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Boxwoods are one of the most popular landscape plants in North Carolina. Well-maintained boxwoods can provide a landscape with a formal, elegant look. However, boxwoods are not immune to insect and disease problems. In fact, one might argue that they have more than their fair share.  Above: Create a formal, elegant look by shaping boxwoods into a circular profile. Below: Boxwoods sculpted into topiary forms.  Those of you who grow boxwoods, particularly the American type (although the English and Japanese are susceptible as well), may have seen damage caused by an insect called boxwood leafminer. The symptoms of boxwood leafminer injury include smaller than normal leaves with yellow blotches covering the top part of the leaf. The bottom of the leaf will be bumpy and blistery, as the leafminer has laid its eggs inside the leaf. Gradually the insects will hatch from the eggs and chew their way out of the leaf. The adult insects then puncture the underside of the leaf and lay eggs back into it. In addition to making a healthy boxwood quite unattractive , these insects are difficult to kill. Adult leafminers are active in mid-April, searching for new leaves to lay eggs in. If needed, this is the best time to treat with a contact insecticide, though they can also be treated with preventative systemic insecticides throughout the year. As always, follow the label directions if using an insecticide.
Above left: Yellow blotches, caused by the boxwood leafminer insect, form on the top part of the leaf. Above right: The bottom of a leaf infected by boxwood leafminers is bumpy and blistery.
light brown color. Once this happens, there is nothing you can do to save the plant, and you should not replant boxwoods in the same area, as they will be likely to develop the same disease, as it is permanently in the soil. Phytophthora is worse in poorly drained soils, so taking steps to improve drainage, such as adding compost or sand to clay soil, may be helpful as a preventative measure.
One of the most common problems of boxwoods is neither an insect nor disease but rather a physiological problem. Many types of boxwoods, particularly the Japanese types, tend to turn a bronze, orange, or reddish color during the winter. Not all leaves will turn this color, perhaps just a few on the tips of branches. This is normal and is caused by winter winds and may be worse when the soil is dry, the pH is too acidic, or if the temperatures vary drastically during the winter. This will generally not kill the plant, but will definitely make it less attractive. In the spring the new foliage often returns to a normal green color. Keeping the plants moist and adjusting the pH to about 7 by adding lime will lessen this type of winter damage. Boxwoods of all types tend to perform best in soils that stay on the dryer side, and in areas of partial to even full shade. As is often the case with landscape plants, planting the right plant in the right place is perhaps the most effective way to limit future problems. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705.
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Over the last month, we’ve had quite a shift in our weather, from extremely dry throughout all of June to quite wet in July, with more rain from Tropical Storm Debby. Plants need water, of course, and since this wet period followed a month of dry weather, initially this moisture was quite welcome. However, too much rain all at once can cause some complications in gardens and landscapes. Let’s talk about a few of these complications. One of the things you commonly see in gardens following a period of wet weather is an outbreak of fungal diseases such as leaf spots and root rots. Leaf spots generally develop when the leaves remain wet for a longer than usual period of time. Root rots can be a problem for a wide variety of plants in poorly drained areas, such as heavy clay soils, or in low spots in the landscape where water pools. Another thing you’ll often see is a surge in mushroom growth. Mushrooms arise in the lawn or garden when there is a type of fungus present in the soil and moisture conditions are high. Many mushrooms are nothing more than a nuisance in the lawn and garden. They can be mowed, picked, or dug out, but will often return if the conditions stay wet. You may notice them in low lying areas or other poorly drained spots where extra water seems to collect. Improving the drainage or diverting water away from these locations might help with long-term mushroom control.
Above left: Leaf spots on Black-Eyed Susans. Above right: Mushrooms popping up in lawns following heavy rainfall. All photos in this blog: Susann C., Extension Master Gardener Volunteer, Pitt County Arboretum.
Many weeds can grow in more adverse conditions than desirable plants, so while your trees, shrubs, and lawn struggled during the dry period in June, many weeds quickly filled in the gaps and then took over once the big July rains came. When the weather is hot, it can be pretty tough to get motivated to pull weeds out of the dry, hard ground.
Now that the ground is soft, however, it’s a perfect opportunity to reclaim some of those out-of-control spots by pulling weeds. It’ll still be a little bit of hard work, but even the deepest-rooted weeds can be pulled out relatively easily after this much rain. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. Watermelons are a favorite vegetable for many gardeners. They grow on fast-growing vines that cover a large area of the garden. At this time of year, watermelons should be at or close to maturity, depending on planting date and management or environmental factors (such as how much rain you got compared to other parts of the county). Watermelon is related to cucumber, pumpkin, and squash. It shares many of the same pests, though they don’t necessarily affect each plant in the same way. Watermelons seem a bit more pest-resistant than those other family members in many cases. Insect problems are limited mainly to aphids and cucumber beetles, and diseases include powdery mildew and various wilt and various leaf spot diseases. Aphids are small, soft-bodied insects, usually yellow, green, or white. They are found on the underside of leaves, and secrete a substance called honeydew that makes the leaves appear shiny and wet. Aphids generally do little direct damage to watermelons, although they may carry viruses that can be very damaging indirectly. They should be sprayed with insecticidal soap. It is important when spraying to cover the underside of the leaves where the insects are found. Cucumber beetles have black and yellow stripes or spots. They also may carry diseases, and the cucumber beetle larvae can damage the plants by boring into the stem, causing the plant to die. Cucumber beetles can be treated with bifenthrin.
Powdery mildew is a disease that causes white fungal patches on the leaves of watermelon vines. The fungus spreads and eventually leaves die, causing the fruit to be exposed and ripen prematurely. Control for this is to plant resistant varieties and to avoid watering the leaves of the plant directly, especially during the day. There are a number of other diseases that may cause wilt or leaf spots that are a large concern for commercial growers, but are generally not a problem for home gardeners. If you do have a problem with watermelons, bring a sample to the cooperative extension office for identification.
 Since watermelons are 95% water, they need adequate rainfall or irrigation to mature properly. Lack of water can stress the plants, which will make them more susceptible to the problems listed above. A good rule of thumb is to provide the plants with about an inch of water every week. They also need a good dose of 10-10-10 fertilizer, and some supplemental calcium to ensure they don’t succumb to blossom end rot.
Luckily, weeds are not usually an issue for home gardeners growing watermelons. Many vegetables can be overtaken by weeds before even getting started, but watermelon vines grow so quickly they normally cover up weeds that would compete with less vigorous plants. Watermelons are generally ready to harvest once the stem begins to turn brown and twist, and the white spot on the bottom of the melon where it contacts the grounds has turned to yellow. Matthew Stevens is the County Extension Director and Horticulture Agent for North Carolina Cooperative Extension’s Pitt County Center. If you have questions about this article or gardening in general, please contact the Pitt County Extension Master Gardeners at [email protected] or 252-902-1705. |
Matt Stevens
Pitt County Extension Director & Horticulture Agent Archives
November 2024
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