Integrated Pest Management

Environmental and food-safety concerns have focused attention on IPM. The concept of IPM is to employ several techniques simultaneously to solve specific pest and disease problems for the long term rather than in the short term. Success relies on an in-depth understanding of the pineapple production system and the ecology and biology of each pest or disease and associated organisms (e.g. vectors, natural enemies). Emphasis must be placed on the importance of each pest or disease from an economic, biological and ecological perspective (Pedigo, 2002). In order to evaluate the importance of the pest or disease, efficient techniques are needed to monitor changes in populations of pest and levels of diseases or pathogen populations. The changes must be correlated with yields and quality.

In most pineapple production systems throughout the world, mealybug wilt must be controlled by the management of ants and mealybugs. Severe infestation may have an impact on the production system and the final product in several ways. As a direct pest, feeding reduces plant growth, fruit quality and yield. The presence of mealybugs on fresh fruit may become a quarantine issue, as well as a quality issue when present in the canned product. The indirect effect and the most severe impact are the resulting mealybug wilt, with high rates of field infestation.

Ants play a major role in the impact of mealybugs and mealybug wilt on pineapple. Soil tillage during fallow eliminates essentially all in-field ants, and new infestations must move into the newly planted field from field border areas. The rate of establishment of permanent ant colonies and mealybug wilt is relatively slow (Beardsley et al., 1982). When ants are controlled, the parasitoid Anagyrus ananatis Gahan (Fig. 9.32) and other biological control agents can maintain

Fig. 9.32. The parasitoid Anagyrus ananatis on a pink pineapple mealybug, Dysmiococcus brevipes.

populations of the pink mealybug below damage thresholds in Hawaii. The use of Amdro® is efficacious, allowing natural biological control agents to function while reducing overall insecticide usage.

Techniques for monitoring ants, using trap stakes, have been developed (Fig. 9.33; Beardsley et al., 1982). Recommendations are to use trap stakes baited with peanut butter/soybean oil at intervals of 30 m (100 ft) along field borders of new plantings.

Trapping must be done in late afternoon, with data being taken after darkness occurs. The first monitoring should start at 3 months following planting and be repeated at 3-month intervals thereafter. When ants are detected, they may be controlled with site-specific applications of ant baits or insecticides. Other monitoring techniques, such as pit-fall traps, honey-vial traps and pineapple-juice traps, have also been used. Threshold levels of ants have not been very well defined and the presence of any ants is considered problematic.

Populations of mealybugs have been monitored with sticky tape placed in the lower part of the pineapple plant (Fig. 9.34; M.W. Johnson, unpublished results). Relatively high levels of mealybug are required for mealybug wilt. Diagnosis of mealybug wilt virus-infected seed material can be done rapidly and inexpensively, using a tissue-blot immunoassay system (Hu et al., 1993), in order to establish virus-free plantings. Evaluation of the impact of virus-free plants on growth and yield has not been completed, but studies are under way (D. Sether, personal communication).

Reniform and root-knot nematode threshold levels at planting for pineapple production in Hawaii have not been well defined.

Peanut Root Knot Nematode
Fig. 9.33. Field sampling for ants using white stakes with the base painted with honey/water (50 : 50) or peanut butter/soybean oil and placed out from 3 to 6 p.m. and read at 7-10 p.m.

Tape on acetate strip

Tape on acetate strip

Mealybug crawler

Fig. 9.34. Sampling technique for mealybugs using acetate strips with double-sided sticky tape placed on leaves in the middle and lower sections of the pineapple plant (M.W. Johnson, unpublished data).

Mealybug crawler

Fig. 9.34. Sampling technique for mealybugs using acetate strips with double-sided sticky tape placed on leaves in the middle and lower sections of the pineapple plant (M.W. Johnson, unpublished data).

Reniform nematode populations in soil stay low until 6-9 months following planting and then peak at 12 months (Sipes and Schmitt, 1994). The field history of nematode populations and their impacts on yield is important in nematode management.

Nematodes are currently managed primarily by soil fumigation and postplant nematocides. A clean fallow period is also used to reduce populations. Crop rotation was used in the early part of the century in Hawaii but has not generally been practised since the discovery of soil fumigants. Crop rotation has not been practical in recent years, because of the high cost of planting and maintaining (irrigation) the rotation crop, along with the inability to develop marketable rotation crops. Non-host cover crops, either within the growing crop or during fallow, have been studied with varying degrees of success (Caswell et al., 1991). Cover crops may be feasible only in highrainfall areas. Fumigation efficacy is influenced to a major degree by the soil-tillage practices prior to fumigation and soil moisture during tillage and at fumigation (Caswell and Apt, 1989). The use of plastic mulch reduces fumigant losses to the atmosphere, as well as reducing the amounts of herbicides required. Efficient nematode control integrates all the above strategies.

Phytophthora heart rot and root rots of pineapple are diseases limited to fine-textured, high-pH soils under wet environmental conditions. Control strategies involve improving surface and internal soil drainage.

Raised planting beds have provided good control under wet conditions but poorer growth under dry conditions. Fosetyl aluminium and ridomil are very effective as preplant dips. Fosetyl aluminium also provides good heart-rot control as a foliar application at 3-6-month intervals and excellent control of P. cinnamomi root rot (Rohrbach and Schmitt, 1994). Resistant cultivars to both P. cinnamomi and P. nicotianae var. parasitica exist but are not commercially viable, due to low yields or poor fruit quality (Rohrbach and Schmitt, 1994).

Both pineapple butt and black rot are caused by the fungus C. paradoxa. The severity of the problem in fresh fruit is dependent on the degree of bruising or wounding during harvesting and packing, the level of inoculum on the fruit and the storage temperature during transportation and marketing. Currently, these diseases are controlled by dipping the crown or fruit in a fungicide prior to planting or shipping of the fruit (Cho et al., 1977). Treatment must be done in 12 h or less from the time the crown or fruit is removed from the plant (Rohrbach and Phillips, 1990).

Inoculum levels on fruit at harvest vary according to the environmental conditions prior to harvest. The high correlation between moisture (rainfall duration) prior to harvest and disease following harvest has resulted in the name water rot. Storing seed material on the mother plants during dry weather, where there is good air circulation and minimal exposure to inoculum-infested soil, provides excellent control. However, stored seed results in poor uniformity of early plant growth and can reduce crop yields. Planting fresh planting material results in more rapid uniform growth. Freshly removed seed material for immediate planting must be dipped in a fungicide within 12 h of removal. Currently, seed materials are dipped in triadimefon.

Black rot is commercially controlled in fresh fruit by minimizing bruising of fruit during harvest and handling, by refrigeration and with chemicals. Fruit must be dipped in a fungicide within 6-12 h following harvest prior to packing and shipping. Currently fruit can be dipped in triadimefon. The 'Red Spanish' cultivar is generally more resistant to C. paradoxa than 'Smooth Cayenne', but, due to low yields and poor quality, this is not an economically viable cultivar.

Pineapple scale only becomes a problem when the balance of biological control is upset, for example by the application of residual, broad-spectrum insecticides (Sakimura, 1966). Quantitative monitoring techniques have not been developed. While a monitoring technique has been developed for the tar-sonemid mite (Fig. 9.35), correlation with the Penicillium-induced fruit diseases has not been well enough established to predict disease.

IPM for pineapple production systems has met with varying success and has not been broadly implemented for several reasons. First, less expensive alternatives are still available. The annual application of Amdro® for ant control in pineapple is much less expensive than the labour required for a detailed ongoing monitoring programme. As long as other alternatives are available, farmers will not learn and implement monitoring activities. Second, in Hawaii, the importation and development of biocontrols have essentially reached a standstill because of environmental concerns for non-target species. Until agriculture is forced by economic or regulatory incentives to implement IPM, traditional pest and disease strategies

Fig. 9.35. Sampling for pineapple fruit mites by washing heart leaves in 70% ethanol. Samples can then be stored and counted.

will be used. Thirdly, IPM does not generally reduce pest and disease levels low enough to meet quarantine requirements, thus requiring other pest- and disease-control strategies.

In Hawaii, an IPM verification programme has been established, which was modelled after the national IPM protocol for potatoes. Multidisciplinary teams, including members from industry, research and extension, identify pests and diseases and recommend IPM practices. IPM protocols are developed based on establishing the best management approaches. Verification of producer practices is done by farm visits and review of records, in order to assign points in relation to each IPM protocol. High scores allow producers to use IPM as a marketing tool and to better educate farmers and consumers as to the value of products grown under IPM principles (A. Hara and R. Mau, personal communication).

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