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Spider mites and rabbits: Pests that defy easy eradication

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Q: I have a healthy ficus that was taken over by spider mites that moved over from an ivy plant. I got rid of the ivy, but hope I can save my ficus. What is the best way to get the mites off the plant?

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A: If you can, put the plant in the shower and hose it down with a hard spray of water. Be sure to spray underneath all of the leaves as well. Follow this up with some insecticidal soap in places the mites still might be evident. Light infestations are relatively easy to control when caught early. Heavy infestations usually result in the plant needing to be thrown away because the spider mites' reproductive cycle gets ahead of one's ability or interest in controlling the mites. Let this be a warning on future plant acquisitions. Carefully check a plant for pests before buying or accepting a plant as a gift. Keep the new plant isolated for a few weeks to be sure you are not introducing a new pest to your other houseplants.

Q: Last year, I started dwarf marigolds from seed under grow lights. I grew many healthy plants. They all took hold, but several weeks later, the whole batch was eaten by some kind of pest. The pests ate the leaves, leaving only the veins, but then the veins disappeared. I read somewhere that thrips and some other pest can do this. What can I do to prevent this in the future? It there a spray I can use? The bugs also attacked my amaranthus in much the same manner. They ate large holes in the leaves and eventually the plants died. I had no problems the previous year and am wondering if I can expect problems this coming year.

A: This sounds like your plantings got devastated by some larval stage of an insect population. Assuming you completely cleaned up the planting area, the likelihood of these same pests returning is greatly reduced. I would suggest that you monitor the plantings every day to check for any initial feeding activity. You might put out some sticky traps in the planting area to see what you catch. This will give you a leg up on the voracious youngsters that may be arriving a few weeks later. When the initial damage starts to show up, get an appropriate insecticide and go to work!

Q: When reading your Web site, you said that red cayenne, jalapenos or habanera fresh peppers could be used to prepare a rabbit repellent. However, you said be careful if you use habanera because the capsaicin concentration is high enough to cause serious damage to the preparer! You went on to say, "Jalapenos should be hot enough to keep the bunnies away. The quickest way to come up with a concoction is to take three fresh peppers and run them through a food processor with enough water added to create a liquid. Pour the liquid through a cheesecloth mesh into a glass quart jar. Add about 2 tablespoons of olive or other vegetable oil, a squirt of Elmer's glue and a drop or two of liquid dishwashing detergent. Use one part of the concentration to 10 parts water. Shake well just before applying. This should discourage the bunnies without hurting them. If not, then make the concentration stronger (30 percent) or use cayenne peppers for extra heat. Be sure to reapply after new growth appears or after a good rain." Is this something that I should squirt directly on the leaves of my euonymus plants? Should I use a squirt bottle? Rabbits ate three of my euonymus plants down to the twigs. We've had an unusually snowy winter with no melting because of the very cold weather. I guess the rabbits only could find my shrubs in this deep snow. Will these shrubs survive?

A: In most instances, if the plant was healthy before being gnawed down by the rabbit, the euonymus or any other woody plant shrub should recover. Spraying the pepper mixture directly on the plants you want to protect is a good idea, but you need to remember to repeat this several times during the winter because it dissipates and washes off. I have found the best way to keep the bunnies away from my woody plants is to feed them like birds. This makes it easy for them to find something to eat and cuts down on their scavenging somewhat. They actually look fat and healthy this winter, even though this is one of the worst winters we've had in a long time. I figure some fortunate predator will appreciate their plumpness at some near future date!

To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or e-mail ronald.smith@ndsu.edu.

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