Miscellaneous Borers & Bugs

CMB Adult female

Comstock mealybug adults in pear calyx

The increase in the acreage of apple trees grown on dwarfing rootstocks, which have a tendency to form burrknots, has led to an increase in problems with the dogwood borer, which infests rootstocks through these burrknots.  American plum borer has been found as an additional species causing injury to fruit tree trunks.  In a statewide survey of dwarf apple orchards in NY, approximately 60% of dwarf apple trees had suffered damage by borers and approx 32% of trees were actively infested.  While we have not determined the effect of borer feeding on dwarf apple trees, we have observed decreased vigor and even death in affected trees.  Borer feeding may also increase the tree’s susceptibility to diseases such as rootstock fireblight.  Dave Kain has overseen our research on this pest, which research has focused on evaluating a range of tactics to control this pest, from insecticide trunk sprays to pheromone mating disruption to novel multi-season trunk barriers.

Dogwood borer adult

Dogwood borer adult

Mullein plant bug (MPB) feeding causes scarring of the fruit, appearing as dark, raised pimples that result in downgrading and, when numerous, deformation and cullage. It is a sporadic but sometimes a potentially devastating pest in New York and other regions.  MPB overwinters as eggs laid behind apple bark that, in most years, hatch around the time of Red Delicious full bloom. In several studies conducted by Dave Kain, we have determined that the crop is most susceptible to damage during the period from bloom through petal fall and that the best insecticide strategy against this pest is to apply an effective material at the pink stage, because by petal fall much of the damage has already been done. We have also determined a preemptive threshold for pink insecticide application using pheromone-baited traps to monitor adult activity the preceding fall.  However, in some seasons, even though numerous nymphs are present, no damage is observed even where insecticides have not been applied at pink.  It is our belief that in seasons when apple blossom development is advanced in relation to MPB development, the crop reaches a less susceptible stage before the bulk of the nymphs have hatched out.

Comstock mealybug has been a problem to growers of processing pears because of contamination and aesthetic reasons.  First, the emergence of crawlers and adult females from the calyx of pears at the packinghouse creates a nuisance to workers. Second, pears to be made into puree typically are not peeled or cored by New York processors, so infestations can potentially result in unacceptable contamination of the product.  Another problem is that the honeydew secreted by the crawlers is a substrate for sooty molds growing on the fruit surface.  We investigated the relationship of fruit infestation levels to the need for management decisions to prevent contamination in the processed product.

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