the root stock of choice there.
'Palmetto Sunrise'
Although these can be devastating for many plants in your garden, they don't seem to hurt roses to any major degree. The reason is that they are not willing to crawl up the spiky staircase or rose prickles that it takes to get a good meal. More information can be seen here: Slugs and Their Management
Treatment: A little bit of beer in a tuna fish can or pie plate will attract and drown all the snails and slugs in a 10 square foot area, if you need to get rid of them. Another method to get rid of the larger snails with shells is the 'Snail Hunt' which can be carried out after sunset. Take a bucket and a flashlight and one by one pick up the snails and put them in the bucket. Do Not Smash them in the garden, because they can leave fertile eggs on the ground even after they are dead. After you have picked up all of the snails that you can find, either chuck them in the garbage, or if you are a sensitive memeber of PETA, take them over the the yard of somebody you don't like or release them in a wild area.