Viburnum Leaf Beetle

If you find your viburnum’s leaves looking a bit odd this spring you may have problems with Viburnum Leaf Beetle, Pyrrahalta viburni.  This beetle was first discovered in North America in 1947 around Ontario’s Niagara region. It has since spread east and south to the Maritime Provinces and the North Eastern United States.  

This beetle larvae is most commonly found on native and imported viburnums including,

European cranberry, high bush cranberry, arrow wood viburnum, Rafinesque viburnum.

It will also feed on Sargent viburnum, wayfaringtree viburnum, nannyberry and blackhaw viburnum. Some resistant viburnum includes Korean spice, leather leaf, double file viburnum and several others.

Scouting for raised egg masses on the upper twigs in early spring can give you a jumpstart on controlling this pest.

The damage can be extensive, consisting mainly of leaf skeletonization by larvae and shot hole feeding by adults. Egg deposition on twigs by females may result in twig die back.

Significant defoliation may occur if the population is high and conditions are favorable. Repeated defoliation may result in plant mortality, and will certainly reduce utility in the landscape.

Viburnum Leaf Beetle produces one generation per year overwintering as eggs deposited on twigs by the females the previous year. Females can lay up to 500 eggs in a season before frost kills the adults.

Lavae emerge in May and feed gregariously on new foliage, skeletonizing leaves down to only the mid ribs. Larvae fall to the ground and pupate and emerge in July to feed on new foliage and create irregular holes in leaves. Adults are active, mating and feeding until the end of the season.

Removing egg masses by pruning is an effective cultural control, ladybugs will also feed on larvae and reduce numbers.

Chemical controls are effective in controlling larvae and adults. Applications should take place to coincide with larval emergence as well as a second application at adult emergence. Systemic insecticides are also effective in controlling both stages.

I.S.A Certified Arborists are industry recognized experts in plant insect and diseases control. Contact your I.S.A. Certified Arborist to see if you have this damaging plant pest.

Pine Needle Scale on Spruce

If you look closely at the needles of your spruce tree and find tiny rice-like flecks of white on them you probably have pine needle scale, Phenecaspis penefolia.  This scale does attack pines, however it is most commonly found on white and Colorado blue spruce. Scots pine, lodge pole pine and Douglas fir are also affected by this pest. Damage can be as little as yellowed follliage, or if the population is high significant defoliation can occur.

The white armor scale cover on these insects looks like small flecks of paint on the host plants needles. You can see the white scale at most times of the year however the female scale may have already died leaving her empty or egg filled scale behind. Eggs are laid in the fall of the year and hatch in the spring of the following year. Eggs hatch in mid may around the time when lilacs are blooming; the crawlers then move to new needles where they insert there mouth pieces and begin sucking sap from the tree. Once they settle in the loose their appendages and start to secrete the waxy scale that will cover them for the rest of their life. Males may or may not be present.

The nymphs are spread from tree to tree by wind or birds. Eggs are laid under the scale by the females in the fall. Typically in northern areas there is one generation per year.

Verdant oil or registered chemical control must be applied when the crawlers are active and exposed. Typically this occurs early May to early June when the common lilac is in bloom. Crawlers will appear over a two to three week window of time so repeated applications of oil may be necessary. Another simple way to determine crawler emergence is to take several infested branches from your plant, put them in a well-sealed zipper bag and put it on your desk or shelf out of the sun. Check the bag daily and when the foliage appears to have fine orange dust or speck on it they have hatched. Again you will be a week ahead of the hatch in the outdoors as your office should be warmer than the woods.

I.S.A Certified Arborists are industry recognized experts in plant insect and diseases control. Contact your I.S.A. Certified Arborist to see if you have this damaging plant pest.

Scale Back?

 

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If you find your arborvitae looking sickly and covered in black sticky scale, chances are you have Fletcher Scale, Parthenolecanium fletcheri. This soft scale attacks a variety of hosts cedars, arborvitae, yews, hemlocks, and occasionally junipers.

The most commonly seen stage of this insect’s life cycle is the female, who forms an almost hemispherical tan/brown protective scale where she is attached to the stem of the host tree or shrub. It is from this protective cover that she inserts her moth parts in to the phloem of the plant and dines on carbohydrate rich sap. This sugar rich diet results in the scale secreting the excess carbohydrate as sticky honey dew that coats the foliage below the scales. This sugar is then attacked by a sooty mold that turns the foliage black. If the infestation is severe the plant will turn yellow and will lose foliage.

Females are the only known sex that these scales exhibit. Reproduction is by parthenogenesis, without sex.

The female lays as many as 600 eggs in May and these will hatch in June, into crawlers that move a short distance to a feeding site. They remain in this feeding site as a second instar nymph, (developmental stage) until next spring when they rapidly develop into mature females.

Control of this pest is not difficult if your timing is perfect. Treating early in the year with appropriate dormant oil reduces the number of overwintering second instar nymphs. Verdant oil or registered chemical control must be applied when the crawlers are active and exposed. Typically this occurs early June to early July.

Because timing varies due to climate, when Japanese tree lilac, or little leaf linden are blooming, you are a week ahead of crawler hatch. Another simple way to determine crawler emergence is to take several infested branches from your plant, put them in a well-sealed zipper bag and put it on your desk or shelf out of the sun. Check the bag daily and when the foliage appears to have fine orange dust or speck on it they have hatched. Again you will be a week ahead of the hatch in the outdoors as your office should be warmer than the woods.

I.S.A Certified Arborists are industry recognized experts in plant insect and diseases control. Contact your I.S.A. Certified Arborist to see if you have this damaging plant pest.