The long cool spring seems to have been great for cool season mites. In North Carolina,
Adult southern red mite. Photo: SD Frank
the most important cool season mites are the spruce spider mite (Oligonychus ununguis) and southern red mite (Oligonychus ilicis). These are among the earliest and most damaging pests in nurseries and landscapes. As their name implies, cool season mites are active in spring and fall when they suck fluid from cells on plant leaves and needles. In hot summer months these mites are dormant. However, it is summer when their damage becomes apparent as chlorophyll bearing cells die. Thus, by the time plants exhibit aesthetic damage the mites are gone and treatment is wasted.
Today I found all stages of Southern red mite on cherry laurel but is feeds on many broadleaf evergreens such as azalea, camellia, holly, and rhododendron. With eggs juveniles and adults all present these mite populations are well underway and deserve attention from nursery and landscape personnel.
Multiple southern red mite life stages on cherry laurel. Photo: SD Frank
Scout plants that had mites or mite damage the previous year as they are likely to have them again because the mites have overwintered as eggs. You can identify plants that had mite last year by looking for fine stippling damage on the old leaves. Turn them over and look with a hand lens for silk webbing, shed skins, and mites. On broadleaf evergreens, look on the underside of leaves for the southern red mite. The most efficient method of scouting for cool season mites (and other mites) is to hold a piece of white paper or a paper plate below a branch and strike it with a pencil or stick to dislodge arthropods. Spider mites will appear as tiny moving specks about the size of the period at the end of this sentence.
Southern red mite damage on cherry laurel. Photo: SD Frank
For more information and control options consult the NCSU insect note at http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/ort077e/ort077e.htm
Sara Prado, an esteemed alumni of our lab, just had her paper selected as Editor’s Choice in Ecological Entomology. When given the choice, parasitoids select the hosts that will increase offspring fitness. Thanks Mom! It turns out this has benefits for biological control in greenhouses because the parasitoids prefer the green peach aphid, an important greenhouse pest, over grain aphids introduced on banker plants.
Nice job Prado!
Read the whole paper here.
On this rainy Tuesday I found boxwood leaf miner adults struggling to emerge from their blister mines. The orange flies were stuck to wet leaves. A few were hovering around. This is the first I have seen this year so it is a good time to check your plants and treat if necessary.
Boxwood leaf miner adult. Photo: SD Frank
The maggots pupate in the leaf blister. As the adult emerges the pupal case get caught on the leaf. This holds the leaf in place so the adult can wriggle out. Boxwoods can be treated with a pyrethroid to prevent flies from landing on the bush to lay eggs but watch out for mite outbreaks. Imidacloprid will kill maggots within the leaves but (based on article above) it is best to apply after flowering.
Boxwood leafminer struggling to emerge from pupal case. The pupal case will be left behind poking out of the leaf. Photo: SD Frank
NCSU Pest News was the original pest blog! This week information on ambrosia beetles, cankerworms, tent caterpillars…..
Other crops are include too if you’re into that.
Eastern tent caterpillars hatched recently
Eastern tent caterpillar nest in a crab apple tree. Photo: SD Frank
and have already established big nests. The easiest way to deal with tent caterpillars is to prune out the nests. Eastern tent caterpillars make nests in the crotch of trees. (Fall webworms make nests at the end of branches). So it you can’t remove the nest you can poke it with a pole pruner. This destroys the nest so many caterpillars fall to the ground and others get eaten by birds. Opening the nest also lets parasitoids in to kill the caterpillars. For severe infestations there are some insecticide options. Products containing Bacillus thuringiensis (Bt) are effective against caterpillars. Other active ingredients labeled for caterpillar control include spinosad, Beauveria bassiana, acetamiprid, acephate, azadirachtin, and bifenthrin. Keep in mind that these caterpillars spend most of their time in a water-proof nest so contacting them is difficult. This limits the efficacy of many insecticide applications.
Boxwood leaf miner larvae are developing fast. I stopped by some boxwood bushes and peeled open some blistered leaves. You can see
Boxwood flowers and leaf blisters. Photo: SD Frank
the larvae wiggling inside. The maggots pupate in the leaf blister and will emerge as adults in a few weeks. The adults hover around boxwood bushes but only for a couple weeks. In addition to the small orange adults you will see pupal casings sticking out of leaves. As the adult emerges the pupal case get caught on the leaf. This holds the leaf in place so the adult can wriggle out. Boxwoods can be treated with a pyrethroid to prevent flies from landing on the bush to lay eggs but again you only have a short window when adults are active. That is why it is good to pick a few leaves each week to see how close they are to emerging. Imidacloprid will kill maggots within the leaves but be careful
Boxwood leafminer larvae inside a leaf mine blister. Photo: SD Frank
because plants are flowering now so it should not be applied. If applying pyrethroids or imidacloprid watch out for mite outbreaks.