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Issue No. 573

The Vegetarian Newsletter 

A Horticultural Sciences Department Extension Publication on 
Vegetable and Fruit Crops 

Eat your Veggies and Fruits!!!!!

Publish Date: 
April, 2012

Squash Bugs

Susan Webb, Extension Specialist, Vegetable Entomology

Entomology and Nematology Department

Squash bugs (Hemiptera: Coreidae) are becoming a serious problem for those growing cucurbits in north central Florida.  Beginning late last spring, these true bugs have been attacking in large numbers and killing seedling squash. The mild winter we had this year and the warm spring seem to have exacerbated the problem this season. In the past, this insect could be found in most squash plantings, but not in numbers that caused serious damage. In this article, I briefly summarize what is known about their biology and management.

Three species of squash bug have been found locally: Anasa tristis (Figs. 1-3), Anasa andresii (Figs. 4-5), and Anasa scorbutica (Figs. 6-7). A. tristis and A. scorbutica have been collected in other parts of the state, but A. andresii has been found only in Alachua, Bradford, and Putnam counties.  An additional species that can occur is Anasa armigera, the horned squash bug (Fig. 8). Most of the information available is about A. tristis because it isconsidered to be the most damaging species. Squash bugs prefer pumpkin and squash (particularly yellow summer squash and zucchini) and do not survive very well on cucumber and muskmelon.

Adults, which are 1.4 to 1.6 cm long (about 0.5 to 0.6 inches), lay clusters of about 12 to 20 eggs that are white to yellowish brown at first, but soon turn dark reddish-brown or bronze. Eggs are often deposited in the V formed by two leaf veins.  The eggs are unusual because they are laid on end and somewhat flattened on 3 sides. The young nymphs feed together when they first hatch and spread out over the plant as they grow, molting five times until reaching the adult stage.  As adults they have fully formed wings and are capable of mating and reproducing.  Squash bugs overwinter as adults under dead leaves, plants, rocks, boards and other debris on the soil surface.

Squash bugs feed in the same way as other true bugs (such as leaffootted bugs and stink bugs). They have piercing-sucking mouthparts that they use to rupture plant cells and feed on the contents, so some of the damage is strictly from feeding. Their saliva contains a toxin, however, that causes wilting and necrosis of leaves, a condition called “anasa wilt.” Young plants are most susceptible to severe damage and can be killed. The more bugs that feed on a plant, the more likely the plant is to suffer damage. Another problem associated with feeding is transmission of a bacterium that causes a disease called Cucurbit yellow vine disease (CYVD). Infected plants wilt, turn yellow, and die.  So far, this disease has been found only once in Florida, in 2007 in watermelon.

Controlling squash bugs, especially the adults, is very difficult. Conventional insecticides, specifically pyrethroids and neonicotinoids, can be effective for controlling young nymphs. For this reason, it is important to examine squash plants for eggs at least once a week, beginning at the time of plant emergence.  For organic growers, there are few options. Lightweight floating row covers can be used to protect young plants, but must be removed when plants begin to flower to allow pollination.  Floating row covers are very effective for excluding all insect pests, but are expensive.  Other suggestions from extension publications from other states and from ATTRA (National Sustainable Agriculture Information Service) include using diatomaceous earth and pyrethrins applied at the base of the plant and the use of kaolin clay as a foliar spray.  The last application of kaolin clay should be one month before harvest because of the difficulty in removing the clay from fruit. A mixture of neem oil and pyrethrins can be effective if treatment begins as soon as eggs are found.  Plastic mulch, while having many benefits for the plant, also provides shelter for squash bugs. Treating the base of the plant can be effective for this reason. Trap crops of earlier planted squash may help protect less preferred crops, such as cucumber, cantaloupe, or watermelon, but insects on the trap crop must be destroyed before the trap crop plants deteriorate.

Sanitation is the key to managing squash bugs. Because adults can live for several months, cleaning up the soil surface after the crop is finished to eliminate refuges is essential. Crop rotation is important because squash bugs only feed on cucurbits. A cucurbit-free period in the summer may help reduce the number of bugs that survive to the next crop. Adults can fly so this practice will not eliminate them if squash or pumpkins are being grown nearby.

Selected references:

Capinera, J. L. 2003. Squash bug, Anasa tristis (DeGeer) (Insecta, Hemiptera, Coreidae).  http://edis.ifas.ufl.edu/in234

Capinera, J. L. 2001. Squash bug, Anasa tristis (DeGeer), Horned squash bug, Anasa armigera (Say), (Hemiptera: Coreidae), p. 244-247, Handbook of Vegetable Pests. Academic Press, San Diego, CA.

Adam, K. L. 2006. Squash bug and squash vine borer: organic controls. http://www.attra.ncat.org/attra-pub/squash_pest.html

Cranshaw, W. 2008. Squash bug: management in home gardens. Fact sheet 5.609, Colorado State University Extension. http://www.ext.colostate.edu/pubs/insect/05609.html


 

Fig. 1. Anasa tristis adult and nymph.  Photo: Lyle Buss, UF.

Fig. 2. Anasa tristis eggs. Photo: Lyle Buss, UF.

Fig. 3. Anasa tristis first instar nymphs. Photo: Lyle Buss, UF.

Fig. 4. Anasa andresii adult. Photo: Lyle Buss, UF.

Fig. 5. Anasa andresii nymphs. Photo: Lyle Buss, UF.

Fig. 6. Anasa scorbutica adult. Photo: Lyle Buss, UF.

Fig. 7. Anasa scorbutica first instar nymph and eggs. Photo: Lyle Buss, UF.

Fig. 8. Anasa armigera adult.  Photo: James Castner, UF.

Advice for Selecting Nitrogen Fertilizers to Manage Soil pH in the Root Zone of Fruit and Vegetable Crops

Guodong Liu

Horticultural Sciences Department, IFAS, University of Florida, 1117 Fifield Hall, Gainesville, FL 32611

Soil pH is also referred to as soil acidity and is defined as the concentration of positively-charged active hydrogen and aluminum ions. Soil pH is critical to fruit and vegetable production because it determines nutrient bioavailability and/or toxicity. In Florida, we have quite a few soil types with different soil pH ranges. Soil pH is determined in part by soil texture, inherent characteristics of the parent material (e.g. limestone, granite, etc.), and the soil organic matter content. Nutrient management can also have an effective impact on soil pH values. In northwest Florida, the predominant soil texture is clay. Clay soils in the northwest are typically quite acidic, often having a pH of less than 5. This soil pH is too acidic for most of crops’ optimum growth due to the risk of aluminum or iron toxicity and of an increased uptake of heavy metals such as zinc potentially leading to nutrient toxicity. However, in south Florida such as in the Homestead area, a predominant soil type is a Krome Gravelly Loam. The Krome soil is a shallow soil over limestone rock, and often has a pH of greater than 8.0. This soil pH is too alkaline to support optimum growth for most commercial fruit and vegetable crops.

The soil pH range for optimum growth of most fruit and vegetable crops is generally in the range of pH 5.5 to pH 6.5 (Splittstoesser, 1990; Havlin et al., 2005). However, the optimal pH range differs with specific crops. For example, the best pH range for apple production is from pH 5.6 to pH 7.5 and the most favorable pH for blueberry is in range from pH 4.5 to pH 5.5.

Then, how should we manage soil pH? There are a few effective methods to adjust soil pH. Liming is the most common way to increase soil pH. If a soil pH is less than pH 5.0 and is used for vegetable production, liming is recommended. If a field is used for blueberry production, liming is recommended if the soil pH is less than 3.6. For liming recommendations, refer to the EDIS publications: http://edis.ifas.ufl.edu/ss492and http://edis.ifas.ufl.edu/ss468.  If your soil pH is greater than pH 8.0, you may need to reduce your soil pH. You can find the most used method to reduce soil pH from this EDIS publication: http://edis.ifas.ufl.edu/ss500.

Except the methods introduced in the EDIS publications, we can also economically and effectively adjust root zone pH by selecting the correct nitrogen fertilizer. Ammonium nitrogen can significantly lower soil pH. However, nitrate nitrogen notably increases root zone pH. Managing soil pH through nitrogen fertilization is quick and effective.  The images below show how different nitrogen fertilizers are to adjust root zone pH (Figures 1 and 2).

If you apply ammonium nitrogen to your soil, the crop reduces root zone pH by approximately 2 units within three hours (Figure 1) because ammonium ions are positively charged. Crops release positive ions such as protons (H+) to neutralize electric charge when the plants take up the nutrient ions. On the contrary, crops extrude hydroxide (OH-) or bicarbonate (HCO3-) ions when they absorb nitrate nitrogen. Therefore, when ammonium nitrogen is present, the root zone pH is reduced, and when nitrate nitrogen is present, the root zone pH is increased.


Figure 1. Ammonium nitrogen reduces root zone pH significantly. The plant on the left is snap bean and on the right, tomato. Prior to the addition of fertilizer, the agar growth medium’s pH was 6.8 (indicated by the purple color). After three hours, the root zone pH reduced to pH 5.0 (indicated by a yellow halo around the roots). Photo by Wei Chieh Lee


Figure 2. Nitrate nitrogen increases snap bean root zone pH significantly. Prior  to the addition of fertilizer, the agar growth medium’s pH was 5.0 (indicated by the yellow color). After three hours, the root zone pH increased to pH 6.8 (indicated by the purple-colored halo around the roots). Photo by Guodong Liu

References

Havlin, J.L., J.D. Beaton, S.L. Tisdale, and W.L. Nelson. 2005. Soil Fertility and Fertilizers: An Introduction to Nutrient Management (7th ed.).  Pearson Education, Inc., Upper Saddle River, New Hersey 07458.

C.L. Mackowiak. 2007. Soil Fertility Management for Wildlife Food Plots. This document is SL248, a fact sheet of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. http://edis.ifas.ufl.edu/ss468.

Mylavarapu, R., K. Hines and T. Obreza. 2011. Diagnostic Nutrient Testing for Commercial Citrus in Florida. This document is SL 279, one of a series of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.http://edis.ifas.ufl.edu/ss492

Splittstoesser, W. E. 1990. Vegetable Growing Handbook: Organic and Traditional Methods (3rd edition). ISBN-10: 0442239718 Van Nostrand Reinhold. Chapman & Hall, New York, NY 10003.

Wright, A. L., E. A. Hanlon, D. Sui, and R. Rice. Soil pH Effects on Nutrient Availability in the Everglades Agricultural Area. This document is SL287, one of a series of the Soil and Water Science Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.http://edis.ifas.ufl.edu/ss500.

Title: Irrigation using evapotranspiration smart controllers in agriculture

Authors: Kati Migliaccio, Isaya Kisekka

Irrigation is used for most crops in Florida even though 44 to 62 inches of rainfall occur annually (depending on the location). It is needed due to the low water holding capacity of Florida soils, the distribution of rainfall by wet and dry seasons, and the intensity of rainfall events which often results in water losses to runoff and drainage.

There are different ways to schedule irrigation for agricultural crops. Some growers have a manual system that is operated as needed, some have automated irrigation systems that are set to irrigate for certain times and days, and some use more complex systems that include an environmental measurement to determine irrigation. These more complex systems typically use soil water content measurements or weather measurements and evapotranspiration (ET) calculations to regulate irrigation. Systems that use soil water content or ET in automating irrigation are termed smart irrigation controllers. Our discussion here will focus on the ET smart controller.  

Historically, ET has been used to estimate irrigation through the following simple idea: Irrigation = ET- rainfall. Irrigation amounts are calculated by estimating ET from historical data and using the historical data to develop an irrigation rate. (Note that ET data are available free of charge from the Florida Automated Weather Network; http://fawn.ifas.ufl.edu/). More recently, smart irrigation controllers that use real-time ET values have made this easier. These ET controllers (Figs. 1 & 2) use real-time weather data, a pre-programmed ET equation, crop coefficients, and other site characteristics to determine an irrigation schedule.

fig1.png

Figure 1: Signal based evapotranspiration (ET) irrigation controller (Credit: S. Michael Gutierrez)

There are two primary types of ET controllers: signal based controllers (Fig. 1) and on-site controllers (Fig. 2). The signal based controller receives weather data from a remote source on a daily basis to update the irrigation schedule. There is an annual fee for data access. The ET equation includes more frequent real-time data measurements than the on-site weather based system. The on-site controller, also called a weather-based controller, uses an on-site sensor to measure weather data and estimates ET to update the irrigation schedule. These systems have no annual fee for data; however they use fewer real-time weather data points to estimate ET and thus can be less accurate.

Description: DSC08800.JPGDescription: DSC08804.JPG

Figure 2: On-site or stand-alone evapotranspiration (ET) irrigation controller (Credit: Nicole A. Dobbs)

Description: Project 09-19-2008 050.jpg

Figure 3: Weather station installed in carambola orchard at the Tropical Research and Education Center for irrigation study (Credit: Tina Dispenza)

      We have used the signal based ET controllers at the Tropical Research and Education Center (TREC) to conduct irrigation research on carambola (Fig. 3). We compared a signal-based ET controller for irrigation to a time-based irrigation schedule and to a historical ET schedule. Our results indicated that ET-based irrigation scheduling from either real-time (signal based) or historical weather data applied a significantly less volume of irrigation water compared to a set-schedule practice (Kisekka et al., 2010). The study also showed no significant difference in irrigation water applied between the two treatments using ET. Since this study was completed, we have been using a signal-based ET controller to irrigate an avocado orchard at TREC. The signal-based ET controller has reduced the irrigation volumes applied, and resulted in water and energy savings.  

There are some things to consider when using ET smart irrigation controllers. The first is that an accurate crop coefficient is needed. Crop coefficients are used to adjust the ET estimated by the controller to predict your crop’s irrigation requirement. The second is to describe the soil type accurately so the controller will integrate the soil’s water holding capacity into the controller’s calculations. The third consideration is to program irrigation events as frequently as needed to ensure that cumulative ET never exceeds the soil water holding capacity.

      To learn more about implementing an irrigation system using ET and ET smart controllers, please refer to the References cited below.

NOTE: The equipment shown is not a recommendation of the University of Florida or the authors of this article but merely an example.

REFERENCES

Dukes, M.D., M.L. Shedd, and S.L. Davis. 2012. Smart irrigation controllers: operation of evapotranspiration-based controllers. AE446. Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, IFAS, UF. URL: http://edis.ifas.ufl.edu/ae446.

Kisekka, I., K.W. Migliaccio, M. D. Dukes, B. Schaffer, J. H. Crane. 2010. Evapotranspiration-Based Irrigation scheduling and Physiological Response in a Carambola (Averrhoa Carambola L.) Orchard. Applied Engineering in Agriculture 26(3): 373-380.

Kisekka, I., K.W. Migliaccio, M.D. Dukes, B. Schaffer, J.H. Crane, and K. Morgan. 2010. Evapotranspiration-Based Irrigation for Agriculture: Sources of Evapotranspiration Data for Irrigation Scheduling in Florida. AE455. Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, IFAS, UF. URL: http://edis.ifas.ufl.edu/ae455, 4 pgs.

Kisekka, I., K.W. Migliaccio, M.D. Dukes, J.H. Crane, and B. Schaffer. 2010. Evapotranspiration-Based Irrigation for Agriculture: Crop Coefficients of Some Commercial Crops in Florida. AE456. Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, IFAS, UF. URL: http://edis.ifas.ufl.edu/ae456, 4 pgs.

Kisekka, I., K.W. Migliaccio, M.D. Dukes, B. Schaffer, and J.H. Crane. 2010. Evapotranspiration-based Irrigation Scheduling for Agriculture. AE457. Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, IFAS, UF. URL: http://edis.ifas.ufl.edu/ae457, 6 pgs.

Kisekka, I., K.W. Migliaccio, M.D. Dukes, J.H. Crane, and B. Schaffer. 2010. Implementing Evapotranspiration-Based Irrigation Scheduling for Agriculture. AE458. Agricultural and Biological Engineering Department, Florida Cooperative Extension Service, IFAS, UF. URL: http://edis.ifas.ufl.edu/ae458, 4 pgs.

Using the Right Actigard® Rate and Application Interval is Key for Optimum Performance on Tomato.

Dr. Gary E. Vallad and Dr. Cheng-Hua Huang, Gulf Coast Research and Education Center, Wimauma, FL, and Dr. Shouan Zhang, Tropical Research and Education Center, Homestead, FL.

Bacterial spot is a destructive foliar disease of tomato, especially in Florida where high temperatures, humidity, and rainfall are ideal for the disease to reach epidemic levels.  Several bacterial species of Xanthomonas are known to cause the disease, although X. perforans is the principal pathogen in Florida.  All foliar tomato tissues are susceptible to bacterial spot.  Symptoms on leaves, petioles, and stems are most common, and begin as small water soaked lesions that eventually turn black and necrotic, rarely exceeding an eighth of an inch in diameter.  Leaf lesions often have a shot hole appearance and often coalesce, especially along leaf margins, causing yellowing and blighting of leaves that leads to premature defoliation of the plant.  Symptoms on green fruit consist of small, whitish upraised blisters that may be surrounded by a faint halo of darker tissue.  As the lesions expand, they become brown and scab-like.  The centers of larger lesions can become depressed and sunken into the fruit, but the ridge surrounding the lesion remains raised. 

Tomato growers have long relied on copper-based bactericides for the management of bacterial spot, often tank-mixing them with the dithiocarbamate fungicide mancozeb to enhance bactericidal activity (Conover and Gerhold, 1981).  However, grower reliance on copper for bacterial spot management led to the development of copper tolerant strains of the pathogen.  These copper-tolerant strains now dominate commercial tomato production areas throughout Florida, greatly compromising the effectiveness of copper, regardless of the copper formulation.  In addition, copper doesn’t degrade in the soil and intensive usage can lead to a buildup in the soil (Koller, 1998).  Recent changes to copper labeling (EPA, 2009) has now introduced limitations on the amount of copper that can be applied to tomato production at 1.6 lbs Cu2+/Acre per a single application and a maximum annual application rate of 8.0 lbs/Acre.  These new restrictions were implemented into new labels beginning in 2011 and also included changes to reentry interval restrictions and required personal protective equipment.

Actigard® (Syngenta Crop Protection, Greensboro, NC) contains the active ingredient acibenzolar-S-methyl, a proven activator of plant defenses (Sticher et al., 1997).  Actigard® has proven effective against a number of plant diseases, including bacterial spot of tomato (Louws et al., 2001; Vallad and Goodman, 2004) although reduced tomato yields have been associated with the use of Actigard® in some studies.  Our program has evaluated Actigard® under diverse field conditions in an effort to optimize its usage pattern while minimizing any negative impact on crop production.  Recent field trials evaluated a range of application rates and frequency for Actigard® on tomato to optimize bacterial spot control (Huang et al., 2012).  Field trials were conducted at the Gulf Coast REC in Wimauma, FL and at the Tropical REC in Homestead, FL using tomato cultivars SecuriTY 28 and FL47.  Trials at the Gulf Coast REC were inoculated with X. perforans after treatments were initiated, while trials at the Tropical REC relied on natural inoculum.  Trials demonstrated that weekly applications of Actigard® from 0.21 oz to 0.56 oz per a 100 gallon broadcast volume gave better control compared to a 14 day application interval.  These application rates on a 7 day interval were statistically equivalent or better in most cases than the copper-mancozeb standard.  Overall, Actigard® had little statistical effect on tomato yields.  Results from some of these trials are presented in Tables 1 and 2.  In the first trial (Table 1), applications of Actigard® on a 7 day interval were statistically superior to the 14 day interval and the water-treated control, and statistically equivalent to the copper standards used.  Actigard® had no impact on total marketable yield when applied on a 7 day interval, with the exception of the highest rate which reduced the yield of extra large fruit; although the observed yield differences were due to the culling of larger fruit with symptoms of target spot (caused by the fungus Corynespora cassiicola).  There was no statistical effect on total fruit yields.  The second trial (Table 2) was quite similar to the first.  Actigard® applications on a 7 day interval were superior to 14 day intervals, and better or equivalent to the copper-mancozeb standard.  Again, treatments had no statistical effect on marketable yield.

Tables 3 and 4 present data from on-farm trials conducted with tomato grower cooperators in Manatee County in 2011.  Both trials were conducted on cultivar Mariana tomatoes under grower conditions.  Treatments were applied weekly, unless noted otherwise, using a CO2 backpack sprayer calibrated to apply 50, 75, and 100 gallons per acre broadcast volumes.  Treatments were established in 30 linear row foot plots with 6 replications per a treatment arranged in a completely randomized block design.  Additional maintenance fungicides and insecticides were added across the trial as necessary.  Trials were rated as natural bacterial spot reached appreciable levels.  Table 3 shows that similar to Table 1 the lower rates of Actigard® are still effective.  However, efficacy against bacterial spot drops as rates fall below the 0.42 oz rate in Table 1 and the 0.5 oz rate in table 3.  Therefore the 0.5 oz/A rate, applied weekly, is recommended for optimum control of tomato bacterial spot.  For Table 4, Actigard® was superior to the standard application of copper and mancozeb (ManKocide) alone, bacteriophage (Agriphage) alone and  a co-application of ManKocide with Actigard®.  Additional trials are in progress to assess the effect of various copper-mancozeb formulations on Actigard® performance.

Actigard® is a chemical activator of plant defenses and has no direct effect on the plant pathogen.  It is the activation of plant defenses that leads to the reduction of disease by impeding pathogen growth on the plant.  Therefore, it is essential to apply Actigard® preventatively to the crop before disease is present for optimum performance and, because the activation process is cyclical, repeat Actigard® applications to maintain effectiveness.  Our results showed that shorter 7 day application intervals were not only superior to longer 14 day application, but allowed for lower application rates.  Although combining shorter application intervals and lower Actigard® rates did not statistically improve total marketable yields, neither did the copper-mancozeb standards.  However, in our trials, using a lower Actigard® rate (0.5 oz/A) at the 7 day interval resulted in marketable and total yields that were statistically equivalent and sometimes numerically higher than the copper-mancozeb standard.  Some data, such as those presented in Table 1, suggest that Actigard® does not confer direct protection to fruit, since a higher number of large fruit were culled in Actigard® treatments due to target spot compared to the copper-mancozeb standard.  Although Actigard® effectively suppressed foliar symptoms associated with target spot.  Therefore, additional applications of protective fungicides are still needed to minimize fruit losses to early blight and target spot.  These results only demonstrate that Actigard® is just one part of an integrated disease management plan and like all products must be combined with other cultural and chemical control strategies for optimum performance.

Table 1. Evaluation of Actigard frequency and rates for the management of bacterial spot and target spot of tomato during the fall 2009 field trial at GCREC, Wimauma, FL.

 

Disease Severity

 

Marketable weight (lbs/trt)

Treatment, rate/100 gal (weeks applied)

3 Nov

1 Dec

AUDPC

Total

X-Large

Actigard 50WG, 1.12 oz (1- 8)

24.8 c

13 f

1002 e

83.0

38 de

Actigard 50WG, 0.56 oz (1- 8)

28 c

11.4 f

1081 de

89.3

47 bcde

Actigard 50WG, 0.42 oz (1- 8)

36.3 bc

14.6 ef

1400 cde

97.0

51 abcd

Actigard 50WG, 0.28 oz (1- 8)

45.8 b

26.4 cde

1886 bc

114.2

48 bcde

Actigard 50WG, 1.12 oz (1, 3, 5, 7, 9)

38.5 bc

20.9 def

1565 cde

91.1

40 cde

Actigard 50WG, 0.56 oz (1, 3, 5, 7, 9)

41.7 bc

29.6 cd

1798 bc

89.6

33 e

Actigard 50WG, 0.42 oz (1, 3, 5, 7, 9)

41.7 bc

23.3 cdef

1703 cd

85.3

48 bcd

Actigard 50WG, 0.28 oz (1, 3, 5, 7, 9)

53.2 b

46.8 ab

2430 b

86.8

42 cde

Regalia, 1 Qt (2 - 9), Cuprofix 40D, 3 lb (2, 4, 6, 8); Penncozeb 75DF, 2 lb (3, 5, 7, 9)

46.8 b

34.3 bc

2037 bc

82.2

53 abc

Cuprofix 40D, 3 lb (2 - 9); Penncozeb 75DF, 2 lb (2 - 9)

39.5 bc

11.4 f

1455 cde

97.8

59 ab

Water-treated Control

84.7 a

57.3 a

3612 a

79.8

43 bcde

P > F

< 0.0001

< 0.0001

< 0.0001

0.2724

0.0039

Listed treatment rates are on a per acre basis unless noted otherwise; 1-9 refer to weekly application dates after planting. Bacterial spot severity was assessed as the percentage of total leaf area affected by disease using the Horsfall-Barratt scale; values were converted to mid-percentages and fit to a lognormal distribution for final statistical analysis.  Area under the disease progress curves (AUDPC) was calculated using the formula: Σ([(xi+xi-1)/2](ti-ti-1)) where xi is the rating at each evaluation time and (ti-ti-1) is the time between evaluations.  Means followed by the same letter are not significantly different at α=0.05. Marketable yield assumes 4356 plants/A and 20 lb/box and includes medium, large, and extra-large fruits.

Table 2. Evaluation of Actigard frequency and rates for the management of bacterial spot of tomato during the spring 2010 field trial at GCREC, Wimauma, FL.

Disease severity (%)

Marketable fruit yield

Treatment, rate/ 100 gal (weeks applied)

18 May

2 Jun

17 Jun

AUDPC

Weight (boxes/A)

Extra large  (numbers/A)

Actigard 50WG, 0.56 oz (2-8)

43.8 dw

83.9 cd

91.0 b

2333 e

1089

32997

Actigard 50WG, 0.42 oz (2-8)

56.3 cd

81.5 d

91.0 b

2396 de

1031

30056

Actigard 50WG, 0.28 oz (2-8).

72.0 ab

83.9 cd

92.1 ab

2567 bc

  936

27770

Actigard 50WG, 0.56 oz (2,4,6,8)

56.3 cd

81.5 d

94.4 a

2421 cde

  942

29512

Actigard 50WG, 0.42 oz (2,4,6,8)

67.3 bc

91.0 ab

94.4 a

2656 b

  965

31363

Actigard 50WG, 0.28 oz (2,4,6,8)

62.3 bc

87.4 bc

93.2 ab

2554 bcd

  991

32888

Actigard 50WG, 1.25 oz (1,2), 0.56 oz (3,6), 0.42 (7)

67.3 bc

91.0 ab

94.4 a

2656 b

  882

27552

Cuprofix Ultra 40D, 3 lb/A (1-7);

   Penncozeb 75DF, 2 lb/A (1-7)

72.0 ab

93.3 a

93.3 ab

2721 ab

  969

30383

Water-treated Control

86.3 a

93.3 a

93.3 ab

2835 a

1062

31581

P > F

0.0003

< 0.0001

0.0053

0.026

0.772

0.9384

Listed treatment rates are based on a 100 gallon broadcast volume per acre basis unless noted otherwise; 2-8 refer to weekly application dates after planting. Bacterial spot severity was assessed as the percentage of total leaf area affected by disease using the Horsfall-Barratt scale; values were converted to mid-percentages and fit to a lognormal distribution for final statistical analysis.  Area under the disease progress curves (AUDPC) was calculated using the formula: Σ([(xi+xi-1)/2](ti-ti-1)) where xi is the rating at each evaluation time and (ti-ti-1) is the time between evaluations.  Means followed by the same letter are not significantly different at α=0.05. Marketable yield assumes 4356 plants/A and 20 lb/box and includes medium, large, and extra-large fruits.

Table 3. On-farm evaluation of Actigard and copper bactericides for the management of bacterial spot of tomato during the spring of 2011 in Parrish, FL.

 

Disease Severity (% foliage):

Treatment, rate /100 gal

5-May

20-May

AUDPC

Actigard, 0.33 oz

6.7

bc

13.0

c

291

c

Actigard, 0.5 oz

3.5

d

6.4

d

151

d

Actigard, 0.75 oz

4.2

cd

4.7

d

156

d

Cuprofix Ultra 40D, 2 lb

   + Penncozeb 75DF, 0.5 lb

10.1

ab

26.3

ab

493

ab

Kocide 3000, 1.5 lb

   + Penncozeb 75DF, 0.5 lb

9.0

b

29.6

ab

487

ab

Nordox 75WG, 2 lb

   + Penncozeb 75DF, 0.5 lb

8.1

b

18.4

bc

378

bc

Water-treated Control

16.4

a

36.3

a

757

a

P =

< 0.0001

< 0.0001

< 0.0001

Listed treatment rates are based on a 100 gallon broadcast volume per acre; treatments were applied weekly beginning after planting. Bacterial spot severity was assessed as the percentage of total leaf area affected by disease using the Horsfall-Barratt scale; values were converted to mid-percentages and fit to a lognormal distribution for final statistical analysis.  Area under the disease progress curves (AUDPC) was calculated using the formula: Σ([(xi+xi-1)/2](ti-ti-1)) where xi is the rating at each evaluation time and (ti-ti-1) is the time between evaluations.  Means followed by the same letter are not significantly different at α=0.05.

Table 4. On-farm evaluation of Actigard, Agriphage, and copper bactericides for the management of bacterial spot of tomato during the fall of 2011 in Parrish, FL.

Disease Severity (% foliage):

Treatment, rate /100 gal

7-Oct

17-Oct

3-Nov

18-Nov

AUDPC

Actigard, 0.75 oz

7.3

d

27.5

c

50.0

e

65.9

d

1955

d

Actigard, 0.75 oz;

   + ManKocide, 4 lbs

18.5

c

54.2

b

75.6

cd

75.6

cd

3064

c

Agriphage 2 pt

   (once a week)

37.5

a

69.3

a

89.6

ab

86.6

a

4026

a

Agriphage, 2 pt

   (twice a week)

24.4

bc

68.7

ab

83.3

bc

78.6

abc

3553

b

ManKocide, 4 lbs

41.6

a

72.5

a

83.3

bc

85.0

ab

4042

a

Water-treated Control

38.1

a

72.5

a

91.8

a

85.0

ab

4118

a

Non-treated Control

27.5

b

71.9

a

85.0

b

77.6

bc

3680

ab

P =

< 0.0001

< 0.0001

< 0.0001

< 0.0001

< 0.0001

Listed treatment rates are based on a 100 gallon broadcast volume per acre; treatments were applied weekly (unless noted otherwise) beginning after planting. Bacterial spot severity was assessed as the percentage of total leaf area affected by disease using the Horsfall-Barratt scale; values were converted to mid-percentages and fit to a lognormal distribution for final statistical analysis.  Area under the disease progress curves (AUDPC) was calculated using the formula: Σ([(xi+xi-1)/2](ti-ti-1)) where xi is the rating at each evaluation time and (ti-ti-1) is the time between evaluations.  Means followed by the same letter are not significantly different at α=0.05.

References:

Conover RA and Gerhold NR. 1981. Mixture of copper and maneb or mancozeb for control of bacterial spot of tomato and their compatibility for control of fungus diseases. Proc. Fla. State Hortic. Soc. 94:154-156.

Environmental Protection Agency, U.S. 2009. Reregistration eligibility decision (RED) for coppers. EPA 738-R-09-304. May 2009.

Huang, C.-H., Vallad, G. E., Zhang, S., Wen, A., Balogh, B., Figueiredo, J. F. L., Behlau, F., Jones, J. B., Momol, M. T., and Olson, S. M. 2012. Effect of application frequency and reduced rates of acibenzolar-S-methyl on the field efficacy of induced resistance against bacterial spot on tomato. Plant Dis. 96:221-227.

Koller W, 1998. Chemical approaches to managing plant pathogens. In: Handbook of Integrated Pest Management, ed. JR Ruberson, Dekker.

Louws FJ, Wilson M, Campbell HL, Cuppels DA, Jones JB, Shoemaker PB, Sahin F, and Miller SA. 2001. Field control of bacterial spot and bacterial speck of tomato using a plant activator. Plant Disease 85:481-488.

Sticher L., MauchMani B, and Métraux JP. 1997. Systemic acquired resistance. Annu Rev Phytopathol 35: 235-270.

Vallad, G. E., and Goodman, R. M. 2004. Systemic acquired resistance and induced systemic resistance in conventional agriculture. Crop Sci. 44:1920-1934.