General Conditions: Nice summer weather this past week, with a brief thunderstorm on the 21st and a very brief shower on the 22nd, giving Hanson 0.48 inches of rain. Soils remain very dry and it is important to remind clients of the need to water their plants, especially trees defoliated by caterpillars. Some of those trees were defoliated last year too and drought stress will only compound their challenge to survive. The following plants are in full bloom: Northern catalpa, Stewartia pseudocamellia (Japanese Stewartia), Stewartia rostrata, Liriodendron tulipifera (Tuliptree), Styrax japonicus, Sinocalycanthus chinensis, Cornus kousa, Hypericum androsaemum ‘Mrs. Gladis Brabazon’,Weston hybrid azaleas, Hydrangea anomala petiolaris, Itea virginica, Spiraea sp., Calycanthus floridus (Common Sweetshrub), Indigofera sp., landscape roses, Kalmia latifolia, Lonicera sempervirens, Rosa rugosa, Clematis sp., Clematis, Salvia sp., Geranium sp., Anemone canadensis, Aruncus dioicus, Persicaria polymorpha, Doronicum sp., Lamium, Foxgloves, Allium, Nepeta sp., Baptisia australis and Baptisia hybrids, Dianthus sp., Tradescantia, Stella d’Oro and other early daylilies, Corydalis lutea, and Valeriana officinalis. Cotinus obovatus (American Smoketree) and Cotinus coggygria (European Smokebush) continue to provide the landscape with their colorful “smoke” and Kousa dogwoods continue to look fabulous. Unfortunately, similar to the 2015 season, the overwintering stems of most Hydrangea macrophylla were winter-killed this past February. This will make two years in a row that many gardeners will not be enjoying the beautiful flowers of Hydrangea macrophylla unless they planted more cold-hardy Hydrangea macrophylla hybrids like ‘Blue Billow’ or ‘Lady-in-Red’ or, one of the repeat blooming hydrangeas like, ‘Endless Summer’, which bloom on new wood.
Pests/Problems: Gypsy moth caterpillars are large and mostly in 5th & 6th instar (only the females go to a 6th instar, (however, curiously, there have been a few, minor observations of 3rd and 4th instars too). Many of the large late instar caterpillars are beginning to pupate and a few have pupated. However, many more gypsy moth caterpillars remain feeding heavily in many areas and in those areas, the trees are bare, and the caterpillar frass continues to fall covering everything below. Driving along Route 3 in the Plymouth area, especially the stretch near exit 5, the oak trees are stripped of leaves and the caterpillars are also feeding heavily on Pinus rigida (pitch pine). Gypsy moth caterpillars are also feeding on maples, white pine, spruce, apple, willow, crabapple, etc. Some landscape clients were complaining that they had had “their trees sprayed in May for the caterpillars” and were wondering what was going on. “Didn’t the spray work?” It took some careful explaining to make them realize that the there were two caterpillar problems: winter moth caterpillars, which finished feeding in late May, and gypsy moth caterpillars which began feeding in mid-May and continued into late June; two different caterpillars which may necessitate two separate spray applications.
Hibiscus sawfly larvae are active. Look for “holes” on the foliage of perennial hibiscus and examine the back of the foliage for the small, slug-like light, green sawfly larvae. If this insect is not managed early, the sawfly feeding will strip the foliage down to the veins. Bacillus thuringiensis (Bt) does not work on sawfly larvae.
Dogwood sawfly larvae remain active feeding on certain dogwood species like Cornus controversa and Cornus racemosa.
Monitor cherry for White Prunicola Scale crawlers and treat if needed.
Monitor for Andromeda lacebug feeding on Pieris japonica, and also monitor rhododendrons for rhododendron lacebug and evergreen azaleas for azalea lacebug. Lacebugs are active for most of the season and can cause serious damage to plants unless managed early.
The following insects remain active: Asiatic garden beetles, White pine sawyer beetle (Asian longhorned beetle look-alike), sunflower moth caterpillars (Homoeosoma electellum), Hemlock woolly adelgid, woolly beech aphid, cottony camellia scale on Meserve hollies and Taxus, Taxus mealybug, earwigs, planthoppers, mosquitoes, aphids, stink bugs,four-lined plant bugs, leafhoppers, lily leaf beetle, slugs, snails, wasps, pine spittlebugs, azalea whitefly, deer flies, horse flies, dog ticks and deer tick nymphs. Mosquitoes are abundant this year. Remind clients to empty containers of standing water or to treat with Bacillus thuringiensis israelensis (Bti). Beneficial insects, like hoverflies, lady bug beetles and six-spotted green tiger beetles, are also active. (See Tawny Simisky’s Insect section of the Landscape Message).
Sod webworm moths remain active on turf.
The following weeds are in full bloom: Japanese honeysuckle (Lonicera japonica - Massachusetts invasive plant), oxeye daisy, bouncing Bet, red and white clover and numerous grasses. Multiflora rose is ending bloom.