Did you know that when the soil or air reaches certain temperatures, this triggers egg hatch on many insect pest species? Damaging larvae emerge to feed on our plants.
Cottony camellia scale is a soft white scale that sucks sap from the leaves of many common landscape plants. Although it is most often seen on hollies, it can also be found on camellia, yew, euonymus, maple, English ivy, hydrangea, and rhododendron.
Scale will excrete “honeydew,” a sticky substance that attracts stinging insects and creates optimal conditions for black sooty mold. Sooty mold will cover the leaves making it difficult for the plant to photosynthesize.
Adult females are about 1/8 inch long, oval and tan in color with a brown outline. They lay white cottony ovisacs containing hundreds of eggs on the undersides of leaves in May. Throughout June the eggs emerge into crawlers. Scale crawlers will be about the size of a mite and amber in color. This period is the only mobile stage in the insect’s life and is also when the insect is most vulnerable since it has not yet developed a hard outer shell.
Timing is everything, and for this reason, we like to spray an organic insecticide, Aza-Direct® exactly at this time in the lifecycle. Pruning out severely diseased branches can also increase air circulation and create conditions that do not favor sooty mold development. Adjusting the soil pH and soil microbiology through amendments can also go a long way in restoring balance.
It may take several seasons to completely control a scale infestation. In severe cases, we will recommend removing the plant. But with a continued treatment plan of proper soil pH, developing microbiology, pruning, and organic insecticide, over time the health of the plant can be restored.
Rose slug sawfly will be out any day now. From a distance, you may notice dingy brown or grey leaves or even skeletonized ones. A small worm will be on the underside – the slug sawfly. Luckily, there is just one generation of this pest per year in our area. We spray our Neem oil product if we see the pest. To help your rose push out new green leaves, we recommend liquid organic foliar feeds weekly or as often as you can manage! Rake up dropped leaves or prune off damaged leaves as appropriate.
Boxwood psyllid shows up on the new growth tips in late spring where eggs overwintered on bud scales. You’ll see curled, cupped margins. Living inside is the immature nymph, sucking sap from the leaves. Eventually, there will be discoloring from green to yellow. This impacts appearance of your boxwood, but not its overall health. We can control boxwood psyllid with insecticidal soap or summer-grade horticultural oil. In many cases, the cupping will be pruned away once new growth has hardened off at the end of June.
More damaging is Boxwood leafminer, which this year coated boxwood leaves with clouds of whiteflies in late May. Leaf blistering and discoloration will follow in June. We turn to the same organic insecticides to control this pest. Multiple applications may be necessary.
We recommend a thinning style of pruning for these shrubs. Site them away from buildings when possible to allow for best air circulation. Soil testing, amending, compost topdressing, and our compost tea program also help keep boxwoods healthy!