Management Issues

The southern pine beetle (SPB; Dendroctonus frontalis) is a rice-sized native bark beetle ranging from Texas to Pennsylvania and from Arizona to Honduras in Central America. Over the last 15-20 years it has been increasing its range northward due in part to higher winter temperatures. It was detected in New Jersey in 2001 and on the south shore of Long Island in September 2014. Considered one of the most destructive insect pests in the country, it has the potential to kill thousands of acres of pines during an outbreak. In 2010 alone, SPB damaged over 14,000 acres of pitch pine (Pinus rigida) in the New Jersey Pinelands.

Pitch pine, the predominant tree species of the Long Island Pine Barrens ecosystem, is a preferred host species for SPB. Attacks are initiated by female beetles when they find a suitable host tree. They release pheromones attracting hundreds to thousands of beetles to a tree, overwhelming it. SPB kills trees in two ways: a) adult female beetles and larvae construct a network of S-shaped tunnels through the cambial layer which prevents the transport of carbohydrates to the roots, and b) SPB introduces blue-stain fungus (Ceratocystis polonica) which impedes the circulation of water throughout the tree, further stressing it. In the New Jersey Pinelands SPB can have up to seven generations in a year and tree mortality can occur in just a few short months.

Why is SPB a threat to our forests?

SPB is now widespread throughout the forests on Long Island and has the potential to seriously impact the Long Island Pine Barrens. Long Island’s forests have never been actively managed. Unlike many other areas of the country and even New York State where forests are managed for timber, our forests do not experience regular thinning, and fire, which is a nature’s way of regulating itself, has been removed from the ecosystem.

This lack of management has created forests that are too dense and full of over-mature trees. This results in unhealthy, stressed forests because all the trees are competing for resources (e.g., water, sunlight, and nutrients) and thus, none are getting what they need to thrive. Stressed trees produce less oleoresin—their primary defense against insect attacks, and so they have lowered resistance to pests like SPB. In addition, without fire to consume leaf litter and other surface fuels to expose mineral soil, once the existing pitch pine trees die new pitch pines cannot germinate which could result in the complete loss of our pine barrens ecosystem.

Management of SPB

A landscape level management plan was developed by the NY State Department of Environmental Conservation (NYSDEC) in collaboration with the US Forest Service (USFS), Cornell University, Dartmouth University, and many others which will help us prioritize management to mitigate impacts of SPB to our forests.

Aerial and ground surveys conducted at BNL have shown that SPB can be found throughout the Lab, both in the central campus area around buildings as well as in the approximately 3,00 acres of forest on site. To date, many hundreds of thousands of trees have been killed by SPB on site. At this point, efforts to suppress infestations would be futile as it is too widespread to be effective.   Mechanical thinning or the selective removal of trees from the forest is the only long-term option that is viable.  When used in conjunction with prescribed fire the benefits are threefold: a) in the short term, more open stands disrupt pheromone communication, b) in the long term, a reduction in tree density results in healthier trees that are more resilient to SBP attacks, and c) prescribed fire also helps to promote pitch pine regeneration by stimulating serotinous cones to release seeds and preparing the seedbed.

Defoliators

BNL like many areas of Long Island has been noticing the effects of insect defoliators. There are two main defoliators that have been working on the pine-oak forests of the Lab, spongy moth (Lymantria dispar) and orange-striped oakmoth (Anisota senatoria).

The spongy moth is a non-native spring defoliator emerging from egg masses about the same time the oak trees are beginning to leaf out. The caterpillars feed on the new leaves through the month of June, then pupate and emerge as adults in late June or early July. Eggs are laid in a velvety mat on the trunks of trees and other vertical surfaces.

The orange-striped oak moth emerges as an adult beginning the first week of July. Females are poor fliers and generally climb up oak trees, release pheromones to attract males. Males mate with the females, who then lay up to 500 eggs on the undersurface of oak leaves. Within 2 weeks the eggs have hatched, and the army of oak worms begin devouring the leaves of the oaks. Observations suggest that there is a feeding preference for red oaks, but once all the foliage of the red oaks have been consumed the caterpillars will switch over to white and black oaks. Feeding lasts from July through September or early October at which time the caterpillars burrow under the forest leaf litter to pupate. The pupae overwinter in the leaf litter to emerge as adults the following July.

The long-term effects of defoliation is not well documented. During years where outbreaks coincide the combined effects of repeated spring defoliation by the spongy moth and late season defoliation by the orange-striped oakmoth has resulted in the death of mature oaks. Fortunately, spongy moth populations have been significantly reduced by the presence of a fungus (Entomophaga maimaga) that was released specifically to act as a biological control agent for this species. The result has been that we have not observed extensive oak mortality due to spongy moth or the combined effects of spongy moth and orange striped oakmoth since the early- to middle-2000s.