Q. I started some cucumber plants indoors and they should be ready to plant next week. Over the past few seasons, I've had a big problem with cucumber beetles. They chew on the seedlings and by midsummer the plants are wilted and dead. I'm an organic gardener and don't want to use any poisons. Any good solutions?
A. Floating row cover material is effective at excluding flying insect pests. It's a light, gauzy material that you drape over garden plants. It needs to be secured to the ground with soil, rocks or boards.
It's especially important to protect new transplants from cucumber beetle feeding. They transmit a bacterial wilt disease that causes mature plants to crash for no apparent reason. Remove the row cover once blossoms open because cucumbers require cross-pollination by bees.
Other organic controls include the botanical insecticides rotenone, neem and pyrethrum.
Q. I want to buy a large amount of compost for my landscape this spring but I don't know how to determine the quality. How do you know you are getting good compost?
A. Compost can vary depending on the materials and the process used to make it. When buying bulk amounts, it is best to do a feel and smell test before the purchase. The compost should look and smell like fluffy, rich soil. It should not be stored in piles over 8 feet high or be steaming.
Any compost that smells like alcohol or methanol or is warm to the touch can harm plants. Compost in this state should be stored outside in low piles (uncovered) and allowed to cure for one to two months before using.
Well-made, finished compost is one of the best investments you can make for your garden. It will slowly release nutrients to your plants while improving soil structure.
Q. Two of my otherwise healthy rhododendrons have brown spots on the leaves. Last year I noticed that something had chewed holes in the leaves. Can you tell me what I can do about these two problems?
A. You probably have one of the common fungal leaf spot diseases that attack rhododendrons. In some cases, the centers of the lesions (the spots) drop out of the leaf. This problem can easily be mistaken for caterpillar feeding.
Leaf spot diseases are not a serious threat to healthy, mature rhododendrons. Prune off and rake up infected leaves and dispose of them in the trash. Keep your plants well-watered during dry periods this summer.
THIS WEEK'S CHECKLIST
1. Avoid the temptation to spray aphids feeding on garden plants. Predators and parasites usually provide effective control. If you must spray to control early severe infestations, use a hard spray of water, insecticidal soap or horticultural oil.
2. Sow bush beans every two weeks to have a continuous harvest throughout the summer.
Garden tips are provided by the Home and Garden Information Center of the Cooperative Extension Service of the University of Maryland. For additional information on these questions, or if you have questions of your own, call the center's hot line at 800-342-2507, or visit its Web site at www.agnr.umd.edu/users/hgic.