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Plant Answer Line Question

Keywords: Cupressus, Moths, Trees--Diseases and pests

I haven't been able to find much about control of cypress tip moth on true cypress (Cupressus). I'm looking for a non-toxic control instead of the WSU recommendation of Orthene. Would Neem possibly work? Spinosad? Both are registered for leaf miners (fly larvae), but this is a moth larvae. Bt won't work because the larvae are inside of the foliage. What's the best timing for a non-toxic? WSU recommends controlling the adults in July-August.


University of British Columbia Botanical Garden's forum has this to say:

"In the west, cypress tip moth sometimes infests cypress (Cupressus and Cupressocyparis) and false cypress (Chamaecyparis); those are also sometimes called cedars. In the east, cedar often refers to Juniperus (red cedar), Thuja or Chamaecyparis (white cedar); all are subject to bagworm infestations and various tip-miners. In the west, timely shearing is the most effective way to control cypress tip moth, and this may also be a tactic in other parts of North America.

"In many cases, infestations occur because there are few natural enemies about to reduce pest levels. Sometimes, pests are attracted to plants that are already weakened by stress. Healthy plants and diverse plantings, together with a reduction in pesticide use, will over time, increase beneficial organisms which will in turn reduce pest levels. Spraying to reduce pests generally affects beneficials to a greater degree than the actual target pest. This is because pest species often have a greater capacity to rebound -- they often reproduce faster, have a greater tolerance for pesticide residues and have a greater capacity to become resistant to pesticides."

Oregon State University's IPM site only mentions chemical controls.

From an online forum, 'Horticulture Guy:'

Q. I have a row of 16 - three year old "Emerald Green" arborvitaes. I suspect they have arborvitae leafminer (cypress tip moth). I have noticed the moths before, but now there are more and I just recently noticed brownish-yellow tips on a couple of the trees. All of them have lots of needles falling from the interior. My problem is that I have received conflicting reports about the proper time to spray for them, and is there anything I can do in the meantime to lesson the damage? Thank you! Linda Brieger - Tacoma, WA

A. The way to gain control over any pest population is to know its life cycle. Spraying is geared toward eliminating the adult form of the insect, which is a moth as the second of the two common names indicates. The most likely reason you may see conflicting reports on when to spray the moths is because of varying times the moth may emerge in different regions where they are present. They are generally active in our area from April to June with a peak of activity in May. The moths lay their eggs during this period and the eggs hatch and then burrow into the needles of the host plant. According to the WSU extension the adult moths are silver-tan and approximately 1/4" in length. External sprays won't have an effect on the larvae once they burrow so you need to spray weekly during this period to catch the larvae as they hatch. Systemic insecticides are able to kill the larvae once they are in the host. You can limit systemic insecticide spraying to one application near the beginning of the activity since they generally remain effective for some time (see labels for instructions). As far as "in the meantime" a sprayless solution is to prune out and destroy infected parts of the host now so that there are less moths in the spring. You can also keep an eye out in the spring for the white cocoons that form after the larvae exit the host to become adult moths. You can remove these as well.

University of California Integrated Pest Management suggests that proper cultural care and removal of susceptible plants is the answer. Excerpt:

Provide proper cultural care to keep plants vigorous. Prune out and dispose of foliage infested with immature leafminers to restore the plant's aesthetic appearance and provide some control. Consider replacing plants especially susceptible to the cypress tip miner. High populations and damage can be reduced on established plantings by applying a broad-spectrum, persistent insecticide such as acephate on susceptible varieties when adult moths are active. Beginning in early spring, examine foliage tips for the cocoons. When these appear, vigorously shake foliage and watch to see if silvery tan, tiny moths fly up then settle back on the foliage. One application to foliage can be made when a large number of tip moths appear, between March and May in California. This reduces browning next season.

You could try using the Neem oil (instead of the more toxic alternatives) although I did not find any information specifically suggesting this as a control for cypress tip moth. The WSU book, Pacific Northwest Landscape IPM Manual (2002) suggests natural parasites which attack this species of insect, but they do not specify the identity of these predators. They state that there are no "biorational pesticide management options" for this pest.

Date 2017-02-11
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Garden Tip

Keywords: Insect pests--Control, Moths

Act in October to defeat the Winter moth (Operophtera brumata). These moths mate in autumn and then the wingless females climb up tree trunks to lay their eggs. In early spring the little green inch-worm like larvae eat flower and leaf buds from the inside out. The many host plants include maples, oaks, crabapples, apple, blueberry, and some spruces such as Sitka spruce. To detect female moths place a band of heavy paper covered with Tanglefoot (a sticky goo available at nurseries) around susceptible tree trunks. If females are found it may be a good idea to spray the tree (trunk and branches) with dormant oil to smoother the eggs for reliable control. If the little caterpillars start "ballooning" out of trees in high numbers spraying with Bt (caterpillar killer) will provide control. For more information go to this University of Massachusetts Extension publication

Date: 2007-03-20
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May 23 2018 14:32:42