Evaluation of the efficacy and yield effect of Timorex Gold for the control of apple scab

Project Code BPI09-060

Project Lead

Drs. Deena Errampalli, Odile Carisse and Jean-Pierre Privé - Agriculture and Agri-Food Canada

Objective

To assess the efficacy of Timorex Gold biopesticide for the control of Venturia inaequalis (apple scab) on apple and to evaluate the effects of applied product on apple yield

Summary of Results

Background

The apple tree (Malus domestica) from the family Rosaceae, is one of the most widely cultivated fruit trees. Canada produces about 450,000 tonnes of apples (0.8% of world production), representing a farm gate value of $85 million. In Canada apple scab, characterized by dark lesions on the leaves and fruit and caused by the fungal pathogen Venturia inaequalis, is a major disease issue facing growers. Diseased leaves will fall early and the fruit will become increasingly covered in scabs. Eventually, the fruit skin will crack, leading to yield decline. Without control measures, apple scab can result in 100% crop loss.

Apple scab is the key disease for scheduling fungicide sprays on apple trees in Eastern Canada. Most current strategies for managing apple scab are based on controlling primary infections in order to avoid epidemic build-up caused by secondary infections, thus reducing or eliminating the need for subsequent fungicide applications during the summer months. To achieve this goal, fungicide applications generally begin in the spring and continue to early summer, resulting in approximately 8 to 10 applications. If this approach fails to achieve adequate control, fungicides must then be applied during the summer and the annual number of sprays could reach 14 to16, depending on the prevailing weather conditions during the summer months.

The number of fungicide sprays made each year in individual orchards is related to cultivar susceptibility and to the intended market (fresh or processed fruits). Control of apple scab relies heavily on the availability and efficacy of fungicides. In Canada, growers are concerned by the possible loss of registration for a number of fungicides used to prevent the disease, as well as some recent reports indicating that there are pathogen populations which are becoming resistant to certain fungicides. It is therefore important to identify and register control products with new modes of action that can control apple scab, ideally with reduced risk for the environment.

Approaches

This project evaluated two biological pesticides, Regalia (Reynoutria sachalinensis extract) and Timorex Gold (Melaleuca alternifolia extract), for their value in assisting the management of apple scab in Canada. The commercial standard fungicide Captan was used as a positive control.

Comparative trials were conducted during 2009 at two AAFC experimental stations: Frelighsburg, QC (Timorex Gold tests only) and Bouctouche, NB (Timorex Gold and Regalia tests). At both sites, data on apple scab were collected at the end of the primary infection period in late spring, in the summer, and at harvest. Trials with Timorex Gold and Regalia were also conducted in Jordan Station, Ontario, with assessments taking place several times during the 2009 growing season and at harvest.

Results

The data collected at the Frelighsburg site clearly showed that Timorex Gold failed to control apple scab. At the end of the primary infection period, the disease was significantly lower in plots sprayed with captan than in plots sprayed with Timorex or water, regardless of the concentration of Timorex Gold. At the summer assessment, scab incidence and severity were significantly higher in plots sprayed with Timorex Gold than in plots sprayed with Captan. At harvest, yield was significantly lower, and fruit scab incidence significantly higher, in plots sprayed with Timorex Gold than in plots sprayed with Captan. Results from this trial demonstrate that Timorex Gold is not an acceptable alternative to standard fungicides for the management of apple scab.

Even though more spray programs were tested at the Bouctouche site, results were in general similar to those obtained at the Frelighsburg site. Overall scab incidence and severity on cluster leaves at the end of the primary infection period were significantly higher in plots sprayed with Timorex Gold, Regalia or water, than in plots sprayed with Captan, although scab incidence and severity on vegetative shoots did not vary significantly between groups. Similar results were obtained at the summer assessment. Overall, the results did not demonstrate an economically acceptable level of efficacy for either Timorex or Regalia.

The picture repeated itself in Jordan Station’s trial, where treatments that include the commercial standard Captan had significantly lower incidence of apple scab on the leaves, as well as a greater yield, than all other treatments. Generally, all rates of Timorex gold and Regalia performed similarly and were no different than the untreated check.

Phytotoxic effects on blossoms were observed in Regalia treatments, and in some of the Timorex Gold treatments at high application rate.

2009 was an unusually wet year with high disease pressure and the results obtained indicate that these biofungicides are ineffective in controlling apple scab under such conditions. No data were generated to establish whether these products have any effect on apple scab under conditions of low disease pressure.

Date modified: