Trees Grown for the Wood Industry Benefit from Herbicides, So Does the Environment

Pare tree

Herbicide Strip to Establish Pine Trees

Loblolly pine is the most important and widely cultivated timber species in the southern United States. Because it grows rapidly on a wide range of sites, it is extensively planted for lumber and pulpwood. Loblolly pines are planted and managed for their fast growth rates. Unmanaged loblolly pine stands can take up to 50 years to mature into sawtimber-size trees. Managed stands can generate sawtimber-size trees much faster, often within 25 to 40 years. During the past twenty years, study after study has reported large gains in growth due to control of competing vegetation (weeds) in pine plantations in the southeast. Herbicides do a great job of getting the trees off quickly while alternatives for controlling weeds (burning, cultivation) have fallen from favor.

“The United States harvests approximately 708,000,000 m3 of wood annually, the highest rate of timber removal of any nation. …The 13 southeastern states (collectively referred to as the South) sustainably produce 60% of the forest products in the United States, more timber products than any other country (outside the United States) in the world.

One crucial component of intensive silviculture is the use of herbicides to control competing vegetation. Herbicides are applied to an estimated 2.0 million acres annually in the South, primarily associated with loblolly pine plantation establishment and stand management. Prescribed burning for vegetation control has declined during the past 2 decades, primarily due to concerns about liability from fire escapes and smoke management. Mechanical site preparation has also declined as more existing plantations and fewer naturally regenerated forests are harvested and replanted. Mechanical site preparation can also cause accelerated erosion losses. Replacing mechanical site preparation practices with herbicide applications lowers the potential for sediment and nutrient pollution of surface waters.”

Authors: McBroom, M. W., et al.
Affiliation: Austin State University
Title: Runoff of silvicultural herbicides applied using best management practices.
Source: Forest Science. 2013. 59(2):197-210.

Organic Cherry Growers Spray Fungicides More Often

Defoliated Cherry Trees

Leaf spot is the most important fungal disease of cherry.  The disease is caused by a fungus known as Coccomyces hiemalis which lives over the winter in the old leaves on the ground.  The first infection of new foliage in the early summer is caused by spores which are discharged from these old leaves.  After the fungus develops on the new leaves, more spores are produced and they may cause further spread of the disease.  Defoliation from leaf spot reduces the number of flower buds and subsequent fruit set for the following year.  Defoliated trees are less cold hardy and may be killed by low temperatures in winter.  Conventional and organic growers who spray regularly and thoroughly every year seldom suffer any serious loss from leaf spot. However, since the spray materials available for organic growers are not as effective as the synthetic chemicals used by conventional growers, the organic growers have to spray more often.

“Cherry leaf spot (CLS)… occurs worldwide and is the most prevalent disease of sour cherry in temperate zones. Epidemics caused by ascospore followed by repeated conidial cycles cause defoliation by midsummer, resulting in low fruit quality. Early defoliation delays acclimation of fruit buds and wood to cold temperatures in the fall, and reduces fruit bud survival during severe winters and fruit set the following spring.

In integrated sour cherry orchards, CLS management typically involves four to eight fungicide treatments per year, starting at petal fall and continuing until late summer. In organic orchards, only a few approved fungicides are available for CLS control, such as sulfur and copper compounds. These compounds are often less effective and more phytotoxic than synthetic fungicides used in integrated fruit growing. Therefore, in Hungarian organic sour cherry orchards, 7 to 12 sprays are applied against CLS in each season.”

Author: Holb, I. M.
Affiliation: University of Debrecen, Hungary.
Title: Effect of sanitation treatments on leaf litter density and leaf spot incidence in integrated and organic sour cherry orchards.
Source: Plant Disease. 2013. 97[7]:891-896.